Ecology

Ecology

Lions_Family_Portrait_Masai_Mara.jpgEcology is the study of the inter-relationship of organisms to each other and to their environment.

The environment constitute the surroundings of an organisms both living and non living (abiotic or physical).

Autecology is the study of individual species within a community. It involves studying the relationship with both biotic and abiotic components of the ecosystem, its cycle and adaptation for survival.

Synecology is the study of different species of organisms interacting among themselves within an ecosystem.

Importance of Studying Ecology

  • Sustainable food production
  • Conservation of natural resources
  • pollution control
  • Control of disease and pests
  • Prediction of adverse weather patterns.
  • Population control
  • Ecotourism

Pollution

Pollution is the release of substances or forms of energy into the environment by human activities in such quantities whose effects are either harmful or unpleasant to human or any other living organisms.
There are three main categories of pollution namely Water, air and Soil pollution.

Air Pollution

Causes of Air Pollution
a) Sulphur based chemicals e.g sulphur (IV) oxde (SO2) and Hydrogen Sulphde (H2S)
They are produced by food preserving industries, manufacture of sulphuric acid and burning based petroleum fuels. Hydrogen sulphide is produced form mineral extractions mines and also from geothermal power stations like Olkaria in Kenya. Volcanic activities also release hydrogen sulphide, carbon (IV) oxide and carbon (II) oxide into the atmosphere.

Effects


i. It leads to bronchitis, pneumonia and heart failure
ii. It slows down the ciliary activities in the respiratory tract hence solid particles reach the alveoli where they caue irritation and interfere with gaseous exchange.
iii. Sulphur (IV) oxide dissolves in rain water and falls as acid rain which tends to lower the pH leading to a fall in crop production.
iv. It also corrodes metals such as iron and aluminum in buildings and monuments.
v. It contaminates blood and suffocates victims when inhaled.
vi. Acid rain causes leaching of magnesium and calcium ions from soils.

b) Oxides of Nitrogen e.g Nitrogen (II) oxide (NO) and nitrogen (IV) oxide No2
These are produced from burning of petroleum fuels and emissions of exhaust fumes in motor vehicles. They are also released during industrial manufacture of nitric acid

Effects
i. They are poisonous to animals to animals affecting respiratory systems when inhaled.
ii. Nitrogen (IV) oxide is carcinogenic.
iii. They diminish visibility of roads.

c) Smoke and Fumes
These contain carbon (II) oxide (CO), carbon (IV) Oxide and carbon particles. These are produced from industries which burn coal and petroleum fuels and also from motor vehicle exhaust. They are also produced from burning of natural gases and charcoal

Effects
i. Smoke and fumes affect the visibility due to smog on roads.
ii. When they settle on stomata they block stomata hence hinder photosynthesis.
iii. They cause green house effect.
iv. Leads to global warming


d) Dust
It is composed of small particles emitted from cement and lime producing industries such as cement works, and also from quarries, road constructions and dusty dry weather roads. Environmental concerns have led many cement manufacturing industries t adopt ‘wet method’ of cement manufacture which doesn’t result into the release of dust in the environment.

Effects
i. Dust settles in leaves thus limiting photosynthesis
ii. It clogs respiratory surfaces of organisms resulting in breathing in difficulties and respiratory diseases iii. It reduces visibility and irritates the yes.

e) Lead (Pb)
This is mainly from the combustion of leaded petrol by motor vehicles. Lead is normally added to petrol to serve as anti-knock compound in vehicle engines so as to improve the efficiency of the engine combustion. Increased environmental awareness has led to phasing out of the use of anti-knock addictive

Effects
i. When inhaled, it is absorbed into blood stream and accumulates into the liver, kidneys and bones of animals affecting psychological functioning of these organs.
ii. It is also thought to interfere with mental development of children.
iii. In plants, it leads to blocking of stomatal pores making it difficult for the plant to carry out gaseous exchange and hence no photosynthesis.

f) Aerosols
An aerosol is a substance that consists of very fine particles of liquid or solid suspended in gas. These include pesticides, insecticides, fungicides, perfumes, air fresheners and spray paints. The main pollutants in these aerosols are Copper, led and chlorofluorocarbon (CFC) compounds.

Effects
i. When inhaled they cause irritation in respiratory organs of animals.
ii. Copper also causes poisoning of water plants and fish.
iii. Copper based chemicals are non-biodegradable hence tend to accumulate I the ecosystem.
iv. CFC causes depletion of the ozone layer leading to increased penetration of Ultra violet rays that causes skin cancer and affects crops.

g) Noise
Noise is the presence of undesirable sound in the atmosphere. It is produced by machines in factories, heavy vehicles, aeroplanes, music players, loud speakers and ‘jua kali’ workshops

Effects
i. Affects hearing in animals.
ii. It is irritant and causes stress in animals


Control of Air pollution
i. Legislation- the government needs to enforce the relevant legislative acts on environmental pollution. ii. Encourage the use of lead free fuels in motor vehicles.
iii. Develop and encourage the use of renewable sources of energy e.g solar and wind energy.
iv. Use CFC free aerosols and appliances.
v. Use biological control methods to control pests, diseases and weeds. This reduces reliance on non-biodegradable chemicals.
vi. Encourage the use of public means of transport as much as possible to minimize consumption of fossil fuel and emission of gas pollutants.
vii. Smoking in public should be banned.
viii. Ear muffs should be used in factories and ‘jua kali’ workshops that generate loud noises.
ix.The masses should be educated on the need for sustainable environmental management.
x. The government should be a signatory to global treaties on environmental conservations.


Water Pollution It involves addition of substances or energy forms into water bodies in quantities thata re harmful to the living organism dependant on that water. Sources of water pollution a) Domestic effluents Untreated sewage from urban centres gets discharged into rivers used for water supplies for domestic purposes. This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It is also full of faecal material and urine which encourage bacterial growth. Kitchen waste also contains detergents that have a lot of phosphates. Effects Water pollution may also cause epidemics of waterborne diseases e.g cholera, typhoid and amoebic dysentery. The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects the aquatic animals such as fish and aquatic plants. The breakdown of theses organic matter releases such as nitrates, phosphates and sulphates which enrich the water body resulting in eutrophication as happened with excessive growth of water hyacinth in lakes. b) Industrial Effluents Industries discharge various effluents into rivers, fresh waters, dams, marshes, seas and oceans. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and there chemicals. Effects The poisonous compounds directly kill aquatic organisms such as fish. Death can also be caused indirectly through eutrophication. These compounds also enter the food chain or accumulate to lethal levels in organisms higher up the trophic level. c) Heat Industries discharge hot water directly into water bodies. This may be from the cooling process or for discharging industrial effluents. Some of the effluents may react among themselves releasing heat into the water. Effects Heat reduces the amount of dissolved gases in water e.g oxygen and carbon (IV) oxide. Thus organisms may die from oxygen deficiency or lack of photosynthesis. Heat releases respiratory rate to abnormal levels causing malfunctioning in the organisms. The hot water may then kill the living organisms directly due to high temperatures. d) Oil spillage Oil is an important pollutant. Oil spillages occur in oceans from oil tanker accidents, offshore oil wells and refineries and also from damaged warships. Effects Oil layer on water reduces oxygen supply to the water and this may lead to death of aquatic life forms. Marine organisms such as fish are killed by clogging of their respiratory surfaces. Marine birds gets their feathers clogged hence the difficult in flight. Oils coats photosynthetic phytoplantktons till they die. There is reduced light penetration into the water hence photosynthesis of a submerged plant is hindered. e) Agro-chemicals Agricultural chemicals include inorganic fertilizers, herbicides and pesticides. The inorganic fertilizers contain phosphates and nitrates. Pesticides may contain heavy metals such as mercury and copper. Other pesticides such as DDT contain chloroflourocarbons which are not easily broken down biologically. These chemicals and fertilizers percolate through soil and after underground seepage they join streams and rivers and eventually into lakes and oceans. Effects Since most of chemicals contain the heavy metals such as copper and mercury, they affect the respiratory activities of aquatic organisms. These chemicals find their way into the organism bodies in small amounts. However they accumulate over a long time and reach toxic levels leading to death. Furthermore they accumulate along food chain becoming lethal at higher trophic levels. Nitrates and phosphates in fertilizers cause eutrophication. f) Lead This is water pollutant mainly from pipes and tanks in domestic water supply systems. Through run-off it finds its way into water bodies like rivers, lakes and oceans. The effects of lead whether inhale or ingested are similar as discussed under air pollution g) Mercury Mercury as a pollutant is released by industries that manufacture chlorine, sodium hydroxide, ores and vinyl plastics. It is also released during combustion of coal and petroleum oils. Fungicides and some cosmetics also contain mercury. The mud in some rivers contains mercury which is converted to methyl mercury by methane producing bacteria. Effects Methyl mercury is volatile and very toxic. It is absorbed by aquatic organisms or through leaves and roots of plants hence entering the food web involving human beings. Mercury poisoning in people results in accumulation of mercury in liver, kidneys and brain affecting the physiological functioning and eventually causes death. Animals eating plants with mercury are poisoned and killed as observed in wood-pigeons. Mercury also interferes with the process of melanin formation leading to skin lightening, blindness paralysis and even death. h) Soil Erosion Through soil erosion, silt is transported into water bodies. Effects This makes water unclean and unfit for human consumption. The silt particularly reduces light penetration hence hindering photosynthesis activity. It also clogs the respiratory surfaces of aquatic organisms. E.g gills in fish and stomata in plants. This interferes with gaseous exchange. Control of Water Pollution a) Legislation b) Industries should control or treat the industrial effluents before discharge into the water bodies. c) Proper treatment and disposal of sewage. Here should be separate systems for disposal of sewage and drinking water. Latrine should be connected properly used in addition to proper personal hygiene to control disease causing agents. d) Encourage the use of unleaded petrol. e) The public should be educated on correct amount of inorganic fertilisers and pesticides to be used. f) Appropriate soil erosion control methods to be put in place such as building of gabions, terraces, mulching and growing of soil cover crops. Soil Pollution Sources of soil pollution Either intentionally or accidentally human beings discharge chemicals into the soil which accumulate to levels that cause harm to soil organisms. a) Oxides of sulphur e.g sulphur (IV) oxide enter the soil through precipitation as acid rain. Acid rain alters the pH therefore affecting plants and animals that cannot tolerate acid soil. However, acid rain may promote the growth of plants that tolerate acidic conditions. Acid rain also causes leaching of minerals leading to loss of soil fertility. b) Aerosols Most aerosols sprayed to control pest and diseases in plants and animals contain heavy metals e.g copper and mercury. The chemicals fall on the soil and are taken up by plants where their concentration increases. As animals eat these plants, toxicity increases and leads to death of animals. These chemicals kill nitrogen fixing soil micro-organisms hence lowering the soil fertility with consequent reduction of plant growth. c) Petroleum Products Petroleum products spilled on land e.g oil tankers. Soils organisms fail to obtain oxygen in oil saturated soils therefore die. Coating of plant leaves or respiratory surfaces of animals also leads to their death. d) Inorganic fertilizers Agricultural inorganic fertlilisers contain phosphates and nitrates. Theses increase soil acidity so that soil micro organism cannot inhabit such soils. Formation of soil organic matter slows down and then stops. Soils become exhausted hence plant and animal life ceases. In addition soil structure ids changed hence encouraging soil erosion. e) Solid Waste Community, household wastes and industrial wastes. Some are biodegradable e.g food residues, old clothing and papers. Others are non-biodegradable e.g rubber, plastic containers, scrap metals and glass bottles. Soil waste is a nuisance and also may ne injurious e.g glass bottles. They destroy the aesthetic state of the environment. They offer breeding grounds for pests, rodents and insect vectors which in turn pose health hazards to human beings. The non-biodegradable solid wastes limit soil aeration thus inhibiting micro-organisms activity. Control of Soil Pollution All solid wastes should be sorted out according to manufacture instructions and specifications , then appropriate disposal methods applied. a) Recycle solid wastes e.g polythene paper and plastic containers, glass bottles, paer and scrap metal b) Household wastes that are biodegradable can be disposed in a compost pit to form compost manure for organic farming. c) Combustible solid wastes .g old clothes, sanitary towels, hair should be burned in incinerators. d) Discourage excessive use of agro-chemicals. e) Biological control of pests and disease to be encouraged. f) Encourage pipeline transportation of petrol and petroleum products to minise risk of spillage. g) Enforce appropriate legislation on proper solid waste management. Radioactive Emissions Nuclear emissions can also be the cause of soil, air and water pollution. Although nuclear energy is available in limitless quantity, its harnessing, management and risks of damage of life are very high. It is based on the destruction of the atom of matter to release energy that holds the constituents of the atom. The form in which this energy is released when atoms are broken down into generally called radiators. Such radiation has very great power and is very destructive if it leaks accidently. The industries in which this energy is produced are called radioactive or nuclear reactors. Some of the common substances broken down to release nuclear energy are uranium, radium, germanium, plutonium and hydrosonium (heavy water). Use of Nuclear Energy Nuclear energy is used in generation of electricity and propelling of nuclear war planes, nuclear propelled ocean vessels, spaceships and submarines. Effects of Radioactive Emissions a) Increased mutation rates with increased abnormalities some of which are inheritable. b) It causes cancer such as borne tumuors and leukaemia. c) Excess doses of radioactive emissions cause so much damage leading to death Control Due to potential dangers of nuclear waste disposal and energy management, the control is only by dialogue between nations with the nuclear technology. HUMAN DISEASES A disease is disorder state of tissue, organ, system or organism, during which its function are not carried on normally. In human beings, disease results from genetic disorders, nutritional deficiencies or infections by other organisms and viruses. Bacterial Diseases a) Cholera This is diseases by a bacterium known as Vibrio cholerae found in infected water and are passed o by flies to food thereby contaminating the food. People living in unhygienic places i.e where sanitation is poor and the domestic water supply is contaminated, can easily contract the disease. Once there is an outbreak of the disease, it spreads rapidly and can cause an epidemic. Symptoms The incubation periods varies between one to six days depending on the magnitude of the infection and the taste of the health of the individual. The bacteria reach the intestines and multiply rapidly. They secret an enzyme called Mucinase which digests the inner lining of the intestines. The exposed intestinal wall then becomes irritated and damaged by the causes violet diarrhoea and vomiting. This is accompanied by severe abdominal pains. The disease develops rapidly and leads to general body dehydration owing to the high frequency of defecation, accompanied by loss of large quantities of water. Death by cholera can be rapid within 24 hours of infection. Prevention and Treatment Sanitary disposal of faeces and refuse is needed to prevent the contamination of water and food. The pit latrine in rural areas should be deep. They should be kept clean to keep away flies. Personal hygiene should be maintained. Domestic water should be boiled and filtered, or chlorinated before use so as to kill bacteria and their spores. The infected persons are infectious and so should be isolated and treated as soon as possible. Treatment involves administering of antibiotics drugs in order o kill the bacteria. Oral rehydration salts should be administered before treatment. b) Typhoid This is also a disease caused by a bacterium called salmonella typhi. The bacteria are passed out either through urine or faeces. Poor disposal of urine and faeces may cause contamination of the water supply from rivers, dams and lakes. Healthy individuals can be infected by taking contaminated water or food. Symptoms Its incubation period last for about two weeks after which a fever and rush develop, followed by severe diarrhea. The bacteria attack the walls of the intestines and cause patches of scores. Patients are advised not to eat solid food as it might irritate the intestinal sores and cause bleeding. In severe attacks the sores may burst and cause perforation in the intestines. This may result in death if the patient is not treated early enough. The bacteria invade the lymph glands around the intestines and then pass into the blood stream. Patients do not develop immunity of this disease and therefore one can be attacked again and again. Prevention and Treatment There should be proper disposal of faeces and urine to prevent spread of the bacteria. Domestic water should be boiled or chlorinated before drinking to kill the bacteria. Hands and cutlery should be washed with clean water before being eaten. Food handlers should be clean, and should be subjected to regular medical check-ups. Healthy people may be vaccinated with attenuated (weakened) typhoid bacteria in order to provide immunity for at least two years. Treatment involves administering antibiotics. Protozoan Diseases a) Amoebic Dysentry Amoebic dysentery is a disease caused by protozoan called entomoelaba histolytica. When the amoeba cysts are ingested, the cysts membrane is digested and the protozoa is released. When they reach the large intestines and colon, the E. histolytica multiply. Symptoms Normally E. histolytcia live within the lumen of the colon and feed on bacteria without harming the host. At certain times, they invade the mucosal wall of the colon and produce a tissue-dissolving enzyme called histolysin. This result in formation of ulcers on the colon wall and the parasites then fed on the red blood cells at the site of the ulcers. This condition usually leads to diarrhea or amoebic dysentery and faeces contain blood. The disease is usually characterized by diarhhoea, dehydration, fever and abdominal pains and severe pain when passing stool. The infection may also become systemic(i.e invade the blood stream), and parasites may reach other tissues or organs of the body such as liver, lungs and brain where they produce abscesses which may be fatal. Prevention and Treatment Prevention of the infection aims at avoiding contamination of food or water with cysts. Control measures include boiling water for drinking, proper food storage and proper faecal disposal. For treatment a number of amoebicides can be used. b) Malaria Malaria is a disease caused by protozoan parasitic called plasmodium. They are four different species of plasmodium namely P. vivax, P. ovale,P. falciparium & P. malariae. The plasmodium is transmitted from an infected person to a healthy person by female anopheles mosquito. When the mosquito bites an infected person it sucks blood containing the parasites. Inside the mosquito, the plasmodia develop into infective stages. When the same mosquito next bites a healthy person it passes on the infective plasmodia from its salivary glands into the blood into the blood system of the healthy person. The incubation period lasts between seven to ten days. During this period that parasites invade the liver cells where they multiply. They are then released into the bloodstream where they now attack and destroy the red blood cells. Symptoms The symptoms of malaria include high regular fevers accompanied by profuse sweating punctuated by chills and shivers, headaches, muscle and joint pains are felt most of the time. The patient lacks appetide and vomits from time to time. There is enlargement of liver and spleen. Anaemia results because of the destruction of red blood cells. In severe attacks, it leads to convulsions in children. Malaria is a killer disease. Prevention and treatment Various methods of prevention are available in the management of malaria. The most recent method is the development of vaccines against the plasmodium. These targets various stages in the life cycle of the parasite hence developing some immunity. Traditionally malaraia has been controlled by use of nets to repellents such as creams and mosquito coils have been used. Insecticides are sprayed in dwelling places and also use of treated mosquito nets. Drainage of stagnant water and clearance of vegetation around houses destroys the breeding and resting sites of mosquitoes hence reduction in their numbers. Tins, plastic containers and polythene papers that hold water should also be destroyed. The use of oil on stagnant water has been useful but it is being replaced by powdery treatment of water of water services. Biological control involves use of fish in pounds to feed on the mosquito larvae. A more recent method involves release of genetically sterilized male mosquitoes to mate hence reducing the number of mosquitoes. People travelling in malaria prone areas are advised to take antimalarial drugs for prevention. Treatment should be preceded by proper diagnosis and the full dosage administered for full care. Under dose often leads to development of resistance. The international Stockholm Convention of which Kenya is signatory restricts the use of DDT to public health where no alternatives are available. However Kenya the leading producer of pyrethrum strongly advocates for the use of natural pyrethroids in mosquito control. These have been proved effective and safer to environment because they are bio-degradable. Although a lot of resources have been channeled into malarial control, it has been difficult to eradicate disease. Several factors continue to frustrate theses efforts. Theses include; • The presence of large reservoir of the parasite in other hosts such as monkeys and birds. • The warm tropical conditions provide extremely suitable breeding conditions hence rapid multiplication of the vectors. • The development to resistance to insecticides used against mosquitoes. Similarly the plasmodium parasite quickly develops resistance against the drug used against it. • The individual countries face financial constraints. Furthermore regional conflicts frustrate co-ordinated program. Government and donor funds are often diverted to purchase weapons and other military ware. Parasitic Worms Askaris Lumbricoides Ascaris lumbricoides is a parasitic roundworm which belongs to the phylum Nemoda. Ascaris Lumbricoides is widespread in distribution and infects small intestines of pigs and human beings. It may also occur in other organs of the body. The genus Ascaris is the largest nematode parasitic to humans. It is characterized by brownish yellow colour with mouth parts having three lips. The male is about 25 cm long and 0.4 cm in diameter, while te female is about 35 cm long and 0.5 cm in diameter. Mode of Transmission The adult female lays eggs in the small intestine of the host. The eggs are passed out with the faeces and may be swallowed by a new host through contaminated water and food. Contaminated vegetables or fruits which are not washed well before being eaten are also the source of infection. There is also direct infection from faeces to mouth by hand s especially in children. When they are swallowed by a host, the eggs shells are dissolved, releasing the larvae. This penetrates the intestinal walls and enters the bloodstream. They move to liver and then to the heart and lungs. In the alveoli they grow and moult twice. The larvae then migrates up to the trachea where they cause irritation and so are coughed out and so may be swallowed down in to the aeosophogus, stomach and small intestines where they finally mature in adults. Effects of the parasite on the Host During the migration of the larvae they cause irritation in the trachea that lead to lung damage and infection with other diseases. If the is heavy, a lot of is digested food is consumed by the parasite in intestine and this leads o malnutrition in host, especially n children. During their cycle in human host, the parasite feed on blood and therefore can cause anaemia on host. Very heavy infection can also lead to intestinal blockage where victims develop large round stomachs. The worms may also enter the bile duct, pancreatic duct and appendix, causing further complications. Adaptative characteristics of Ascaris lumbricoides to its parasitic mode of life 1. Ascaris lumbricoides has two hosts, human beings and pigs. This ensures that it always has a ready host for survival. 2. It lays many eggs to increase the chance of survival even when some are destroyed. 3. The eggs have protective shell to survive harsh environmental conditions. 4. Ascaris lumbricoides have a thick elastic cuticle which protects it against the digestive enzymes of the host enabling it to survive in the alimentary canal. 5. It has tissues tolerant to low oxygen concentration characteristic of the gut. 6. It has a muscular pharynx through which it sucks digested food from host intestine into its own gut. Prevention and treatment Proper sanitary disposal methods are required especially the availability and proper use of toilet facilities. High standards of personal hygiene should be observed such as washing hands after a visit to the toilet. Hygienic handling and cleaning of fruits and vegetables is necessary. Drinking water should be boiled. Treatment involves use of drugs to kill the worms or inactivate the eggs. Schistomomiasis (Bilharzia) This is a parasite disease of the blood. It is caused by a flatworm of the phylum platyhelminthes of the genus Schistosoma. There are three different species odf the schistosoma that infet human beings. These include Schitosoma mansoni, Schistoma haematobium and Schistosoma japonicum. The parasite is found in fresh water canals, lakes, dams, rice-growing fields and other similar habitats. Modes of transmission The parasite is spread when people drinking water contaminated by larval form called cercariae. Also the parasite can penetrate the skin when bathing or wading through water conatini the larvae. Once in the body they get into the bloodstreams and migrate to the liver where they mature into adults. After coupling of the adult worms, eggs are shed into the blood vessels or alimentary tract. When the faeces or urine containing eggs are disposed of into water, the eggs hatch into larvae called miracidia. The miracidia find and penetrate the water snails such as Biomphalaria and Bulinus. It is from the snails that infective stages cercariae emerge and can now infect human beings who stand, bath or drink in such water. Effects of Parasite on its Hosts The parasite damages the host skin when penetrating and this causes itching. Once in the blood the adult schistosoma releases chemical substances that cause fever. The adult worms have spines which they use to tear through the veins and enter into the intestines or urinary bladder. This causes blood to appear in urine or stool. This can eventually lead to anaemia. The person also experiences abdominal pains and diarrhea. If untreated, the disease can result in death due to exhaustion or by infection from other diseases due to reduced body immunity. Adaptative Characteristic of Schistosoma The parasite has suckers for attachment so that they are not dislodged. The parasite has two hosts, that is the secondary host, the snail and the primary host, the human being. This increases its chances of transfer to several hosts and from one place to another. The cercariae larvae and eggs of the parasite have glands that secrete lytic enzymes which soften tissue to allow for penetration into the hosts. Some larval forms e.g miracidia, are encysted and can remain dormant and viable until they come into contact with a human being. The parasite reproduces through larval forms e.g cercariae, and redia in snails. This makes it very difficult to eradicate the parasite and also increases its chances of transmission and survival. The adult worm in blood produces chemical substances which protect it against the hosts defence mechanism. The worms are of separate sexes. The male form a gynecophoric canal in which it carries the female. This ensures that the e

Water Pollution

It involves addition of substances or energy forms into water bodies in quantities thata re harmful to the living organism dependant on that water.

Sources of water pollution
a) Domestic effluents Untreated sewage from urban centres gets discharged into rivers used for water supplies for domestic purposes. This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It is also full of faecal material and urine which encourage bacterial growth. Kitchen waste also contains detergents that have a lot of phosphates.
Effects Water pollution may also cause epidemics of waterborne diseases e.g cholera, typhoid and amoebic dysentery. The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects the aquatic animals such as fish and aquatic plants. The breakdown of theses organic matter releases such as nitrates, phosphates and sulphates which enrich the water body resulting in eutrophication as happened with excessive growth of water hyacinth in lakes.

b) Industrial Effluents Industries discharge various effluents into rivers, fresh waters, dams, marshes, seas and oceans. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and there chemicals. Effects The poisonous compounds directly kill aquatic organisms such as fish. Death can also be caused indirectly through eutrophication. These compounds also enter the food chain or accumulate to lethal levels in organisms higher up the trophic level.

c) Heat Industries discharge hot water directly into water bodies. This may be from the cooling process or for discharging industrial effluents. Some of the effluents may react among themselves releasing heat into the water. Effects Heat reduces the amount of dissolved gases in water e.g oxygen and carbon (IV) oxide. Thus organisms may die from oxygen deficiency or lack of photosynthesis. Heat releases respiratory rate to abnormal levels causing malfunctioning in the organisms. The hot water may then kill the living organisms directly due to high temperatures.

d) Oil spillage Oil is an important pollutant. Oil spillages occur in oceans from oil tanker accidents, offshore oil wells and refineries and also from damaged warships. Effects Oil layer on water reduces oxygen supply to the water and this may lead to death of aquatic life forms. Marine organisms such as fish are killed by clogging of their respiratory surfaces. Marine birds gets their feathers clogged hence the difficult in flight. Oils coats photosynthetic phytoplantktons till they die. There is reduced light penetration into the water hence photosynthesis of a submerged plant is hindered.

e) Agro-chemicals Agricultural chemicals include inorganic fertilizers, herbicides and pesticides. The inorganic fertilizers contain phosphates and nitrates. Pesticides may contain heavy metals such as mercury and copper. Other pesticides such as DDT contain chloroflourocarbons which are not easily broken down biologically. These chemicals and fertilizers percolate through soil and after underground seepage they join streams and rivers and eventually into lakes and oceans. Effects Since most of chemicals contain the heavy metals such as copper and mercury, they affect the respiratory activities of aquatic organisms. These chemicals find their way into the organism bodies in small amounts. However they accumulate over a long time and reach toxic levels leading to death. Furthermore they accumulate along food chain becoming lethal at higher trophic levels. Nitrates and phosphates in fertilizers cause eutrophication.

f) Lead This is water pollutant mainly from pipes and tanks in domestic water supply systems. Through run-off it finds its way into water bodies like rivers, lakes and oceans. The effects of lead whether inhale or ingested are similar as discussed under air pollution

g) Mercury Mercury as a pollutant is released by industries that manufacture chlorine, sodium hydroxide, ores and vinyl plastics. It is also released during combustion of coal and petroleum oils. Fungicides and some cosmetics also contain mercury. The mud in some rivers contains mercury which is converted to methyl mercury by methane producing bacteria. Effects Methyl mercury is volatile and very toxic. It is absorbed by aquatic organisms or through leaves and roots of plants hence entering the food web involving human beings. Mercury poisoning in people results in accumulation of mercury in liver, kidneys and brain affecting the physiological functioning and eventually causes death. Animals eating plants with mercury are poisoned and killed as observed in wood-pigeons. Mercury also interferes with the process of melanin formation leading to skin lightening, blindness paralysis and even death.

h) Soil Erosion Through soil erosion, silt is transported into water bodies. Effects This makes water unclean and unfit for human consumption. The silt particularly reduces light penetration hence hindering photosynthesis activity. It also clogs the respiratory surfaces of aquatic organisms. E.g gills in fish and stomata in plants. This interferes with gaseous exchange.

Control of Water Pollution
a) Legislation
b) Industries should control or treat the industrial effluents before discharge into the water bodies.
c) Proper treatment and disposal of sewage. Here should be separate systems for disposal of sewage and drinking water. Latrine should be connected properly used in addition to proper personal hygiene to control disease causing agents.
d) Encourage the use of unleaded petrol.
e) The public should be educated on correct amount of inorganic fertilisers and pesticides to be used.
f) Appropriate soil erosion control methods to be put in place such as building of gabions, terraces, mulching and growing of soil cover crops.

Soil Pollution Sources of soil pollution Either intentionally or accidentally human beings discharge chemicals into the soil which accumulate to levels that cause harm to soil organisms.
a) Oxides of sulphur e.g sulphur (IV) oxide enter the soil through precipitation as acid rain. Acid rain alters the pH therefore affecting plants and animals that cannot tolerate acid soil. However, acid rain may promote the growth of plants that tolerate acidic conditions. Acid rain also causes leaching of minerals leading to loss of soil fertility.
b) Aerosols Most aerosols sprayed to control pest and diseases in plants and animals contain heavy metals e.g copper and mercury. The chemicals fall on the soil and are taken up by plants where their concentration increases. As animals eat these plants, toxicity increases and leads to death of animals. These chemicals kill nitrogen fixing soil micro-organisms hence lowering the soil fertility with consequent reduction of plant growth. c) Petroleum Products Petroleum products spilled on land e.g oil tankers. Soils organisms fail to obtain oxygen in oil saturated soils therefore die. Coating of plant leaves or respiratory surfaces of animals also leads to their death. d) Inorganic fertilizers Agricultural inorganic fertlilisers contain phosphates and nitrates. Theses increase soil acidity so that soil micro organism cannot inhabit such soils. Formation of soil organic matter slows down and then stops. Soils become exhausted hence plant and animal life ceases. In addition soil structure ids changed hence encouraging soil erosion. e) Solid Waste Community, household wastes and industrial wastes. Some are biodegradable e.g food residues, old clothing and papers. Others are non-biodegradable e.g rubber, plastic containers, scrap metals and glass bottles. Soil waste is a nuisance and also may ne injurious e.g glass bottles. They destroy the aesthetic state of the environment. They offer breeding grounds for pests, rodents and insect vectors which in turn pose health hazards to human beings. The non-biodegradable solid wastes limit soil aeration thus inhibiting micro-organisms activity. Control of Soil Pollution All solid wastes should be sorted out according to manufacture instructions and specifications , then appropriate disposal methods applied. a) Recycle solid wastes e.g polythene paper and plastic containers, glass bottles, paer and scrap metal b) Household wastes that are biodegradable can be disposed in a compost pit to form compost manure for organic farming. c) Combustible solid wastes .g old clothes, sanitary towels, hair should be burned in incinerators. d) Discourage excessive use of agro-chemicals. e) Biological control of pests and disease to be encouraged. f) Encourage pipeline transportation of petrol and petroleum products to minise risk of spillage. g) Enforce appropriate legislation on proper solid waste management. Radioactive Emissions Nuclear emissions can also be the cause of soil, air and water pollution. Although nuclear energy is available in limitless quantity, its harnessing, management and risks of damage of life are very high. It is based on the destruction of the atom of matter to release energy that holds the constituents of the atom. The form in which this energy is released when atoms are broken down into generally called radiators. Such radiation has very great power and is very destructive if it leaks accidently. The industries in which this energy is produced are called radioactive or nuclear reactors. Some of the common substances broken down to release nuclear energy are uranium, radium, germanium, plutonium and hydrosonium (heavy water). Use of Nuclear Energy Nuclear energy is used in generation of electricity and propelling of nuclear war planes, nuclear propelled ocean vessels, spaceships and submarines. Effects of Radioactive Emissions a) Increased mutation rates with increased abnormalities some of which are inheritable. b) It causes cancer such as borne tumuors and leukaemia. c) Excess doses of radioactive emissions cause so much damage leading to death Control Due to potential dangers of nuclear waste disposal and energy management, the control is only by dialogue between nations with the nuclear technology. HUMAN DISEASES A disease is disorder state of tissue, organ, system or organism, during which its function are not carried on normally. In human beings, disease results from genetic disorders, nutritional deficiencies or infections by other organisms and viruses. Bacterial Diseases a) Cholera This is diseases by a bacterium known as Vibrio cholerae found in infected water and are passed o by flies to food thereby contaminating the food. People living in unhygienic places i.e where sanitation is poor and the domestic water supply is contaminated, can easily contract the disease. Once there is an outbreak of the disease, it spreads rapidly and can cause an epidemic. Symptoms The incubation periods varies between one to six days depending on the magnitude of the infection and the taste of the health of the individual. The bacteria reach the intestines and multiply rapidly. They secret an enzyme called Mucinase which digests the inner lining of the intestines. The exposed intestinal wall then becomes irritated and damaged by the causes violet diarrhoea and vomiting. This is accompanied by severe abdominal pains. The disease develops rapidly and leads to general body dehydration owing to the high frequency of defecation, accompanied by loss of large quantities of water. Death by cholera can be rapid within 24 hours of infection. Prevention and Treatment Sanitary disposal of faeces and refuse is needed to prevent the contamination of water and food. The pit latrine in rural areas should be deep. They should be kept clean to keep away flies. Personal hygiene should be maintained. Domestic water should be boiled and filtered, or chlorinated before use so as to kill bacteria and their spores. The infected persons are infectious and so should be isolated and treated as soon as possible. Treatment involves administering of antibiotics drugs in order o kill the bacteria. Oral rehydration salts should be administered before treatment. b) Typhoid This is also a disease caused by a bacterium called salmonella typhi. The bacteria are passed out either through urine or faeces. Poor disposal of urine and faeces may cause contamination of the water supply from rivers, dams and lakes. Healthy individuals can be infected by taking contaminated water or food. Symptoms Its incubation period last for about two weeks after which a fever and rush develop, followed by severe diarrhea. The bacteria attack the walls of the intestines and cause patches of scores. Patients are advised not to eat solid food as it might irritate the intestinal sores and cause bleeding. In severe attacks the sores may burst and cause perforation in the intestines. This may result in death if the patient is not treated early enough. The bacteria invade the lymph glands around the intestines and then pass into the blood stream. Patients do not develop immunity of this disease and therefore one can be attacked again and again. Prevention and Treatment There should be proper disposal of faeces and urine to prevent spread of the bacteria. Domestic water should be boiled or chlorinated before drinking to kill the bacteria. Hands and cutlery should be washed with clean water before being eaten. Food handlers should be clean, and should be subjected to regular medical check-ups. Healthy people may be vaccinated with attenuated (weakened) typhoid bacteria in order to provide immunity for at least two years. Treatment involves administering antibiotics. Protozoan Diseases a) Amoebic Dysentry Amoebic dysentery is a disease caused by protozoan called entomoelaba histolytica. When the amoeba cysts are ingested, the cysts membrane is digested and the protozoa is released. When they reach the large intestines and colon, the E. histolytica multiply. Symptoms Normally E. histolytcia live within the lumen of the colon and feed on bacteria without harming the host. At certain times, they invade the mucosal wall of the colon and produce a tissue-dissolving enzyme called histolysin. This result in formation of ulcers on the colon wall and the parasites then fed on the red blood cells at the site of the ulcers. This condition usually leads to diarrhea or amoebic dysentery and faeces contain blood. The disease is usually characterized by diarhhoea, dehydration, fever and abdominal pains and severe pain when passing stool. The infection may also become systemic(i.e invade the blood stream), and parasites may reach other tissues or organs of the body such as liver, lungs and brain where they produce abscesses which may be fatal. Prevention and Treatment Prevention of the infection aims at avoiding contamination of food or water with cysts. Control measures include boiling water for drinking, proper food storage and proper faecal disposal. For treatment a number of amoebicides can be used. b) Malaria Malaria is a disease caused by protozoan parasitic called plasmodium. They are four different species of plasmodium namely P. vivax, P. ovale,P. falciparium & P. malariae. The plasmodium is transmitted from an infected person to a healthy person by female anopheles mosquito. When the mosquito bites an infected person it sucks blood containing the parasites. Inside the mosquito, the plasmodia develop into infective stages. When the same mosquito next bites a healthy person it passes on the infective plasmodia from its salivary glands into the blood into the blood system of the healthy person. The incubation period lasts between seven to ten days. During this period that parasites invade the liver cells where they multiply. They are then released into the bloodstream where they now attack and destroy the red blood cells. Symptoms The symptoms of malaria include high regular fevers accompanied by profuse sweating punctuated by chills and shivers, headaches, muscle and joint pains are felt most of the time. The patient lacks appetide and vomits from time to time. There is enlargement of liver and spleen. Anaemia results because of the destruction of red blood cells. In severe attacks, it leads to convulsions in children. Malaria is a killer disease. Prevention and treatment Various methods of prevention are available in the management of malaria. The most recent method is the development of vaccines against the plasmodium. These targets various stages in the life cycle of the parasite hence developing some immunity. Traditionally malaraia has been controlled by use of nets to repellents such as creams and mosquito coils have been used. Insecticides are sprayed in dwelling places and also use of treated mosquito nets. Drainage of stagnant water and clearance of vegetation around houses destroys the breeding and resting sites of mosquitoes hence reduction in their numbers. Tins, plastic containers and polythene papers that hold water should also be destroyed. The use of oil on stagnant water has been useful but it is being replaced by powdery treatment of water of water services. Biological control involves use of fish in pounds to feed on the mosquito larvae. A more recent method involves release of genetically sterilized male mosquitoes to mate hence reducing the number of mosquitoes. People travelling in malaria prone areas are advised to take antimalarial drugs for prevention. Treatment should be preceded by proper diagnosis and the full dosage administered for full care. Under dose often leads to development of resistance. The international Stockholm Convention of which Kenya is signatory restricts the use of DDT to public health where no alternatives are available. However Kenya the leading producer of pyrethrum strongly advocates for the use of natural pyrethroids in mosquito control. These have been proved effective and safer to environment because they are bio-degradable. Although a lot of resources have been channeled into malarial control, it has been difficult to eradicate disease. Several factors continue to frustrate theses efforts. Theses include; • The presence of large reservoir of the parasite in other hosts such as monkeys and birds. • The warm tropical conditions provide extremely suitable breeding conditions hence rapid multiplication of the vectors. • The development to resistance to insecticides used against mosquitoes. Similarly the plasmodium parasite quickly develops resistance against the drug used against it. • The individual countries face financial constraints. Furthermore regional conflicts frustrate co-ordinated program. Government and donor funds are often diverted to purchase weapons and other military ware. Parasitic Worms Askaris Lumbricoides Ascaris lumbricoides is a parasitic roundworm which belongs to the phylum Nemoda. Ascaris Lumbricoides is widespread in distribution and infects small intestines of pigs and human beings. It may also occur in other organs of the body. The genus Ascaris is the largest nematode parasitic to humans. It is characterized by brownish yellow colour with mouth parts having three lips. The male is about 25 cm long and 0.4 cm in diameter, while te female is about 35 cm long and 0.5 cm in diameter. Mode of Transmission The adult female lays eggs in the small intestine of the host. The eggs are passed out with the faeces and may be swallowed by a new host through contaminated water and food. Contaminated vegetables or fruits which are not washed well before being eaten are also the source of infection. There is also direct infection from faeces to mouth by hand s especially in children. When they are swallowed by a host, the eggs shells are dissolved, releasing the larvae. This penetrates the intestinal walls and enters the bloodstream. They move to liver and then to the heart and lungs. In the alveoli they grow and moult twice. The larvae then migrates up to the trachea where they cause irritation and so are coughed out and so may be swallowed down in to the aeosophogus, stomach and small intestines where they finally mature in adults. Effects of the parasite on the Host During the migration of the larvae they cause irritation in the trachea that lead to lung damage and infection with other diseases. If the is heavy, a lot of is digested food is consumed by the parasite in intestine and this leads o malnutrition in host, especially n children. During their cycle in human host, the parasite feed on blood and therefore can cause anaemia on host. Very heavy infection can also lead to intestinal blockage where victims develop large round stomachs. The worms may also enter the bile duct, pancreatic duct and appendix, causing further complications. Adaptative characteristics of Ascaris lumbricoides to its parasitic mode of life 1. Ascaris lumbricoides has two hosts, human beings and pigs. This ensures that it always has a ready host for survival. 2. It lays many eggs to increase the chance of survival even when some are destroyed. 3. The eggs have protective shell to survive harsh environmental conditions. 4. Ascaris lumbricoides have a thick elastic cuticle which protects it against the digestive enzymes of the host enabling it to survive in the alimentary canal. 5. It has tissues tolerant to low oxygen concentration characteristic of the gut. 6. It has a muscular pharynx through which it sucks digested food from host intestine into its own gut. Prevention and treatment Proper sanitary disposal methods are required especially the availability and proper use of toilet facilities. High standards of personal hygiene should be observed such as washing hands after a visit to the toilet. Hygienic handling and cleaning of fruits and vegetables is necessary. Drinking water should be boiled. Treatment involves use of drugs to kill the worms or inactivate the eggs. Schistomomiasis (Bilharzia) This is a parasite disease of the blood. It is caused by a flatworm of the phylum platyhelminthes of the genus Schistosoma. There are three different species odf the schistosoma that infet human beings. These include Schitosoma mansoni, Schistoma haematobium and Schistosoma japonicum. The parasite is found in fresh water canals, lakes, dams, rice-growing fields and other similar habitats. Modes of transmission The parasite is spread when people drinking water contaminated by larval form called cercariae. Also the parasite can penetrate the skin when bathing or wading through water conatini the larvae. Once in the body they get into the bloodstreams and migrate to the liver where they mature into adults. After coupling of the adult worms, eggs are shed into the blood vessels or alimentary tract. When the faeces or urine containing eggs are disposed of into water, the eggs hatch into larvae called miracidia. The miracidia find and penetrate the water snails such as Biomphalaria and Bulinus. It is from the snails that infective stages cercariae emerge and can now infect human beings who stand, bath or drink in such water. Effects of Parasite on its Hosts The parasite damages the host skin when penetrating and this causes itching. Once in the blood the adult schistosoma releases chemical substances that cause fever. The adult worms have spines which they use to tear through the veins and enter into the intestines or urinary bladder. This causes blood to appear in urine or stool. This can eventually lead to anaemia. The person also experiences abdominal pains and diarrhea. If untreated, the disease can result in death due to exhaustion or by infection from other diseases due to reduced body immunity. Adaptative Characteristic of Schistosoma The parasite has suckers for attachment so that they are not dislodged. The parasite has two hosts, that is the secondary host, the snail and the primary host, the human being. This increases its chances of transfer to several hosts and from one place to another. The cercariae larvae and eggs of the parasite have glands that secrete lytic enzymes which soften tissue to allow for penetration into the hosts. Some larval forms e.g miracidia, are encysted and can remain dormant and viable until they come into contact with a human being. The parasite reproduces through larval forms e.g cercariae, and redia in snails. This makes it very difficult to eradicate the parasite and also increases its chances of transmission and survival. The adult worm in blood produces chemical substances which protect it against the hosts defence mechanism. The worms are of separate sexes. The male form a gynecophoric canal in which it carries the female. This ensures that the e

CONCEPTS OF ECOLOGY

Example_of_Biologically_Mediated_Habitats.jpgBiosphere/ecosphere is the part of the earth and atmosphere inhabited by living organisms.

The habitat is a specific locality with a particular set of conditions where organisms live. Habitats are categorized into Terrestrial (Land) and aquatic(Water).

An ecological niche is the position that animal occupies in a habitat. It includes physical space where the organism is found and its role in that habitat in terms of feeding relationships and other interactions with other species.

Population refers to all members of a given species in a particular habitat, at a particular time.

Community refers to all organisms belonging to different species that interact in the same habitat. A community therefore is made up of populations.

An ecosystem is a natural unit composed of abiotic and biotic factors whose interactions leads to self-sustaining system e.g a small bond or a large ecosystem such as tropical forest.

Biomass is the total dry weight of living organisms at a particular tropic level or per unit area e.g total weight of maize crop per hectare.

Carrying Capacity is the maximum number of organisms an area can comfortably support without depletion of the available resources.

FACTORS OF ECOSYSTEM

Abiotic factors

Light

green-leaves-and-sun.jpgThe sun is the main source of energy to all life on earth. Green plants and photosynthetic bacteria need light to manufacture their food. Animals depend on plants for food.

Light affects living things in terms of intensity, quality and duration. Light intensity and quality affects photosynthesis, flowering and germination of plants while in animals affects migration, hibernation and reproduction.
A photographic light meter is used to measure light intensity while the seechi disc measures light penetration in water.

90_09_7_web.jpgTemperature

Biochemical processes of most organisms function effectively within a narrow range of temperature. Temperature varies due to seasons, altitude, latitude and also diurnally especially in hot deserts.

This therefore affects the distribution of organisms in a habitat. Temperature variations influence the distribution of organisms more in terrestrial habitats than aquatic habitats. Living organisms must develop necessary physiological and behavioral adaptations to cope with extremes of temperatures.

Atmospheric Pressure

The atmosphere has a definite weight and so it exerts pressure on the earth. On the surface of the earth, atmospheric pressure varies with altitude. Variations I atmospheric pressure affects the amount of Oxygen available for respiration and of carbon (IV) oxide for photosynthesis. Thes two gases affect the distribution of organisms.

Humidity

It refers to the amount of water vapour in the atmosphere. When humidity is high there is much water vapour and vice versa.

Humidity affects the rate at which water evaporates from the surface of organisms such as in transpiration or sweating. This in turn affects their distribution on earth. Paper Hydrometer is used to measure or a wet and dry bulb hydrometer

Wind

Wind is moving air. It increases the rate of water loss from the organisms, therefore affecting their distribution.

  • Wind is also important in formation of rain. In deserts winds form sand dunes which can be habitats for other organisms.
  • Wind causes wave formation in lakes and ocean, which enhance aeration of water in this water bodies.
  • Trees in areas experiencing a strong winds may have stunted growth and distorted growth.
  • Wind also disperses spores and seeds hence influence disposal and migration of flying animals
  • Wind wafts scent hence determines the positioning of hinting animals with respect to their prey in a habitat.
  • A wind vane or windsock is used to determine the direction of prevailing wind.
  • Anemoter is used to measure the speed of wind.

Salinity

It refers to the salt concentration of water, causing a division of the aquatic environment into marine, estuarine and fresh water.

Saline conditions immediately outside the body of organism pose the problem of water loss from the body to the environment. Only animals with suitable osmoregulation adaptations can occupy such habitats.

Salinity can be determined by calculating percentage of of salts on water or by the acid-base titration method.

pH ( Hudrogen ion Concerntration)

pH is is the measure of how acidic or alkaline water is in aquatic animals or soil solution. It influences the distribution of plants and animals in soil and fresh water ponds. Some plants drive well in acidic conditions while others in alkaline conditions.

The pH of a soil can be altered by leaching fertilizers’ applied or soil exhaustion. pH is expressed in terms of Ph scale by use of BDH universal indicator solution or paper and pH meter.

Abiotic factors





Roskapostituksen esto
Valitse mikä tahansa numero, joka on suurempi kuin 2. Syötä sama valitsemasi numero molempiin seuraaviin kenttiin.

Ecology

Ecology is the study of the inter-relationship of organisms to each other and to their environment.

The environment constitute the surroundings of an organisms both living and non living (abiotic or physical).

Autecology is the study of individual species within a community. It involves studying the relationship with both biotic and abiotic components of the ecosystem, its cycle and adaptation for survival.

Synecology is the study of different species of organisms interacting among themselves within an ecosystem.

Importance of Studying Ecology

  • Sustainable food production
  • Conservation of natural resources
  • pollution control
  • Control of disease and pests
  • Prediction of adverse weather patterns.
  • Population control
  • Ecotourism

CONCEPTS OF ECOLOGY

Biosphere/ecosphere is the part of the earth and atmosphere inhabited by living organisms.

The habitat is a specific locality with a particular set of conditions where organisms live. Habitats are categorized into Terrestrial (Land) and aquatic(Water).

An ecological niche is the position that animal occupies in a habitat. It includes physical space where the organism is found and its role in that habitat in terms of feeding relationships and other interactions with other species.

Population refers to all members of a given species in a particular habitat, at a particular time.

Community refers to all organisms belonging to different species that interact in the same habitat. A community therefore is made up of populations.

An ecosystem is a natural unit composed of abiotic and biotic factors whose interactions leads to self-sustaining system e.g a small bond or a large ecosystem such as tropical forest.

Biomass is the total dry weight of living organisms at a particular tropic level or per unit area e.g total weight of maize crop per hectare.

Carrying Capacity is the maximum number of organisms an area can comfortably support without depletion of the available resources.

FACTORS OF ECOSYSTEM

Abiotic factors

Light

The sun is the main source of energy to all life on earth. Green plants and photosynthetic bacteria need light to manufacture their food. Animals depend on plants for food.

Light affects living things in terms of intensity, quality and duration. Light intensity and quality affects photosynthesis, flowering and germination of plants while in animals affects migration, hibernation and reproduction.
A photographic light meter is used to measure light intensity while the seechi disc measures light penetration in water.

Temperature

Biochemical processes of most organisms function effectively within a narrow range of temperature. Temperature varies due to seasons, altitude, latitude and also diurnally especially in hot deserts.

This therefore affects the distribution of organisms in a habitat. Temperature variations influence the distribution of organisms more in terrestrial habitats than aquatic habitats. Living organisms must develop necessary physiological and behavioral adaptations to cope with extremes of temperatures.

Atmospheric Pressure

The atmosphere has a definite weight and so it exerts pressure on the earth. On the surface of the earth, atmospheric pressure varies with altitude. Variations I atmospheric pressure affects the amount of Oxygen available for respiration and of carbon (IV) oxide for photosynthesis. Thes two gases affect the distribution of organisms.

Humidity

It refers to the amount of water vapour in the atmosphere. When humidity is high there is much water vapour and vice versa.

Humidity affects the rate at which water evaporates from the surface of organisms such as in transpiration or sweating. This in turn affects their distribution on earth. Paper Hydrometer is used to measure or a wet and dry bulb hydrometer

Wind

Wind is moving air. It increases the rate of water loss from the organisms, therefore affecting their distribution.

  • Wind is also important in formation of rain. In deserts winds form sand dunes which can be habitats for other organisms.
  • Wind causes wave formation in lakes and ocean, which enhance aeration of water in this water bodies.
  • Trees in areas experiencing a strong winds may have stunted growth and distorted growth.
  • Wind also disperses spores and seeds hence influence disposal and migration of flying animals
  • Wind wafts scent hence determines the positioning of hinting animals with respect to their prey in a habitat.
  • A wind vane or windsock is used to determine the direction of prevailing wind.
  • Anemoter is used to measure the speed of wind.

Salinity

It refers to the salt concentration of water, causing a division of the aquatic environment into marine, estuarine and fresh water.

Saline conditions immediately outside the body of organism pose the problem of water loss from the body to the environment. Only animals with suitable osmoregulation adaptations can occupy such habitats.

Salinity can be determined by calculating percentage of of salts on water or by the acid-base titration method.

pH ( Hudrogen ion Concerntration)

pH is is the measure of how acidic or alkaline water is in aquatic animals or soil solution. It influences the distribution of plants and animals in soil and fresh water ponds. Some plants drive well in acidic conditions while others in alkaline conditions.

The pH of a soil can be altered by leaching fertilizers’ applied or soil exhaustion. pH is expressed in terms of Ph scale by use of BDH universal indicator solution or paper and pH meter.

Biotic inter-relationships

Competition

It two different species require a common resource whose availability is limited, they are said to be in competition for it. This resources includes nutrients, space, light or mates.

Intraspecific is competition between individuals of the same species while interspecific is the competiton of different species. In such competition organisms with structural and behavioural adaptations survive while others without such adaptations die out or migrate.

Closely related species can live together without competition e.g Browsers and grazers living in the same habitat i.e the Zebra eats the softer shoots, followed by wilder beast and later on, the gazelle which the more fibrous remnants of the same grass.

Predation

This is the food relationship in which one organism kill another for food and feeds on it either wholly or in part. The organism that feed on another for food is called predator while one killed is called prey.

Predators have sharp eyes, fastflight, modified beaks and talons, strong jaws, carnassials teeths, large claws streamlined bodies among others.

Parasitism

It is the relationship in which an organism obtains nutrients from other living organism without killing it. This organism that live on or in another living organism is called parasite while the one which nutrients are obtained is called Host.

A parasite benefits in terms of food and shelter from the host while causing the hostsome harmful effect. Parasites found outside the body of the parasites are called ectoparasites e.g ticks, while those found inside the body of the hosts are called endoparasites e.g plasmodium.

Parasites weaken their host, cause or transmit disease which may kill their hostthus reducing their numbers and distribution.

Symbiosis

This is the association between organisms of different species in whoich both organisms benefit e.g Rhizobium bacteria which live in the root nodules in the leguminous plants. The plants benefits from the nitrates fixed by Rhizobium bacteria whike the bacteria benefit from shelter and carbohydrates provided by plants. This relationship enables such plants to thrive on nitrogen deficient soils.

Saprophytism

This is type of nutrition where organisms obtain nutrients from dead organic matter hence causing decomposition. Organisms which feed on this matter are known as saprophytes and include fungi and bacteria. Decomposition releases nutrients into the ecosystem which are then made available to other living organisms.

Nitrogen Cycle

It refers to the cycling of nitrogen and its compounds in nature. Nitrogen is essential in the manufacture of proteins by organisms. However, organisms cannot utilize the free nitrogen in the atmosphere. Instead, plants absorp nitrogen in form of nitrates and assimilate it into plant proteins. Animals then obtain the nitrogen in form of proteins either by eating plants or other animals.

It is therefore necessary that the free atmospheric nitrogen is converted into a form that can be utilised by through the process called nitrogen fixation. Biological nitrogen fixation is done by nitrogen-fixingmicro-organisms. These include symbiotic bacteria such as rhizobium of the root nodules of legumes. They convert nitrogen gas into ammoia which is then utilsed by plants to make proteins. Biological fixation is also done by frre-living bacteria e.g Azotobacter and Clostridium and some algae e.g anabaena, Chlorella and Nostoc. These organism fix nitrogen into ammonia which is then converted to nitrates.

Non-biological nitrogen fixation is achieved through lightening. During thunderstorms, the lighting energy combines atmospheric nitrogen with Oxygen to form nitrous acid and nitric acid. These are then chemically converted to nitrates.

Plants absorb nitrates from the soil and convert them into plant proteins. Thus animals obtain the nitrogen in form of proteins directly or indirectly from plants. These are digested into amino acids and assimilated into animal proteins.

When organisms die (or waste and droppings), saprophytic bacteria and fungi breakdown their protein material in their bodies into ammonia. In the process of nitrification, ammonia is eventually converted into nitrates. This is done by nitrifying bacteria e.g Nitrosomonous and Nitrococcus which oxidizes ammonia into nitrites and Nitrobacter bacteria which convert nitrites into nitrates. The process if nitrification enriches the soil with nitrates.

Some micro organisms reduce nitrates to nitrites, ammonia to and even nitrogen gases which are not useful to plants, the process called denitrification. Examples of such bacteria are pseudonomous denifrications & thiobacillus denitrifications. They utilize the oxygen released in the process of respiaration and this process denies the soil of fixed nitrogen gas.

ENERGY FLOW IN AN ECOSYSTEM

The sun is the natural source of energy. It is this energy that is trapped by green plants for photosynthesis. This process produces food which is potential energy in chemical form e.g glucose. Therefore, green plants are called producers in an ecosystem.

Green plants are eaten by animals e.g herbivores which the primary Consumers. They in turn are eaten by carnivores, usually referred to as secondary consumers e.g dogs. The secondary consumer is eaten by tertiary Consumer e.g leopard.

When the leopard ides its eaten by a vulture which is referred to as quaternary consumers. These feeding levels, that is producers and consumer levels are referred to as trophic levels. When living organisms die, they are decomposed by bacteria and fungi which are referred to as decomposers. The energy moves from one trophic level to the next i.e producers to the consumers.

Decomposers

Dead bodies of organisms and waste material from their body form a source of energy and nutrients for many other organisms known as decomposers. Most decomposers are bacteria and fungi.

The decomposers breakdown organic materials into simple substances which are made available for re-use by other organisms thus the materials are recycled in the ecosystem. The rate at which decomposers work on substrate differs depending on climate and type of substrate.


Food Chains

Food chain is the linearly representation of the flow of energy from producer to other organisms. It is composed producers, consumers and decomposers. e.g
Producer ----> Primary cionsumer----->secondary consumer---à Decomposers.

Specifics examples rae as follows:

  • Grass ---> Grashopper-->Bird
  • Napier grass---> Goat--->human
  • Kikuyu Grass-->mouse-->snake-->Hawk
  • Algae-->Mosquito larvae-->tilapia-->Nile perch-->Human

When the decomposers are included in the food chain they are ussualy placed at te end as shown below

Litter-->Earthwort-->Frog-->Snake-->Bacteria and Fungihttp://www.squizzes.com/wp-content/uploads/2012/06/complete-circle-foodchain.jpg


Food Webs

In a community where populations live and interact, simple food chains rarely exist. Most associations concerned with energy flow are made of several interconnecting food chains forming food webs.

An example of food web: the African savannah grass Cymbopogon afronardus is eaten by termites which are in turn eaten by chicken. The chicken are the consumed by human beings. This so far, constitutes a simple food chain. The relationship between this grass and other organisms, however, is not as simple. The same grass is also eaten by grasshopper and sheep. At various stages other consumers are involved forming a food web.

Ecological Pyramids

The efficiency of transfer from one trophic level to another can be summarized diagrammatically in form of pyramids. These pyramids give pictorial representation of feeding relationships and energy flow in an ecosystem. They are useful on comparing different ecosystems, showing seasonal variations in an ecosystem or change in components of an ecosystem. T

There are three types of pyramids;

  • Pyramid of numbers

In a natural ecosystem there is progressive decrease in the numbers of organisms constituting any trophic or feeding level in a food chain. The greatest in number are the producers followed in decreasing order by primary consumers, secondary consumers, tertiary consumers and atleasts of all quaternary consumers.

When this numbers are drawn to scale the above food relationships produce a pyramid-shaped histograph or pictograph called Pyramid of numbers.
Construction of Pyramid of Numbers

  1. Use data collected or provided
  2. From the data identify and draw the most suitable food chain.
  3. Indicate the numbers at each trophic level in the food chain.
  4. Choose a suitable scale of data.
  5. Using the choosen scale draw a horizontal rectangular bar to represent the number of producers as the base of the pyramid.
  6. Progressively draw the horizontal bars of the other trophic levels in their ascending order.

NB; ensure that the width of the bars is uniform.

  • Interpretation of Pyramid of Numbers

As a general principle, the body size of the organisms increases at each trophic level from the base to the apex of the pyramid as their number increases. At each trophic level much of the energy is lots in respiration and thus fewer organisms can be supported at the succeeding level.

However, ther ar cases in which the number of organisms will not decrease at each succeeding level. E.g many caterpillars feeding on one cabbage.

  • Pyramid of Biomass

The biomass of organism is its constant dry weight. When the biomas measurements area carried out in a given ecosystem of known dimension and components, the statistical representation also produces pyramid shaped histogram. The producers have the highest biomas per unit area and in decreasing order are followed by the primary consumers, secondary consumers, tertiary consumers and quaternary consumers.


POPULATION

A population is a group of organism belonging to the same species in a particular habitat.

The following are some characteristic of population;

  • Density refers to the number of individuals per unit area.
  • Dispersion is the spread or distribution of organism in the habitat.
  • Population growth refers to the rate of increase in numbers.

Population growth rate is influenced by such as food availability, space, diseases, pests and predators.

Populations Estimation Methods

In natural populations, the density of organisms in a habitat can be by body counts. Sometimes a sample is used to determine plant population.

A sample is a small number of individuals taken form habitat that is representative of the whole population. Samples are used where the area to be studied is too big to enable all living organisms there into be studied.

Sampling can be carried out using the following methods;

  • Quadrat Method

A quadrat is a square frame of known area made of wood or metal. The standard quadrat is one square metre, but small quadrats can be used if only small area is being studied.

The qudrat method is suitable for small plants like grass, herbs and small slow moving animals.

  • Line transect

A line transect may be used to find out the distribution of species of plants in an area. A line transect is taken by running a robe across the plot and markingoff equidistant points. Counts are made at each points(stations). Only tjose plants along the line are identified, counted and recorded. Ussulaly a large number of transects are required to obtain mier accurate results.

A line transect is particularly useful in studying transition in habitats and population through area.

  • Belt transect

A belt transect is taken by running two ropes parallel to each other and about one metre apart along the length of the plot. Counts are made between the ropes at marked points. Fewer belt transects are requird t built up a realistic picture of the distribution and abundance of plant species in an ecosystem compared to the line transect. Qudrats may be used together with the belt transect

Belt transect are suitable in estimation of plant populations. This can be equally used to estimate the populations of animals.

  • Capture-recapture method

It is possible to estimate the total number of individukas in a populations by repeated sampling. After selecting the study area determine its size and choose the organism to be studied. Select an appropriate technique for organism capture.

Catch the organism, count mark and release the back to the habitat. Catch and mark as many organisms under study, recording the first number marked and released (FM).

After twenty four hours, re-examine the experimental area and collect as many as possible organism including those that show paint marks. Record their number of organisms collected, Second Capture (SC) and the number of those that were marked with paint i.e Marked Recaptured (MR). then, if P represents total population

FM/P=MR/SC OR P=MM * SC/MR

Assumptions

  • No organism moves in or oat of the area between two counts.
  • The released animals mix freely with the remaining population.
  • The mark does not alter the animals behavior.
  • Thee marked animals will have enough time to mix with the rest.
  • The population number does not vary during the study period.

This method is suitable for highly mobile animals like insects, birds, small mammals and fish.


ADAPTATIONS OF PLANTS TO VARIOUS HABITATS

Adaptations is a change in an organisms that increases its chance of survival in a specific environment. These changes maybe behavioral, structural or physiological. Plants posses different adaptations based on their habitats classifield as follows;

  • Xerophytes
  • Mesophytes
  • Hydrophytes
  • Halophytes

Xerophytes

They are plants adapted to withstand a dry habitat, or to endure conditions of prolonged drought as in arid and semi arid areas.
They are characterized by the following conditions
i. Unpredicted and poorly distributed rainfall which is usually less than 250 mm but hardly exceeds 350mm per year.
ii. Very high day temperatures but very low night temperatures which result in high diurnal temperature ranges.
iii. They are windy.
iv. Low humidity Adaptations of Xerophytes to their Habitats
i. Leaves are reduced in size such as the scale like leaves of whistling pine or modified to spines as cactus. This reduces the surface area over which transpiration occurs.
ii. Shedding of leaves during drought to reduce surface exposed to transpiration.
iii. Leaves have thick waxy cuticle to minimize the rate of cuticular transpiration.
iv. Some leaves are folded to reduce the rate of transpiration by not exposing stomata to environmental factors.
v. Some have sunken stomata which accumulate moisture in sub stomatal air spaces leading to low diffusion gradient thus reducing transpiration rate
vi. Most xerophytes show reduced number of stomata that lowers the rate of transpiration.
vii. Some xerophytes experience reversed stomatal rhythm.
viii. Some plants have deep roots to absorb water from deep in the soil.
ix. Some plants store water in large parenchyma cells contained in succulent stems and leaves.
x. Some xerophytes have a short life cycle to evade drought, hence some survive as seeds or as underground penetrating organs e.g corns and bulbs.
Mesophytes
A plant living under normal conditions of water supply or in well-watered soil is described as Mesophyte. They are predominantly found in ecosystems such as savannah, rain forests and reserve forest.
They have the following genera conditions:
a) Adequate rainfall ranging from 950-1800mm that’s distributed throughout the yaer.
b) Humidity is relatively high.
c) Thick clouds are common.
d) Moderate to high temperatures, with diurnal effect.
e) Less windy
f) Shallow water table.
Adaptations of Mesophytes to their Habitats
Depending on their habitats some have features to reduce water loss while others have to increase water loss. They include;
a) They grow tall in dense population in order to compete for light among various plants.
b) They have mosaic leaves to reduce overlapping and overshadowing of leaves so that leaves are exposed to light for photosynthesis.
c) Some have broad leaves to with thin cuticle and many stomata on both leave surface to encourage high rate of transpiration.
d) Some mesophytes have shallow rooted and thus develop buttress roots or prop roots for extra support e.g Ficus natalansis while others in drier areas are deep rooted in order to absorb enough water.
e) Some have waxy and glossy surfaces to reflect the strong light rays and drip off rain water.

Hydrophytes
Plant which normally wholly or partly in fresh water. Their habitats are characterized by the following conditions;
i. They have low concentration of dissolved gases such as Oxygen and the water medium is of low density.
ii. Waves and currents are usually common.
iii. Light is less abundant under water.
Adaptations of Hydrophytes to their Habitats
a) Most emergent and floating types have broad leaves with maximum number of stomata on the upper surface. This provides a large surface area for gaseous exchange and allows quick loss of excess water. b) Some submerged hydrophytes have leaves which are deeply dissected into threadlike straws in order to provide maximum light for photosynthesis. Their leaves have numerous and sensitive chloroplasts that photosynthesize under low light intensities.
c) Hydrophytes have large air-filled tissues (aerenchyma). The air in the aerenchyma reduces the density giving the buoyancy to the plant and also assists in gaseous exchange.
d) They have poorly developed roots that lack root hairs to reduce absorption of water.
e) Flowers raised above the water to allow for pollination.

Halophytes
These are plants which are able to tolerate very salty conditions in soil and marine water.
These habitats are characterized by the following conditions;
i. They have very high concentration of mineral salts.
ii. They have low concentration of dissolved gases especially in marine water.
iii. Light intensity is low in marine water.
iv. Currents and waves are common in seas.
Note: temperature in marine environment is generally stable.

Adaptations of Halophytes to their habitats
a) They have root cells which concentrate a lot of salts in them and this enables them to take in water by osmosis in the normal way.
b) Some plants have salt glands that secrete excess salts.
c) Many of them have water storage tissues.
d) Some plants like mangrove have Pneumatophores (breathing roots) which emerge above water to obtain atmospheric oxygen for respiration.
e) Mangroves growing on mid flats have buttress roots for support and anchorage.
f) Their fruits have got large aerenchymatous tissue for air storage that makes them buoyant.


EFFECTS OF POLLUTION ON HUMAN BEINGS AND OTHER ORGANISMS
Living organisms depend on non-living environment for their oxygen, Carbon (IV) Oxide, water and minerals. They also depend on each other and cannot live in complete isolation. Organisms have formed different kind of communities, which interact with the physical environment of the ecosystem. Each animal and plant influences its own ecosystem. An organism in the community may become numerous, or a pest may invade the area and upset the balance of ecosystem which is usually restored naturally. Human beings influence almost all ecological systems on earth. They have an advantage over other organisms since they can exchange the ecosystem for their own use. To satisfy their physical and biological needs, human beings depend on what their environment can offer. They grow their crop but also depend on their resources like water, air, other plant and animals, which all form part of the environment. The natural resources are limited, for example, it is difficult to increase the amount of land. While interacting with the environment, human beings often misuse the natural resources. Some of the activities include deforestation, soil erosion, overgrazing and pollution. The human being has also misused plants and animals exterminating many of them. If human beings are to continue to survive, they must understand the environment and use natural resources in it in a responsible way, not only for themselves but also for future generations. It is such realizations that have dawned on many nations, which have formed International Committees to regulate various environmental issues that include the UNEP.


Pollution
Pollution is the release of substances or forms of energy into the environment by human activities in such quantities whose effects are either harmful or unpleasant to human or any other living organisms.
There are three main categories of pollution namely Water, air and Soil pollution.

Air Pollution

Causes of Air Pollution
a) Sulphur based chemicals e.g sulphur (IV) oxde (SO2) and Hydrogen Sulphde (H2S)They are produced by food preserving industries, manufacture of sulphuric acid and burning based petroleum fuels. Hydrogen sulphide is produced form mineral extractions mines and also from geothermal power stations like Olkaria in Kenya. Volcanic activities also release hydrogen sulphide, carbon (IV) oxide and carbon (II) oxide into the atmosphere. Effects i. It leads to bronchitis, pneumonia and heart failure ii. It slows down the ciliary activities in the respiratory tract hence solid particles reach the alveoli where they caue irritation and interfere with gaseous exchange. iii. Sulphur (IV) oxide dissolves in rain water and falls as acid rain which tends to lower the pH leading to a fall in crop production. iv. It also corrodes metals such as iron and aluminum in buildings and monuments. v. It contaminates blood and suffocates victims when inhaled. vi. Acid rain causes leaching of magnesium and calcium ions from soils. b) Oxides of Nitrogen e.g Nitrogen (II) oxide (NO) and nitrogen (IV) oxide No2 These are produced from burning of petroleum fuels and emissions of exhaust fumes in motor vehicles. They are also released during industrial manufacture of nitric acid Effects i. They are poisonous to animals to animals affecting respiratory systems when inhaled. ii. Nitrogen (IV) oxide is carcinogenic. iii. They diminish visibility of roads. c) Smoke and Fumes These contain carbon (II) oxide (CO), carbon (IV) Oxide and carbon particles. These are produced from industries which burn coal and petroleum fuels and also from motor vehicle exhaust. They are also produced from burning of natural gases and charcoal Effects i. Smoke and fumes affect the visibility due to smog on roads. ii. When they settle on stomata they block stomata hence hinder photosynthesis. iii. They cause green house effect. iv. Leads to global warming d) Dust It is composed of small particles emitted from cement and lime producing industries such as cement works, and also from quarries, road constructions and dusty dry weather roads. Environmental concerns have led many cement manufacturing industries t adopt ‘wet method’ of cement manufacture which doesn’t result into the release of dust in the environment. Effects i. Dust settles in leaves thus limiting photosynthesis ii. It clogs respiratory surfaces of organisms resulting in breathing in difficulties and respiratory diseases iii. It reduces visibility and irritates the yes. e) Lead (Pb) This is mainly from the combustion of leaded petrol by motor vehicles. Lead is normally added to petrol to serve as anti-knock compound in vehicle engines so as to improve the efficiency of the engine combustion. Increased environmental awareness has led to phasing out of the use of anti-knock addictive Effects i. When inhaled, it is absorbed into blood stream and accumulates into the liver, kidneys and bones of animals affecting psychological functioning of these organs. ii. It is also thought to interfere with mental development of children. iii. In plants, it leads to blocking of stomatal pores making it difficult for the plant to carry out gaseous exchange and hence no photosynthesis. f) Aerosols An aerosol is a substance that consists of very fine particles of liquid or solid suspended in gas. These include pesticides, insecticides, fungicides, perfumes, air fresheners and spray paints. The main pollutants in these aerosols are Copper, led and chlorofluorocarbon (CFC) compounds. Effects i. When inhaled they cause irritation in respiratory organs of animals. ii. Copper also causes poisoning of water plants and fish. iii. Copper based chemicals are non-biodegradable hence tend to accumulate I the ecosystem. iv. CFC causes depletion of the ozone layer leading to increased penetration of Ultra violet rays that causes skin cancer and affects crops. g) Noise Noise is the presence of undesirable sound in the atmosphere. It is produced by machines in factories, heavy vehicles, aeroplanes, music players, loud speakers and ‘jua kali’ workshops Effects i. Affects hearing in animals. ii. It is irritant and causes stress in animals Control of Air pollution i. Legislation- the government needs to enforce the relevant legislative acts on environmental pollution. ii. Encourage the use of lead free fuels in motor vehicles. iii. Develop and encourage the use of renewable sources of energy e.g solar and wind energy. iv. Use CFC free aerosols and appliances. v. Use biological control methods to control pests, diseases and weeds. This reduces reliance on non-biodegradable chemicals. vi. Encourage the use of public means of transport as much as possible to minimize consumption of fossil fuel and emission of gas pollutants. vii. Smoking in public should be banned. viii. Ear muffs should be used in factories and ‘jua kali’ workshops that generate loud noises. ix. The masses should be educated on the need for sustainable environmental management. x. The government should be a signatory to global treaties on environmental conservations. Water Pollution It involves addition of substances or energy forms into water bodies in quantities thata re harmful to the living organism dependant on that water. Sources of water pollution a) Domestic effluents Untreated sewage from urban centres gets discharged into rivers used for water supplies for domestic purposes. This sewage contains disease causing micro-organisms such as bacteria, viruses and protozoa. It is also full of faecal material and urine which encourage bacterial growth. Kitchen waste also contains detergents that have a lot of phosphates. Effects Water pollution may also cause epidemics of waterborne diseases e.g cholera, typhoid and amoebic dysentery. The faecal material is broken down by saprophytic bacteria and fungi which lead to depletion of dissolved oxygen in water. This in turn affects the aquatic animals such as fish and aquatic plants. The breakdown of theses organic matter releases such as nitrates, phosphates and sulphates which enrich the water body resulting in eutrophication as happened with excessive growth of water hyacinth in lakes. b) Industrial Effluents Industries discharge various effluents into rivers, fresh waters, dams, marshes, seas and oceans. The effluents contain toxic metallic compounds of mercury, arsenic and cadmium in addition to acids and there chemicals. Effects The poisonous compounds directly kill aquatic organisms such as fish. Death can also be caused indirectly through eutrophication. These compounds also enter the food chain or accumulate to lethal levels in organisms higher up the trophic level. c) Heat Industries discharge hot water directly into water bodies. This may be from the cooling process or for discharging industrial effluents. Some of the effluents may react among themselves releasing heat into the water. Effects Heat reduces the amount of dissolved gases in water e.g oxygen and carbon (IV) oxide. Thus organisms may die from oxygen deficiency or lack of photosynthesis. Heat releases respiratory rate to abnormal levels causing malfunctioning in the organisms. The hot water may then kill the living organisms directly due to high temperatures. d) Oil spillage Oil is an important pollutant. Oil spillages occur in oceans from oil tanker accidents, offshore oil wells and refineries and also from damaged warships. Effects Oil layer on water reduces oxygen supply to the water and this may lead to death of aquatic life forms. Marine organisms such as fish are killed by clogging of their respiratory surfaces. Marine birds gets their feathers clogged hence the difficult in flight. Oils coats photosynthetic phytoplantktons till they die. There is reduced light penetration into the water hence photosynthesis of a submerged plant is hindered. e) Agro-chemicals Agricultural chemicals include inorganic fertilizers, herbicides and pesticides. The inorganic fertilizers contain phosphates and nitrates. Pesticides may contain heavy metals such as mercury and copper. Other pesticides such as DDT contain chloroflourocarbons which are not easily broken down biologically. These chemicals and fertilizers percolate through soil and after underground seepage they join streams and rivers and eventually into lakes and oceans. Effects Since most of chemicals contain the heavy metals such as copper and mercury, they affect the respiratory activities of aquatic organisms. These chemicals find their way into the organism bodies in small amounts. However they accumulate over a long time and reach toxic levels leading to death. Furthermore they accumulate along food chain becoming lethal at higher trophic levels. Nitrates and phosphates in fertilizers cause eutrophication. f) Lead This is water pollutant mainly from pipes and tanks in domestic water supply systems. Through run-off it finds its way into water bodies like rivers, lakes and oceans. The effects of lead whether inhale or ingested are similar as discussed under air pollution g) Mercury Mercury as a pollutant is released by industries that manufacture chlorine, sodium hydroxide, ores and vinyl plastics. It is also released during combustion of coal and petroleum oils. Fungicides and some cosmetics also contain mercury. The mud in some rivers contains mercury which is converted to methyl mercury by methane producing bacteria. Effects Methyl mercury is volatile and very toxic. It is absorbed by aquatic organisms or through leaves and roots of plants hence entering the food web involving human beings. Mercury poisoning in people results in accumulation of mercury in liver, kidneys and brain affecting the physiological functioning and eventually causes death. Animals eating plants with mercury are poisoned and killed as observed in wood-pigeons. Mercury also interferes with the process of melanin formation leading to skin lightening, blindness paralysis and even death. h) Soil Erosion Through soil erosion, silt is transported into water bodies. Effects This makes water unclean and unfit for human consumption. The silt particularly reduces light penetration hence hindering photosynthesis activity. It also clogs the respiratory surfaces of aquatic organisms. E.g gills in fish and stomata in plants. This interferes with gaseous exchange. Control of Water Pollution a) Legislation b) Industries should control or treat the industrial effluents before discharge into the water bodies. c) Proper treatment and disposal of sewage. Here should be separate systems for disposal of sewage and drinking water. Latrine should be connected properly used in addition to proper personal hygiene to control disease causing agents. d) Encourage the use of unleaded petrol. e) The public should be educated on correct amount of inorganic fertilisers and pesticides to be used. f) Appropriate soil erosion control methods to be put in place such as building of gabions, terraces, mulching and growing of soil cover crops. Soil Pollution Sources of soil pollution Either intentionally or accidentally human beings discharge chemicals into the soil which accumulate to levels that cause harm to soil organisms. a) Oxides of sulphur e.g sulphur (IV) oxide enter the soil through precipitation as acid rain. Acid rain alters the pH therefore affecting plants and animals that cannot tolerate acid soil. However, acid rain may promote the growth of plants that tolerate acidic conditions. Acid rain also causes leaching of minerals leading to loss of soil fertility. b) Aerosols Most aerosols sprayed to control pest and diseases in plants and animals contain heavy metals e.g copper and mercury. The chemicals fall on the soil and are taken up by plants where their concentration increases. As animals eat these plants, toxicity increases and leads to death of animals. These chemicals kill nitrogen fixing soil micro-organisms hence lowering the soil fertility with consequent reduction of plant growth. c) Petroleum Products Petroleum products spilled on land e.g oil tankers. Soils organisms fail to obtain oxygen in oil saturated soils therefore die. Coating of plant leaves or respiratory surfaces of animals also leads to their death. d) Inorganic fertilizers Agricultural inorganic fertlilisers contain phosphates and nitrates. Theses increase soil acidity so that soil micro organism cannot inhabit such soils. Formation of soil organic matter slows down and then stops. Soils become exhausted hence plant and animal life ceases. In addition soil structure ids changed hence encouraging soil erosion. e) Solid Waste Community, household wastes and industrial wastes. Some are biodegradable e.g food residues, old clothing and papers. Others are non-biodegradable e.g rubber, plastic containers, scrap metals and glass bottles. Soil waste is a nuisance and also may ne injurious e.g glass bottles. They destroy the aesthetic state of the environment. They offer breeding grounds for pests, rodents and insect vectors which in turn pose health hazards to human beings. The non-biodegradable solid wastes limit soil aeration thus inhibiting micro-organisms activity. Control of Soil Pollution All solid wastes should be sorted out according to manufacture instructions and specifications , then appropriate disposal methods applied. a) Recycle solid wastes e.g polythene paper and plastic containers, glass bottles, paer and scrap metal b) Household wastes that are biodegradable can be disposed in a compost pit to form compost manure for organic farming. c) Combustible solid wastes .g old clothes, sanitary towels, hair should be burned in incinerators. d) Discourage excessive use of agro-chemicals. e) Biological control of pests and disease to be encouraged. f) Encourage pipeline transportation of petrol and petroleum products to minise risk of spillage. g) Enforce appropriate legislation on proper solid waste management. Radioactive Emissions Nuclear emissions can also be the cause of soil, air and water pollution. Although nuclear energy is available in limitless quantity, its harnessing, management and risks of damage of life are very high. It is based on the destruction of the atom of matter to release energy that holds the constituents of the atom. The form in which this energy is released when atoms are broken down into generally called radiators. Such radiation has very great power and is very destructive if it leaks accidently. The industries in which this energy is produced are called radioactive or nuclear reactors. Some of the common substances broken down to release nuclear energy are uranium, radium, germanium, plutonium and hydrosonium (heavy water). Use of Nuclear Energy Nuclear energy is used in generation of electricity and propelling of nuclear war planes, nuclear propelled ocean vessels, spaceships and submarines. Effects of Radioactive Emissions a) Increased mutation rates with increased abnormalities some of which are inheritable. b) It causes cancer such as borne tumuors and leukaemia. c) Excess doses of radioactive emissions cause so much damage leading to death Control Due to potential dangers of nuclear waste disposal and energy management, the control is only by dialogue between nations with the nuclear technology. HUMAN DISEASES A disease is disorder state of tissue, organ, system or organism, during which its function are not carried on normally. In human beings, disease results from genetic disorders, nutritional deficiencies or infections by other organisms and viruses. Bacterial Diseases a) Cholera This is diseases by a bacterium known as Vibrio cholerae found in infected water and are passed o by flies to food thereby contaminating the food. People living in unhygienic places i.e where sanitation is poor and the domestic water supply is contaminated, can easily contract the disease. Once there is an outbreak of the disease, it spreads rapidly and can cause an epidemic. Symptoms The incubation periods varies between one to six days depending on the magnitude of the infection and the taste of the health of the individual. The bacteria reach the intestines and multiply rapidly. They secret an enzyme called Mucinase which digests the inner lining of the intestines. The exposed intestinal wall then becomes irritated and damaged by the causes violet diarrhoea and vomiting. This is accompanied by severe abdominal pains. The disease develops rapidly and leads to general body dehydration owing to the high frequency of defecation, accompanied by loss of large quantities of water. Death by cholera can be rapid within 24 hours of infection. Prevention and Treatment Sanitary disposal of faeces and refuse is needed to prevent the contamination of water and food. The pit latrine in rural areas should be deep. They should be kept clean to keep away flies. Personal hygiene should be maintained. Domestic water should be boiled and filtered, or chlorinated before use so as to kill bacteria and their spores. The infected persons are infectious and so should be isolated and treated as soon as possible. Treatment involves administering of antibiotics drugs in order o kill the bacteria. Oral rehydration salts should be administered before treatment. b) Typhoid This is also a disease caused by a bacterium called salmonella typhi. The bacteria are passed out either through urine or faeces. Poor disposal of urine and faeces may cause contamination of the water supply from rivers, dams and lakes. Healthy individuals can be infected by taking contaminated water or food. Symptoms Its incubation period last for about two weeks after which a fever and rush develop, followed by severe diarrhea. The bacteria attack the walls of the intestines and cause patches of scores. Patients are advised not to eat solid food as it might irritate the intestinal sores and cause bleeding. In severe attacks the sores may burst and cause perforation in the intestines. This may result in death if the patient is not treated early enough. The bacteria invade the lymph glands around the intestines and then pass into the blood stream. Patients do not develop immunity of this disease and therefore one can be attacked again and again. Prevention and Treatment There should be proper disposal of faeces and urine to prevent spread of the bacteria. Domestic water should be boiled or chlorinated before drinking to kill the bacteria. Hands and cutlery should be washed with clean water before being eaten. Food handlers should be clean, and should be subjected to regular medical check-ups. Healthy people may be vaccinated with attenuated (weakened) typhoid bacteria in order to provide immunity for at least two years. Treatment involves administering antibiotics. Protozoan Diseases a) Amoebic Dysentry Amoebic dysentery is a disease caused by protozoan called entomoelaba histolytica. When the amoeba cysts are ingested, the cysts membrane is digested and the protozoa is released. When they reach the large intestines and colon, the E. histolytica multiply. Symptoms Normally E. histolytcia live within the lumen of the colon and feed on bacteria without harming the host. At certain times, they invade the mucosal wall of the colon and produce a tissue-dissolving enzyme called histolysin. This result in formation of ulcers on the colon wall and the parasites then fed on the red blood cells at the site of the ulcers. This condition usually leads to diarrhea or amoebic dysentery and faeces contain blood. The disease is usually characterized by diarhhoea, dehydration, fever and abdominal pains and severe pain when passing stool. The infection may also become systemic(i.e invade the blood stream), and parasites may reach other tissues or organs of the body such as liver, lungs and brain where they produce abscesses which may be fatal. Prevention and Treatment Prevention of the infection aims at avoiding contamination of food or water with cysts. Control measures include boiling water for drinking, proper food storage and proper faecal disposal. For treatment a number of amoebicides can be used. b) Malaria Malaria is a disease caused by protozoan parasitic called plasmodium. They are four different species of plasmodium namely P. vivax, P. ovale,P. falciparium & P. malariae. The plasmodium is transmitted from an infected person to a healthy person by female anopheles mosquito. When the mosquito bites an infected person it sucks blood containing the parasites. Inside the mosquito, the plasmodia develop into infective stages. When the same mosquito next bites a healthy person it passes on the infective plasmodia from its salivary glands into the blood into the blood system of the healthy person. The incubation period lasts between seven to ten days. During this period that parasites invade the liver cells where they multiply. They are then released into the bloodstream where they now attack and destroy the red blood cells. Symptoms The symptoms of malaria include high regular fevers accompanied by profuse sweating punctuated by chills and shivers, headaches, muscle and joint pains are felt most of the time. The patient lacks appetide and vomits from time to time. There is enlargement of liver and spleen. Anaemia results because of the destruction of red blood cells. In severe attacks, it leads to convulsions in children. Malaria is a killer disease. Prevention and treatment Various methods of prevention are available in the management of malaria. The most recent method is the development of vaccines against the plasmodium. These targets various stages in the life cycle of the parasite hence developing some immunity. Traditionally malaraia has been controlled by use of nets to repellents such as creams and mosquito coils have been used. Insecticides are sprayed in dwelling places and also use of treated mosquito nets. Drainage of stagnant water and clearance of vegetation around houses destroys the breeding and resting sites of mosquitoes hence reduction in their numbers. Tins, plastic containers and polythene papers that hold water should also be destroyed. The use of oil on stagnant water has been useful but it is being replaced by powdery treatment of water of water services. Biological control involves use of fish in pounds to feed on the mosquito larvae. A more recent method involves release of genetically sterilized male mosquitoes to mate hence reducing the number of mosquitoes. People travelling in malaria prone areas are advised to take antimalarial drugs for prevention. Treatment should be preceded by proper diagnosis and the full dosage administered for full care. Under dose often leads to development of resistance. The international Stockholm Convention of which Kenya is signatory restricts the use of DDT to public health where no alternatives are available. However Kenya the leading producer of pyrethrum strongly advocates for the use of natural pyrethroids in mosquito control. These have been proved effective and safer to environment because they are bio-degradable. Although a lot of resources have been channeled into malarial control, it has been difficult to eradicate disease. Several factors continue to frustrate theses efforts. Theses include; • The presence of large reservoir of the parasite in other hosts such as monkeys and birds. • The warm tropical conditions provide extremely suitable breeding conditions hence rapid multiplication of the vectors. • The development to resistance to insecticides used against mosquitoes. Similarly the plasmodium parasite quickly develops resistance against the drug used against it. • The individual countries face financial constraints. Furthermore regional conflicts frustrate co-ordinated program. Government and donor funds are often diverted to purchase weapons and other military ware. Parasitic Worms Askaris Lumbricoides Ascaris lumbricoides is a parasitic roundworm which belongs to the phylum Nemoda. Ascaris Lumbricoides is widespread in distribution and infects small intestines of pigs and human beings. It may also occur in other organs of the body. The genus Ascaris is the largest nematode parasitic to humans. It is characterized by brownish yellow colour with mouth parts having three lips. The male is about 25 cm long and 0.4 cm in diameter, while te female is about 35 cm long and 0.5 cm in diameter. Mode of Transmission The adult female lays eggs in the small intestine of the host. The eggs are passed out with the faeces and may be swallowed by a new host through contaminated water and food. Contaminated vegetables or fruits which are not washed well before being eaten are also the source of infection. There is also direct infection from faeces to mouth by hand s especially in children. When they are swallowed by a host, the eggs shells are dissolved, releasing the larvae. This penetrates the intestinal walls and enters the bloodstream. They move to liver and then to the heart and lungs. In the alveoli they grow and moult twice. The larvae then migrates up to the trachea where they cause irritation and so are coughed out and so may be swallowed down in to the aeosophogus, stomach and small intestines where they finally mature in adults. Effects of the parasite on the Host During the migration of the larvae they cause irritation in the trachea that lead to lung damage and infection with other diseases. If the is heavy, a lot of is digested food is consumed by the parasite in intestine and this leads o malnutrition in host, especially n children. During their cycle in human host, the parasite feed on blood and therefore can cause anaemia on host. Very heavy infection can also lead to intestinal blockage where victims develop large round stomachs. The worms may also enter the bile duct, pancreatic duct and appendix, causing further complications. Adaptative characteristics of Ascaris lumbricoides to its parasitic mode of life 1. Ascaris lumbricoides has two hosts, human beings and pigs. This ensures that it always has a ready host for survival. 2. It lays many eggs to increase the chance of survival even when some are destroyed. 3. The eggs have protective shell to survive harsh environmental conditions. 4. Ascaris lumbricoides have a thick elastic cuticle which protects it against the digestive enzymes of the host enabling it to survive in the alimentary canal. 5. It has tissues tolerant to low oxygen concentration characteristic of the gut. 6. It has a muscular pharynx through which it sucks digested food from host intestine into its own gut. Prevention and treatment Proper sanitary disposal methods are required especially the availability and proper use of toilet facilities. High standards of personal hygiene should be observed such as washing hands after a visit to the toilet. Hygienic handling and cleaning of fruits and vegetables is necessary. Drinking water should be boiled. Treatment involves use of drugs to kill the worms or inactivate the eggs. Schistomomiasis (Bilharzia) This is a parasite disease of the blood. It is caused by a flatworm of the phylum platyhelminthes of the genus Schistosoma. There are three different species odf the schistosoma that infet human beings. These include Schitosoma mansoni, Schistoma haematobium and Schistosoma japonicum. The parasite is found in fresh water canals, lakes, dams, rice-growing fields and other similar habitats. Modes of transmission The parasite is spread when people drinking water contaminated by larval form called cercariae. Also the parasite can penetrate the skin when bathing or wading through water conatini the larvae. Once in the body they get into the bloodstreams and migrate to the liver where they mature into adults. After coupling of the adult worms, eggs are shed into the blood vessels or alimentary tract. When the faeces or urine containing eggs are disposed of into water, the eggs hatch into larvae called miracidia. The miracidia find and penetrate the water snails such as Biomphalaria and Bulinus. It is from the snails that infective stages cercariae emerge and can now infect human beings who stand, bath or drink in such water. Effects of Parasite on its Hosts The parasite damages the host skin when penetrating and this causes itching. Once in the blood the adult schistosoma releases chemical substances that cause fever. The adult worms have spines which they use to tear through the veins and enter into the intestines or urinary bladder. This causes blood to appear in urine or stool. This can eventually lead to anaemia. The person also experiences abdominal pains and diarrhea. If untreated, the disease can result in death due to exhaustion or by infection from other diseases due to reduced body immunity. Adaptative Characteristic of Schistosoma The parasite has suckers for attachment so that they are not dislodged. The parasite has two hosts, that is the secondary host, the snail and the primary host, the human being. This increases its chances of transfer to several hosts and from one place to another. The cercariae larvae and eggs of the parasite have glands that secrete lytic enzymes which soften tissue to allow for penetration into the hosts. Some larval forms e.g miracidia, are encysted and can remain dormant and viable until they come into contact with a human being. The parasite reproduces through larval forms e.g cercariae, and redia in snails. This makes it very difficult to eradicate the parasite and also increases its chances of transmission and survival. The adult worm in blood produces chemical substances which protect it against the hosts defence mechanism. The worms are of separate sexes. The male form a gynecophoric canal in which it carries the female. This ensures that the e

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