8. Amphibians
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8.1 Amphibians: aquatic animals on land?
Amphibians are animals that are suited to living both in water and on land. Frogs are the most common group of amphibians.
Typically, frogs can be found in wet forests. Their spawns can be seen in ponds and ditches.
Are amphibians aquatic animals or land animals? What kinds of factors contribute to them being considered aquatic animals? What about the factors that make you think of them as land animals?
8.2 Frog ponds
In April, when winter turns into spring and ponds lose their ice covers, frogs begin leaping towards their home pools. The season of reproduction has begun.
Most often, people will notice frog reproduction only after their spawning has already taken place. Frogs spawn during the night in shallow waters, such as ditches or small ponds. The reproductive cycle of frogs may take only a few days. After reproducing, frogs begin their journey back to their home forests, where they begin their preparations for the coming winter.
Frogs spawning.
Frogs reproduce in the water and juvenile frogs develop into adult frogs in the water. However, frogs have also adapted to the life on dry land. They have feet that they can walk with, and lungs that they use to breathe while on the ground.
8.3 The life cycle of a frog
Frog reproduction begins with spawning. During the course of a few weeks, the fertilized eggs hatch into frog larvae or tadpoles.
Fertilized frog eggs.
Frog larvae have adapted to life in water. They have gills, which makes it possible for them to filter oxygen from water. In addition, they also have a long tails, making movement in water easier.
Frog larvae are called tadpoles. They are herbivores, eating algae that they find in the water. They develop and grow in water for 2–3 months. During this time, they develop eyes, limbs, and lungs. Slowly, their tail shrinks away. Finally, the tadpoles move to land and start to eat small animals.
The life cycle of a frog progresses through the egg and tadpole stages into the adult stage. It is an example of a metamorphosis.
Frogs reach reproductive maturity at the age of two years. When this occurs, they navigate back to their home pool to spawn.