Life Cycles of Animals - Science Lessons for Grade 5 Students
All of the stages in an animal’s life make up its life cycle. Animal life cycles can be different in the number of stages of growth the offspring go through before they become adults.
Life cycle of a cockroach
A female cockroach lays many eggs, and all of them are in an egg case. From each egg hatches a young cockroach called nymph. The nymph looks similar to an adult cockroach, but is smaller and does not have wings. A nymph will moult about eight times before it grows into an adult cockroach. As an adult, the cockroach will then produce new young of its own. Thus, the life cycle of a cockroach has three main stages – egg, nymph and adult.
Life cycle of a mosquito
A female mosquito lays groups of eggs in water. A mosquito larva, called a wriggler, hatches from each egg. The wriggler grows just beneath the surface of the water. It takes in air through a special tube. The mosquito larva moults several times as it grows. It then changes into a pupa. The outer covering of the pupa then splits open and an adult mosquito emerges. Thus, the life cycle of a mosquito has four stages – egg, larva, pupa and adult. The changes in form that the body of a mosquito undergoes during its life cycle is known as metamorphosis.
Mosquitoes can spread diseases to people. By understanding the life cycle of a mosquito, we can reduce the number of places where mosquitoes can breed around our home.
Life cycle of a butterfly
A female butterfly lays eggs on a plant that will provide food for its young. Many eggs are usually laid at one time. A butterfly larva, called a caterpillar, hatches from each egg. The larva does not look like an adult butterfly. It has a worm-like body.
The larva feeds on leaves and moults several times as it grows. When the larva reaches its full size, it stops eating. It then changes into a pupa. Inside the hard pupa covering, many changes are taking place. When the pupa case breaks open, an adult butterfly comes out. The adult butterfly will then produce new young of its own. Like that of the mosquito, the life cycles of a butterfly has four stages – egg, larva, pupa and adult.
Life cycle of a fish
A female fish lays eggs in water. Many eggs are laid at once. Young fish called fry hatch from each egg. As the young fish grow, they get larger and look more like their parents. As an adult, the fish will then produce young of its own.
Life cycle of an amphibian
The word amphibian comes from a Greek word meaning ‘both life’. This is because amphibians have a life cycle that usually begins in water and then moves onto land.
A female frog lays eggs in water. The frog larva, called a tadpole, hatches from each egg. The tadpole does not look much like an adult frog. It has a fish-like body and tail.
As the tadpole grows older, its tail gets shorter and it begins to develop legs. Its gills also get smaller and it begins to develop lungs. As an adult, the frog moves from water and onto land.
The life cycle of an amphibian thus has three stages – egg, larva and adult.
Life cycle of a reptile
Sea turtles, which are reptiles, live in the sea, but female sea turtles move onto land to lay eggs in the sand. A young turtle hatches from each egg and makes its way to the sea. The young sea turtle looks like its parents. As it grows it gets larger. As an adult, the sea turtle will return to the same beach where it was hatched to lay eggs of its own.
Life cycle of a bird
Let’s us take a look at the life cycle of a bird, by looking at the life cycle of a chicken.
An egg is laid by a female chicken, called a hen. The egg is kept warm by the hen sitting on it. After about 21 days, the young chick inside the egg uses its beak to break out of the egg.
The chick has short fluffy feathers. It also has legs, wings and a beak, like its parents. As the chick gets older, it grows new feathers and looks more and more like its parents. As an adult, the chicken will be able to produce eggs and produce young of its own.
Thus, the life cycles of reptiles and birds have three stages – egg, young and adult.