Reproduction in Animals
Concept: Life Cycle of Animals
What is Life cycle?
Life cycle refers to the series of changes in an organism from birth until death.
Every living organism, i.e., all plants and animals, undergoes various changes from the time they are born until they die.
Life cycle of birds:
- All birds lay eggs in their nests.
- Birds incubate their eggs by sitting on them.
- This incubation helps in the development of the embryo inside the egg.
- The egg matures into a hatchling that comes out on hatching of the egg.
- It takes 21 days for the hatching of an egg.
Life cycle of frogs:
- Frogs are amphibians who reproduce in water.
- The eggs laid by frogs are prone to destruction due to several natural factors. Hence, to compensate for this loss, frogs lay many eggs in clusters called spawns.
- These spawns are covered with a transparent jelly-like substance that protects the eggs from water.
- The breeding season for frogs varies according to the climatic conditions. It usually occurs during the spring season in temperate climates and during the rainy season in tropical climates.
Stages of development in the life cycle of a frog:
- Egg: Females lay eggs in the water that are fertilised by the male gametes later. The fertilised eggs develop and mature into tadpoles, which are the larvae of frogs. It takes around 2-3 weeks for hatching of the larva from the fertilised eggs.
- Tadpole: Tadpoles have gills for breathing, a mouth and a long tail for swimming. After the first two weeks of hatching, the tadpoles show less movement.
- Once they are strong enough, they start swimming and feed on the algae and other aquatic vegetation.
- In the later stages of development, metamorphosis leads to the development of limbs. The gills and tail disappear on maturation.
|1-3 weeks after fertilisation||
|After 7-10 days of hatching||
|After 6 weeks of hatching||
|After 9 weeks of hatching||
|After 12 weeks of hatching||
Life cycle of cockroaches:
- Cockroaches reproduce by laying eggs.
- The life cycle of a cockroach can be divided into the following stages—
|Stage||Name of the stage||Characteristics|
Life cycle of butterflies:
The different stages in the life cycle of a butterfly are described below—
- Egg stage: Butterflies lay eggs on plant leaves. Different species of butterflies lay eggs in different seasons.
- Caterpillar or larva stage: This stage is also called the eating and growing stage.
- When the larva hatches out of the eggs, they feed enormously on the leaves and grow in size.
- While growing, the caterpillar splits its skin and sheds it about four or five times.
- The food eaten by a caterpillar during this time is stored and used later as an adult.
- Caterpillars can grow 100 times their size during this stage.
- When the caterpillar matures fully, it stops eating and becomes a pupa.
- The pupa may be found hanging or hidden among the leaves.
- During this stage, the special cells present in the larva start growing rapidly.
- They form the legs, wings, eyes and other parts of an adult butterfly.
- The adults have long legs, long antennae, and compound eyes and fly using their large colourful wings.
- An adult butterfly does not grow further.
- Life span of a butterfly is about 15-30 days.
|Stage||Number of days|
|Egg stage||3-7 days|
|Caterpillar stage||2-5 weeks|
Lifespan:The period from the birth to death of an organism.
Metamorphosis: The biological process of transformation of a larva into a complete adult.
Moulting: The natural process by which animals shed their old skin.
Incubation: The process of providing heat to the eggs.
Hatchling:The young chick that comes out of the egg.
Did You Know?
- The cocoon of a silkworm is used for making silk.
- Insects show complete and incomplete metamorphosis.
- Complete metamorphosis occurs when the larva is very active, and gorging on food and the pupa is inactive. Incomplete metamorphosis consists of a nymph that looks like a miniature form of the adult.
- A frog completely sheds its skin once a week.
- Some frogs swallow the tadpoles and keep them in their vocal sacs for 60 days, protecting them and allowing them to grow.