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Reproduction – The process by which organisms produce young once of their own kinds is called reproduction.
Why do animals reproduce?
Animals reproduce to ensure the continuity of life and survive of same kind.
Life span – The total time period for which an organism lives is called life span.
Egg laying animals – Those animals that reproduce by laying eggs are called egg-laying animals. Ex- Insects, fish, frogs, snakes, lizards, snails, birds and crocodiles
Birds – An animal that lays eggs and has wings and a body covered with feathers are called birds.
How do birds care their young ones?
All birds reproduce by laying eggs.
Birds build nests to lay eggs and to raise their young ones.
The mother bird sits on their eggs to keep them warm.
Birds nurture (dekhabhal karana) their eggs until these eggs hatch into young ones.
Unborn growing baby inside egg is called embryo.
When the baby bird hatches from the egg, they do not have feathers.
Parent’s birds teach them to learn fling and searching for food.
When the chicks are fully grown and independent, they leave them to face the challenges.
Life cycle – The different stages of development of an embryo to become an adult are called life cycle.
Incubation – The process in which the parent sits on its eggs to keep them warm are called incubation.
Egg – An oval object that is produced by a female bird and which contains a baby bird is called egg.
Describe the structure egg:
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The outer hard cover of egg is called shell.
Shell is made of calcium carbonate.
The white jelly-like substance inside shell is called albumen.
Albumen is rich in protein.
The yellow part inside shell is called yolk.
Yolk contains fat that is the source of food.
The chick forms and grows inside the yolk.
The growing chick is called embryo.
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What helps an embryo to nourish inside a bird’s egg?
An embryo to nourish by the yolk inside a bird’s egg
Fish –The animal that lives in the water and breathes through gills is called fish.
Fishes lay thousands of eggs in water.
Baby fishes hatch out of the eggs.
The eggs and the baby fishes are eaten by other fishes.
Amphibians – Those animals which live on land as well as water are called amphibians.
Ex– Frog, snakes etc.
Life cycle of a frog:
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Metamorphosis – The process by which a tadpole under goes several changes from birth to becoming an adult is called metamorphosis.
Note-
Tadpole has no legs but has a long tail and breathes through gills in water.
An adult frog breathes through lungs.
Reptiles – Those animals that crawls or moves on its belly or on small short legs is called reptiles. Ex – Lizards, turtle, snakes etc
Lizards, turtle and snakes also lay eggs but do not give any parental care.
Most of their laid eggs are eaten by other animals.
Insects – Those small arthropod animals that have six legs are called insects.
Insect has generally one or two pairs of wings
Most of the insects such as butterflies, grasshoppers, cockroaches and houseflies lay eggs.
The process of shedding off old skin by a nymph to become an adult is called moulting.
Young one of insects resembling the adult is called nymph.
The larva of butterfly is called caterpillar and larva of housefly is called maggot.
The tiny worms that hatch from egg of butterfly and housefly is called larva/caterpillar.
Life Cycle of Butterfly:
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Animals that give birth to young ones:
Mammals –Those animals that give birth to young ones are called mammals.
Ex- dogs, cats, monkeys, tigers, cows, elephants, horses and humans etc.
The baby develops inside the mother’s body.
After their birth they feed on mother’s milk till they learn to feed by their own.
Whales and dolphins live in water but they give birth to young ones.
Bat is flying mammal which gives birth to young ones.
How do mammals take care their young ones?
Mammals take care of their young ones for a long time.
The mother feeds the baby with her milk
She cleans them and keeps them warm.
She protects them from their enemies.
She teaches them to hunt for their food.
Note – Human beings take care of their children for longest time in compared to other animals.
