Animals : How Life Goes On

              Animals : How Life Goes On

Living things do not live for ever. They die after completing there their lifespan. For life to go on, living things must produce more of their own kind. The process by which living beings produce more of their own kind, is called reproduction.

Animals reproduce in two different ways. Some give birth to young ones whereas some lay eggs. Later the young ones hatch from the these eggs. Humans, cats, cow , sloth , elephant many other animal give birth to young ones. Frogs, catfish, sunfish , snake , crocodile , hen are some lay eggs

Some Animals Give Birth To Young Ones 

Mammals 

Animals which give birth to young ones and feed on their milk are called mammals. They are most developed among all animals. There bodies are covered with hair. Some examples are elephant, tiger, cat, dogs, kangaroo , pandas, rhino are some mammals. Bats are the only mammals that can fly. The smallest living mammal Kitti' s hog- nosed bat. This is about to 1 inch long and weighs about to 2 grams! Whales and Dolphins are look like fishes and have hairless bodies are mammals.

Care of the young ones

Mammals take care of their babies for a long period of time.  Usually the mother cares for the young. She feeds the babies, cleans them and keep them warm. She protects them from enemies. As they grow, the mother teaches them to find food and live on their own. 

In certain mammals father also helps. He hunts for food and guards the young ones. Humans are the only mammals that who look after not only their children but also their grandchildren too. 

Some Animals Lay Eggs 

Birds 

Birds reproduce by laying eggs . Most birds build nest and lay eggs.,  They sit on the eggs to keep them warm. After some times the eggs hatch and baby birds come out. The eggs of all birds have a similar internal structure. Each egg has a hard protective shell. Within the shell is the white called albumen. Whithin the albumen is a round, yellow yolk. The chick is formed and grows inside the yolk. A growing baby is called an embryo. The chick embryo uses the yolk as food. The embryo develops only if the egg is kept warm. The chick comes out after 21 days. 

A frog' s egg develops into a tadpole. It keeps growing and slowly changes into a adult frog ( Fig. 8.7. ) . 

A fish lays thousands of eggs at a time in water. Out of these few hundred fishes grow into a baby fish. Many eggs are eaten by big fish . Some kind of fishes like Clown Fish , Giant Pacific Octopus guard their eggs. Giant Pacific Octopus lay more than thousands of eggs and the female guards for a long period and without a food, so the female lose a lot of her body weight and die their. In a group of Clown Fish , their will be only on female to be the queen, if the queen die the every males decide a male Clown Fish and the fish can change its gender into female in 1 day.  Reptiles like lizards, turtles , snakes , crocodile and alligators are lay eggs in holes in ground. Crocodiles babies gender are based in the tempreture. If it is more than 30 degree, no female can from in the egg, only male can born, if it is less 30 degree , both females and males can from in the eggs. Nowadays the tempreture of the earth is getting very hot , so mostly male crocodiles come from the egg , so in few years , crocodiles may also can be extinct.  Reptiles lay eggs and go away and never come.

Many eggs are eaten by other animals. Some eggs get warmth the heat of the sun and hatch.  Not only birds, but animals like frog and fish. They lay their eggs in water. They care for their babies only for a short time. All insects hatch form eggs. Some insects like cockroaches and grasshoppers have 3 stages in their life cycle.

The baby insect which comes out of the egg is called nymph.

It is very similar to its parents. After moulting many times , it's changes into a adult. Other insects like houseflies and butterflies have 4 stages in their life cycle. The young one that hatches from the egg of these insects is called larva. It is very different from the parents.  It looks more like a worm. The larvae of different insects have different names. The larva of a housefly is called a maggot. The larva of a butterfly is called caterpillar. The larva eats leaves and grows rapidly. After some times it stops eating and form a cover around it, called pupa. Later the pupa bursts open and the butterfly comes out. Adult insects do not look after the babies. 

Notes: 

The champion egg layer is the Giant Clam, which lives in ocean bed. It produces 100 crore of eggs at a time and does this year after after year for about 30 years. Can you tell how many eggs it lays during its lifetime ?