Animal Life (Extra Information-1) Class 4 Notes Science

Aquatic Animals                                           

All water animals swim by paddling and pushing water. Different animals use different: organs for swimming.                                                        

Fishes use three types of fins for swimming. The paired fins help them to move forward. The unpaired fins help them their balance. The tail fin is used to change direction.

Frogs use their webbed feet to swim. Their long, strong hind legs help them to hop on land. Turtles use their four paddle like limbs as flippers to swim. Penguins too have two flippers which are actually short, strong wings.

Fig: A frog using its webbed feet to swim

Insects

All insects have six legs. Most insects use their legs to move.

Ants and cockroaches use their legs for crawling. Grasshoppers and locusts use their long, strong hind legs for hopping. Water insects like water boatman use its legs as oars to paddle and to swim. Butterflies, bees and houseflies have wings to help them fly. Their wings are not like the wings of birds as they have no feathers, bones of strong muscles. They are thin, delicate and made up of tiny scales.

Fig: Insects

Reptiles

Crocodiles, lizards, tortoise and turtles have short limbs to help them crawl. Snakes are legless reptiles. They crawl with the help of scales or plates on the underside of their body Strong muscles and a flexible backbone help them to move.

Fig: Reptiles

Birds

Birds fly with their wings which are actually their forelimbs. They use their hind limbs or legs to:

• Land on the ground
• Walk, run, hop, perch
• Scratch the ground
• Catch their prey

The wings of birds are special as they have feathers. The wings are attached to the breast bone. Strong muscles help birds to flap their wings and fly.

The bodies of birds are very light and their bones are hollow, making it easy for them to rise in the air and fly. All birds have wings but some birds are unable to fly. Ostrich, emu, rhea and kiwi are flightless birds. Their wings are too weak for them to be able to fly.

Humans

Humans use their lower limbs or legs to stand and to support their body. That is why, unlike other animals, humans stand straight on their two legs and have an erect posture. They use their legs for walking and running.

Humans use their upper limbs or arms to do a variety of things like picking up, carrying, holding and catching things.

The thumb is opposite to the other four fingers. This makes it easy for humans to hold things and do different kinds of work.

Fig: Humans

Migration

The mass movement of animals from one place to another at certain times of the year is called migration. Siberian cranes use to migrate to India during winters, as it is warmer here than in their home country, where very cold weather makes it difficult to get food or even to stay alive. Some other animals migrate to escape harsh weather, to search for food, water and also to breed. Arctic terns make the largest migration from north to south pole every winters and then back again in summers.