Classification of Animals

Arthropoda are classified into following four subgroups or classes:

1. Arachnida — Examples: scorpions, spiders
2. Crustacea — Examples: lobsters, shrimps
3. Myriapods — Examples: centipedes, millipedes
4. Insect — Examples: ants, beetles

a. Two characteristics of bird are:

1. Their skeleton is very light because their bones have large air cavities. They have horny beaks and no teeth.
2. They are the only animals whose body is covered with feathers.

b. Two characteristics of amphibians are:

1. They breathe with lungs on land, and through their moist skin in water.
2. They are cold-blooded animals.

c. Two characteristics of reptiles are:

1. Their skin is covered with horny epidermal scales.
2. They breathe through lungs.

Fish has special breathing organ called gills. The gills have numerous thin blood capillaries. Fish takes in water through the mouth and this water passes through the gills. The capillaries absorb the oxygen that is dissolved in the water and release the carbon dioxide in the water. In this way the fish exchange gases.

Birds have different adaptations in their body that help them to fly. Their bones are hollow with large air cavities in them which makes them light. Such bones are known as pneumatic bones. This keeps the body of birds light and makes it easy for them to fly. Other vertebrates either have solid bones or their bones are filled with bone marrow.

Birds are the only animals whose body is covered with feathers.

The animals that do not have a back bone or vertebral column are called invertebrates.

A radially symmetrical body is a body that can be divided vertically into two equal halves along any plane passing through the central point.

Nephridia are the special organs of excretion in annelids.

A rigid external covering of the body found in some invertebrates that provides support and protection to their body is called an exoskeleton. It is different from backbone in the following ways:

1. Exoskeleton is present outside the body while backbone is present inside the body.
2. Exoskeleton is shell like or chitinous covering above the body present in some invertebrates but backbone is bony structure found inside the body of vertebrates.

Animals of class Amphibia can live both on land and in water. Two examples of amphibians are salamander and frog.

Three most important features of birds are:

1. Their skeleton is very light because their bones have large air cavities. They have horny beaks and no teeth.
2. They are the only animals whose body is covered with feathers.
3. Their forelimbs are modified into wings and hind limbs are adapted for walking, perching or swimming.

Invertebrate do not have a backbone, while vertebrate have it.

Cnidarians have radially symmetrical body.

Planaria and liver fluke live in the intestines of humans and cattle.

Earthworms are considered as a farmer's friend.

Annelids have special organs called nephridia for excretion.

Arthropods have paired appendages with many joints.

Arthropods have compound eyes.

Most arthropods have a tough outer body covering called exoskeleton.

A snail belongs to the mollusca phylum.

Echinoderms have a mouth on the lower side and an anus on the upper side.

False

Corrected statement — Vertebrates are animals with a backbone.

True

False

Corrected statement — Birds are warm blooded animals.

False

Corrected statement — Amphibians can live on land as well as in water.

True

1. They are warm-blooded animals.
2. They give birth to babies.
3. They have hair on their body.

Animals without a backbone whose body is soft and often covered by a hard shell are called mollusca.

Invertebrates with jointed legs belong to the arthropods phylum.

Fish obtain oxygen from water through gills.

Vertebrates that spend a part of their life on land but reproduce in water are called amphibians.

Mammals are warm-blooded animals and have hair on their body.

Spider

Reason — Spiders are classified under arachnida while others are insect.

Eel

Reason — Eel is a fish while others are reptiles.

frog

Reason — Frog is amphibian while shark, seahorse and carp are classified under class pisces

jellyfish

Reason — Jellyfish is a cnidarian but others are echinoderms.

Earthworm

Reason — Earthworm is annelid while others are molluscs.

butterfly

Reason — Butterfly is an arthropod (insect) while others are cnidarians.

The animal is a mollusc as it has a soft body and arm-like tentacles and also an internal shell. It belongs to the Invertebrates group.

Fish is a cold-blooded animal. It means it changes its body temperature according to the change in temperature of the environment. So, the body temperature of a fish will decrease when the temperature of water drops.

Amphibians require water to complete their life cycle. Adult amphibians tend to stay near water to lay their eggs in water.

Sea water

Reason — Sponges are mostly found in sea water, only a few species are found in fresh water.

pin worm

Reason — Hydra, jellyfish and sea anemone are cnidarians.

tentacles

Reason — The finger-like structures present around the mouth of cnidarians are called tentacles.

soft, cylindrical, segmented, bilaterally symmetrical body

Reason — The body of annelids is soft, cylindrical, segmented and bilaterally symmetrical.

earthworm

Reason — Earthworm and leech have nephridia for excretion.

beetle

Reason — Beetle is an insect and has an exoskeleton.

arachnids

Reason — Scorpions and spiders are arachnids, a subgroup of arthropoda.

does not change with the change in the temperature of the environment

Salamander

Reason — Salamander is an amphibian while turtle, alligator and crocodile are reptile.

birds

Reason — Birds have air cavities in their bones to make their body light.

Mammals

Reason — Mammals have four-chambered heart while amphibians and most of reptiles have three-chambered heart. Fishes have two chambered heart.

False

Corrected Statement — Arthropods have a rigid outer covering called exoskeleton.

True

False

Corrected Statement — A centipede is a myriapod.

True

False

Corrected Statement — Reptiles lay eggs with a leathery waterproof shell and are cold-blooded animals.