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Chapter 3

Classification of Animals

Class 7 - Living Science Biology Ratna Sagar


Check your progress 1

Question 1

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

Answer

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

Question 2

Cnidarians have ............... symmetrical body.

Answer

Cnidarians have radially symmetrical body.

Question 3

............... and ............... live in the intestines of humans and cattle.

Answer

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

Question 4

............... are considered as a farmer's friend.

Answer

Earthworms are considered as a farmer's friend.

Question 5

Annelids have special organs called ............... for excretion.

Answer

Annelids have special organs called nephridia for excretion.

Check your progress 2

Question 1

............... have paired appendages with many joints.

Answer

Arthropods have paired appendages with many joints.

Question 2

Arthropods have ............... eyes.

Answer

Arthropods have compound eyes.

Question 3

Most arthropods have a tough outer body covering called ............... .

Answer

Most arthropods have a tough outer body covering called exoskeleton.

Question 4

A snail belongs to the ............... phylum.

Answer

A snail belongs to the mollusca phylum.

Question 5

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

Answer

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

Check your progress 3A

Question 1

Vertebrates are animals without a backbone.

Answer

False

Corrected statement — Vertebrates are animals with a backbone.

Question 2

In fishes, fins are the organs of locomotion.

Answer

True

Question 3

Birds are cold blooded animals.

Answer

False

Corrected statement — Birds are warm blooded animals.

Question 4

Amphibians can only live on land.

Answer

False

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

Question 5

Aves have horny beaks and do not have teeth.

Answer

True

Check your progress 3B

Question 1

Tick the statements that are true for mammals.

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

Answer

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

Tick the most appropriate answer

Question 1

Sponges are mostly found in

  1. distilled water
  2. sea water
  3. dirty water
  4. tap water

Answer

Sea water

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

Question 2

Which one of the following is not a cnidarian?

  1. pin worm
  2. Hydra
  3. jellyfish
  4. sea anemone

Answer

pin worm

Reason — Hydra, jellyfish and sea anemone are cnidarians.

Question 3

The finger-like structures present around the mouth of cnidarians are called

  1. pseudopodia
  2. tentacles
  3. spines
  4. bristles

Answer

tentacles

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

Question 4

Annelids have a

  1. soft, unsegmented, bilaterally, symmetrical body
  2. soft, cylindrical, segmented, bilaterally symmetrical body
  3. soft, segmented, bilaterally symmetrical body
  4. soft, segmented, laterally symmetrical body

Answer

soft, cylindrical, segmented, bilaterally symmetrical body

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

Question 5

Which of the following has nephridia for excretion?

  1. spider
  2. tapeworm
  3. earthworm
  4. shrimp

Answer

earthworm

Reason — Earthworm and leech have nephridia for excretion.

Question 6

Which of the following has an exoskeleton?

  1. octopus
  2. snail
  3. leech
  4. beetle

Answer

beetle

Reason — Beetle is an insect and has an exoskeleton.

Question 7

Scorpions and spiders are

  1. crustaceans
  2. arachnids
  3. myriapods
  4. insects

Answer

arachnids

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

Question 8

The body temperature of warm-blooded animals

  1. keeps fluctuating
  2. changes according to the temperature of the environment.
  3. does not change with the change in the temperature of the environment
  4. decreases when the temperature of the environment increases.

Answer

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

Question 9

Which of the following is an amphibian?

  1. turtle
  2. salamander
  3. alligator
  4. crocodile

Answer

Salamander

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

Question 10

Bones with large air cavities are present in

  1. cnidarians
  2. fish
  3. annelids
  4. birds

Answer

birds

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

Question 11

............... have four-chambered heart.

  1. Amphibians
  2. Mammals
  3. Fish
  4. Reptiles

Answer

Mammals

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

Fill in the blanks

Question 1

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

Answer

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

Question 2

Invertebrates with jointed legs belong to the ............... phylum.

Answer

Invertebrates with jointed legs belong to the arthropods phylum.

Question 3

Fish obtain oxygen from water through ............... .

Answer

Fish obtain oxygen from water through gills.

Question 4

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

Answer

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

Question 5

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

Answer

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

Write true or false. Correct the false statements.

Question 1

Arthropods have a soft outer covering called endoskeleton.

Answer

False

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

Question 2

A tapeworm is a flatworm that lives in the human intestine.

Answer

True

Question 3

A centipede is an insect.

Answer

False

Corrected Statement — A centipede is a myriapod.

Question 4

Fish have fins, scales and they breathe through gills.

Answer

True

Question 5

Reptiles lay eggs with a hard shell and are warm-blooded animals.

Answer

False

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

Differentiate between

Question 1

flatworms and roundworms

Answer

Sl.
No.
FlatwormsRoundworms
1.Flatworms belong to phylum Platyhelminthes.Roundworms belong to phylum Nematoda.
2.The body is thin and flattened or leaf-like or ribbon-like.The body is cylindrical, narrow, unsegmented and bilaterally symmetrical.
3.They have only one opening, for intake of food and excretion.They have two openings — mouth for intake of food and anus for excretion.
4.They show sexual and asexual reproduction.They reproduce sexually.
5.They are hermaphrodite.Male and female exist separately.

Question 2

arthropoda and mollusca

Answer

Sl.
No.
ArthropodaMollusca
1.Body of Arthropoda is segmented.Body of Mollusca is unsegmented.
2.Arthropoda have jointed legs.Mollusca do not have jointed legs.
3.Arthropoda have exoskeleton.Mollusca have coiled shell.
4.For example — spider and ant.For example — octopus and snail.

Question 3

radially symmetrical body and bilaterally symmetrical body

Answer

Sl.
No.
Radially symmetrical bodyBilaterally symmetrical body
1.It means that the body can be divided vertically into two equal halves along any plane passing through the central point.It can be divided into two identical halves only through one plane.
2.Coelenterates have a radially symmetrical body.Flatworms have bilaterally symmetrical body.

Question 4

amphibians and pisces

Answer

Sl.
No.
PiscesAmphibians
1.Pisces are aquatic.Amphibians can live on both land and water.
2.Body of Pisces is smooth and slimy and is covered with scales for protection.Amphibians have thin, moist skin which may be smooth or rough.
3.In Pisces, limbs are modified into fins.Amphibians have two pairs of limbs.
4.Pisces have gills to breath.Amphibians breathe through lungs on land and through their moist skin in water.
5.Pisces have two chambered heart.Amphibians have three chambered heart.

Question 5

aves and mammals

Answer

Sl.
No.
AvesMammals
1.Aves lay eggs.Mammals give birth to babies.
2.Aves have feathers on body.Mammals have hairs on their body.
3.Aves have light bones with air cavities.Mammals have solid bones.
4.Aves do not produce milk.Mammals produce milk and suckle their young ones.
5.Aves do not have teeth.Mammals have teeth.

Question 6

warm-blooded and cold blooded animals

Answer

Sl.
No.
Warm-blooded animalsCold-blooded animals
1.Body temperature of warm-blooded animals remains constant and is not affected by the temperature of their surroundings.Body temperature of cold-blooded animals changes with the temperature of their surroundings.
2.For example: Mammals and BirdsFor example: Fish and Reptiles

Match the following

Question 1

Sl.
No.
Column AColumn B
1.molluscsfeed milk to young ones, warm-blooded
2.spongesbag-like body with tentacles around the opening
3.flatwormsfins, gills and cold-blooded
4.mammalsbody with large opening and many small pores all over
5.fishhard shell, soft body
6.cnidarianssoft body without a body cavity and one opening only
7.arthropodsjointed legs, exoskeleton
8. cylindrical, unsegmented body with mouth at one end and anus at the posterior end

Answer

Sl.
No.
Column AColumn B
1.molluscshard shell, soft body
2.spongesbody with large opening and many small pores all over
3.flatwormssoft body without a body cavity and one opening only
4.mammalsfeed milk to young ones, warm-blooded
5.fishfins, gills and cold-blooded
6.cnidariansbag-like body with tentacles around the opening
7.arthropodsjointed legs, exoskeleton

Find the odd one out. Give reasons.

Question 1

ant, cockroach, spider, dragonfly

Answer

Spider

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

Question 2

snake, alligator, eel, turtle

Answer

Eel

Reason — Eel is a fish while others are reptiles.

Question 3

frog, shark, seahorse, carp

Answer

frog

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

Question 4

sea urchin, starfish, brittle star, jellyfish

Answer

jellyfish

Reason — Jellyfish is a cnidarian but others are echinoderms.

Question 5

snail, oyster, earthworm, octopus

Answer

Earthworm

Reason — Earthworm is annelid while others are molluscs.

Question 6

jellyfish, Hydra, sea anemone, butterfly

Answer

butterfly

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

Answer the following in short

Question 1

What are invertebrates?

Answer

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

Question 2

What do you mean by radially symmetrical body?

Answer

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

Question 3

What are the special organs of excretion in annelids?

Answer

Nephridia are the special organs of excretion in annelids.

Question 4

What is an exoskeleton? How is it different from the backbone?

Answer

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.

Question 5

Which class of animals can live both on land and in water? Give two examples.

Answer

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

Question 6

Write three most important features of birds.

Answer

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.

Answer the following in detail

Question 1

Name the different classes of arthropods. Write two examples of each class.

Answer

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

Question 2

Write two characteristics each of

a. birds.
b. amphibians.
c. reptiles.

Answer

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.

Question 3

How do fish exchange gases?

Answer

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.

Question 4

How are the bones of birds different from those of other vertebrates?

Answer

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.

Question 5

What is the most notable characteristic of birds that is not found in any other group of animals?

Answer

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

Identify the odd one out

Question 1

Given below is a table consisting of different groups of animals and their characteristics features. Some of the features are incorrect. Identify the odd one out in each.

Sl.
No.
GroupCharacteristic featuresOdd one out
1.Poriferaporous animals, have tentacles, fixed to surface
2.Pisceslive in water, scaly skin, warm blooded, fins for swimming
3.Amphibiacold blooded, lungs in adults, scaly skin
4.Avescold blooded, wings, feathers, bones with large air cavities

Answer

Sl.
No.
GroupCharacteristic featuresOdd one out
1.Poriferaporous animals, have tentacles, fixed to surfacehave tentacles
2.Pisceslive in water, scaly skin, warm blooded, fins for swimmingwarm blooded
3.Amphibiacold blooded, lungs in adults, scaly skinscaly skin
4.Avescold blooded, wings, feathers, bones with large air cavitiescold blooded

Complete the table

Question 1

Look at the pictures and complete the table.

Answer

AnimalGroup to which it belongsWhere it livesTwo other members of the same groupOne characteristic feature of the group
Ascaris Living Science Biology Ratna Sagar Solutions ICSE Class 7Nematodafreshwater, marine and terrestrial environment, lives in intestine as parasitepinworm, whipwormunsegmented cylindrical body
Earthworm Living Science Biology Ratna Sagar Solutions ICSE Class 7Annelidamoist soil, pond waterPolychaete, leechsegmented body
Snail Living Science Biology Ratna Sagar Solutions ICSE Class 7Molluscafreshwater, marine and terrestrial environmentoctopus, squidsoft, unsegmented body with an outer hard shell
Butterfly Living Science Biology Ratna Sagar Solutions ICSE Class 7Arthropoda (insect)air and landant, houseflycompound eyes
Spider Living Science Biology Ratna Sagar Solutions ICSE Class 7Arthropoda (arachnida)terrestrialcockroach, scorpionsfour pairs of jointed limbs
Starfish Living Science Biology Ratna Sagar Solutions ICSE Class 7EchinodermataMarine waterbrittle star, sea urchinMouth on lower side and anus on upper side
Shrimp Living Science Biology Ratna Sagar Solutions ICSE Class 7Arthropoda (crustacean)Marine and Fresh waterlobsters, shrimpsJointed legs
Frog Living Science Biology Ratna Sagar Solutions ICSE Class 7Amphibialand and watertoad, salamanderThin, moist skin which may be smooth or rough
Parakeet Living Science Biology Ratna Sagar Solutions ICSE Class 7Avesland and aircrow, sparrowBody covered with feathers
Lizard Living Science Biology Ratna Sagar Solutions ICSE Class 7Reptilesterrestrialsnake, turtleDry skin covered with scales

Classify the given animals

Question 1

Classify the given animals into different categories indicated:

jellyfish, liver fluke, pinworm, Ascaris, tapeworm, Hydra, sea anemone into Cnidarians, Platyhelminthes and Nematoda.

Answer

CnidariansPlatyhelminthesNematoda
jellyfishliver flukepinworm
Hydratapewormascaris
sea anaemone

Question 2

Classify the given animals into different categories indicated:

crab, millipede, fly, ant, scorpion, centipede, spider, lobster, moth, prawn into Arachnids, Crustaceans, Myriapods and Insects.

Answer

ArachnidsCrustaceansMyriapodsInsects
scorpionlobstermillipedefly
spiderprawncentipedeant
crabmoth

Question 3

Classify the given animals into different categories indicated:

seahorse, turtle, mouse, dog, shark, alligator, lion, crocodile, eel, pomfret, snake into Pisces, Reptiles and Mammals.

Answer

PiscesReptilesMammals
seahorseturtlemouse
sharkalligatorlion
eelsnakedog
pomfretcrocodile

Think and answer

Question 1

This animal has a soft body and arm-like tentacles. You dissect the animal and find that it has an internal shell. Is the animal a cnidarian or a mollusc? Which group does this animal belong to?

Answer

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.

Question 2

What happens to the body temperature of a fish when the temperature of water drops?

Answer

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.

Question 3

Why do adult amphibians tend to stay near water?

Answer

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

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