ICSE Solutions for Chapter 3 Classification of Animals Class 7 Biology Selina Publisher


Activity 3

Look at the four animals shown alongside.
Which four classes of vertebrates are represented by them ? Name these classes.
Answer
1. Class Mammalia
2. Class Mammalia
3. Class Reptilia
4. Class Pisces

Review Questions


Multiple Choice Questions


1. Tick (✓) the appropriate answer:
(i) Identify the aquatic animal with scaly skin which breathe with gills –
(a) Rohu
(b) Tortoise
(c) Sparrow
(d) Rat
Answer
(a) Rohu

(ii) The unicellular organism causing malaria –
(a) Amoeba
(b) Paramecium
(c) Euglena
(d) Plasmodium
Answer
(d) Plasmodium

(iii) Identify the animal which is not an Arthropoda —
(a) Prawn
(b) Butterfly
(c) Earthworm
(d) Spider
Answer
(c) Earthworm

(iv) Scientist who introduced binomial nomenclature is —
(a) Charles Darwin
(b) Carolus Linnaeus
(c) Robert Hooke
(d) Gregor Mendel
Answer
(b) Carolus Linnaeus

Short Answer Questions


1. Give two examples of each of the following:
(i) Amphibians
(ii) Segmented worms
(iii) Reptiles
(iv) Coelenterates
(v) Arthropods
(vi) Flatworms
Answer

(i) Amphibians:
  1. Frog
  2. Toad
(ii) Segmented worms:
  1. Earthworm
  2. Leech
(iii) Reptiles:
  1. Snake
  2. Lizard
(iv) Coelenterates:
  1. Hydra
  2. Jellyfish
(v) Arthropods:
  1. Crab
  2. Centipede
(vi) Flatworms:
  1. Tapeworm
  2. Liverfluke

2. Give names of two animals which are found as parasites inside the human intestine.
Answer
  1. Tapeworm
  2. Ascaris

3. Name one example each of an animal which shows the following characteristics:
(i) Fixed animals with a pore-bearing body:
(ii) Star-shaped body:
(iii) Can live in water as well as on land:
(iv) Has a flattened ribbon-like body:
Answer
(i) Fixed animals with a pore-bearing body: sponge
(ii) Star-shaped body: Star-fish
(iii) Can live in water as well as on land: Frog
(iv) Has a flattened ribbon-like body: Tapeworm

4. Write one difference each between the following pairs:
(i) Porifera and Coelenterata.
(ii) Arthropoda and mollusca.
(iii) Invertebrates and Vertebrates
(iv) Platyheminthes and Nematoda
Answer
(i) Difference between Porifera and Coelenterata.

Porifera

Coelenterata

Body is porous i.e. bears many tiny pores to draw water into the body cavity.

Sac-like body with only one opening i.e. mouth.

Example: Sponge

Examples: Jelly fish, hydra, sea-anemone

(ii) Difference between Arthropoda and mollusca.

Arthropoda

Mollusca

1. These are animals with exoskeleton (vertebrate).

1. Move with the help of a muscular foot.

2. They have segmented body.

2. Soft body which is not segmented.

3. They may or may not have wings.

3. Body enclosed in a hard shell.

Example: Crab

Example: Octopus

(iii) Difference between Invertebrates and Vertebrates

Invertebrates

Vertebrates

1. The animals which do not have a back bone.

1. The animals which have a back bone or a vertebral column.

2. They are further classified into nine groups.

2. They are further classified in to five groups.

Example: Octopus, Starfish.

Example: Human Being, Lizard.

(iv) Difference between Platyheminthes and Nematoda

Platyheminthes

Nematoda

 

1. Body thin and flattened.

1. Body is rounded and unsegmented.

2. Mostly live as parasites in the bodies of other animals (hosts)

2. Mostly live as parasites in the body of animals including humans.

Example: Tapeworm.

Example: Roundworm commonly called Ascaris.

5. Match the animals given under column A with their respective classification
group given under column B 
Column A Column B
(i) Sponge (a) Amphibia
(ii) Snail (b) Reptilia
(iii) Butterfly (c) Mollusca
(iv) Toad (d) Arthropoda
(v) Lizard (e) Porifera
Answer
Column A Column B
(i) Sponge (e) Porifera
(ii) Snail (c) Mollusca
(iii) Butterfly (d) Arthropoda
(iv) Toad (a) Amphibia
(v) Lizard (b) Reptilia

6. Write the characteristics of class Aves with reference to their body covering and jaws.
Answer
The characteristics of class Aves are:
  1. Body is covered with feathers.
  2. They have wings to aid flying
  3. They have scales on legs.
  4. They have no teeth.
  5. They have jaws provided with horny beaks

7. Categories the following animals under their appropriate columns of classification.

Animals

Dog, Grasshopper, Rat, Scorpion, Toad, Butterfly, Lizard, Turtle, Frog, Bat, Snail, Honey bee, Pigeon, Liverfluke, Leech, Cattle, Snake, Rohu, Parrot, Ascaris, Earthworm, Cow, Rabbit, Monkey, Elephant

Classification

Worms, Mollusca, Fishes, Amphibians, Reptiles, Birds, Mammals
Answer
Worms: Arthropods, Butterfly, Ascaris, Scorpion, Honey bee, Liverfluke, Leech, grasshopper, Earthworm
Mollusca: Snail
Fishes: Rohu
Amphibians: Toad, Frog
Reptiles: Snake, Lizard, Turtle
Birds: Parrot, Pigeon
Mammals: Rat, Bat, Dog, Cattle, Cow, Rabbit, Monkey, Elephant

Practice Questions


A. Fill in the blanks.

1. _______ do not have a backbone, while vertebrates have it.
2. Cnidarians have _______ symmetrical body.
3. _______ and liver fluke live in the intestines of human beings and cattle.
4. _______ are considered as farmers’ friend of farmers.
5. Annelids have special organs of excretion called ______.
6. ________ live in the digestive tract of many vertebrates including human beings.
7. Most arthropods have a tough outer body covering called ________.
Answer
1. Invertebrates do not have a backbone, while vertebrates have it.
2. Cnidarians have radially symmetrical body.
3. Tapeworm and liver fluke live in the intestines of human beings and cattle.
4. Earthworms are considered as farmers’ friend of farmers.
5. Annelids have special organs of excretion called nephridia.
6. Tapeworms live in the digestive tract of many vertebrates including human beings.
7. Most arthropods have a tough outer body covering called exoskeleton.

B. Fill in the blanks

1. _______ have three pairs of jointed legs.
2. Some _______ have two pairs of legs per segment.
3. A ______ has an external coiled shell.
4. ______ is an example of a crustacean.
Answer
1. Insects have three pairs of jointed legs.
2. Some myriapods have two pairs of legs per segment.
3. A snail has an external coiled shell.
4. Lobster is an example of a crustacean.

Exercises


A. Select the most appropriate answer.

1. The finger-like structures present around the mouth of cnidarians are called
a. pseudopodia.
b. tentacles.
c. spines.
d. bristles.
Answer
b. tentacles.

2. Organs of excretion in annelids are
a. gills.
b. nephridia.
c. suckers
d. lungs.
Answer
b. nephridia.

3. Annelids have a
a. soft, unsegmented, bilaterally symmetrical body.
b. soft, cylindrical, segmented, bilaterally symmetrical body.
c. soft, segmented, bilaterally symmetrical body.
d. soft, segmented, laterally symmetrical body.
Answer
c. soft, segmented, bilaterally symmetrical body.

4. Scorpions and spiders are
a. crustaceans.
b. arachnids.
c. myriapods.
d. insects.
Answer
b. arachnids.

5. The body temperature of warm-blooded animals
a. keeps fluctuating.
b. changes according to the temperature of the environment.
c. does not change with the change in the temperature of the environment.
d. decreases when the temperature of the environment increases.
Answer
c. does not change with the change in the temperature of the environment.

6. Bones with large air cavities are present in
a. cnidarians.
b. fish.
c. annelids.
d. birds.

7. Milk in the body of mammals is produced by
a. sweat glands.
b. salivary glands,
c. mammary lands.
d. none of these.
Answer
c. mammary lands.

B. Fill in the blanks.
1. The animals without a backbone whose body is soft and often covered by a hard shell are _______.
2. Invertebrates with jointed legs belong to _______.
3. The backbone of vertebrates is made up of a number of small bones called _______.
4. Fishes obtain oxygen from water through _______.
5. Vertebrates which spend a part of their life on land but reproduce in water are called ________.
Answer
1. The animals without a backbone whose body is soft and often covered by a hard shell are molluscs.
2. Invertebrates with jointed legs belong to arthropods.
3. The backbone of vertebrates is made up of a number of small bones called vertebrae.
4. Fishes obtain oxygen from water through gills.
5. Vertebrates which spend a part of their life on land but reproduce in water are called amphibian.

C. Match the following.
Group   Characteristics
1. Molluscs a. Feed milk to young ones warm-blooded
2. Sponges b. Bag-like body with tentacles around the opening
3. Flatworms c. fins, gills and cold-blooded
4. mammals d. body with large opening and many small pores all over 
5. Fish e. jointed legs, exoskeleton
6. Cnidarians f. have only one opening
7. Arthropods g. hard shell, soft body
Answer
Group   Characteristics
1. Molluscs e. jointed legs, exoskeleton
2. Sponges d. body with large opening and many small pores all over 
3. Flatworms f. have only one opening
4. mammals a. Feed milk to young ones warm-blooded
5. Fish c. fins, gills and cold-blooded
6. Cnidarians b. Bag-like body with tentacles around the opening
7. Arthropods g. hard shell, soft body

D. Differentiate between
1. Flatworms and Roundworms
2. Insects and Crustaceans
3. Amphibians and Pisces
4. Aves and Mammals
5. Radially Symmetrical and Bilaterally Symmetrical body
6. Warm-blooded and Cold-blooded animals
Answer

1. Difference between Flatworms and Roundworms
Flatworms Roundworms
1. They are also called as Platyhelminthes. 1. They are also called as Nemathelminthes.
2. They have flat ribbon like bodies. 2. They have cylindrical bodies.
3. They have a single opening to take in food and get rid of wastes. 3. They have two separate openings for the mouth and anus.
4. e.g. Tapeworm, liver fluke. 4. e.g. Pinworm, Ascaris.
 
2. Difference between Insects and Crustaceans
Insects Crustaceans
1. Body of insects is divided into three regions-head, thorax and abdomen. 1. Head and thorax are fused in crustaceans.
2. Most of them have three pairs of legs. 2. They have many number of jointed legs.
3. Most of them have wings. 3. Wings are absent.
4. e.g. Housefly, butterfly. 4. e.g. Crab, lobster.
 
3. Difference between Amphibians and Pisces
Amphibians Pisces
1. They can live both on land and in water. 1. They live in water.
2. Body of amphibians is covered with slimy- slippery skin. 2. Their body is covered with scales.
3. They breathe through lungs and skin. 3. They breathe through gills.
4. e.g. Frogs, toad. 4. e.g. Shark, sea-horse.
 
4. Difference between Aves and Mammals
Aves Mammals
1. Their body is covered with feathers. 1. They have hair on their body. 
2. Forelimbs are modified into wings to fly. 2. Forelimbs exist as hand, paw or hooves.
3. They have a horny beak with no teeth. 3. They have a mouth with teeth.
4. They lay eggs. with no teeth. 4. They give birth to young ones.
5. They don’t have mammary glands.
 5. They have mammary glands i.e. they suckle their babies.
6. They have hollow bones. 6. They have solid bones.
7. e.g. Crow, parrot. 7. e.g. Humans, dog.
 
5. Difference between Radially symmetrical and Bilaterally symmetrical body
Radially symmetrical Bilaterally symmetrical 
1. It is a body that can be divided vertically into two equal halves along any plane passing through the central point. 1. It is a body that can be divided into two equal halves only through one plane.
2. Examples: Starfish, jellyfish, Hydra, corals, etc. 2. Examples: Tapeworm, insects, lizard, humans, etc.
 
6. Difference between Warm-blooded and Cold-blooded animals.
Warm-blooded Cold-blooded
1. The temperature of the body of warm-blooded animals remains constant and does not change with the temperature of their surroundings. 1. The temperature of the body of cold-blooded animals changes with the temperature of their surroundings.
2. Examples: Birds, humans, dogs, etc.  2. Examples: reptiles, fish, frogs, etc.

E. State if the following statements are true or false. Correct the statement if it is false.

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

2. Arthropods have a soft, outer covering called endoskeleton.
False 
Arthropods have a tough, outer covering called exoskeleton.

3. Insects belong to the amphibian group of animals.
False 
Insects belong to the arthropod group of animals.

4. Fish have fins, scales and they breathe through gills.
True

5. Reptiles have a scaly skin. They lay eggs with a hard shell and are warm-blooded animals.
False  
Reptiles have a scaly skin. They lay eggs with a hard shell and are cold-blooded animals.

F. Find the odd one out. Give reasons.

1. Ant, cockroach, spider, dragonfly
Answer
spider: spider is odd one out because it is an arachnid whereas rest three are insects.

2. Frog, shark, seahorse, carp
Answer
frog: frog is an amphibian while other three are fishes.

3. Snail, oyster, earthworm, octopus
Answer
earthworm: earthworm is an annelid whereas rest three are Molluscs.

4. Snake, alligator, eel, turtle
Answer
eel: eel is a fish whereas the other three animals are reptiles.

5. Sea urchin, starfish, brittle star, jellyfish
Answer
jellyfish: jellyfish belongs to Cnidarians whereas the rest three are echinoderms. 

6. jellyfish, Hydra, sea anemone, butterfly
Answer
butterfly : butterfly is an insect whereas rest three are Cnidarians.

G. Write short answers. 


1. What are invertebrates ?
Answer
Invertebrates are animals without a backbone, e.g. Insects, worms.

2. (a) What do you mean by radially symmetrical body ? 
(b) Give two examples of Platyhelminthes.
Answer
(a) Radially symmetrical body is the body that can be divided into two identical halves
along any plane. Examples: Star fish, jelly fish.
(b) Two examples of Platyhelminthes are tapeworms and liver fluke.

3. Name the special organs of excretion in annelids?
Answer
Annelids have a special organ of excretion called nephridia.

4. What is an exoskeleton ? How is it different from a backbone ?
Answer
Exoskeleton is a tough outer covering of an animal body.
Difference between Exoskeleton and Backbone

Exoskeleton

Backbone

1. It is a rigid external covering of the body that provides support and protection to the body.

1. It is an internal skeleton (endoskeleton) that provides support and protection to the body.

2. It is present in invertebrates.

2. It is present in vertebrates.

3. It is in the form of shell, or scales or feathers, etc.

3. It is made up of number of vertebral joined to form a vertebral column.

4. Examples: Crab, lobster, spiders, scorpions, etc.

4. Examples: Humans, fish lions, dogs, etc.

5. Write two examples of myriapods.
Answer
Centipede and Millipede

6. How are the bones of birds different from those of other vertebrates ?
Answer
The bones of birds have large air cavities (are hollow) and hence are light. This enables them to fly. On the other hand, bones of other vertebrates are dense and solid and form a heavy skeleton.

H. Answer in detail.


1. Write a short note on annelids.
Answer
Annelids are invertebrates which include segmented worms. They are found in moist soil and pond water. They have a soft, cylindrical and bilaterally symmetrical body. Their body surface is marked into ring-like compartments called segments which help in movement. They have a special organ of excretion called nephridia. 
Examples : Leech and earthworm.

2. Name the different classes of arthropods. Write one characteristic feature of each class.
Answer
Arthropods are inverteberates with joined legs, segmented body and bilaterally symmetrical body which is divided into head, thorax and abdomen.

Arthropods are further classified into:
  1. Arachnids – They have fused head and thorax, four pairs of legs, hard exoskeleton, no wings and antennae. Examples : Scorpions and spiders.
  2. Crustaceans – They have fused head and thorax, appendages on all segments, variable number of jointed legs and two pairs of antennae extending from the head. Examples: lobsters and shrimps.
  3. Myriapods – Body divided into large number of segments and have two pairs of legs per segment (example: millipede) or one pair of legs per segment (Example: centipede). Number of legs may vary from 20 to 200.
  4. Insects – Their body is divided into head, thorax and abdomen. They have three pairs of legs, two pairs of wings (some have one pair or none) and a pair of antennae. Examples : ants and butterflies.

3. Write two characteristics each of
a. birds
b. amphibians .
c. reptiles
d. mammals
Answer
a. Two characteristics of Birds:
  1. They are warm blooded animals with feathers on their body.
  2. They have horny beak and do not have teeth.
b. Amphibians:
  1. They are animals which can live both on land and in water.
  2. They breathe through lungs and skin.
c. Reptiles:
  1. They are land animals with dry scaly skin on then- body.
  2. They breathe through lungs.
d. Mammals:
  1. They are warm blooded animals with hair on their body.
  2. They give birth to babies and are the only animals that produce milk for nourishing their young ones.

4. List two notable characteristic of birds which is not found in any other group of animals?
Answer
  1. The most notable characteristic of birds which is not found in any other group of animals is the presence of feathers. They are the only animals on earth which have a backbone as well as feathers which cover their entire body.
  2. Also, their skeleton is light as their bones have air cavities and are hollow. They also have beaks with no teeth.

5. Why are mammals regarded as the most advanced animals ?
Answer
Mammals are regarded as the most advanced animal because they are the most recently evolved vertebrates who have the most advanced, complex brain, are the only animals that produce milk for their young ones and give birth to babies.

6. How will you classify animals according to the food they eat ?
Answer
On the basis of food they eat, animals are classified as –
1. Herbivores – They eat only green plants as food. Examples : cow, goat, etc.
2. Carnivores – They eat only the flesh of other animals as food. Examples : tiger and lion, etc.
3. Omnivores – They eat both plants as well as the flesh of other animals as food.
Examples : bear, crow, man, etc.

7. List four characteristics of reptiles.
Answer
Four characteristics of reptiles are :
  1. They are cold blooded vertebrates.
  2. They have dry skin covered with scales.
  3. They lay eggs that have leathery shells.
  4. They breathe through lungs.
Examples: Lizard, crocodile.

8. How do fish exchange gases ?
Answer
Fish exchange gases in water through gills. Gills enable the fish to obtain oxygen dissolved in the water.

9. How are the bones of birds different from those of other vertebrates ?
Answer
The bones of the birds are hollow and filled with large air cavities. This makes their skeleton light and enable them to fly. On the other hand, bones of other vertebrates are dense and solid and form a heavy skeleton.

10. You are asked to classify an animal in the correct group. The 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 molluscs? Explain your answer.
Answer
The animal is a mollusc because although both molluscs and cnidarians have soft bodies and tentacles but only molluscs have shells (internal or external) and cnidarians don’t.

11. How do warm-blooded and cold-blooded animals differ?
Answer
Warm blooded animals are those animals whose body temperature remain same and is not affected by the temperature of their surroundings, e.g. Birds, Humans. Cold blooded animals change their body temperature with the change in the temperature of their surroundings, e.g. Fish, reptil

I. Classify the given animals into different categories indicated.


1. Jellyfish, liver fluke, pinworm, Ascaris, tapeworm, Hydra, sea anemone into cnidarians,
Platyhelminthes and Nemathelminthes.
Answer
(i) Cnidarians - Jelly fish, Hydra, sea anemone.
(ii) Platyhelminthes - Liver fluke, tapeworm.
(iii)  Nemathelminthes - Pinworm, Ascaris.

2. Crab, millipede, butterfly, ant, scorpion, centipede, spider, lobster, moth, prawn into arachnids, crustaceans, myriapods and insects.
Answer
(i) Arachnids - Scorpion, spider.
(ii)  Crustaceans - Crab, lobster, prawn.
(iii) Myriapods - Millipede, centipede.
(iv) Insects - Fly, ant, moth.

J. Give reasons for the following.


1. What happens to the body temperature of a fish when the temperature of water drops ?
Answer
Since fish are cold blooded animals, the temperature of their body also drops when the
temperature of water drops.

2. Why do adult amphibians tend to stay near water ?
Answer
Adult amphibians tend to stay near water because they have to return to water to reproduce and they always lay their eggs in water.
Example: frog. 

K. Given below are groups of animals, and their characteristics features. Some of the features are incorrect. Identify the odd one out in each.
Group Characteristic Features Odd one out
Porifera Porous animals, have tentacles, fixed to surface  
Amphibia Cold blooded, lungs in adults, scaly skin  
Aves  Cold blooded, wings feathers, bones with large air spaces  
Pisces Live in water, scaly skin, warm blooded, fins for swimming  
Answer
Group Characteristic Features Odd one out
Porifera Porous animals, have tentacles, fixed to surface  Have tentacles
Amphibia Cold blooded, lungs in adults, scaly skin  Scaly skin
Aves  Cold blooded, wings feathers, bones with large air spaces  Cold blooded
Pisces Live in water, scaly skin, warm blooded, fins for swimming  Warm blooded

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