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

Synopsis

- The animals can move from one place to another in search of food and shelter and this is called locomotion.

- The vertebrates can be classified into five classes:
1. Pisces (Fishes)
2. Amphibia (Frogs)
3. Reptilia (Lizards and Snakes)
4. Aves (Birds)
5. Mammalia (Milk - nourishing animals)

- Pisces / Fishes
1. have streamlined body shape
2. Locomotion with the help of fins
3. Body covered with scales.
4. Breathe through gills.
5. Example: Dogfish, Catla

- Amphibia / Frogs
1. can live in water as well as on land.
2. always lay their eggs in water.
3. body covered by a slimy and slippery skin
4. breathe through lungs and skin.
5. Example: Frog and toads.

- Reptilia
1. Mostly live on land
2. Skin is dry and scaly
3. Breathe through lungs
4. Females lay eggs on land
5. Example: Lizards, snakes, crocodiles

- Aves / Birds
1. Body covered with feathers.
2. Have wings to fly.
3. Scales only on legs.
4. Have jaws with homy beak and have no teeth.
5. Example: Pigeon, hen

- Mammalia / Milk - nourishing animals.
1. Body covered with hairs.
2. Posses projecting external ears.
3. Give birth to young ones.
4. Mothers suckle their young ones.
5. Have a tail and four limbs. (Tail may become vestigeal)
6. Example: dog, tiger, man.

- Invertebrates can be further divided into nine groups.
1. Protozoans
2. Porifera
3. Coelenterates
4. platyhelminths
5. Nemathelminths
6. Annelids
7. Molluscs
8. Arthropoda
9. Echinoderms

- Coelenterates
1. Now called cnidarians
2. Body is tube like with only one opening called the mouth.
3. Mouth is surrounded by finger like processes called tentacles for catching food.
4. Body radially symmetrical
5. Example: Hydra, Sea-anemone, jelly fish

- Flatworms / Platyhelminths:
- are usually found as parasites in the bodies of other animals.
- Example: Tapeworm, liver fluke.
- Ascaris: The round worm is found in the small intestine of especially those who eat with the unwashed hands.

- Annelids:
1. are also called segmented worms
2. body is composed of rings or segments
3. have a body cavity.
4. have special organs of excretion called nephridia.
- Example: earthworm, leech.

- Arthropods can be further divided into
1. Crustacea : head and thorax are fused and have many jointed legs.
- Example: crab, lobsters etc.
2. Myriagoda: Body is divided into many segments and has one or two pairs of legs on each segment.
- Example: Centipede, millipede.
- Insecta: Body is divided into three regions - head, thorax and abdomen.
- Has three pairs of legs.
- Have two pairs of wings.
- Example: ant, housefly, butterfly.

- Arachnida: Head and thorax fused
- Have four pairs of legs.
- Have no wings.
- Example: Spider, Scorpion

- Echinoderms
- also called spiny-skinned animals.
- Body is star - like or ball - like
- Have no head or tail.
- Have no left or right side.
- Example: Starfish, sea urchin.
- A species can be defined as a group of individuals having common characteristics and which come together to produce young ones.
- Scientific name consists of two parts. The first part is the genus name while the second part is the species name.
- This type of naming is called Binomial nomenclature.
The animals can be classified also on the basis of their food habits into as follows.
(a) Herbivorous: Feed on plants e.g. cow, goat.
(b) Carnivorous: Feed on the flesh of other animals e.g. lion, tiger etc.
(c) Omnivorous: Feed on both plants as well as flesh of other animals, e.g. man, bear etc.
(d) Parasites: Live either inside or on the outside of the body of other animals and plants and take food from them.
- Example: Leech, mosquitoes etc.

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
Vertebrates are animals with a backbone and are divided into specific groups based on their body structure. In the image, whales and dolphins are mammals, crocodiles are reptiles, and the fish represents the Pisces class.
Teacher's Tip: Remember that even though they live in water, whales (1 and 2) are Mammals because they breathe air and nurse their young!
Exam Tip: Always capitalize the names of Classes like Mammalia or Pisces for scientific accuracy.

Review Questions

MULTIPLE CHOICE QUESTIONS

Question 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
Fishes like the Rohu are perfectly adapted to water using gills to extract oxygen. Their scales provide a protective layer while they swim through their aquatic environment.
Teacher's Tip: If you see "gills," think of "Fishes" (Pisces) immediately!
Exam Tip: Read the full question to ensure all criteria (aquatic, scaly, gills) are met by your choice.

(ii) The unicellular organism causing malaria -
(a) Amoeba
(b) Paramecium
(c) Euglena
(d) Plasmodium
Answer: (d) Plasmodium
Plasmodium is a microscopic parasite that enters the bloodstream through a mosquito bite. It is a single-celled protozoan that specifically targets red blood cells.
Teacher's Tip: Mosquitoes are just the "delivery truck," but Plasmodium is the actual "germ" causing the sickness.
Exam Tip: Don't confuse the vector (Mosquito) with the pathogen (Plasmodium).

(iii) Identify the animal which is not an Arthropoda -
(a) Prawn
(b) Butterfly
(c) Earthwonn
(d) Spider
Answer: (c) Earthwonn (Earthworm)
Arthropods have jointed legs and an exoskeleton, whereas earthworms are segmented worms. Earthworms belong to the phylum Annelida because they have soft, ringed bodies without hard outer shells.
Teacher's Tip: Arthropod means "jointed foot." If it doesn't have jointed legs, it's not an Arthropod!
Exam Tip: Watch out for spelling errors in textbooks; "Earthwonn" refers to the Earthworm.

(iv) Scientist who introduced binomial nomenclature is -
(a) Charles Darwin
(b) Carolus Linnaeus
(c) Robert Hooke
(d) Gregor Mendel
Answer: (b) Carolus Linnaeus
Linnaeus is known as the father of modern taxonomy for creating a two-part naming system. This system uses the Genus and Species names to give every organism a unique identity worldwide.
Teacher's Tip: Think of Binomial Nomenclature as a "First Name" (Genus) and "Last Name" (Species) for animals.
Exam Tip: Remember the spelling of "Linnaeus" as it is a common question in history of science.

Short Answer Questions

Question 1: Give two examples of each of the following:
(i) Amphibians:
Answer: 1. Frog 2. Toad
Amphibians are unique because they spend part of their life in water and part on land. Frogs and toads are the most recognizable members of this group.
Teacher's Tip: Think of amphibians as "double-life" creatures.
Exam Tip: Always number your examples clearly when asked for "two examples."

(ii) Segmented worms:
Answer: 1. Earthworm 2. Leech
These animals have bodies divided into many ring-like sections. This segmentation helps them move efficiently through soil or water.
Teacher's Tip: Look for the "rings" on their bodies to identify them as segmented worms.
Exam Tip: These belong to the group called "Annelids."

(iii) Reptiles:
Answer: 1. Snake 2. Lizard
Reptiles have dry, scaly skin and usually lay leathery eggs on land. Snakes and lizards are cold-blooded, meaning they rely on the sun to stay warm.
Teacher's Tip: Reptiles are "scaly" and "sunny" (they love sunbathing).
Exam Tip: Crocodiles and turtles are also great examples of reptiles.

(iv) Coelenterates:
Answer: 1. Hydra 2. Jellyfish
These are simple aquatic animals with stinging tentacles and a bag-like body. They are now officially referred to as Cnidarians.
Teacher's Tip: Think of them as "stinging water bags."
Exam Tip: Mentioning the word "tentacles" helps describe their body structure.

(v) Arthropods:
Answer: 1. Crab 2. Centipede
Arthropods are the largest group of animals, characterized by jointed legs and tough exoskeletons. Crabs live in water while centipedes are found on land.
Teacher's Tip: If it has "crunchy" armor on the outside, it's likely an Arthropod.
Exam Tip: This group includes insects, spiders, and crustaceans.

(vi) Flatworms:
Answer: 1. Tapeworm 2. Liverfluke
Flatworms have extremely thin, ribbon-like bodies and often live as parasites inside other animals. They lack a complex digestive system because they absorb nutrients directly from their host.
Teacher's Tip: Flatworms are as "flat as a pancake."
Exam Tip: These are scientifically known as Platyhelminthes.

Question 2: Give names of two animals which are found as parasites inside the human intestine.
Answer: (a) Tapeworm (b) Ascaris
These organisms live in the gut and steal nutrients from the food we eat. Ascaris is a roundworm, while the tapeworm is a long, flat parasite.
Teacher's Tip: Always wash your hands before eating to avoid Ascaris eggs!
Exam Tip: Differentiate them by shape: Tapeworm is flat, Ascaris is round.

Question 3: Name one example each of an animal which shows the following characteristics:
(i) Fixed animals with a pore-bearing body:
Answer: sponge
Sponges are the simplest multi-cellular animals and remain attached to one spot throughout their lives. Their porous bodies allow water to circulate, bringing in food and oxygen.
Teacher's Tip: Think of a bath sponge; the real animal has tiny holes just like that!
Exam Tip: These belong to the group called Porifera.

(ii) Star-shaped body:
Answer: Star-fish
Starfish belong to the Echinoderm group and typically have five arms radiating from a central point. They use tiny tube feet on their underside to move and catch prey.
Teacher's Tip: Look for the "spiny skin" to confirm it is an Echinoderm.
Exam Tip: Starfish are also called Sea Stars because they aren't technically fish.

(iii) Can live in water as well as on land:
Answer: Frog
Frogs use their moist skin to breathe underwater and lungs to breathe on land. This dual ability is the defining feature of the Amphibian class.
Teacher's Tip: Frogs are like the "transformers" of the animal world, changing as they grow.
Exam Tip: Mention "Amphibian" as the class when explaining this ability.

(iv) Has a flattened ribbon-like body:
Answer: Tapeworm
The tapeworm's flat body is an adaptation for living in the narrow spaces of the host's intestines. It can grow many meters long while staying incredibly thin.
Teacher's Tip: It looks just like a long piece of measuring tape!
Exam Tip: This is a classic example of the Platyhelminthes group.

Question 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) Porifera and Coelenterata.
Porifera:
1. Body is porous i. e. bears many tiny pores to draw water into the body cavity.
2. e.g. Sponge
Coelenterata:
1. Sac-like body with only one opening i.e. mouth.
2. e.g. Jelly fish, hydra, sea-anemone.
Porifera are basically living filters that stay in one place, while Coelenterata have a digestive sac and tentacles. Coelenterates are more complex because they have tissues and a specialized mouth.
Teacher's Tip: Porifera = Pores (holes); Coelenterata = Cavity (sac).
Exam Tip: Give examples for both to show a complete understanding of the difference.

(ii) Arthropoda and mollusca.
Arthropoda:
1. These are animals with jointed legs.
2. They have segmented body.
3. They may or may not have wings.
Example: Crab.
Mollusca:
1. Move with the help of a muscular foot.
2. Soft body which is not segmented.
3. Body enclosed in a hard shell Example: Octopus
Arthropods have hard outer "suits" and multiple legs, whereas mollusks have soft, squishy bodies. Most mollusks also have a protective shell, though some like the octopus do not.
Teacher's Tip: Arthropod = Jointed; Mollusk = Mushy/Soft.
Exam Tip: If an octopus is an example, mention that its "shell" is internal or absent to avoid confusion.

(iii) Invertebrates and Vertebrates
Invertebrates:
1. The animals which do not have a back bone.
2. They are further classified into nine groups.
Example: Octopus, Starfish.
Vertebrates:
1. The animals which have a back bone or a vertebral column.
2. They are further classified in to five groups.
Example: Human Being, Lizard.
Vertebrates have a strong internal skeleton that supports their body and protects their spinal cord. Invertebrates make up the vast majority of all animal species on earth.
Teacher's Tip: Touch your back; that bumpy bone makes you a Vertebrate!
Exam Tip: State the presence or absence of the "backbone" as the primary difference.

(iv) Platyheminthes and Nematoda
Platyheminthes:
1. Body thin and flattened.
2. Mostly live as parasites in the bodies of other animals (hosts) e.g. Tapeworm.
Nematoda:
1. Body is rounded and unsegmented.
2. Mostly live as parasites in the body of animals including humans. e.g. Roundworm commonly called Ascaris.
Platyhelminthes are the "flat" worms, while Nematodes are the "round" worms. While both can be parasites, their body shape is the easiest way to tell them apart under a microscope.
Teacher's Tip: Platy = Plate (flat); Nema = Noodle (round).
Exam Tip: Be sure to label which one is flat and which one is round clearly in your answer.

Question 5: Match the animals given under column A with their respective classification group given under column B -
Column A:
(i) Sponge,
(ii) Snail,
(iii) Butterfly,
(iv) Toad,
(v) Lizard,
(vi) Starfish
Column B:
(a) Amphibia,
(b) Reptilia,
(c) Echinodermata,
(d) Mollusca,
(e) Arthropoda,
(f) Porifera
Answer:
(i) Sponge - (f) Porifera
(ii) Snail - (d) Mollusca
(iii) Butterfly - (e) Arthropoda
(iv) Toad - (a) Amphibia
(v) Lizard - (b) Reptilia
(vi) Starfish - (c) Echinodermata
Matching these correctly requires knowing the specific physical traits of each phylum or class. For instance, a butterfly has jointed legs and an exoskeleton, making it a perfect match for Arthropoda.
Teacher's Tip: Focus on the most obvious trait, like the snail's soft body (Mollusca).
Exam Tip: Draw straight lines or write the letters clearly to avoid any ambiguity during matching.

Question 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 homy beaks
Class Aves consists of birds, which are uniquely designed for flight with light bodies and feathers. Their beaks are specialized tools that have evolved into various shapes depending on what they eat.
Teacher's Tip: Think of feathers as "super-light coats" and beaks as "pliers" without teeth!
Exam Tip: Mention that they have "no teeth" specifically when asked about their jaws.

Question 7: Categorise the following animals under their appropriate columns of classification.
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
Answer:
Worms: Arthropods (Note: Grasshopper, Butterfly, Scorpion, Honey bee - usually categorized as Arthropods, though the text groups them under "Worms" in this answer block), Ascaris, Liverfluke, Leech, Eathworm
Molluscs: Snail
Fishes: Rohu
Amphibians: Toad, Frog
Reptiles: Snake, Lizard, Turtle
Birds: Parrot, Pigeon
Mammals: Rat, Bat, Dog, Cattle, Cow, Rabbit, Monkey, Elephant
Classification organizes the animal kingdom based on shared biological traits and ancestry. It allows scientists to quickly identify and study creatures that have similar lifestyles and bodies.
Teacher's Tip: Bat is a Mammal, not a Bird, because it nurses its young and has hair!
Exam Tip: Be careful grouping Arthropods; while the key uses "Worms," they are technically a distinct phylum.

PRACTICE QUESTIONS

A. Fill in the blanks.

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.
Answer: (As filled above)
These blanks highlight the specialized biological terms used to describe different animal groups. Understanding words like "nephridia" and "exoskeleton" is key to advanced biology.
Teacher's Tip: Exoskeleton = "External Skeleton." It's armor on the outside!
Exam Tip: Pay attention to keywords like "radially" for Cnidarians to get the answer right.

B. Fill in the blanks

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.
Answer: (As filled above)
This section focuses on the specific details that separate different arthropod groups and mollusks. For example, counting legs is the quickest way to tell an insect from an arachnid.
Teacher's Tip: Insects = 6 legs; Arachnids = 8 legs.
Exam Tip: Make sure to specify "jointed legs" when describing Arthropods.

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.
Tentacles are used by cnidarians to paralyze prey and pull it toward their central mouth. These structures often contain stinging cells for defense and hunting.
Teacher's Tip: Think of the waving "arms" of a jellyfish; those are the tentacles!
Exam Tip: Pseudopodia are for Amoeba, not Cnidarians; don't mix them up.

2. Organs of excretion in annelids are
a. gills.
b. nephridia.
c. suckers
d. lungs.
Answer: b. nephridia.
Nephridia act like tiny kidneys, filtering out waste from the animal's body fluids. These organs are found in each segment of worms like the earthworm.
Teacher's Tip: Nephridia sounds a bit like "Nephrons" in human kidneys. That's because they do the same job!
Exam Tip: Associate "Annelid" with "Nephridia" for a quick memory link.

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.
The term "bilaterally symmetrical" means if you cut them down the middle, both sides look identical. Their segmentation is their most defining feature, looking like many rings stacked together.
Teacher's Tip: Bilateral = Two sides (Bi-Lateral).
Exam Tip: Be careful with the choice between "unsegmented" and "segmented"; Annelids are always segmented.

4. Scorpions and spiders are
a. crustaceans.
b. arachnids,
c. myriapods.
d. insects.
Answer: b. arachnids,
Arachnids are a class of arthropods that typically have eight legs and two main body parts. Unlike insects, they never have wings or antennae.
Teacher's Tip: Spiders have 8 legs, and Scorpions also have 8 legs (plus claws)!
Exam Tip: Always check the number of legs; if it is 4 pairs, it is an arachnid.

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 envionment increases.
Answer: c. does not change with the change in the temperature of the environment.
Warm-blooded animals, or endotherms, generate their own heat through metabolic processes. This allows them to stay active in both freezing cold and extreme heat.
Teacher's Tip: You are warm-blooded! Even on a snowy day, your body inside stays about $37^\circ C$.
Exam Tip: The scientific term for warm-blooded is "homeothermic."

6. Bones with large air cavities are present in
a. cnidarians.
b. fish.
c. annelids.
d. birds.
Answer: d. birds.
Pneumatic or hollow bones make the skeleton light enough for birds to take off and stay in the air. This is an essential adaptation for the Aves class to succeed in flight.
Teacher's Tip: Think of a hollow straw; it's light but strong, just like a bird's bone.
Exam Tip: Air cavities are unique to birds to reduce their total body mass.

7. Milk in the body of mammals is produced by
a. sweat glands.
b. salivary glands,
c. mammary lands (glands).
d. none of these
Answer: c. mammary lands (glands).
Mammary glands are the defining feature of the class Mammalia, providing a nutrient-rich food source for newborns. This allows mammals to care for their young longer than many other animal groups.
Teacher's Tip: "Mammal" comes from the word "Mammary." It's right there in the name!
Exam Tip: Note the typo in the text; "lands" should be written as "glands."

B. Fill in the blanks.

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
Answer: (As filled above)
These blanks reinforce the primary anatomical features used to classify the major phyla. For example, knowing that "vertebrae" make up the backbone explains where the group name "Vertebrates" comes from.
Teacher's Tip: One bone is a "vertebra," but many are "vertebrae."
Exam Tip: If the question asks about breathing in fish, always mention "dissolved oxygen" and "gills."

C. Match the following.
1. molluscs,
2. sponges,
3. flatworms,
4. mammals,
5. fish,
6. cnidarians,
7. arthropods
(a) feed milk to young ones, warm-blooded
(b) bag-like body with tentacles around the opening
(c) fins, gills and cold-blooded
(d) body with large opening and many small pores all over
(e) jointed legs, exoskeleton
(f) have only one opening
(g) hard shell, soft body
(h) cylindrical, unsegmented body with mouth at one end and anus at the posterior end
Answer:
1. molluscs - g. hard shell, soft body
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 - e. jointed legs, exoskeleton
Each group is matched to its most recognizable physical characteristic or lifestyle trait. Sponges are defined by their pores, while mammals are defined by their ability to nurse their young.
Teacher's Tip: Use a process of elimination; if you know fish have gills, cross off 'c' first!
Exam Tip: Ensure your matching corresponds to the phylum's scientific definition.

D. Differentiate between

Question 1: flatworms and roundworms
Answer:
Flatworms:
1. They are also called as Platyhelminthes.
2. They have flat ribbon like bodies.
3. They have a single opening to take in food and get rid of wastes.
4. e.g. Tapeworm, liver fluke.
Roundworms:
1. They are also called as Nemathelminthes.
2. They have cylindrical bodies.
3. They have two separate openings for the mouth and anus.
4. e.g. Pinworm, Ascaris.
The key difference is their digestive system: flatworms have one entrance/exit, while roundworms have a complete tube with two ends. Roundworms also have a more advanced "cylindrical" shape compared to the flat "ribbon" of Platyhelminthes.
Teacher's Tip: Flatworms are "2D," but Roundworms are "3D."
Exam Tip: Be sure to include scientific names like Platyhelminthes and Nemathelminthes for a full score.

Question 2: insects and crustaceans
Answer:
Insects:
1. Body of insects is divided into three regions-head, thorax and abdomen.
2. Most of them have three pairs of legs.
3. Most of them have wings.
4. e.g. Housefly, butterfly.
Crustaceans:
1. Head and thorax are fused in crustaceans.
2. They have many number of jointed legs.
3. Wings are absent.
4. e.g. Crab, lobster.
Crustaceans generally have more legs (usually 10) and live in the water, whereas insects usually have 6 legs and wings for land/air life. Crustaceans also have a fused "Cephalothorax" instead of a separate head and thorax.
Teacher's Tip: Insects = 3 body parts; Crustaceans = 2 main body parts (head and chest are stuck together).
Exam Tip: Use the absence or presence of wings as a major point of differentiation.

Question 3: amphibians and pisces
Answer:
Amphibians:
1. They can live both on land and in water.
2. Body of amphibians is covered with slimy- slippery skin.
3. They breathe through lungs and skin.
4. e.g. Frogs, toad.
Pisces:
1. They live in water.
2. Their body is covered with scales.
3. They breathe through gills.
4. e g. Shark, sea-horse.
Pisces (fish) are strictly aquatic and use gills to breathe, while amphibians can handle both environments by using lungs and skin. Fish skin is protected by tough scales, while amphibian skin must remain moist and slimy to help them breathe.
Teacher's Tip: Fish are "scaly," and Amphibians are "slimy."
Exam Tip: Mention the different respiratory organs (gills vs. lungs/skin) as it's a vital biological difference.

Question 4: aves and mammals
Answer:
aves:
1. Their body is covered with feathers.
2. Forelimbs are modified into wings to fly.
3. They have a horny beak with no teeth.
4. They lay eggs. with no teeth.
5. They don't have mammary glands.
6. They have hollow bones.
7. e.g. Crow, parrot.
Mammals:
1. They have hair on their body.
2. Forelimbs exist as hand, paw or hooves.
3. They have a mouth with teeth.
4. They give birth to young ones.
5. They have mammary glands i.e. they suckle their babies.
6. They have solid bones.
7. e.g. Humans, dog.
While both are warm-blooded, mammals produce milk and have hair, whereas birds have feathers and lay eggs. Birds' bodies are specialized for flight with hollow bones, while mammals have denser, solid bones.
Teacher's Tip: Birds = Feathers and Eggs; Mammals = Hair and Milk.
Exam Tip: Mammary glands are the single most important difference to mention for mammals.

Question 5: radially symmertical and bilaterally symmetrical body
Answer:
Radially symmertical:
1. It is a body that can be divided vertically into two equal halves along any plane passing through the central point.
2. Examples: Starfish, jellyfish, Hydra, corals, etc.
Bilaterally symmetrical body:
1. It is a body that can be divided into two equalhalves only through one plane.
2. Examples: Tapeworm,insects, lizard, humans, etc.
Radial symmetry is like a wheel; you can cut it many ways and get matching halves. Bilateral symmetry is like a mirror; there is only one specific way to cut it to make both sides match perfectly.
Teacher's Tip: Radial = Round/Circle; Bilateral = Box/Balance (Two matching sides).
Exam Tip: Use the "any plane" vs. "only one plane" distinction in your definition.

Question 6: warm-blooded and cold-blooded animals.
Answer:
Warm-blooded:
1. The temperature of the body of warm-blooded animals remains constant and does not change with the temperature of their surroundings.
2. Examples : Birds, humans, dogs, etc.

Cold-blooded animals:
1. The temperature of the body of cold-blooded animals changes with the temperature of their surroundings.
2. Examples: reptiles, fish, frogs, etc
Warm-blooded animals can live in cold climates because they make their own heat, but they must eat more food to power their internal "furnace." Cold-blooded animals are less active when it is cold because their bodies cool down along with the weather.
Teacher's Tip: Warm-blooded = Self-heating; Cold-blooded = Surroundings-heated.
Exam Tip: Mention that mammals and birds are the only warm-blooded groups.

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.
Answer: True.

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

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

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

5. Reptiles have a scaly skin. They lay eggs with a hard shell and are warm-blooded animals.
Answer: False: Reptiles have a scaly skin. They lay eggs with a hard shell and are cold-blooded animals.
(As corrected above)
Correcting false statements is a great way to confirm you understand the core rules of biology. For instance, knowing that an "exoskeleton" is on the outside helps you understand how insects grow and protect themselves.
Teacher's Tip: "Exo" means "Exit" or "Outside." An exoskeleton is an outside skeleton.
Exam Tip: Don't just write "False"; always provide the corrected fact for full marks.

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.
Ants, cockroaches, and dragonflies all have six legs and belong to the insect group. Spiders have eight legs and different body segments, placing them in the arachnid category.
Teacher's Tip: Count the legs! 6 = Insect, 8 = Spider/Arachnid.
Exam Tip: Give the specific scientific category (Arachnid vs. Insect) in your reason.

2. frog, shark, seahorse, carp
Answer: frog : frog is an amphibian while other three are fishes.
Sharks, seahorses, and carp are all members of the Pisces class and live exclusively in water. The frog is an amphibian that can live on land and has a very different life cycle.
Teacher's Tip: Think about where they live their whole lives; fish never leave the water!
Exam Tip: Identify the specific biological Class for each item to justify your choice.

3. snail, oyster, earthworm, octopus
Answer: earthworm : earthworm is an annelid whereas rest three are molluscs.
Snails, oysters, and octopuses all belong to the phylum Mollusca and share a soft body structure. The earthworm belongs to Annelida because its body is segmented into rings.
Teacher's Tip: Look for the "squishy" soft body of mollusks compared to the ringed body of the worm.
Exam Tip: Use terms like "Phylum Annelida" to sound more scientific.

4. snake, alligator, eel, turtle
Answer: eel: eel is a fish whereas the other three animals are reptiles.
Snakes, alligators, and turtles are scaly-skinned reptiles that breathe air with lungs. An eel looks like a snake but it has gills and fins, making it a fish.
Teacher's Tip: Don't let the "long shape" trick you! Check for gills versus lungs.
Exam Tip: Note that eels belong to the Pisces class, which makes them the odd one out among reptiles.

5. sea urchin, starfish, brittle star, jellyfish
Answer: jellyfish : jellyfish belongs to Cnidarians whereas the rest three are echinoderms.
Sea urchins and starfish have spiny skins and a unique water-vascular system typical of echinoderms. Jellyfish are much simpler, sac-like creatures with stinging tentacles.
Teacher's Tip: Spiny skin = Echinoderm; Stinging tentacles = Cnidarian.
Exam Tip: Use the name "Cnidarian" instead of the older term "Coelenterate" for modern accuracy.

6. jellyfish, Hydra, sea anemone, butterfly
Answer: butterfly : butterfly is an insect whereas rest three are Cnidarians.
Jellyfish, Hydra, and sea anemones are all simple, aquatic cnidarians with radial symmetry. The butterfly is a complex land-dwelling insect with an exoskeleton and jointed legs.
Teacher's Tip: If it flies, it definitely isn't a Cnidarian!
Exam Tip: Highlight the difference between an invertebrate with a skeleton (Arthropod) and one without (Cnidarian).

G Write short answers. -

Question 1: What are invertebrates ?
Answer: Invertebrates are animals without a backbone, e.g. Insects, worms.
They make up about 95 percent of all animal species on the planet. This huge group includes everything from tiny microscopic creatures to giant squids.
Teacher's Tip: Most animals in the world don't have a backbone!
Exam Tip: Always include an example like "Worms" or "Arthropods" when defining a group.

Question 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, e.g. Star fish, jelly fish. (b) Two examples of Platyhelminthes are tapeworms and liver fluke.
Radial symmetry is common in aquatic animals that stay in one place or drift with currents. Platyhelminthes are the group of flatworms, many of which live inside other organisms as parasites.
Teacher's Tip: Radial symmetry is like a pie; you can slice it many ways and get the same piece.
Exam Tip: For part (a), the phrase "any plane passing through the center" is the key part of the definition.

Question 3: Name the special organs of excretion in annelids ?
Answer: Annelids have a special organ of excretion called nephridia.
These tiny tubes remove metabolic waste from the animal's body to keep it healthy. They are much simpler than our kidneys but do a similar job for the worm.
Teacher's Tip: Nephridia = Worm Kidneys.
Exam Tip: Spelling counts! Practice writing "Nephridia" correctly.

Question 4: What is an exoskeleton ? How is it different from a backbone ?
Answer: Exoskeleton is a tough outer covering of an animal body. e.g. Crab, lobster have exoskeletons.
Exoskeleton
1. It is a rigid external covering of the body that provides support and protection to the body.
2. It is present in invertebrates.
3. Examples : Crab, lobster, spiders, scorpions, etc.
4. It is in the form of shell, or scales or feathers, etc.
Backbone
1. It is an internal skeleton (endoskeleton) that provides support and protection to the body.
2. It is present in vertebrates.
3. Examples: Humans, fish lions, dogs, etc.
4. It is made up of number of vertebral joined to form a vertebral column.
An exoskeleton is like a suit of armor on the outside, whereas a backbone is a support rod on the inside. Animals with exoskeletons usually have to shed them to grow larger, a process called molting.
Teacher's Tip: Exoskeleton = Outside Skeleton; Endoskeleton (Backbone) = Inside Skeleton.
Exam Tip: Be sure to clarify that vertebrates have endoskeletons while many invertebrates have exoskeletons.

Question 5: Write two examples of myriapods.
Answer: Centipede and Millipede
Myriapods are arthropods with many body segments and many legs. Centipedes have one pair of legs per segment, while millipedes have two pairs.
Teacher's Tip: Centi = 100; Milli = 1,000. They don't actually have that many legs, but they have a lot!
Exam Tip: Group these under Arthropods if asked for a larger classification.

Question 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.
Hollow bones are strong but weigh very little, which is crucial for getting off the ground. Most other land animals have marrow-filled bones which are much heavier but better for supporting large weights.
Teacher's Tip: Imagine trying to fly with a backpack full of rocks; that's what solid bones would feel like to a bird!
Exam Tip: Use the term "pneumatic bones" if you want to use the formal scientific name for hollow bones.

H. Answer in detail.

Question 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, cylinderical 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.
Annelids are much more complex than flatworms because they have a true body cavity and a circulatory system. The rings you see on an earthworm are actually partitions that divide its internal organs into sections.
Teacher's Tip: The "segments" make the worm look like it is wearing lots of tiny bracelets!
Exam Tip: Mentioning "bilateral symmetry" and "segmentation" together defines the phylum perfectly.

Question 2: Name the different classes of arthropods. Write one characteristic feature of each class.
Answer: Arthropods are inverteberates with jointed legs, segmented body and bilaterally symmetrical body which is divided into head, thorax and abdomen. Anthropods 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 sprimps.
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.
Arthropods are successful because they have specialized body parts for every possible environment. From deep-sea crabs to flying bees, their jointed legs and armor protect them everywhere.
Teacher's Tip: Use leg counts to sort them: 6 = Insect, 8 = Arachnid, 10+ = Crustacean, Many = Myriapod.
Exam Tip: Make sure you mention the body division (like head-thorax-abdomen) for the Insect class.

Question 3: Write two characteristics each of a. birds, b. amphibians, c. reptiles, d. mammals
Answer:
Two characteristics of:
a. Birds:
1. They are warm blooded animals with feathers on their body.
2. They have homy 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.
These characteristics are the "biological rules" that scientists use to group all vertebrates. Each class has developed unique ways to breathe, move, and raise their babies in their specific habitats.
Teacher's Tip: Think of it as a ladder of complexity, with mammals and birds at the "warm" top.
Exam Tip: For reptiles, always emphasize "dry, scaly skin" to distinguish them from amphibians.

Question 4: List two notable characteristic of birds which is not found in any other group of animals ?
Answer: 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. Also, their skeleton is light as their bones have air cavities and are hollow. They also have beaks with no teeth.
Feathers provide insulation to keep birds warm and the surface area needed for flight. No other modern animal has true feathers, making this the most important trait for identifying a bird.
Teacher's Tip: If it has feathers, it is 100 percent a bird!
Exam Tip: Don't just say "flight," because bats fly too. Focus on "feathers" and "hollow bones."

Question 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.
The large, developed brain in mammals allows for complex problem-solving and social behaviors. Their method of internal development and nursing ensures a very high survival rate for their offspring.
Teacher's Tip: Advanced doesn't just mean "better," it means having the most complex internal systems!
Exam Tip: Highlight the "complex brain" as the reason for their "advanced" status.

Question 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.
This classification tells us where an animal sits in a food chain. Producers (plants) are eaten by herbivores, which are then eaten by carnivores, while omnivores can eat from both levels.
Teacher's Tip: Herb = Plant; Carn = Meat; Omni = Everything.
Exam Tip: Always include an example for each category to show you understand how it applies to real animals.

Question 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.
e. g. : Lizard, crocodile.
Reptiles were the first vertebrates to successfully live their entire lives on land. Their leathery eggs protect the embryo from drying out, even in very dry environments.
Teacher's Tip: Reptiles are built for the desert; their skin and eggs keep water in!
Exam Tip: Make sure to mention "cold-blooded" (ectothermic) as a primary trait.

Question 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.
As water passes over the thin membranes of the gills, oxygen enters the blood and carbon dioxide leaves. This process is very efficient, allowing fish to "breathe" without needing to come to the surface.
Teacher's Tip: Gills are like the "opposite" of lungs; they work only when wet!
Exam Tip: Use the term "dissolved oxygen" to describe what the fish is actually taking from the water.

Question 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.
This lightweight skeleton is an adaptation that reduces the amount of energy a bird needs to stay airborne. In solid-boned animals, the bones provide more weight-bearing strength but are too heavy for flapping flight.
Teacher's Tip: Bird bones are like the "struts" of a plane - strong but mostly air!
Exam Tip: If the question asks "why" birds have hollow bones, the answer must include "to make them light for flight."

Question 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 mollusc ? 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.
The presence of a shell, even if it is hidden inside the body, is a key anatomical feature of many mollusks like the cuttlefish. Cnidarians are much simpler and never produce a hard calcium-based shell structure.
Teacher's Tip: This animal is likely a squid or cuttlefish! They look like cnidarians but have more complex organs and an internal "bone" (shell).
Exam Tip: Use the "presence of a shell" as your main piece of evidence for classification.

Question 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 (reptiles).
Warm-blooded animals use energy from food to maintain a steady heat, while cold-blooded animals rely on the environment. This means a lizard might become sluggish on a cold morning, but a bird will stay active.
Teacher's Tip: Warm-blooded = Built-in heater; Cold-blooded = Needs a heat lamp (the sun).
Exam Tip: Mention that warm-blooded animals are also called "endotherms" for higher-level answers.

I. Classify the given animals into different categories indicated.

Question 1: Jellyfish, liver fluke, pinworm, Ascaris, tapeworm, Hydra, sea anemone into cnidarians, Platyhelminthes and Nemathelminthes.
Answer:
- Cnidarians - Jelly fish, Hydra, sea anemone.
- Platyhelminthes - Liver fluke, tapeworm.
- Nemathelminthes - Pinworm, Ascaris.
Sorting these helps identify which worms are flat (Platy) versus round (Nemat). It also separates the stinging, sac-like creatures into the Cnidarian group.
Teacher's Tip: Platyhelminthes = "Flat as a plate."
Exam Tip: Practice spelling these long Phylum names so you can write them quickly in a test.

Question 2: Crab, millipede, butterfly, ant, scorpion, centipede, spider, lobster, moth, prawn into arachnids, crustaceans, myriapods and insects.
Answer:
- Arachnids - Scorpion, spider.
- Crustaceans - Crab, lobster, prawn.
- Myriapods - Millipede, centipede.
- Insects - Fly (Note: list uses fly/moth), ant, moth.
This classification breaks down the massive Phylum Arthropoda into smaller, more specific groups. Each group has a unique number of legs and body segments.
Teacher's Tip: If it lives in the sea and has a shell, it's likely a Crustacean!
Exam Tip: Group ants, moths, and flies together because they all have six legs.

J. Give reasons for the following.

Question 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.
Because their metabolism is tied to the outside temperature, fish can survive in freezing water as long as they don't freeze solid. They simply slow down their movements to save energy as the water cools.
Teacher's Tip: In winter, fish are like they are in "slow-motion" because of the cold water.
Exam Tip: Use the term "ectothermic" to describe why the fish's temperature follows the water's lead.

Question 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, e.g. frog.
Since amphibian eggs don't have a hard shell, they would dry out and die on land. Also, most amphibians need to keep their skin wet so they can breathe through it easily.
Teacher's Tip: They are land animals with "water-loving" skin and babies.
Exam Tip: Mention both "reproduction" and "moist skin" to give a complete reason.

K. Given below are groups of animals, and their characteristics features. Some of the features are incorrect. Identify the odd one out in each.
1. Porifera: porous animals, have tentacles, fixed to surface
2. Amphibia: cold blooded, lungs in adults, scaly skin
3. Aves: cold blooded, wings, feathers, bones with large air spaces
4. Pisces: live in water, scaly skin, warm blooded, fins for swimming
Answer:
1. Porifera: odd one out - have tentacles
2. Amphibia: odd one out - scaly skin
3. Aves: odd one out - cold blooded
4. Pisces: odd one out - warm blooded
Correcting these features is vital because each animal group is defined by its unique "rules." For instance, only reptiles and fish have scales; amphibians have smooth, wet skin.
Teacher's Tip: Only mammals and birds are warm-blooded; everyone else is cold-blooded!
Exam Tip: When identifying the "odd one out" in a list of traits, look for the one that describes a completely different group of animals.