ICSE Class 6 Biology Chapter 3 Classification of Animals

Classification Of Animals

Syllabus

A. Animals: Vertebrates and invertebrates. Fish, amphibians, reptiles, birds, mammals. Molluscs, worms (without legs). Arthropods (with jointed legs and bodies) - insects, arachnids, crustaceans, millipedes/centipedes. Common examples of these categories.

B. Classification and the need for it - a few examples of scientific names. Classification may be based on several criteria; a group of items may be classified in many different ways - what are other possible ways of classifying animals? Open-ended practical exercises based on actual observations of students.

Practical observation of live/preserved specimens of animals (Caution: Students should be instructed not to pick up or handle any unknown animals. Many invertebrates can sting; others are poisonous.)

Drawing simple animals from specimens - live and preserved (Drawing from specimens is an essential skill in which students need practice).

Groups of students may create bulletin board displays on common Indian animals: endangered species; unusual animals - modifications and adaptation to their life-style/environment.

Teacher's Note

Classification helps us organize thousands of different animals into manageable groups, much like how we organize our books by genre or subject in a library for easy finding.

There are thousands and thousands of different kinds of animals found on earth. These animals are of various shapes and sizes. Their sizes range from the tiny Amoeba (which we cannot see through our naked eyes) to giant-sized elephants, whales and sharks. Despite vast differences in their sizes, they all are animals.

Though there are many different features among animals, they show certain common features. For example, animals cannot prepare their food by themselves, they feed either on plants or on other animals. They are heterotrophic.

Most animals move from one place to another mainly in search of food or for shelter. Such a movement is called locomotion.

Classification Of Animals

Depending on the presence and absence of backbone, animals are classified into two categories (A) vertebrates and (B) invertebrates.

A. Vertebrates

Animals with a backbone (vertebral column) are called vertebrates. They are classified into five groups (classes):

(i) Class Pisces (Fishes)

The main features/characteristics of pisces are as follows:

Aquatic animals with a streamlined body (narrowed at both ends).

Swim with the help of fins.

Body covered with scales.

Breathe through gills.

Common examples: Almost all fishes (Fig. 3.1) and to name a few Rohu, Catla, Mahasheer, Electric ray fish, Dogfish.

Figure 3.1 shows Rohu, Catla, Electric ray, and Dogfish.

Teacher's Note

Fish are perfectly adapted to water life with streamlined bodies that reduce water resistance, similar to how modern cars are designed to be aerodynamic for speed.

(ii) Class Amphibia (Frogs)

The main characteristics of amphibians are as follows:

They live in water as well as on land.

They lay their eggs in water.

Their body is covered by a slimy and slippery skin.

They breathe through lungs and skin.

Common examples: Frog and toad. See figures 3.14 and 3.15 on page 29.

(iii) Class Reptilia (Lizards and Snakes)

The main characteristics of reptiles are as follows:

Mostly land vertebrates.

Skin is dry and scaly.

Breathe through lungs.

Females lay soft shelled eggs on land.

Common examples: Lizards, snakes, tortoise, crocodiles, etc. (Fig. 3.2).

Figure 3.2 shows a Lizard, Tortoise, and Crocodile.

Teacher's Note

Reptiles like snakes and crocodiles have dry scaly skin that helps them conserve water, an adaptation useful in dry environments much like how desert plants have waxy coatings.

(iv) Class Aves (Birds)

The main characteristics of aves are as follows:

Body covered with feathers.

Have wings to fly.

Scales only on legs.

Jaws provided with horny beak and have no teeth.

Females lay hard shelled eggs.

Common examples: Peacock, ostrich, parrot, pigeon, bulbul, sparrow, etc. (Fig. 3.3).

Figure 3.3 shows a Bulbul and a Sparrow.

(v) Class Mammalia (Milk-nourishing animals)

The main characteristics of mammals are as follows:

Body covered with hair.

Possess projecting external ears.

Give birth to young ones (babies).

Mothers suckle their young ones with their own milk.

Usually, have a tail and four limbs.

Common examples: Cow, dog, dear, camel, lion, tiger, elephant, rat, and humans (Fig. 3.4).

Figure 3.4 shows a Cow, Rat, and Deer.

Teacher's Note

Mammals are warm-blooded creatures that care for their young by nursing them with milk, a unique characteristic that allows for strong bonding between mother and offspring.

B. Invertebrates (Animals without backbone)

The animals that do not have a back bone are called invertebrates. Based on their different characteristics, the invertebrates are further divided into nine groups.

(i) Single-celled animals (Protozoan)

Small, microscopic, single-celled.

Occur everywhere - in soil, in water and even inside the bodies of other animals including humans.

Some may cause diseases like malaria, dysentery, etc.

Common examples: Amoeba, Paramecium, Plasmodium (malarial parasite) (Fig. 3.5).

Figure 3.5 shows Amoeba and Paramecium.

(ii) Pore bearing animals (Poriferans) - Sponges

Mostly found in sea, very few occur in fresh water.

Fixed to some object or to the bottom of the pond or ocean.

Body is porous, i.e. bear many tiny pores to draw water into the body cavity, and one large pore to pass it out.

Common example: Sponge (Fig. 3.6).

Figure 3.6 shows a Sponge.

Teacher's Note

Sponges are nature's filter feeders, drawing in water through tiny pores and extracting nutrients, much like how water filters work in our homes to clean water.

(iii) Hollow sac-like animals (Coelenterates, now called Cnidarians)

Aquatic animals.

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

Mouth surrounded by finger-like projections called tentacles for catching food.

The body is radially symmetrical, that is, the body can be divided into two identical halves along any plane.

Common examples: Jellyfish, hydra, sea-anemone (Fig. 3.7).

Figure 3.7 shows Hydra and Sea Anemone.

(iv) Flatworms (Platyhelminthis)

Body thin and flattened.

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

Common example: Tapeworm (Fig. 3.8).

The human tapeworm occurs in the intestine and may gain a length of about six metres. It looks like a long ribbon with a small head-like part at the front end. It absorbs the already digested food from the human intestine. People who eat pork or beef may get infected by this worm.

Figure 3.8 shows a Tapeworm.

(v) Roundworms (Nemathelminths)

Body elongated and unsegmented.

Some are thread-like.

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

Common example: The human roundworm (Ascaris) (Fig. 3.9) lives in the small intestine of humans, commonly in children who eat with unwashed hands.

Figure 3.9 shows Ascaris (Human roundworm).

(vi) Segmented worms (Annelids)

Body composed of rings or segments.

They have a body cavity.

They have special organs for excretion called nephridia.

Common examples: Earthworm, leech (Fig. 3.10).

Figure 3.10 shows a Leech.

(vii) Soft bodied shelled animals (Molluscs)

Soft body which is not segmented.

Body enclosed in a hard shell.

Common examples: Snail, slug, pearl oyster, octopus (Fig. 3.11).

Figure 3.11 shows an Octopus.

Teacher's Note

Molluscs like snails use their hard shells as protection from predators, much like how we use helmets to protect ourselves while cycling or playing sports.

(viii) Animals with jointed legs (Arthropods) (Fig. 3.12)

Body is divided into three regions- head, thorax and abdomen; and in most cases, covered by a tough covering.

Body has paired appendages with many joints.

They are further divided into four classes.

(a) Crustacea - Head and thorax (middle part) are fused, have many jointed legs.

Examples - Crab, shrimps, lobsters, prawn, etc.

(b) Myriapoda - Body is divided into many segments, one or two pairs of legs on each segment.

Common examples - Centipede, millipede.

(c) Insecta - Body is divided into three regions - head, thorax and abdomen.

Have three pairs of legs.

Usually, have two pairs of wings.

Common examples - Ant, housefly, butterfly.

(d) Arachnida - Head and thorax fused.

Have four pairs of legs.

Have no wings.

Common examples - Spider, ticks, scorpion.

Figure 3.12 shows Prawn, Butterfly, and Spider.

(ix) Spiny-skinned Animals (Echinoderms)

Body is rough and spiny, and is star-like or ball-like.

No head or tail, no left or right side.

Common examples: Starfish, sea urchin (Fig. 3.13).

Figure 3.13 shows a Sea urchin.

Teacher's Note

Echinoderms like starfish have the remarkable ability to regenerate lost arms, a survival mechanism more advanced than most animals we encounter in daily life.

This is a preview of the first 3 pages. To get the complete book, click below.