NEET Biology Class 9 Chapter 3 Diversity in Living Organisms Notes

Diversity in Living Organism Introduction

• Just look around, you see a large variety of living organisms, be it a plant, tree, bird, dog, spider, lizard and so on. Besides these, there are different kinds of crop plants like rice, wheat, and sugarcane.
• Then, there are wild plants like keekar. In a forest, you would find strange wild animals and plants. In a sea, you would find aquatic animals like whale, corals, sea anemones, etc.
• In a pond, you would find fish, earthworms, frog, and some water birds. Then, there are a number of parasites like ticks and mites.
• Besides these, there are several organisms that we cannot see by our naked eyes but they are all around us.
• All these organisms show similarities indicating mutual relationships. At the same time, these organisms are very different from all others to a lesser or greater extent.
• The diversity is not only present amongst different organisms but also among individuals of same organism.

Read And Learn More: NEET Class 9 Biology Notes

Diversity in Living Organism Activity:

Let us perform an activity to understand how diversity is found among individuals of same organism?

Consider yourself and your friend.

• Are you both of same height?
• Does your eye, nose or any other part look exactly like your friend’s?
• Is your hand span the same as your friend’s hand-span?

You would find that you both are roughly of same age but no external feature is similar in two of you- be it eyes, height, shape of mouth, nose, body shape etc.

• But if you compare a monkey with yourself and your friend, what would you see?
• Obviously, you would find that you and your friend have a lot of similarities and you both are quite different from Monkey.
• But, suppose you add a dog to your comparison? Then you would find that the monkey had more similarities with us than a dog.
• Now think of all the different forms of organisms that occur on earth.
• There are more than a million kinds of living things that exhibit an infinite variety in form, structure and living places.
• The range of variation found among microorganisms, plants, fungi, and animals is known as biodiversity.

Biodiversity is the richness of species of living organisms. Currently there are 1.7-1.8 million organisms, all of which are unique in themselves. With such a vast number of organisms, it becomes almost impossible for us to study each and every one of them at the individual level. Thus this task of studying the diversity of living organisms can be made easier and effective if these organisms are arranged in an orderly manner.

Before this, let us recognize the vast diversity in the living world both in size and complexity.

Variety in Size:

Think of the following varieties of plants:

• Huge trees like banyan, peepal, pine and so on. They have profuse branches and lots of leaves.
• Trees like palms and coconuts, with almost no branches.
• Medium-sized plants like banyan, rose, sugarcane, wheat etc.
• There are almost shortest lawn grass.

Similarly, there are huge varieties of animals on the earth Think of the following:

• Animals ranging from huge elephants or whales in the sea through the medium-sized dog to the small insects like butterflies or ants.
• Tiny animals like bacteria and Amoeba, which cannot be seen through naked eyes.

Variety in Complexity:

Examples:

In animals:

• Human body: Human body is extremely complex with so many different organs. Each organ in turn is composed of a variety of cells, each performing different tasks.
• Bird’s body: The body of bird is complex in some other ways. They have wings supported by bones and covered by feathers.
• Frog body: The body of frog is less complex than ours. They have three-chambered heart whereas we (human body) have four chambered heart.

In plants:

• Trees with tough wood produce flowers, fruits and seeds. On the contrary, trees like Pine produce seeds but no fruits.
• Plants like ferns produce neither seeds nor fruits but they do have leaves and roots.
• Organisms, like fungi have neither leaves, nor stem nor roots. Fungi have a network of fiaments.
• Green plants have green colour pigment called chlorophyll and thus can synthesise their own food while there are non green plants like fungi which can decompose food and absorb nutrition directly

Classification

There are enormous varieties of living organisms on earth. This enormous variety of life around us has evolved on the earth over millions of years. Some are closely related to each other, some are distantly similar and some are very different.It is practically impossible to study each and every individual. Also it is very difficult to remember their names, characters and uses.

Grouping and classifying organisms on the basis of similarities and differences helps us to know about them even if we have not seen them directly. Thus, classification is the arrangement of organisms into groups and subgroups on the basis of their similarities and dissimilarities.

Importance of Classification:

• Classification makes the study of large number of living organisms easy.
• It gives an idea of whole range of diversity found in organisms.
• It provides information about inter-relationships among organisms.
• It gives an idea of the evolution of various groups of organisms. Evolution is the complex process by which the characteristics of living organisms change over many generations.
• It gives a system for the identification of known and unknown organisms.

Classification and Evolution:

• All living organisms are identified and categorized on the basis of their body design in form and function. Some characteristics are likely to make more wide-ranging changes in body design than others. There is a role of time in this as well. So, once a certain body design comes into existence, it will shape the effects of all other subsequent design changes, simply because it already exists.
• In other words, characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later.
• This means that the classification of life forms is closely related to their evolution. So, what an evolution is? Evolution is the accumulation of inherited changes within populations over time. A population is a group of individuals of one species that live in the same geographic area at the same time. The term evolution does not refer to changes that occur in an individual within its lifetime.
• Instead, it refers to changes in the characteristics of populations over the course of generations. These changes may be so small that they are difficult to detect or so great that the population differs markedly from its ancestral population. Eventually, two populations may diverge to such a degree that we refer to them as different species.

Evolution has two main perspectives:

Microevolution: The minor evolutionary changes of populations usually viewed over a few generations, is known as microevolution.

1. Macroevolution: The major evolutionary events usually viewed over a long period, such as formation of different species from common ancestors, is known as macroevolution.
2. Based on evolution, organisms can be divided into two types:
3. Primitive organism or lower organism: It is an organism which has a simple body structure and ancient body design that have not changed much over a period of time.
4. Advanced organism or higher organism: Organisms that have complex body structure and evolution, are known as advanced organisms.

For example, An Amoeba is more primitive than starfish. Amoeba has a simple body structure and primitive features as compared to starfish.

Basis of Classification:

• Organisms are classified on the basis of characteristics. It could be in terms of appearance or behavior. These characteristics give clues about how species evolved.
• The most important thing is to decide which characteristic is to be used as the basis for the broadest divisions. Then we will have to pick the next set of characteristics for making sub-groups within these divisions. This process of classification within each group can then continue using new characteristics each time.
• But before this, let us understand what a characteristic is? A characteristic is a particular form or a particular function found in large number of organisms.
• For example Most ofus have five figers on each hand. This is a human characteristic. Humans can run but banyan tree cannot, is also a characteristic, which can be used to classify humans and trees.
• Characteristics that create fundamental differences among life forms are used for raising kingdoms, divisions and other larger groups. New traits of lesser fundamental nature in turn are used to produce small groups and their sub-groups.
• It is just like building a wall of stone. The stones used will have different shapes and sizes. The stones at the top of the wall would not inflence the choice of stones that come below them.
• On the other hand, the shapes and sizes of stones in the lowermost layer will decide the shape and size of the next layer and so on. The stones in the lowermost layer are like the characteristics that decide the broadest divisions among living organisms.

They are independent of any other characteristics in their effects on the form and function of the organism. The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level.

In this way, we can build up a whole hierarchy of mutually related characteristics to be used for classification

Hierarchy of Classification:

• Classification is not a single-step process but involves a hierarchy of steps. Each step in the hierarchy represents a rank or category. Since the category is a part of overall taxonomic arrangement, it is called the taxonomic category. All categories together constitute the taxonomic hierarchy.
• Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as a taxon (plural. taxa). The taxa ranges from having very broad characteristics to much more specific characteristics.

• Species: The smallest taxon is species. At the species level, organisms look alike and are able to breed with one another.
• Genus: The next largest taxon is genus. At the genus level, there is a group ofsimilar species that are closely related.
• Family: Agroup oftwo more genera (plural ofgenus) with common characteristics make a family. For example, lion (Panthera leo), tiger (Panthera tigris) and the domestic cat (Felis domesticus) make the family Felidae.
• Order: A group ofrelated families make an order. For example, the family ofcats (Felidae) and the family ofdogs, foxes, etc. (Canidae) is grouped under the order Carnivora.
• Class: Related orders make a class. For example, several orders like those of the tigers, cats, dogs, monkeys, bats and humans belong to the class Mammalia.
• Phylum: A phylum is the largest category with related classes grouped together. For example, the classes ofmammals, birds, reptiles, amphibians and fishes together constitute the phylum Chordata. In plants, the corresponding category is named division.
• Kingdom: Kingdom is the largest group of organisms differentiated on very general similarities. For example, plant and animal kingdoms. The plant kingdom comprises all kinds of plants while animal kingdom comprises all kinds ofanimals.

The hierarchical classification of human is:

• Kingdom- Animalia
• Phylum- Chordata
• Class- Mammalia
• Order- Primata
• Family- Hominidae
• Genus- Homo
• Species- sapiens

Now you must be wondering how organisms are placed in various categories?

• The basic requirement to categorize organism is to have knowledge of characters of an individual or group of organisms.
• So, we choose the fundamental characteristics among several other characteristics. For example, plants differ from animals in the absence of locomotion, chloroplasts, cell wall etc.
• But only locomotion is considered as the basic fundamental feature and is used to distinguish between plants and animals.
• This is because the absence of locomotion in plants gave rise to many structural changes such as the presence of cell wall for protection and the presence of chloroplast for photosynthesis, as they cannot move around in search of food like animals.
• Thus, all these features are a result of locomotion and therefore, locomotion is considered to be a fundamental characteristic. By choosing the fundamental characteristic, we can make broad division in living organisms as the next level of characteristic is dependent on these. This goes on to form a hierarchy of characteristics.
• Let us know and discuss how an organism is named.

Naming An Organism- Binomial Nomenclature:

Biologists have devised techniques for identification, naming and grouping of various organisms. There is a need to standardize the naming of living organisms such that a particular organism is known by the same name all over the world. This process is called nomenclature. Nomenclature is the process of giving scientific names to plants and animals.

Thus, in order to facilitate the study, numbers of scientists have established procedures to assign a scientific name to each known organism. This is acceptable to biologists all over the world.

Scientific names are based on agreed principles and criteria, which are provided in International Code for Botanical Nomenclature (ICBN) and the International Code of Zoological Nomenclature (ICZN) for plants and animals respectively. The scientific names ensure that each organism has only one name. Biologists follow universally accepted principles to provide scientific names to known organisms.

Carl Linnaeus devised a binomial system of nomenclature in which an organism is given two names.

• A generic name that it shares with other closely related organisms which has features similar enough to place them in the same group.
• A specific name that distinguishes the organism from all other species. No other organism can have the same combination of genus and species.

Certain conventions are followed while writing the scientifi names:

1. The name of the genus begins with a capital letter.
2. The name of the species begins with a small letter.
3. When printed, the scientific name is given in italics.
4. When written by hand, the genus name and the species name have to be underlined separately

Let us understand the way of providing scientific names by taking an example of mango.  The scientific name of mango is written as Mangifera indica. In this, Mangifera represents the genus while indica, is a particular species, or a specific epithet. Similarly, the scientific name of human is written as Homo sapiens.

Other universal rules of nomenclature are as follows:

1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.

Question 1. Rewrite the scientific names of the following organisms in their correct form.
Answer:

Question 2. Rearrange the following in the correct sequence starting from smallest to highest category. Genus, Species, Order, Class, Family, Kingdom, Phylum
Answer: Species, Genus, Family, Order, Class, Phylum, Kingdom

The Two Kingdom Classification

Linnaeus classified the living world into two kingdoms- Plantae and Animalia in 1758.

1. Kingdom Plantae: The plant kingdom comprises all kinds of plants. It includes Bacteria, Fungi, Algae, Bryophytes, Ferns, Gymnosperms and Angiosperms.
2. Kingdom Animalia: The animal kingdom comprises all kinds of animals. It includes protozoans, Hydra, worms, insects, spiders, fishes, frogs, snakes, birds and mammals including humans. Classification of organisms into plants and animals were easily done and was easy to understand, inspite, a large number of organisms did not fall into either category.

For example:

• Euglena cannot be assigned with certainty to a specific kingdom because it shares characteristics of both plants and animals. It possesses chlorophyll like plants but lacks cell wall. It has autotrophic mode of nutrition but in dark it has heterotrophic mode of nutrition like animals.

• Similarly, Virus belongs to neither plant kingdom nor the animal kingdom, as they share characteristics of both living and non-living organisms.

Hence the two kingdom classification used for a long time was found inadequate. To overcome such problems a new scheme of classification was recommended by R.H. Whittaker in 1969.

The Five Kingdom Classification

R.H. Whittaker proposed a five-kingdom classification of living organisms on the basis of Linnaeus’ two kingdoms classification. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, Animalia.

The main criteria in this classification are as follows:

1. On the basis of absence or presence of membrane-bound organelles: All living organisms are divided into two broad categories of prokaryotes and eukaryotes. This division led to the formation of kingdom MONERA, which includes all prokaryotes.
2. On the basis of cellularity (whether organisms are unicellular or multicellular): Unicellular eukaryotes form kingdom PROTISTA, and multicellular eukaryotes form kingdom FUNGI, PLANTAE, and ANIMALIA.
3. Cell wall: The kingdom ANIMALIA are then separated from kingdom PLANTAE on the basis of cell wall. Kingdom animalia lack cell wall.
4. Mode of nutrition: Since, fungi and plants both contain a cell wall; they are separated into different kingdoms on the basis of their modes of nutrition. FUNGI have saprophytic mode of nutrition while PLANTS have autotrophic mode of nutrition.

Let us now study each of these five kingdoms one by one.

1. Kingdom Monera (Unicellular prokaryotes): It is a kingdom of prokaryotes and includes bacteria and blue-green algae.

Characteristics:

1. Monera includes unicellular (single-celled) organisms.
2. They are prokaryotes. Their chromosome material is not enclosed within a nuclear membrane. It means, their genetic material is not organized into a nucleus. It lies directly inside the cytoplasm and is called nucleoid.
3. Membrane-bound cell organelles like mitochondria; golgi apparatus, lysosomes, etc are absent.
4. Cell wall may or may not be present.
5. The mode of nutrition may be autotrophic or heterotrophic.

Examples: Bacteria (Vibrio cholerae, Salmonella typhi) and blue-green algae (e.g. Anabaena, Nostoc)

2. Kingdom Protista (Greek protistos- First of all)- Unicellular eukaryotes:

Characteristics:

• Protista includes unicellular (single-celled) organisms.
• They are eukaryotes. They have well-defined membrane-bound nucleus.
• Membrane bound organelles like nucleus, mitochondria, endoplasmic reticulum, golgi bodies are present.
• Cell walls like Monerans, may or may not be present.
• The mode of nutrition is diverse.
  • Some protists like Amoeba and Paramecium can ingest food like animals.
  • Some protists like Euglena have chlorophyll and manufacture their own food like the plants. In the absence of light they become heterotrophic and ingest other protists like protozoa. This dual mode of feeding resulted in their placement both in plant and animal kingdom.

Examples: Diatoms, Euglena, Amoeba, Paramecium

3. Kingdom Fungi (Latin fungus- Mushroom)- Common bread molds (Rhizopus and Mucor), Mushrooms are some common types of fungi.

Characteristics:

1. Fungi are basically multi-cellular. Yeast is an exception in being unicellular.
2. The body of fungi is made of thread-like structures called hyphae. The hyphae grow in the form of a mat like structure called mycelium.
3. The cell wall is generally composed of chitin (a nitrogen containing carbohydrate).
4. They do not contain chlorophyll and hence are heterotrophic. Most of them are decomposers, hence fungi are also known as kingdom of multi-cellular decomposers. They may be saprophytic (depend on dead or decaying organic matter for their food) or may be parasitic (depend on living organisms for their food).

For example: Yeast, Mushroom (Agaricus), Rhizopus (Bread Mould), Penicillium.

Lichen:

Lichens are dual organisms that are formed by permanent symbiotic association between an algae and a fungus. They co-exist for mutual benefic. This type of relationship is known as symbiosis. The alga manufactures food for itself and for the fungus.

Fungus provides protection to alga and helps in fiation and absorption of water and minerals. Lichens can tolerate prolonged drought and drastic variations in temperature. Also, they are very sensitive to air pollution.

4. Kingdom Plantae (Multicellular Eukaryotes):

Characteristics:

1. They are multicellular eukaryotes.
2. All plants contain plastids. Plastids are double membrane organelle that possesses photosynthetic pigments. They are called chloroplast.
3. They are usually autotrophic. Chloroplast contains a green colour pigment called chlorophyll and prepares own food by the process ofphotosynthesis.
4. Cells have cell wall made ofcellulose.

Kingdom plantae shows a lot of diversity, because of which, it has been divided into four divisions: Algae, Bryophyta, Pteridophyta, and Spermatophyta (Gymnosperms and Angiosperms)

1. Division thallophytic (Greek: thallus-undifferentiated, phyton-plant):

Characteristics:

1. Plants of this division do not have well-differentiated body designs.
2. The body design is simple (i.e. not differentiated into stem, root, and leaves). It is often called thallus.
3. They are unicellular.

Thallophyta includes a single sub-division of algae.

Algae:

1. Algae are thallophytes that are capable of manufacturing their own food through photosynthesis.
2. The body of algae is simple with little differentiation of body design.
3. The form and size of algae is highly variable. The size ranges from unicellular microscopic forms like Chlamydomonas to colonial forms like Volvox and to the filamentous forms like Ulothrix and Spirogyra.
4. They are of three main groups: Green algae, Red algae and Brown algae.

Algae are responsible for almost 50% of fiation (Photosynthesis). Algae are also used as food; some important algae which are used as food are Porphyra, Laminaria and Sargassum.

Examples: Spirogyra, Ulothrix, Chara, Volvox, etc.

2. Division bryophyta (Greek: bryon-moss, phyton-plant):

You must have seen green velvety layer growing on damp soil or on the walls of flower-pots. What are these? Actually these are
Bryophytes i.e. mosses or liverworts.

Characteristics:

1. It is a division of non-vascular plants having an embryo stage in their developmental process.
2. They are the simplest land plants and are known as amphibians
   of plant kingdom as they live in moist areas.
3. The plant body is commonly differentiated to form stem and
   leaf-like structure.
4. It is thallus like and prostrate or erect and attached to
   the substratum by unicellular or multi-cellular rhizoids.
5. They have no specialized tissue for the conduction of water and other substances from one part of the body to another.
6. Plant body ofbryophytes is gametophyte. Sporophyte lives as a parasite over it.
7. The sex organs are multicellular, male sex organ is called antheridium and produces antherozoids whereas female sex organ is archegonium and produces a single egg.

Examples: It includes various mosses and liverworts.

3. Division pteridophyta (Greek. pteris-fern, phyton-plant):

Characteristics:

1. It is a division of seedless vascular plants. Hence commonly known as vascular cryptogams.
2. Pteridophytes represent the highest group of cryptogamae.
3. Unlike bryophytes, the main dominant plant body is sporophyte which is differentiated into true root, stem and leaves.
4. They have well developed vascular system (Xylem and Phloem).
5. Sporophytes bear sporangia which produces spore, on germination these spores give rise to gametophyte called prothallus. Prothallus bears the male and female sex organs antheridia and archegonia respectively.
6. Seeds are absent. They produce naked embryos called spores.

Examples: Selaginella, Equisetum, Marsilea, etc

4. Spermatophyta (Greek. sperma: seed, phyton: plant):

Characteristics:

1. It is a division of seed-producing plants. A seed has an embryo that contains reserve food for its future growth.
2. The main plant body is sporophyte which is differentiated into stem, leaves and roots.
3. Male and female gametophytes are distinct. They are small and dependent on sporophyte for their nutrition.
4. They have well-developed vascular tissues throughout the plant body. ‘
5. The reproductive process produces seeds which on germination forms a new plant.

Spermatophyta has two sub-divisions- Gymnospermae and Angiospermae.

Sub-division Gymnospermae (Greek. Gymnos-naked, sperma-seed):

Characteristics:

1. Gymnosperms include plants that bear naked seeds.
2. Plants are evergreen, woody and perennial. It includes medium sized trees, and shrubs
3. Sporangia are formed over modified leaflike structure called sporophylls.
4. Sporophylls are of two types: Megasporophyll bears megasporangium (ovule) whereas microsporophyll bears microsporangium (pollen sac).
5. The microsporophyll and megasporophyll form the male and female cones which produced male and female gametes respectively.

Examples: Cycas, Pinus (Pine), Cedrus (Deodar) Cycas Pinus

Sub-division Angiospermae (Greek. Angios-cover, spermae-seed)

Characteristics:

1. These are flowering plants, in which seeds are enclosed by a protective structure called fruits.
2. These are highly evolved group of plants.
3. Sporophylls are aggregated to form flowers.
4. The reproductive organs are aggregated into flowers. The male sex organs are called stamen and female sex organs are called pistil.
5. The seed contains an embryo together with the nourishment-containing cotyledons (one in some and two in others).

On the basis of number of cotyledons (fleshy embryonic leaves), the angiosperms are divided into two groups:

1. Dicotyledonae (Dicots):

1. The angiosperms with two cotyledons are called dicots.
2. Their leaves have reticualte venation with a network of veins.
3. The root system has prominent tap root.
4. The flowers have five or multiple office petals.

Examples: Pea, potato, Rose, Banyan, Apple, etc.

2. Monocotyledonae (Moncots):

1. The angiosperms with only one cotyledon are called monocots.
2. Their leaves have parallel venation.
3. The root system consists of firous roots.
4. The flowers have three or multiple of three petals.

Examples: Maize, wheat, rice, sugarcane, Banyan, Coconut etc.

Activity:

Let us perform a small activity to understand the difference between monocot and dicot plant:

1. Take some seeds of green gram, wheat, maize, and peas.
2. Soak them in water.
3. Once they become tender, try to split the seed.

What did you observe? Do all the seeds break into two nearly equal halves?

The seeds that split open into two equal halves are dicot seeds and the seeds that do not split in equal halves are the monocot seeds.

Question 1. Name the kingdom to which the following organisms belong.

1. Algae
Asnwer: Plantae: Thallophyta

2. Blue-green algae
Answer: Monera

3. Ferns
Answer: Plantae: Pteridophyta

4. Mushroom
Answer: Fungi

5. Flowering plant
Answer: Plantae: Angiospermae

Question 2. What are the three basic criteria that have been taken into consideration for the five kingdom classification of living organism?

Three criteria are:

1. Unicellular or multi-cellular
2. Eukaryotes or prokaryotes
3. Autotrophs or heterotrophes

5. Kingdom Animalia (Multi-cellular Eukaryotes):

Characteristics:

1. Members of kingdom animalia are multi-cellular eukaryotes.
2. They have heterotrophic mode of nutrition.
3. Almost all the animals are mobile. They move about in search of food or for other needs. Sponges and corals are however sedentary.
4. Cell wall is absent.

The kingdom Animalia is very vast and highly varied. It is subdivided into following nine phyla:

1. Porifera (Sponges)
2. Cnidaria or coelenterate (Jelly fishes and corals)
3. Platyhelminthes (Flatworms)
4. Aschelminthes (Roundworms)
5. Annelida (Earthworms)
6. Arthropoda (Insects, crabs, Spider)
7. Mollusca (Snails)
8. Echinodermata (Starfish, Sea urchins)
9. Chordata (Animals with backbone)

Basis of Classification of Animals:

1. Organization: Organisation is the structural differentiation of animal body. It can be divided into three levels:

1. Cellular level: In cellular level of organization, tissues do not differentiate. However, different types of cells may occur. e.g. Porifera (sponges).
2. Tissue level: In tissue level of organization, cells are organized into tissues but organs are absent. e.g. Coelenterata.
3. Organ level: In organ level of organization, cells are organized into tissues, tissues into organs and organs into organ system. e.g. Nemathelminthes and higher animals.

2. Body Symmetry:

Body symmetry is defined as similarity in arrangement of parts. It is of two types:

1. Radial symmetry: In radial symmetry, the body can be divided into two equal halves by any vertical plane passing through the central axis. It is found in Sponges, Coelenterates and Echinoderms.
2. Bilateral symmetry: In bilateral symmetry, body is divisible into two equal halves by only one plane. It is found in platyhelminthes, nematode, annelida, mollusca, arthropoda and chordate.

3. Germinal Layers: Germinal layers are primary layers that differentiate in embryo to form tissues and organs. It includes outer ectoderm, middle mesoderm and inner endoderm.

On the basis of germinal layers, animals are of two types:

1. Diploblastic animals: Animals that have two germinal layers- outer ectoderm and inner endoderm are called diploblastic. Mesoderm is absent in these animals. It includes Porifera and Coelenterate.
2. Triploblastic animals: Animals that bear three germinal layers- ectoderm, mesoderm and endoderm is known as triploblastic. It includes Plateyhelminthes to Chordate.

4. Coelom (Body Cavity): Coelom is a mesoderm-lined flid filed cavity that occurs between the alimentary canal and body wall. It provides shock proofenvironment to various body organs.

On the basis of the presence or absence of coelom, animals are divided into three types:

1. Acoelomate: Animals that lack coelom are acoelomate.
   Examples: Porifera, Coelenterata, Platyhelminthes.
2. Pseudocoelomate: Pseudocoelomate lacks true coelom. A cavity called pseudocoelom is present, which is not lined by mesoderm.
   Example: Nemathelminthes.
3. Coelomate: A true coelom lined by mesoderm is present.
   Example: Annelida, Mollusca, Arthropoda, Echinodermata and chordata

1. Phylum Porifera (Animals bearing pores):

1. These are the simplest multicellular, diploblastic, acoelomate animals.
2. They are mostly marine but few are found in freshwater.
3. Body consists ofa hollow tube, and found attached to the rocks.
4. The cells are loosely held together and do not form tissues.
5. They have porous body with numerous pores for entry of water carrying food and oxygen and a single opening for the exit of water.

Examples: Spongilla, Sycon, Euplectella.

2. Phylum Colenterata (Cnidaria):

1. They are exclusively marine animals except for few like Hydra that are found in fresh water.
2. They are multicellular, diploblastic animals with tissue grade of organization.
3. Body shows radial symmetry with a central gastrovascular cavity with a single opening, called hypostome.
4. Tentacles that surround the mouth capture the prey paralyzed by their stinging cells and push it into the mouth. The same mouth throws the undigested left out food out of the body again.

Examples: Hydra, Aurelia (Jelly fish), Physalia (Portugese man of war).

3. Phylum Platyhelminthes (platy: flt, helminthes-worms): Flat worms

1. The body is soft, elongated, dorso-ventrally flattened and leaflike with bilateral symmetry. Hence, known as flatworms.
2. The animals are triploblastic, acoelomate with tissue grade of organization.
3. They are generally endoparasites found in animals including human beings.
4. Digestive cavity (when present) with a single opening, the mouth. Anus is absent.
5. A specialized cell called flme cell helps in osmoregulation and excretion.

Examples: Planaria, Taenia (Tape worm), Fasciola (Liver flke).

4. Phylum Nemathelminthes (nema-thread, helminth-worm)- Roundworms:

1. The body of organisms belonging to this phylum are cylindrical and elongated.
2. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals with organ level of organization.
3. Alimentary canal is complete with well developed muscular pharynx and anus.
4. Sexes are separate (dioecious) i.e. male and females are distinct.

Examples: Ascaris (Round worm), Wuchereia (Filaria worm), etc.

5. Phylum Annelida (annulus-ring, lidos-form): The segmented animals

1. Annelids are bilaterally symmetrical, triploblastic and coelomate animals.
2. They are soft, elongated, vermiform, cylindrical or dorsoventrally flattened.
3. They exhibit organ-system level ofbody organization.
4. Body is metamerically segmented externally by transverse grooves and internally by septa.
5. Digestive system is well developed. Alimentary canal is tube like and extends straight from mouth to anus.

Examples: Nereis, Pheretima (Earthworm), Leech, etc

6. Phylum Arthropoda (arthro-jointed, poda-legs): Animals with jointed legs

1. This is the largest phylum of Animalia which includes insects.
2. The body is triploblastic, bilaterally symmetrical and metamerically segmented with organ level of organization.
3. Body is also covered by a hard chitinous exoskeleton.
4. The body consists of head, thorax and abdomen with jointed legs.
5. Alimentary canal is complete. Mouth and anus lies at the opposite ends of the body.
6. Excretion takes place by Malpighian tubules (insects) and green glands (crab and prawn).

Examples: This is the biggest phylum with four major kinds of organisms.

1. Insects, such as cockroaches and butterflies, have three pairs of legs and usually two pairs of wings.
2. Spiders and scorpions have four pairs of legs.
3. Prawns and crabs have many pairs of legs.
4. Centipedes (hundred legs) and millipedes (thousand legs) have paired legs on each body segment.

7. Phylum Mollusca (Soft-bodied animals):

1. It is the second-largest phylum of the animal kingdom and an ancient group that lived on this planet from over 500 million years.
2. They are triploblastic coelomates and usually with bilateral symmetry.
3. They are terrestrial, marine, and freshwater inhabitants.
4. The body is soft and divided into three regions- head, dorsal visceral mass, and ventral foot. Foot is meant for creeping and for other kinds of locomotion.
5. The body is protected by a hard calcareous shell.

Examples: Snails, Slugs, Octopus, Cuttlefish, etc.

8. Phylum Echinodedrmata (echinos: spiny, derma: skin): The spiny-skinned animals

1. All are marine, triploblastic and coelomate.
2. Adults are radially symmetrical and larvae are bilaterally symmetrical.
3. The most distinctive feature is the presence of water vascular system with an array of radiating canals and tube-like appendages called tube feet. Tube feet are used for locomotion, capturing of food and respiration.
4. Exoskeleton is spiny.
5. Head is absent and five radially arranged arms are present.

Examples: Starfish, Sea urchin, Sea cucumber etc.

9. Phylum Chordata (Greek. Chorde-string):

1. It is a phylum of triploblastic bilaterally symmetrical animals.
2. All members of this phylum possess:
   1. Flexible rod-like notochord along the mid-dorsal axis of the body. The notochord is later replaced by a backbone (vertebral column).
   2. A hollow dorsal nerve cord.
   3. Paired gill slits
   4. A tail extending behind the anal opening.

Phylum Chordata is divided into three sub-phyla:

1. Subphylum Urochordata (uro:tail): In urochordata, the notochord is present in the tail of the larva and disappears in the adult.

Example: Herdmania.

2. Subphylum Cephalochordata (cephalo: head): In cephalochordata, notochord extends upto the anterior end of the body and persists throughout the life.

Example: Amphioxus

Subphylum Vertebrata: In organisms belonging to sub phylum Vertebrata, notochord is replaced by vertebral column in adults. It is the largest group in Chordata

Vertebrata is divided into two subphyla, i.e. Agnatha and Gnathostomata:

1. Agnatha includes a single class Cyclostomata, while
2. Gnathostomota is divided into six classes: Chondrichthyes (fiSh), Osteichthyes (fish), Amphibia (frog), Reptilia (lizard), Aves (birds) and Mammalia (Animals with milk gland).

1. Class: Cyclostomata:

1. All members of cyclostomata are ectoparasites on some fishes.
2. Body is long, elongated with 6-15 pairs of gill slits for respiration.
3. Skin is smooth, soft, slimy and scaleless.
4. Cyclostomata includes vertebrates which have suctoral mouth. Mouth does not possess jaws. The group is therefore, called agnatha.
5. Endoskeleton is cartilaginous, notochord persist throughout life.
6. Heart is two chambered and circulation is closed type.

Example: Lamprey

1. Superclass: Pisces:

1. They are exclusively aquatic animals with streamlined body covered with scales.
2. Pisces are cold-blooded animals.
3. Notochord is persistent.
4. Heart is two chambered and respiration occurs by gills. Gills are able to withdraw oxygen dissolved in water.
5. They have fis for locomotion and balancing.

Pisces is divided into two classes:

I. Class: Chondrichthyes (Cartilaginous fishes):

1. Cartilaginous fishes have their skeleton made of cartilage.
2. Gills are exposed (not covered by any gill cover). Operculum is absent.
3. The swim bladder is absent.
4. The mouth is ventral in position.

Example: Shark

2. Class: Osteichthyes (Bony Fishes):

1. Bony fishes have skeletons made of bones.
2. Gills are covered by an operculum.
3. The swim bladder is present.
4. The mouth is terminal in position.

Example: Rohu, Catla etc.

2. Superclass: Tetra Poda: [Greek tetra = four, podas = foot]]

1. Class: Amphibia (amphi: dual, bios-life):

1. The animlas are amphibious in nature that means they can live on land as well as in water.
2. Like pisces, they are cold blooded animals. Body temperature changes with that of external environment.
3. Skin is smooth and without scales. It has large number of mucus glands that keep the skin moist.
4. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
5. Respiration is by gills, lungs and through skin.
6. The heart is three chambered (two auricles and one ventricle).
7. They lay eggs in water.

Examples: Toad, Frog, Salamanders, Newt, etc.

2. Class Reptilia (Latin. Repre: to crawl): Creeping vertebrates:

1. They are mostly terrestrial animals and their body is covered by dry and cornifind skin, epidermal scales.
2. Body varies in form and is usually divided into head, neck, trunk and tail.
3. Reptiles are poikilotherms (cold blooded animals).
4. Respiration takes place through lungs.
5. Heart is three chambered except for crocodiles which have four chambered heart.
6. They lay eggs on land. They are oviparous.

Examples: Lizards, Snakes, Turtles etc.

3. Class Aves (Latin. Avis: bird):

1. The body is streamlined to reduce air resistance during flight.
2. They are warm-blooded, tetrapodous vertebrates.
3. They are the fling animals, having exoskeleton of feathers.
4. Forelimbs are modified into wings while hind limbs have four clawed digits meant for walking, running or perching.
5. Jaws are prolonged to form horny beak. Teeth are absent.
6. Bones are very light because of air spaces. This helps the bird to lighten the body weight for flight.
7. They lay eggs with calcareous shell. They are oviparous.
8. Heart is four-chambered.
9. Respiratory system possesses well-developed lungs with air sacs attached to them.
10. Birds have keen sense of sight.

Examples: Ostrich, Crow, Parrot, Eagle, Pigeon etc.

4. Class Mammalia (latin. Mamma: breast):

1. They are the most evolved animals of animal kingdom. They have well developed brain.
2. They are endothermous (warm-blooded) animals. They maintain a fied body temperature.
3. The body is covered by hair. Skin has sweat glands to regulate their body temperature.
4. The females have milk producing glands called mammary glands.
5. They are the only animals which-nourish their young ones with milk.
6. Two pairs of pentadactayl limbs are present. Digits in the fore limbs and hind limbs are generally five and ending as claws, nail and hoof.
7. Limbs are variously adapted for walking, running, climbing, burrowing, swimming or fling.
8. Respiration occurs by lungs, heart is four-chambered.
9. They generally give birth to young ones except Platypus and Echidna that lays eggs. Kangaroos give birth to very poorly developed young ones.

Examples: Kangaroo, Dog, Man, Chimpanzee, Elephant, etc.

Question 1. Name the phylum showing the following characteristics:

1. Soft body enclosed in a hard calcareous shell.
Answer: Mollusca

2. Body supported by flxible rod like notochord.
Answer: Chordata

3. Animals with jointed legs.
Answer: Arthropoda

Question 2. Identify the correct matching pairs of phylum/class and its examples.

1. Chordata: Sparrow
2. Pisces: Whale
3. Amphibia: Crocodile
4. Mammalia: Kangaroo
5. Reptilia: Toad

Answer:

(1) and (2) are correctly matched pairs of phylum/class and its examples.

Question 3. Name the phylum to which following organisms belong.

1. Butterfly
Answer: Arthropoda

2. Starfish
Answer: Echinodermata

3. Jellyfish
Answer: Coelenterata

4. Tapeworm
Answer: Platyhelminthes

5. Sponge
Answer: Porifera

Choose the correct answer for the following questions:

Question 1. Which of the following birds is not capable of offling?

1. Peacock
2. Sparrow
3. Owl
4. Kiwi

Answer: 4. Kiwi

Question 2. Which of the following animal is capable of changing its body color?

1. King cobra
2. Chameleon
3. House lizard
4. Flying lizard

Answer: 2. Chameleon

Question 3. Which of the following is not a bird?

1. Owl
2. Bat
3. Kite
4. Ostrich

Answer: 2. Bat

Question 4. Which of the following is a mammal?

1. Crocodile
2. Whale
3. Shark
4. Turtle

Answer: 2. Whale

Question 5. Which of the following is not a fish?

1. Flyingfish
2. Catfish
3. Dogfish
4. Silverfish

Answer: 4. Silverfish