9th Class Science Diversity in Living Organisms

Diversity in Living Organisms

Category : 9th Class

Diversity in Living Organisms

Chapter Overview

Introduction
Biodiversity of India
Why do we classifying organisms
What is the basis of classification?
Classification and evolution
Hierarchy of classification Groups
Detailed classification of Kingdom planate
Detailed classification of Kingdom Animalia
Nomenclature

Introduction

It is believed that life on our planet Earth first originated around 3.6 billion years ago.

Since then many different types of organisms have evolved on the earth. We observe various types of living organisms like insects, birds worms, mammals and plants around us. Every organism in this world, whether, a plant, an animal or a microorganism is unique in itself. This uniqueness of individuals forms the basis of the diversity (or species richness) among the living organisms.

The term 'biodiversity’ (L. diversitas = variety) was coined by Walter G. Rosen in 1986.

Biodiversity can be defined as, the variability among living organisms from all sources including, terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are a part; this includes diversity within species, between species and of ecosystems.

For instance, compare yourself with your friend. Both of you have different looks, different figure, different heights and different qualities. But both are identified on the basis of certain characteristics. Now compare over selves and our friends with a monkey. The monkey is quite different from us that is because we and our friends have close similarities. The differentiation becomes sharp if we compare ourselves and monkey with a cow. Naturally we and monkey have more similarities in comparison to a cow. It can be concluded that each and every organism possess a distinct form that distinguishes it from others.

Various Ways of Expressing Biodiversity

Biodiversity can be expressed in the following ways:

(a) Genetic variability within a species: It includes the differences in body shape and size, colour etc. expressed due to genetic differences.

(b) Diversity of population of a species: This is expressed in terms of the number of individuals within a local group as well as the distribution of a species in geographical range.

(c) Diversity of species within a natural community: It includes the varieties of different species in a particular habitat.

(d) Ecosystem Diversity: The diversity at the level of community and ecosystem has four perspective.

(i) Point Diversity: This is a diversity on the smallest scale i.e., the diversity of micro- habitat.

(ii) Alpha Diversity: It includes the diversity of organisms sharing the same habitat and also called local diversity.

(iii) Beta Diversity: It refers to the rate of replacement of species along a gradient of habitats or community within a given geographical area.

(iv) Gamma Diversity: It refers to the diversity of the habitats in the whole geographical area.

Biodiversity of India

India has a great wealth of biodiversity in its forests, wetlands and marine areas. It has wide range of habitats ranging from tropical rainforests to alpine type of vegetation and from temperate forests to coastal wetland forests. India has fertile river plains and high plates and several major rivers including river Ganga, Brahamputra and Indus. Indian climate shows a great diversity also. It has various biogeographic and topographic areas having great diversity.

The ministry of Environment and Forest Government of India records 47,000 species of plants, and 81,000 species of animals. This contributes about 7% and 6.5% respectively of global flora and fauna.

Table. 2.1. Number and Percentage of species of Flora and Fauna in India

Sr. No.	Taxon	Number of Species	Percentage
1.	Bacteria	85	0.08
2.	Algae	2500	2.3
3.	Fungi	23000	21.2
4.	Bryophyta	2564	2.4
5.	Pteridophyta	1022	0.9
6.	Gymnosperms	64	0.06
7.	Angiosperms	15000	13.9
8.	Insects	53430	49.3
9.	Molluscs	5050	4.7
10.	Pisces	2546	2.4
11.	Amphibia	204	0.2
12.	Reptiles	446	0.4
13.	Aves	1228	1.1
14.	Mammals	372	0.3
	Total	108276	100.0

Why do we classifying organisms

When we tend to study the development and evolution of all the huge and mind blowing forms of living organisms on the earth. But, if we want to study of each them one by one, we do not have enough time to try and understand all of them. Hence, we need to look for similarities and dissimilarities among the living organisms, which will allow us to group them into different classes or categories and then study different classes or categories as a whole. So on the basis of similarities and dissimilarities amongst the organisms they are classified into different groups.

Whenever, we try to differentiate an animal from a plant, we will have to check the characteristics which may clear more basic differences among them. For instance, the organisms, which manufacture their own food are autotrophic (i.e., plants) while those which do not manufacture their own food are heterotrophs (i.e., animals). In this way, the main broad groups of organisms can be made.

Thus classification of wide variety organism makes study of them easier we can know more about them and make use them.

More about Taxonomy

Taxonomy is a branch of science which deals with the identification, classification and nomenclature of the living organisms. Taxonomy means arrangement according to rules.
Carol us Linnaeus (1707-1778) is known as the father of taxonomy. Linnaeus a Swedish doctor published many research papers on plants. He published his most popular book "Systema Naturae" from which all fundamental taxonomical researches have been taken.

He gave binomial system of nomenclature for naming the living organisms and classifying them.

Aristotle, a Greek thinker (384-233 BC) was the first to classify various living things as plants and animals. He is also known as the father of biology.

Importance of Classification

Diversity: It provides information regarding the diversity of living organisms.
Inter-relations: It gives information about inter-relationship between different categories of organisms.
System of identification: Classification provides a system for identification of known and unknown organisms.
Evolution: Classification based on natural relationship, resemblance and differences, gives information about phylogeny or the evolutionary history of various groups of organisms.
Information: Study of one or two members of a group gives information about the traits of the whole group.
Base of Biological Sciences: All biological sciences depend upon a system of classification for study of organisms. e.g. Physiology, Pathology, Mycology, Bio-geography etc.

What is the Basis of Classification

Classification of living organisms is based on similarities and dissimilarities of basic characteristics. A new set of characteristics of lesser basic nature are then used to originate small groups and their subgroups. It is just like building a wall of stones. The stones used will have different shapes and sizes. The stones at the top of the wall would not influence the choice of stones that come below them. The stones of the lower most layer will decide the types of stones on the next level and next level on the next.

Classification of organisms may be defined as a system of arrangement of organisms into different groups and sub groups on the basis of their similarities, dissimilarities and relationship.

Attempts of classifying living organisms have been made since time of immemorial. There are three major systems of classification, artificial, natural and phylogenetic.

4.1 Artificial System of Classification

In artificial system, the organisms are classified according to convenience, mainly for an aid to identification, using a few easily recognizable characters. A Swedish scientist Carolus Linnaeus (1707-1778) developed an artificial system of classification of plants in his book Species plantarum. He also published a book in 1735 called Systerna Nature. In this book, he classified, described and named plants, animals and minerals. His classification was based on the sexual characters (i.e., number and arrangement of stamens and carpels in the flower).

4.2 Natural Systems of Classification

The natural systems of classification were based on natural relationships (related affinities taking into consideration all the important characters of the organisms). The last and most important natural system of classification was given by Bentham and Hooker (1862-83). The system employs those characteristics which are relatively constant and related to body form, design, anatomy, cytology, embryology, biochemistry and physiology of organisms. It produces a hierarchical classification. Some examples are as follows—

(a) Complexity of cell structure: The cells are of two types, prokaryotic cells and eukaryotic cells. In prokaryotic cells the nuclear matter (i.e., genetic material) is not organised in to a nucleus. Membrane bound cell organelles are also absent. This causes an effect on every aspect of their cell design. In eukaryotic cells, well organised nucleus and membrane bound cell organelles are present. Biochemical pathways of the two types of cells are organised in different ways. Their mode of cell division and ability to form multicellular structures are also different.

All organisms having prokaryotic cells are now placed in kingdom monera.

(b) Complexity of body structure: Organisms can be unicellular or multicellular. The cells which group together to form a single organism (also called multicellular organism) make use of the division of labour. Hence in their body, all cells cannot be similar to each other. Instead, individual groups of cells will perform specialised functions, eg., proofers, coelenterates, helminthes.

This makes a very basic difference in the body design of organism. As a result, an Amoeba (unicellular) and a frog (multicellular) are very different in their complexity of body structure.

(c) Modes of Nutrition: Living organism producing its own food through the process of photosynthesis is called autotroph. But, if the organism is consuming the food from outside, it is called heterotroph. As a result of autotrophic or heterotrophic mode of nutrition, the body designs of the both is different from each other.

(d) Life Styles: On the basis of the mode of nutrition, organisms are of three types –

(i) Producers, manufacture their own food through the process of photosynthesis,

(ii) Consumers are animals and some related forms which feed on other organisms for obtaining food,

(iii) Decomposers are heterotrophic organisms which feed on organic remains, eg., fungi and many bacteria. Organisms of each life style have varied levels of design and organisation of their body.

(e) Organisation of plants: On the basis of organisation of the body, plants are classified m to bryophytes, pteridophytes and spermatophytes.

(e) Organisation of animals: Study of development of animal body, organisation of different Parts and specialisation of organs for different functions provide basis for classification of animals.

4.3 Phylogenetic system of classification

Such a classification is based on the presumed ancestry of the organisms. The systems of this group have attempted to classify organisms from simple to complex ones establishing their genetic and ancestral relationship.

Classification and Eoolution

We have studied already that the organisms are identified and, classified on the basis of their design in form and function. The body design, however, is not a constant feature. 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 likely to be more basic than characteristics that have come into existence later.

This means that the classification of organisms will be closely related to their evolution.

Now a question arises here as to what is evolution? Most life forms that we see today have arisen by an accumulation of changes in body design that allow the organism possessing them to survive better. The idea of evolution was described for the first time by Charles Darwin in 1859 in his book, the Origin of Species.

This idea of evolution can be connected to classification. Thus, there are some organisms with primitive body design that has not changed much over a period of time. These are known as Primitive organism. On the other hand there are other group of organisms which have acquired their peculiar body design quite recently. They may be considered as the advanced or recent organisms. Since the complexity in body design is likely to increase over evolutionary time, it may not be wrong to say that primitive organisms are simpler, while recent organisms are more complex.

The Hierarchy of classification Groups

In biological classification, an organism is placed in a system which relates it to all the other living organisms. This is done by arranging all the organisms into groups or categories known as taxa (singular taxon). Each group is divided into smaller groups which are further divided into smaller groups and so on. Thus a system of arranging taxonomic categories in a descending order on the basis of their relative dimensions is called hierarchy of categories. It was introduced by Linnaeus and is called Linnaean hierarchy. The hierarchy of major categories is given below:

Kingdom
	Phylum/Division
		Class
			Order
				Family
					Genus
						Species

Kingdom: If is the highest taxonomic category in biological classification. It is a group of phyla (in case of animals) or divisions (in case of plants), eg.. Kingdom Protista, kingdom fungi etc.
Division/Phylum: Division (in case of plants) or phylum (in case of animals) is a taxonomic category which is subordinate to kingdom. Division/Phylum is a group of related classes, eg', Phylum porifera.
Class: It is a taxonomic category which is subordinate to division and represents a group of related orders. e.g. class-monocotyledonous.
Order: An order is a group of closely related families. For example, the family Felidae (which includes cats) and the family canidae (which includes dogs) are assigned to the order carnivora because both cats and dogs have large canine teeth and are flesh eaters.
Family: It represents a group of some related genera. For example, the genus Felis of cats and the genus Panthera of lion, tiger and leopard are placed in one family because all these animals have retractile claws.
Genus: It is a group of related species which is subordinate to the category of family g,g. Panthera, Solarium.
Species: Species is the lowest taxonomic category regarded as basic unit of classification.

It is a group of similar individuals which resemble each other in morphology, breed among themselves but not with others and probably descended from a common ancestor. For example, Solarium nigrum (Makoy), Passer domestica (Goraiya).

The hierarchical classification of human being is as follows:
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Order	Primates
Family	Hominidae
Genus	Homo
Species	sapiens (Homo sapiens)

Classification Systems

Various systems of classification have been given from time to time. Some are shown below-

Two Kingdom system of classification

Biologists, since the time of Aristotle had divided the living world into two kingdoms, i.e. plantae and animalia. Carolus Linnaeus also divided the living organisms into two kingdoms like Aristotle.

Kingdom Plantae: If includes all the plant forms such as bacteria, fungi, algae, lichen?,

bryophyta, ferns, gymnosperms and angiospersms.

Fig. 6.1: Systems of classification (a) two kingdoms

Kingdom Animalia: It includes all the animal forms like protozoans, sponges, Hydra, worms, insects, snails, fishes, frog, birds, snakes and mammals.

Table. 6.2. Differences between Plants and Animals

	Characters	Plants	Animals
1.	Shape	Plants have less definite shape.	Animals have definite shape.
2.	Branching	They are usually branched.	They are unbranched except sponges.
3.	Growth	The growth is unlimited and continues till death. The growth regions are localised at the tips.	The growth is limited and it stops long before death. The growth regions are not localized.
4.	Mode of nutrition	They are usually autotrophic and feed on inorganic substances.	They are heterotrophic and feed on complex organic compounds.
5.	Chlorophyll	They have chlorophyll.	They lack chlorophyll.
6.	Locomotion	They are fixed and cannot perform locomotion except few unicellular motile forms.	They can move from one place to another except sponges and corals.
7.	Reserve food	Reserve food is starch and oil.	Reserve food is glycogen and fat
8.	Response	They are less sensitive and respond slowly	They are highly sensitive and respond quickly
9.	Cell wall	Cell wall is present	Cell wall is absent
10.	Organ system	Organ Systems are absent	Organ system such as digestive system, circulatory system, nervous system etc. are present.

Drawback: Two kingdom system of classification had following drawbacks:

Some organisms neither fit into kingdom Plantae nor into animalia. For example Fungi, which do not have chlorophyll have been placed in plant kingdom. The prokaryotic bacteria and blue green algae are also placed in plant kingdom. Unicellular organisms have been classified with multicellular organisms. Euglena resembles plants as well as animals for some of their features. Viruses belong to neither plant kingdom nor animal kingdom. Hence for grouping such type of organisms, a German Zoologist, Ernst Haeckel, in 1866 and 1894, raised third kingdom and named it Protista for such type of unicellular organisms.

Five Kingdom System of Classification

In 1969, an American ecologist Robert Whittaker classified all living organisms into five broad categories called kingdoms, namely,

Kingdom: Monera: It includes prokaryotic bacteria cyanobacteria, actinomycetes, archaebacteria etc.
Kingdom: Protista: It includes unicellular eukaryotic organisms such as unicellular algae, slime molds and protozoans.
Kingdom: Fungi: It includes all fungi.
Kingdom: Plantae: It includes all multicellular green plants.
Kingdom: Animalia: It includes all multicellular animals.

This classification is very much used currently. These five kingdoms were classified on the basis of following criteria:

Fig. 6.3: Five kingdom

(i) Complexity of cell structure (prokaryotic or eukaryotic)

(ii) Body organization (unicellular or multicellular)

(iii) Mode and source of nutrition (autotrophic or phototrophic)

(iv) Phylogenetic relationship.

Table. 6.4: Important characteristics of five kingdoms

	Characteristics	Monera	Protista	Fungi	Plantae	Animalia
1.	Cellularity	Unicellular	Unior	Unior	Mufti-cellular	Multicellular
2.	Nature of cell	Prokaryotic	Eukaryotic	Multicellular	Eukaryotic	Eukaryotic
3.	Cell wall is made up of	Peptidoglycan	If present, can be diverse in nature	Eukaryotic	Cellulose	Absent
4.	Mode of neutrino	Auto-or heterotrophic	Auto-or	Chitinous	Autotrophic	Heterotrophic
5.	Asexual reproduction	Amitosis	Binary and Multiple Fission Syngamy	Heterotrophic (Saprophytic/Pa rasitic)	Vegetative	Replaced by regeneration
6.	Sexual reproduction	?	Syngamy	Spores Syngamy	Syngamy with alternation of generation	Syngamy
7.	Examples	Eubacteria, Cyanobacteria Archaebacteria	Protozoans, slime molds	Bread mould, yeast mushrooms	Alage, Bryophyta, Pteridophyta Gymnosperms, Angiosperms	Non- chordates and chordates

6.5 Kingdom: Monera

Kingdom Monera (GK. Monos single) includes the most primitive, smallest, simplest and the most plentiful prokaryotes. They were the first inhabitants of the earth and they still continue to flourish. They are characterised by the following:

The organisms are mostly unicellular. The cyanobacteria are however, filamentous.
The genetic material is not organised into a nucleus. It lies directly inside the cytoplasm and is called nucleoid.
The genetic material is circular, double-stranded, helical DNA. It lacks histone proteins.
Membrane bound cell organelles like plastids, mitochondria, endoplasmic reticulum, Golgi body, lysosomes etc. are absent. They have 70s ribosomes.
Cell wall is generally present. Some prokaryotes do not have cell wall.
Flagella, if present, they have 9+0 organisation.
Nutrition is varied. Both autotrophic and heterotrophic modes of nutrition are found.

Both these have several subtypes.

All nitrogen fixing organisms belong to kingdom monera (eg., Rhizobium in root nodules of legumes). Some monera take parts in ammonification, nitrification and DE nitrification.

Kingdom monera includes true bacteria, actinomycetes, cyanobacteria (blue green algae; BGA), Mycoplasma and archaebacteria.

1. True bacteria or Eubacteria: They are unicellular and morphologically least complex microscopic organisms. They rarely exceed \[10\mu \]in length and \[2\mu \] in diameter. The cell wall is composed of peptidoglycan. The cell of bacteria vary in shape. They may be spherical (cocci), rod shaped (bacilli), cork-screw shaped (spirillum) or filamentous.

Fig. 6.6: Cyanobacteria

Fig. 6.7: Different forms of bacteria

Some bacterial cells possess long thread like structures called flagella (singular flagellum).

The flagella are made up of a protein flagellin. Some bacterial cells possess extremely minute, nonflagellar but straight hair-like appendages called pili or fimbriae.

Archaebacteria: They are unique type of prokaryotic microscopic organisms living in extremes of environments. They represent the oldest form of life that has survived in almost all the geological changes on earth. Most archaebacteria are autotrophic and only a few, photosynthesize.
Cyanobacteria: They include blue green algae (EGA). They are photosynthetic, prokaryotic organisms that occupy a wide range of habitats and grow almost everywhere. They contain chlorophyll and other photosynthetic pigments and therefore, synthesize organic food in presence of light by the process called oxygenic photosynthesis.

Some cyanobacteria like Anabaena, Nostoc etc, fix atmospheric nitrogen and improve soil fertility.

Fig. 6.8: Cyanobacteria

Actinomycetes: It is a group of unicellular, branched and filamentous bacteria which are found commonly in soil, fresh-water, food stuffs, manure etc. e.g., Antinomies etc.

5. Mycoplasma: They are unicellular, non- motile prokaryotic microorganisms which lack a distinct cell wall. They occur in soil, sewage water and decaying organic matter. Some mycoplasma occur parasitically in plants and animals including human beings. They cause many diseases in plants and animals.

Fig. 6.9: Mycoplasma

6.9: Kingdom: Protista

Kingdom Protista (Gk. Protista’s - first of all) includes many kinds of unicellular eukaryotic organisms such as unicellular algae, protozoans and slime molds. They are characterized by the following:

They are mostly aquatic and live wherever there is water. Some protestant occur parasitically in plants and animals.
The cell structure is typically eukaryotic and microscopic. The protoplasm is enclosed by a distinct plasma membrane. In addition, some protists have an outer covering of pellicle, cuticle, shell or cellulosic cell wall.
The genetic material is composed of double stranded, helical DNA with complex proteins.

The nucleus is enclosed by a nuclear membrane and has nucleolus.

The cytoplasm contains membrane bound cell organelles such as plastids, mitochondria, endoplasmic reticulum, Golgi apparatus etc.
They are either autotrophic, heterotrophic or parasitic.
Some of the make use of appendages such as hair-like cilia or whip-like flagella for moving around.

The Protists have been divided into three major groups-

The protistan algae
Slime moulds and
Protozoans

The Protistan Algae

These are unicellular eukaryotic algae found in water bodies. They usually grow and cover the surface of water body and move on the mercy of water current. They are considered as the major producers of aquatic ecosystem eg., Din of flagellates, Diatoms and Euglena.

Fig. 6.10: Protistan algae A. Din of lamellate; B. Diatom; C. Euglena

Slime Moulds

They include very interesting and peculiar organisms which have the characters of both animals and fungi. They either occur as free living multinucleate mass of protoplasm (the plasmodium) or aggregates of amoebae (the pseudoplasmodiu m). The vegetative parts do not possess cell wall. Mode of nutrition is holozoic i.e., organic substances, e.g., Physarium.

Protozoan Protist

These are unicellular, eukaryotic organism. The cells may be uninucleate, nucleate or multinucleate. Cell walls are usually absent. Sometimes naked cells are covered by pellicle or hard shells. These are solitary or colonial, free living or parasitic or symbiotic in nature. They vary in forms, shape (i.e., spherical, oval, bell-shaped, spindle shaped, slipper-like or irregular) and symmetry. Cytoplasm is often differentiated into outer ectoplasm and inner endoplasm Mode of nutrition is mainly holozoic. e.g. Amoeba, Paramecium, Nactiluca, Giardia, Trypanosoma etc.

Fig. 6.11: Some examples of Protozoa

Fig. 6.12: Paramecium

6.13 Kingdom: Fungi

Fungi (L. Fungus = a mushroom) are thallus like buildup of single cell or cells that possess definite cell wall and true nucleus but lack chlorophyll. Kingdom fungi is characterized by the following:

Members are thalloid (body is not differentiated into root stem and leaves), unicellular or multicellular, filamentous or mycelial. Single filament is called hypha and their cluster is called. Mycelium
They possess a definite cell wall containing chitin (a tough complex sugar) or fungal cellulose or both.
They lack chlorophyll and are unable to synthesize their own food by the process of photosynthesis. They are therefore, saprophytes as they use decaying organic matter as their food.
The reserve food material is glycogen and oil.
They have two distinct phases in their life cycle-The vegetative phase and the reproductive phase. The vegetative phase is concerned mainly with assimilation of food. The mycelium absorb soluble food material from the surrounding.
Reproductive phase is mainly concerned with reproduction. Asexual reproduction occurs mainly by the formation of spores. Sexual reproduction occurs by the formation of sex organs and fusion of gametes. During reproduction the fungus starts producing aerial fructifications and reproductive bodies. These fruiting bodies are sometimes coloured and are visible with naked eyes.

Examples: Yeast (Sacharomyces) Bread mould (Rhizopus, Mucor), Pink bread mould (Neurospora), Green mould (Penicillium)y Cup fungi (Peziza), Gill or button Mushroom (Agaricus campestris), rust (Puccinia), smut (Ustilago), Morchella etc.

6.14: Some Example of fungi

Lichens: They constitute a small group of thallophyta and autotrophic organisms. They form a unique combination of two, completely different individuals, of which one belongs to algae and other Fungi. The algal component is called phycobiont and the fungal component is known as mycobiont. The algal partner manufactures food with the help of photosynthesis while the fungal partner provides protection and also absorbs water and mineral salts. The two components or partners remain in close contact and appear to be a single plant. Therefore, lichens are also known as composite or dual organism.

Examples: Crustose lichens (Rhizocarpon, Graphis), foliose lichens (Parmelia) and fruticose lichens (Usnea, Alectoria).

Fig. 6.15: Lichens. A-Crustose lichen; B-Foliose lichen; C-Fruticose lichen

Mycorrhizae: A symbiotic relationship between fungal hyphae and roots of higher plants is known as mycorrhiza. The fungal partner at the mycorrhiza obtains organic food from the roots of the higher plant and in return the plant supplies minerals to the fungus. They are important to water absorption for plants growing in dry conditions.

6.16: Kingdom: Plante

Kingdom plantae includes all eukaryotic, multicellular and autotrophic green plants which manufacture their own food in the presence of sun-light with the help of a green pigment chlorophill by the process of photosynthesis. Some of the important characteristics of kingdom plantae are as follow:

The members of plantae are multicellular eukaryotic have chlorophyll to synthesize their own food by the process of photosynthesis.
Mode of nutrition is autotrophic. The reserve food material is generally starch and fat.
Cells have a large central vacuole and rigid cell wall composed of cellulose.
The plants are mostly non-motile, being anchored to the substratum. A few forms are free-floating in fresh or marine water.
Growth of plants is indefinite and new organs are continuously added throughout life.
They are considered as producers in the biosphere.

6.17. Kingdom: Animalia

Kingdom animalia includes, multicellular, eukaryotic and heterotrophic organisms having holozoic nutrition. They lack cell wall. Some of the important characteristics of kingdom Animalia are as follows:

These organisms, we eukaryotic, multicellular and without chlorophyll.
The cells of those organisms lack cell walls and plastids.
Central vacuoles are absent but small vacuoles may be found.
Most of the animals are free moving (except sponges and some coelenterates).
Nutrition is primarily holozoic (invective).
Growth of organisms stops at maturity.
Reproduction is generally sexual and the haploid stage is represented only by gametes.

Detailed Classification of Kingdom Planate

Kingdom plantae is further classified into different divisions on the basis of:

(i) Whether the plant body has well differentiated distinct components.

(ii) Whether the differentiated plant body has special tissues for mineral, water and food transportation.

(iii) Ability of plants to bear spores or seeds.

(iv) Whether the seeds are enclosed within fruits.

Eichler divided the kingdom plantae into two subkingdoms, cryptogamae and phanaerogamae in 1883.

Subkingdom: Cryptogamae (Gr. Krypto -hidden, gamos-marriage)-This kingdom includes those plants which do not produce external flower .or seeds, i.e., flowers and seeds are absent.

Thus, they are considered to bear hidden reproductive organs. The cpmmon means of reproduction is by spores. The embryo, if present, is naked. Plants of subkingdom cryptogamae are also called lower plants, flowerless and seedless plants. Sub-kingdom cryptogamae includes three divisions-Thallophyta, bryophyta and pteridophyta.

Subkingdom: Phanaerogamae (Gk. Phaneros - visible; amos-marriage)—Subkingdom phanaerogamae includes those plants which produce external flowers and seeds. The plant body is sporophytic (having paired set of chromosome; diploid) and differentiated into true roots, stem and leaves. Vascular tissue are present which forms a vascular system. Sex organs are well developed and multicellular. After fertilization, an embryo developes from fertilized egg.

Therefore, they are also called seed plants. Phanaerogamae has single division of spermatophyta.

7.1. Division: Thallophyya (Algae)

Thallophyta (Gk. Thallos - undifferentiated, phyton - plant) is a division of plantae which includes Algae. The term 'algae' was coined by C. Linnaeus which means 'sea weeds'. The division is characterized by the following—

Plants are generally aquatic, may be found in fresh water or in marine water. However, some are terrestrial and grow in moist places.
Plants are not differentiated into true roots, stented leaves. Therefore, they are thalloid.
Their vegetative structure is greatly variable i.e. they may be unicellular and motile (Chlamydomonas) or heterotrichous (Coleochaete) etc. or have a giant body as kelps.
They are autotrophic plants having chlorophyll and other pigments.
Cell wall is generally composed of cellulose or both cellulose and pectose.
Reserve food material is starch.

7. Reproduction is both asexual and sexual type. Reproductive organs are unicellular and non-jacketed. Embryo is absent.

Fig. 7.2: Algae A. Chlamydomonas; B. Chlorella; C. Volvox; D. Hydrodictyon; E. Ulothrix; F. Spirogyra; G. Zygnema; H. Coleochaete scutata; I. Coleochaete pulvinata; J. Ulva.

Table. 7.3: Differences between Algae and Fungi

Algae	Fungi
1. They are autotrophic in nature.	1. They are heterotrophic in nature
2. Photosynthetic pigments are present.	2. They lack photosynthetic pigments.
3. They are mostly aquatic.	3. They are mostly terrestrial.
4. Cell wall is made up of cellulose.	4. Cell wall is made up of Chitin.
5. Reserve food material is starch.	5. Reserve food material is oil or glycogen.

7.4 Division: Bryophyta

The division Bryophyta (Gk. Bryon - Moss, Phyton - Plants) includes the simplest and most primitive non-vascular land plants having an embryo stage in their life cycle. Bryophytes are the first land or terrestrial plants and they are often called' amphibians of plant kingdom'.

Characteristic features of bryophyta are:

Plants grow in moist and shady places but a few are aquatic.
The plant body is a gametophyte i.e., gametophytic generation is the dominant phase of the life cycle. It is a green thallus and lacks true leaves and roots. Plants are fixed by means of hair-like rhizoids.
Vascular tissues are absent.
Sex organs are multicellular and are surrounded by a sterile jacket.
Zygote develops into a multicellular embryo which forms sporophyte.
The sporophyte is semi-parasite on the gametophyte.
Distinct heteromorphic alternation of generations present.

Examples: Liverworts (Riccia, Marchantia), hornworts (Anthoceros), mosses (Funaria Polytrichum).

Fig. 7.5: Bryophytes A-B Riccia; C. Marchantia; D. Pellia; E. Anthoceros; F. Funaria; G. Polytrichum; H. Pogonatum

Gametophyte (Gr. gametos = spouse, phyton = plant)—It is haploid (i.e. having one set of chromosomes) plant structure which produces gametes directly.

Sporophyte (Gr. Sporos = seed, phyton = plant). It is diploid (i.e. having two set of chromosomes) plant structure, which produces haploid spores through the process of meiosis.

Sporophyte originates from diploid zygote or fusion product of gametes.

Emrayophytes: Plants which have an embryonic stage in their life cycle, eg. Bryophytes, pteridophytes, seed plans.

7.6. Division: Dteridophyta

The plants of division pteridophyta (Gr. pteis = fern, phyton = Plant) are, Sometimes, called the vascular cryptogams. They are the most primitive living and fossil vascular plants.

Characteristic features of pteridophytes are:

Plants grow in a variety of habitats and are mostly terrestrial thriving well in abundant moisture and shade. Some are aquatic eg. Marsilea, Azolla, Salvinia etc. and a few are epiphytes.
The plant body is a differentiated into root, stem and leaves.
Plant body is a sporophyte i.e. sporophytic generation is dominant:
All the plant parts possess vascular tissue (xylem and phloem) organized in definite stele.
Reproduction occurs by means of spores produced inside the sporangia. Plants may be homosporous (i.e. produce only one type of spores (e.g. Pteridium, Lycopodium etc.) or heterosporous i.e. produce two different types of spores-smaller micrp spores and larger megaspores in separate sporangia (e.g. Marsilea, Selaginella).
Spores, on germination, give rise to small haploid gametophytes or prothalli.
Gametophytes bear sex organs i.e. antheridia and archegonia.
Sex organs are multicellular and are surrounded by the sterile jacket.
Flowers and seeds are not produced. A thin film of water is required for swimming of male gametes to reach to archegonia.
The fertilized egg developes into embryo.

Examples: Selaginella, Equisetum, Marsilea, Lycopodium, Azolla, Pteridium, Adiantum. etc.

Fig.7.6: Some examples of pteridophyta

7.7. Subdivision: Gymnospermae

Gymnospermae (Gk. Gymno - naked; Sperma - seed) is the subdivision of spermatophyte (seed plants) in which the seeds are naked and the sporophylls are aggregated to form cones.

Characteristic features of gymnosperms are:

Gymnosperms are most primitive and simple seed plants.
They are usually perennial, evergreen and woody plants.
Vascular tissues are well developed but xylem lacks vessels and phloem lacks companion cells.
Sporophylls are aggregated to form cones. There are separate male and female cones.

The male spores are called microspore or pollen grains. They are produced inside microsporangia.

The female egg is formed inside the ovule.
In Gymnosperms, the ovules are not enclosed within the ovaries so that they are naked.
Pollination occurs by wind. After fertilization, the ovules become seeds. Thus, the seeds are naked and not enclosed inside the fruit. Gymnospermae includes the following two groups-

(i) Cycadae-Example-Qycas etc.

(ii) Conferee-Examples-Pinus, Cedrus, Ginkgo, Thuja etc.

Fig. 7.8: Some examples of gymnosperms

7.9. Subdivision: Angiospermae

The group angiospermae (Gk. angeion - case; sperma - seed) is the subdivision of spermatophyta which includes flowering plants in which the seeds are enclosed in fruits.

Characteristic features of angiosperms are—

The plants produce flowers. Therefore, they are called flowering plants. The flowers bear stamens and carpels.
The stamens are male reproductive organs which produce pollen grains. The carpels are female reproductive parts which bear ovules. After fertilization, the ovules develop into seed and ovary develops into fruit. Thus the seed are protected and enclosed within the fruits.
The seeds enclose embryo, the miniature of plant body. The embryo has plumule (produces shoot), redicle (produces root) and cotyledons (seed leaves). The cotyledons represent embryonic leaves which expand and become green when the seed germinates. On the basis of number of cotyledons in the embryo, the angiosperms, are grouped into two classes- dicotyledonous and monocotyledon.

(a) Class Dicotyledoneae

The class dicotyledoneae includes those flowering plants in which the embryo possess two cotyledons (embryonic leaves). The plants bear a prominent tap root system. Their leaves have reticulate venation, with a network of veins, vascular bundles are arranged in a ring.

Examples: Pea (Pisum satiuum), Potato (Solanum tuberosum). Gram (Cicer arietinum), Mango (Mangifera indica\ mustard (Brassica campestris). Rose (Rosa indica) etc.

(b) Class Monocotyledonae

The class monocotyledonae includes those flowering plants in which the embryo possess single cotyledon. The plants have fibrous root system and parallel venation in their leaves.

Vascular bundles are scattered.

Examples: Doob grass (Cynodon dactytilon), Maize (Zea mays), wheat (Triticum vulgare), Rice (Oryza satiua)

Fig. 7.10

Table 7.11: Differences between dicotyledons and Monocotyledons

Do You Know

Smallest	gymnosperm	Zamia pygmea
Digest	gymnosperm	Sequoia sempervirens (111.25 meter)
Smallest	angiosperm	Wolffia
Bigest	angiosperm	Banyan tree
Tallest	angiosperm	Eucalyptus
Largest	flower	Rafflesia

Detailed Classification of Kingdom Animalia

Kingdom animalia is further classified into several phyla (sing. phylum) mainly on the basis of certain criteria.

Some of the criteria of classifying animals are given below—

Organisation of animal body: There are three distinct levels of structural organisations.

These are:

(a) Cellular level: The body is formed by loosely aggregated cells. Tissues are not differentiated. Different types of cells may occur e.g., porifera.

(b) Tissue level: The body is made up of tissues of specialized cells, and organs are absent. e.g., coelenterata.

(c) Organ level: The body has organised tissue, organs and systems e.g., platyhelminthes.

(d) Organ System level: Cells are organised into tissues, tissues into organs and organs into organ systems, e.g., nematoda and higher animals.

Body symmetry: Animals having their parts arranged in such a way that their body can be divided into two similar halves by one or more planes, are called symmetrical. Symmetry is of two types: (i) Radial symmetry: The body is discoid or cylindrical where similar parts occur all around the central axis. Any vertical plane passing through the central axis will divide the body into two equal halves, e.g., Echinoderms, many sponges etc. (ii) Bilateral Symmetry—Body is divisible into two equal halves by only one plane e.g., Platyhelminthes, nematoda, chordate etc.

Cephalization: It is development of head in the anterior part of the animal body.

Mode of origin of mouth: Animals belong to two categories on the basis of the origion of mouth:

(a) Mouth arising from or near the blastopore ofgastrula, the animals are called protostomia

(b) Mouth arising anteriorly and anus develops from the blastopore. The animals are called deuterostomia.

Germinal layers: These are the primary layers that differentiate in the embryo. These layers can be two or three in number. All tissues and organs of the animal body develop from them. On the basis of germinal layers, the animals are of two types—

(a) Diploblastic Animals: They have two germinal layers i.e., outer ectoderm and inner endoderm. e.g., porifera, coelenterate.

(b) Triploblastic Animals: They have three germinal layers i.e., outer ectoderm, middle mesoderm and inner endoderm e.g., platyhelminthes to chordata.

Coelom or Body cavity: It is mesoderm lined fluid filled space that occurs between alimentary tract and body wall which provides shock proof environment to various body organs.

Depending upon the presence or absence of coelom, the animals are grouped into three categories.

(a) Acoelomate: Coelome is absent, e.g., porifera, coelenterata and platyhelminthes. In Platyhelminthes a mesoderm is present but it does not form a cavity.

(b) Pseudo coelomate: Animals having body cavity that does not arise from the mesoderm called pseudo coelomate e.g., nematoda.

(c) Coelomate or Eucoelomate: A true coelome lined by mesoderm is present. On the basis of origin, true coelom is of two types:

(i) Schizocoelom: Mesoderm develops as a distinct layer from a single cell of embryo. It split to gives rise a body cavity e.g., annelida, mollusca, arthropoda. In arthropoda true coelome is reduced. Another large cavity develops around the body organs by fusion of blood filled spaces.

Such a cavity is called haemocoel.

(ii) Enter coelom: It develops from pouches pinched off from endoderm lining of embryonic gut e.g., echinoderms, chordates. In vertebrates, the enter coelom is solid.

Presence or absence of notochord: Some animals possess a skeletal rod, called notochord, at some stage of their life. All those animals which have notochord are grouped under the phylum chordata and those which do not have notochord are grouped together as nonchordata.

8.1. Phylum: Porifera

Phylum porifera includes plant-like creatures commonly called the sponges. Members of this phylum are diploblastic, acoelomate having cellular level organisation, porous body with a canal system and sedentary habit.

Mostly found in marine water but a few species are also found in fresh water (e.g., Spongilld).
Only the young forms or larvae are motile. In adult stage they attach themselves to submerged substratum and become stationary (sessile).
Sponges may be vase-like, rounded, sac-like or branched.
They are simplest multicellular animals. There are no tissues, organs and organ systems.
Thus they have cellular level' of organisation. The cells are loosely held together and perform life functions more or less independently.
They have porous body with innumerable pores called ostia and a single exhalent pore called osculum.
The body cavity of sponges is called spongocoel.
Canal system is a characteristic feature of sponges. It is a system of pores, canals and chambers through which water circulates with the help of flagellated choanocytes (collar cells).

Water brings food and oxygen.

The body has covering of hard skeleton. It consists of spicules of calcium carbonate, silica or spongin fibres.
Digestion is intracellular which takes place within the individual cells. Mouth, digestive cavity and anus are absent.
Reproduction is by both asexual (by budding and gemmule formation) and sexual methods. Power of regeneration is well developed.

Examples: Sycon, Levcosolenia

Euplectella Euspongia

Spongilla, Cliona.

Fig. 8.2: Some examples of Porifera

8.3. Phylum: Cnidaria a coelenterata

(Gk. Koilos - hollow; enteron-mtestme)

Cnidaria or coelenterata is a phylum of diploblastic, acoelomate animals having tissue level organisation, gastrovascular cavity and cnidoblasts. Characteristic features of phylum cnidaria are—

All animals are aquatic and mostly marine, except a few like Hydra which are found in freshwater.
They may be solitary or colonial.
They are metazoans with tissue-level organisation. They possess all the four basic types of the tissues as in higher animals like epithelial, muscular tissue, connective tissue, and nervous tissue.
Animals are radially symmetrical (the anthozoan have bi-radial symmetry).
Coelenterates have a central cavity called coelenteron orgastro vascular cavity.
Body has a single aperture, the mouth. There is no anus. The mouth serves both for taking food and for throwing out fasces. The mouth often bears slender flexible processes called tentacles.
The body wall of cnidarians is supplied with special stinging cells, called cnidoblasts, for offence and defense purpose.
Digestion is both intracellular and extra cellular.
Respiration and excretion take place through general body surface.
The soft body may be supported by horny or calcareous skeleton. Hard skeleton occurs in corals.

11. Reproduction is usually asexual (by budding) in the polyp form and sexual in the medusa form. Fertilization may be external or internal. Gonads are simple without conducts.

Fig. 8.4.: L.S. of Hydra

Examples:

Hydra, Obelia, Millepora (Coral), Physalia (Portugese Man of war), Porpita etc.

e.g., Aurelia (jelly-fish), Rhizostoma.

Gorgonia (sea-fan) Corallium (red coral), Tubipora (organ pipe coral) Fungia (mushroom coral), Pennatula (sea-pen), Metridium (sea anemone).

Fig. 8.5.: Some examples of Coelenterata (Cnidaria)

Table 8.6: Differences between Porifera and Coelenterata

Porifera	Coelenterata
1. Animals have cellular level of organization.	1. Animals have tissue level of organisation.
2. The body of organisms has a number of in halent (incurrent) pores or ostia and a single exhalent (current).	2. Body of organisms has only a single opening.
3. Muscle and nerve cells are absent.	3. Muscle and nerve cells appear for the first time in coelenterates.
4. Digestion is intracellular.	4. Digestion is both extra and intracellular.
5. Appendages are absent.	5. Appendages are in the form of tentacles.
6. The special cells are collar cells or	6. Special cells are cnidoblasts.

8.7. Phylum: Ctenophora (Gk. ktenos- comb; Phora - To bear)

The animals are generally marine, solitary and free-swimming.
They are generally transparent and of variable shape e.g., oval in Ctenoplana and flattened Velamen.
They are bi-radially symmetrical and triploblastic.
They have tissue level of organisation.
Nematocytes are absent but colloblast (adhesive cells) are present.
No polymorphism or dimorphism occurs.

Example: Pleurobrachia (Comb. jelly), Cesium (Venus's girdle), Ctenoplana, Beroe etc.

Fig. 8.8: Some exampales of Ctenophora

Phylum: Platyhelminthes (Gk. Platy - flat; helminthes-worms)

Platyhelminthes is a phylum of flatworms where body is dorsoventrally flattened, triploblastic but acoelomate with organ level of organisation and bilateral symmetry. General characters of Phylum Platyhelminthes are:

Platyhelminthes are metazoa with organ level of organisation.
Animals are triploblastic i.e., they possess all the three germ layers-ectodenn, mesoderm and endoderm.
Body is soft, elongated, usually dorsoventrally flattened, leaf-like or ribbon-like.
Animals possess bilateral symmetry (body can be divided into two halves by just one plane). Body cavity (coelom) is absent.
Most of the animals belonging to this phylum are parasites. A few of them are however free living. The parasite forms attach to the host by suckers and hooks.
Digestive cavity (If present) is with a single opening, the mouth. Anus is absent.
Circulatory and respiratory systems and skeleton are absent.
Excretory system consists of blind tubules called protonephridia. Blind end of a tubule bears a tuft of a flagellum or cilia and is called a flame bulb or flame cell.
Most of animals are hermaphrodite (an animal has both male and female reproductive organs). Life history includes a variety of larvae.

Examples: Fasciola, Taenia solium, Dugesia, Planaria acetabulum

Fig. 8.9: Some examples of Platyhelminthes

8.10. Phylum: Nematode or Aschelminthes

The round-worms (Gk. nema - thread; helminth-worm; Nemathelminthes).

Nematoda or nemathelminthes or Aschelminthes is a phylum of triploblastic, bilaterally symmetrical but cylindrical worms having pseudocoelom, primitive organ system level of organisation and an elastic cuticle on the outside. General characteristics of phylum are:

Most of the animals are parasitic and few are free living in soil and water.
Body of animals is cylindrical and elongated, so are called roundworms because they appear circular in cross section. Body is unsegmented.
Size of body varies from microscopic to several centimeters in length.
The body wall is covered with a tough and resistant cuticle. Cilia are absent.
The body cavity present between the body wall and the digestive tract is not a true coelom. It is called the pseudo coelom.
Digestive system has both mouth and anus.
Respiratory and circulatory systems are absent.
Sexes are separate (unisexual) and female produce large number of eggs.

Examples: Ascaris (common roundworm), Ancylostoma (hook worm), Wuchereria (filarial worm that causes elephantiasis) Enterobius, (pin worm).

Table. 8.11: Differences between male and female Ascans

Male Ascaris	Female Ascaris
1. Smaller in size.	1. Bigger than male Ascaris.
2. Posterior end is curved.	2. Posterior end is straight.
3. Two pineal setae (project out through cloacal aperture and help in repro- diction) are present.	3. Absent.

Fig. 8.12: Some examples of Nematoda

Table. 8.13: Differences between Platyhelminthes and Nemathelminthes

Platyhelminthes	Nemathelminthes
1. Body is dorsoventraly flat or leaf-like or ribbon-like.	1. Body is cylindrical and elongated.
2. They are acoelomate	2. They are pseudo coelomate
3. Digestive tract is incomplete.	3. Digestive tract is complete.
4. Animals are hermaphrodite.	4. Animals are unisexual.

The Phylum annelida consists of triploblastic, bilaterally symmetrical eucoelomate animals having organ system level of organisation and metameric ally segmented body. The body shows a similar segmental differentiation of organs. Thus they are called segmented animals. General characteristics of phylum annelida are-

It is a large group of animals found in wet habitats such as moist soil, fresh water as well as sea water. Some animals are parasites (e.g., leech).
Body is elongated, cylindrical and segmented (metameric segmentation).
They are triploblastic. Exoskeleton is absent, body is covered by a thin cuticle.
Body is bilaterally symmetrical.
Alimentary tract is tube-like, complete and extends straight from mouth to anus.
They are the first animals to develop true coelom. Coelom allows true organs to be packaged in the body structure. There is thus, extensive organ 'differentiation.
Blood vascular system is closed type. Haemoglobin is present in blood plasma.
Respiration occurs through or moist skin.
Excretory system consists of excretory units called nephridia.
Some of the anterior body segments concentrate to form head, called cephalisation.
Body bears lateral appendages for locomotion in the form of chitinous setae or parapodia.
Sexes may be separate (unisexual) or united (Hermaphrodite).
Phylum Annelida includes the following three classes:

Nereis (sand worm or clamworm), Aphrodite (sea mouse).

Pheretima (earthworm),

Hirudinaria (leech).

Fig. 8.14: Some examples of Annelida

8.15. Phylum Arthropoda (Gk. arthros-jointed; podos - foot)

Phylum arthropoda is largest phylum and includes about 900,000, species. They are found on land, in the soil, in fresh water, in sea water and as parasites on and in the bodies of animals as well as plants. They are found everywhere from altitude of over 5,000 meters on the mountain to depths of more than 4,500 metres in the sea. General characteristics of phylum arthropoda are as follow:

Body triploblastic, bilaterally symmetrical.
The body is metameric ally segmented externally, by transverse grooves and internally by septa. The segments may be grouped into two regions-cephalothorax (head and thorax together) and abdomen, three regions-head, thorax and abdomen or head and trunk.
Some or all the body segments bear jointed appendages (legs).
Coelom or body cavity is reduced and contains blood and is called the haemocoel.
Exoskeleton of arthropods is light-weight, tough and composed of structural polysaccharide called chitin.
The alimentary canal is complete. Mouth is provided with movable appendages. Anus lies at the opposite end of the body.
Respiration occurs by, gills, trachea or book lungs.
Excretion takes place by Malpighi an tubules (insects) and green glands (in crabs and prawn)
In several arthropods, compound eyes are present, in which mosaic vision is produced.
Sexes are separate. The development of the animal may involve metamorphosis.

Phylum arthropoda is divided into the following five classes—

Examples:

e.g., Peripatus.

Palaemon (prawn), Daphnia (water-flea), Cancer (tree-crab) etc.

e.g., Scolopendra (centipede), Julus (millepede) etc.

Musca domestica (house fly). Apis (honey bee), Anopheles (mosquito), Lepisma (silver fish), Culex (mosquito), Cimex (bed bug), Gryllus (house cricket), Pieries (butterfly) etc.

Palamnaeus (scorpion), Limulus (king crab), Argus (tick), Aranea (spider), Sacroptes (itch mites).

Fig. 8.15. Some examples of Arthropoda

Fig. 8.16: Some examples of Insect

Table 8.17: Differences between Annelids and Arthropods

Annelids	Arthropods
1. Animals have unjointed appendages.	1. Animals have jointed appendages.
2. They have true coelom or body cavity.	2. True coelom is reduced, blood filled with body cavity called haemocoel is present.
3. Blood circulatory system is closed type i.e. Blood flows inside blood vessels,	3. Blood circulation is open type i.e. Blood flows through large sinuses or spaces.
4. A chitinous exoskeleton is absent.	4. A chitinous exoskeleton is present.
5. Excretory organs are nephridia.	5. Excretory organs are malpighian tubules and green glands.
6. Sensory organs are less developed.	6. Sensory organs are well-developed.
7. Locomotory organs are setae or parapodia.	7. Locomotory organs are legs and wings.

8.18. Phylum: Mollusea (L. Molluscus-soft)

Mollusca includes triploblastic, soft bodied but shelled animals with reduced coelom Characteristic features of phylum mollusca are:

The animals varies in size from microscopic to giant forms like octopus.
The animal body is soft and unregimented without external appendages. Body is bilaterally symmetrical.
Body is divisible into an anterior head, a ventral muscular foot and a hard dorsal visceral mass. The entire body is covered by a fold of thin skin, called mantle which secretes a hard and tough calcareous shell of one or more pieces. Foot is used in locomotion.
Body cavity is called haemocoel. True coelom is reduced and restricted to the pericardial cavity and the lumen of the gonads and nephridia.
Digestive tract or alimentary canal is complete.
Respiration usually takes place by gills (called the ctenidia) mantle or a lung of the mantle.
Excretion takes place by a pair of metanephridia.
Sensary organs of touch, smell, taste, equilibrium and vision one percent (in some).
Sexes are usually separates.

Examples:

e.g.. Chiton.

Pila (apple snail), Limax (gray slug), Aplysia (sea hare)

Dentalium (tusk shell).

Unio (fresh water mussel), Pinctada (indian pearl oyster),

Loligo (squid). Octopus (devil fish), Nautilus, Sepia (cuttle-fish)..

Fig. 8.19:

Fig. 8.20: Some examples of Mollusca

8.21. Phylum: Echinodermata (Gk. echinos-spiny; derma - skin)

The phylum echinodermata includes totaly marine, gregarious (live in groups), slow moving and free living animals. They are pelagic or benthonic, while a few are sessile.

The shape of animals may be star-like, cylindrical, melon-like, disc-like or flower-like.
Body lacks head, but has oral and aboral surfaces. Five radial areas called ambulacra found at oral surface.
Body is triploblastic, enter ocoelomic, un segmented, radially symmetrical in adult and bilateral in the larvae.
Body wall is covered with spiny hard calcareous (CaCOs) plates (ossicles) that forms a rigid or flexible endoskeleton.
Body cavity is modified into a unique water vascular system with tube feet, which helps in respiration and locomotion.
Digestive system is usually complete.
Excretory organs absent.
Reproduction by sexual and asexual methods. Power of regeneration is well developed.

Sexes are separate.

Example: Antedon.

(Feather star).

Holothuria (sea cucumber)

Echinus (sea urchin).

e.g., Asterias (star-fish),

Ophioderma (brittle star),

Fig. 8.22

Fig. 8.23.: Some examples of Echinodermata

8.24: Phylum: Chordata (Gk. Chorda - String)

Chordata is a phylum of triploblastic bilaterally symmetrical, enterocoelomic animals characterised by the presence of dorsal hollow nerve cord, post-anal tail, gill slits, and a dorsal no to chord at any stage of their life cycle.

Characteristics

Notochord (Gk. noton-boick, chorde-cord)—Notochord is a long rod-like structure which develops between dorsal nervous system and gut. It functions as a support structure that provides points for attachment to muscles. In higher chordates, notochord is transformed .into cranium and vertebral column.
Dorsal Hollow Nerve Cord: It occurs above the notochord. In higher chordates it gets modified into brain and spinal cord.
Pharyngeal Gill Slits: They are paired respiratory structures also called gill pouches which remain functional throughout life in fishes and larval stage of amphibians. In others they occur only in embryo.
Post anal Tail: It is founds in most chordates for balancing, protection of genital and anal regions.

Other Characters

The animals of phylum chordata have bilateral symmetry, organ system level organisation, triploblastic body development, enter coelom, pronounced cephalization, closed blood circulatory system, well developed excretory system based on kidneys and an integumentary system.

Fig. 8.25: A hypothetical animal to show the four basic characteristics of chordates

8.26. Subphylum Protochordata (Aerania)

Protochordata is a group of non-vertebrate animals which do not possess brain, cranium, vertebral column, jaws and paired appendages. They have a single layered epidermis. Notochord is present atleast in some stage of life. Dorsal hollow nerve cord, gill slits, postanal tail present.

They are triploblastic, bilaterally symmetrical, enterocoelomic, with organ system level organisation. They are mainly marine animals. Protochordata has three sub-phyla-hemicordata, urochordata and cephalochordata. Hemichordata has been taken out of protochordata and placed in a separate phylum because notochord like structure is structurally different and is called stomochord.

Hemichordata (Tiemi-half, chordato-notochord)

It includes chordata-like bilaterally symmetrical, triploblastic animals having pharyngeal gill slits and hollow chord called stomochord in the anterior region.

The animals are exclusively marine, soft worm-like which generally occur in burrows,

2. Body is divisible into three parts-proboscis, collar and trunk.

Fig. 8.27: Balanoglossus

‘Buccal diverticulum’, earlier regarded as a 'notochord' is present in proboscis.
No nephridia. Single glomerulus connected to blood vessels has a excretory function.
Respiration occurs through gills.

Example: Balanoglossus (Tongue worm. Acorn worm).

Urochordata (uros-tail; chordata notochord)

It includes exclusively marine animals where the adult undergoes retrogressive metamorphosis.

They are commonly known as tunicatesi

Animals have bag-like soft body.
The notochord is present in the tail of the larva and disappears in the adult.
Dorsal tubular nerve cord of larva degenerates to form a ganglion in adult.
Pharynx, however, contains several gill slits in the adult.

Example: Herdmania (sea sauirt). Oikouleura. Pvrosoma. Doliolum. salaa.

Fig. 8.28

Cephalochordata (cephalos-hesid, chordata notochord)

It includes fish-like chordates without a head.
The notochord extends upto anterior end of the body and persists throughout life.
Dorsal tubular nerve cord also extends throughout the length of the body.
Pharyngeal gill slits are present.
Head and jaws are absent.

Example—Amphioxus, Cephalodiscus.

Fig. 8.29:

8.30. Sub-afuflum vertebrata (Craniata)

Those chordates in which the notochord has been replaced by an endoskeleton of vertebral column and cranium while the dorsal nerve cord has been transformed into brain and spinal cord are placed in subphylum vertebrata. Like other chordates, the vertebrates are, triploblastic, enterocoelomic, segmented, bilaterally symmetrical with paired gill pouches, complex differentiation of body tissues and organs.

Notochord is present in embryonic stages. Respiration is by gills in aquatic animals and by lungs in terrestrial animals. Sexes are separate. Subphylum vertebrata includes following two sections-Agnatha and Gnathostomata.

Section—Agnatha (Gk. a without; gnathos jaws).

Section agnatha includes only one class Cyclostomata.

Clasg-Cyclostomata-(Gk. Kyklos circle; stoma mouth) Cyclostomata includes vertebrates which have a suctorial mouth. They are the most primitive vertebrates known to humans. Characteristics features of cyclostomates are-

Body is long, elongated and eel-like.
Mouth is round, suctorial and without jaws.
They are ectoparasites and use their mouth to stick to the back of other fishes.
Skin is soft, smooth, slimy and scaleless.
Nostril is single and median.
Respiration is through gills contained in pouch (which are 5 to 15 pairs in hag fishes and pairs in lampreys).
Heart is two chambered.
Endoskeleton is cartilaginous and the notochord is in the form of cylindrical rod and persists throughout life.
Gonad is single. Fertilization is external. Development is indirect or direct Amnocoete larva occurs in life cycle of petromyzon.
They are aquatic, occur in fresh or marine water. Both free living and ectoparasitic forms.

Examples: Lamprey (Petromyzon). Hag fish (Myxine)

Fig. 8.31: Examples of Cyclostomata

Section 2: Gnathostomata (Gk., gnathos jaws; stoma mouth)

Section gnathostomata includes, the vertebrates with jaws and paired appendages. Section gnathostomata is divided into two super classes-Pisces and Tetrapoda.

Super class: Pisces: Includes two classes-chondrichtyes & Osteichthyes.
Superclass: Tetrapoda: Includes four classes-Amphibia, Reptilia, Aves and Mammalia.

Class 1: Condrichthyes (Gk. chondros - cartilage; ichthy - fish - cartilaginous fishes) Class condrichthyes includes cartilaginous fishes i.e., the endoskeleton is made up of cartilage. Characteristic features of this class are:

These are mostly marine and generally large in size.
Streamlined body is either laterally compressed and spindle-shaped or dorsoventrally flattened and disc-shaped.
Mouth is usually ventral.
Skin is tough and covered with minute placoid scales.
They possess five to seven pairs of gills. Gills are not covered by gill cover or operculum.

Gills are respiratory organs. Without a swim bladder or lung.

They have fins for locomotion (swimming) and balance. Fins may be paired (pectoral fins, pelvic fins) or median (dorsal fin, caudal fin and anal fin).
Caudal fin is asymmetrical or heterocercal. Muscular tail is used for movement.
Heart is two chambered.
Cloaca is present (cloaca is common chamber that is connected to reproductive tract posterior part of digestive tract and urinary system).
Digestive system has a J-shaped stomach and intestine has spinal valves.
Sense of smell, vibration reception and electro receptor are well developed.
Excrete urea. (Ureotelic)

Examples: Scoliodon (dog-fish, Indian shark). Torpedo (electric ray), Pristis (saw-fish) Sphyrna (hammer-headed shark), Chimaera (rat fish), Trygon (sting ray)

Fig. 8.32: Few Cartilaginous fishes

Class 2: Osteichthyes (Gk. osteon bone; ichthys - fish - Bony fishes)

Class osteichthyes indues fishes having endoskeleton of bones, anterior mouth, and operculum covering gill slits and an air or swim bladder. Characteristic features of this class are-

These are found in fresh water as well as in sea water.
Body is usually spindle-shaped and size varies from 10 mm to 4 metres.
Body is covered with cycloid, rhomboid and ctenoid scales.
They possess 4 pairs of gills. Gills are covered by operculum.
Mouth is usually terminal in position.
An air bladder is present. It helps in maintaining buoyancy.
Caudal fin is symmetrical or homocercal.
A separate opening anus is present, for elimination of faecal matter cloaca is absent.
They excrete ammonia (ammonotelic).
Heart is two chambered containing one auricle and one ventricle.
Animals are cold-blooded.
They lays eggs and fertilization is external.

Examples: Labeo rohita (Rohu), Hippocampus (sea horse), Exocoetus (flying fish), Anabas (climbing perch), Caulophyryne jordani (Angler fish), Pterois uolitans (Lion fish)

Fig. 8.33: Some common bony fishes

Table 8.34: Differences between Cartilaginous and Bony fishes

Cartilaginous Fishers	Bony Fishes
1. They have cartilaginous endoskeleton.	1. They have bony endoskeleton.
2. They have 5-7 pairs of gill slits. Gills are without operculum.	2. They have 4 pairs of gill slits. Gills are covered by an operculum.
3. Mouth is ventral in position.	3. Mouth is terminal in position.
4. Caudal fin is heterocercal.	4. Caudal fin is homocercal.
5. Swim bladder is absent.	5. Air bladder is usually present.

Do You Know

Gambusia (a fish) eats mosquito larvae. It is used to control mosquitoes.
In Seahorse, Hippocampus, male bears a broad pouch in which the female lays eggs.
Lung fishes have three chambered heart.
Flying fish does not fly but glides.
Most of the amphibians undergo hibernation (winter sleep) and aestivation (summer sleep) to overcome the unfavorable conditions.
Limbless amphibian-Ichthyophis.
Limbless reptile-snake.
Following are not fishes:

Silver fish (insect). Whale fish (mammal). Jelly fish. (coelentrate). Devil fish (mollusc), Ichthyophis (amphibian)

Class 3: Amphibia (Gk. amphi double or both; bios life)

Class amphibia includes vertebrate animals with aquatic larval stage, terrestrial adult stage and pentadactyl limbs without claws. Characteristic features of class amphibia are-

The animals are amphibious in nature, i.e., they can live on land as well as in water.
Amphibians are cold blooded animals.
The body varies in form. The skin is smooth, moist, rich in mucous and poison glands.

Scales are absent.

They have two pairs of pentadactyl limbs, each with 4-5 or fewer digits. One pair or both the pairs of limbs are absent in some cases.
Heart is three chambered: two auricle and one ventricle.
Respiration takes place by gills, lungs or skin.
External ear is absent (but ear drum present). Nictitating membrane (third eye lid) is present. Lateral line sense organs occur in larval stage and some aquatic adults.
Sexes are separate. Fertilization is external. They are oviparous i.e. they lay eggs.

Examples: Rana tigrina (Indian frog), Bufo (toad), Salamandra, Hyla (tree frog), Necturees (mud puppy), Ichthyophish.

Fig.35: Some examples of Amphibian

Class 4: Reptilia (L., repre - to crawl; Creeping vertebrates)

Class reptilia includes ectothermic or cold-blooded, terrestrial or aquatic vertebrates with covered with dry water-proof skin having horny epidermal scales or dermal scute plates.

They were the first vertebrates fully adapted for life on dry land.

The animals of class reptilia are mostly terrestrial and live in warmer regions. Some are aquatic and live in water.
The body varies in form and is usually differentiated into head, neck, trunk, and tail.
They .have two pairs of pentadactyl limbs. Each digit ends in claw. In snakes and some lizards limbs are absent.
Teeth are usually present in all reptiles except in turtles and tortoises.
Respiration occurs by lungs only. Gills are absent.
Heart is three or incompletely four chambered (in crocodiles have a four-chambered heart.
Most reptiles are carnivorous or insectivorous (Tortoises are herbivorous).
Lateral line sense organs are totally absent.
Land reptiles are uriotelic (excrete uric acid) and aquatic reptiles are ammonotelic (excrete ammonia).
Sexes are separate. Fertilization is internal. Development takes place inside the hard- shelled egg. Embryo is protected inside the egg by extra embryonic membranes.

Examples:

Naja (cobra), Python, Hemidactylus (house wall lizard), Colotes (garden lizard), Chelone (green turtle), Chameleon (arboreal lizard), Crocodilus (Crocodile) Gavialis (gharial).

Fig. 8.36: Soome examples Reptilia

Table. 8.37: Differences between Amphibian and Reptilia

Amphibian	Reptilia
1. They have glandular, smooth and moist skin.	1. They have non-glandular, dry and keratinized skin.
2. Scales are absent.	2. Scales are present over the body.
3. Digits do not possess claws.	3. Digits end in claws.
4. Heart is three chambered.	4. Heart is incompletely four chambered.
5. Fertilization is external.	5. Fertilization is internal.
6. Extra embryonic membranes are absent.	6. Extra embryonic membranes are present.
7. Eggs have a soft covering.	7. Eggs have a hard covering or 'shell

Class 5: Ayes (Birds)

Class aves includes warm-blooded, tetrapodus vertebrates having fore-limbs modified into wings, body covered with feathers and jaws modified into horny toothless beak.

Birds are found in all continents, seas and most islands.
They are amongst the most beautiful animals. They range in size from smallest humming bird to largest ostrich.
Body is divided into head, neck, trunk and tail.
Jaws are prolonged to form horny beak. Teeth are absent.
Fore-limbs are modified into wings while hind limbs have four clawed digits, which are adapted for walking, running, perching or digging.
Bones are very light because of air spaces (pneumatic bones).
Oesophagus is modified to store and soften the food.
Respiration takes place only by lungs.
Larynx is absent. Instead, voice is produced by a special organ, the syrinx. It is present at the base of trachea.
Heart is four chambered.
Sexual dimorphism is found in many birds. Fertilization is internal. All birds are egg laying. Egg contains large amount of yolk and hard calcareous shell.

12. Cloaca is present.

Fig.8.38: Some examples of Aves

Examples: Columba (Pigeon), Struthio camelus (Ostrich), Passer domesticus (house- narrow), Milvus (Kite), Pavo (Pea fowl), Gallus (fawl), Coruus splendens (crow), Gypus (vulture).

Class 6: Mammalia (L. mamm breast) (mammals)

Class mammalia includes warm blooded, hairy, tetrapod vertebrates having mammary ylands in the females for suckling the young ones.

Mammals are the most advanced group of animals with a very well developed brain.
They maintain a fixed body temperature, they are therefore, warm-blooded.
Body is divisible into head, neck, trunk and tail.
The body is covered by hair.
Oil glands and sweat glands are present in the skin.
The females have mammary or milk producing glands. They are the only animals which nourish their young ones with milk.
In mammals, an external ear known as pinna is present.
They possess a muscular diaphragm dividing trunk into thorax and abdomen.
Heart is four chambered.

Fig. 8.39: Some examples of Mammalia

Teeth are of different types (hetero dont) and are present in sockets (the codont)
Fore-limbs and hind-limbs have five digits each and the digits end up with claws, hoofs or nails. Limbs are adapted for walking, running, burrowing, swimming and even flying (bats)
Sexes are separate and fertilization is internal.
Most mammals have well-developed placenta and are viviparous, (i.e., the female given birth to the young ones).
Duck-Billed Platypus and Echidna are egg laying mammals. Kangaroos and their relative give birth to very poorly developed young ones. They are nourished in mothers pouch or marsupium.

Examples: Rattus (rat), Felis (cat), Canis (dog), Macropus (Kangaroo), Pteropus (flying fox) Macaco, (monkey), Panthera tigris (tiger), Camelus (camel), Fanambulus (squirrel), Homo sapiens (man).

Table 8.40: Differences between Aves and Mammalia

Aves	Mammalia
1. Forelimbs of Aves are modified into wings.	1. Wings are absent. In flying fox, however patagin help in true flight
2. The body is covered with feathers and scales.	2. The body is covered with hair. Feathers and scales are absent.
3. Skin is dry and without gland. Only a single preen gland is present,	3. Skin bears a number of sweat and oil glands.
4. Mammary glands are absent.	4. Females possess mammary glands for feeding the young ones.
5. Diaphragm is absent.	5. A muscular partition called diaphragm is present between abdomen and thorax.
6. Bones are hollow and pneumatic which possess air cavities.	6. Bones do not possess air cavity.
7. A toothless beak is present.	7. Jaws do not form a beak. Teeth are present.
8. Lungs possess external air sacs.	8. External air sacs do not occur over lungs.
9. Larynx is non-functional. Instead syrinx is present.	9. Larynx is functional. Syrinx is absent.
10. Egs possess a lot of yolk.	10. Eggs have little yolk.
11. Birds are oviparous.	11. Mammals are viviparous with the exception of a few species.

Do You Know

Emu, Ostrich, Kiwi, and Penguin are some flightless birds.
Ornithology is-study of birds.
Largest animal-Blue Whale.
Egg laying mammals-Duck-Billed Platypus and Echidna.
Kangaroo lays undeveloped young ones.
Tiger is our national animal.
Whale, Dolphin, Seal and Walrus are aquatic mammals,
National bird is Pauo cristatus (Peacook).

Nomenclature (L. nomen Name; Calare call)

Different organisms around us are identified by their own distinct names. The names are, therefore, necessary for identification of an individual as well as to distinguish an individual from the other. In Biology, the organisms are grouped into different obligate categories. Deferent catagories used in taxonomy are species, genus, family, order, class, phyla etc. A number of species are grouped into a genus. A number of genera are grouped into a family and several families are grouped in an order. Such a way several orders are grouped under a class and several classes are placed under a phyla/division. Similarly several phyla or divisions are grouped into other higher category king dom.

What is nomenclature?

Nomenclature is the system of providing distinct and specific names to living organisms. It involves the principles governed by set of rules formulated by international bodies so that a particular organisms or taxon is known by its specific name throughout the world.

Common vernacular names and scientific names

Biological nomenclature is of two types-common vernacular names and scientific names.

The naming of the organism started with the human civilization. The common names have been handed down from generaton to generation. They are names given to organisms by local people in different regions of the world. For example, a dog is named Kutta in Hindi, Kukur in Bengia, Kutra in Marathi and naai in Tamil. English people call it a dog. A dog may be known by some other names in some other states and countries. Similarly the bird that we know as Gauraiya in Hindi, in India and Pakistan, is known by different names in other countries-house sparraw in England, Pardal in Spain, Musch in Holland, Suzune in Japan and so on. These names are not understood elsewhere. Morever, the same common name may be used for different kind of animals. For example, the name Kenchua is used both for the earthworm and A scans. It is therefore, important to have a single scientific name to be followed all over the world.

Some Examples are here:

S. No.	Plant	Botanical Name
1.	Wheat	Triticum aestivum
2.	Rice	Oryza sativa
3.	Pea	Pision rativum
4.	Mango	Mangifera indica
5.	Potato	Solanum tuberosum
6.	Peanus	Arachis hyporea
7.	China rose	Hibiscur rosa-sinensis
8.	Lady?s finger	Abelmoschus esculentus
9.	Mustard	Brassica campestris
10.	Sugarcane	Saccharum officinarum

S. No.	Plant	Botanical Name
1.	Rat	Rattus rattus
2.	Cobra	Maga naga
3.	Horse	Eguuas caballus
4.	Dog	Canis familiaris
5.	Cat	Felis domestica
6.	Tiger	Panthera tigris
7.	Blue whale (largest animal)	Balaenoptera musculus
8.	Lion	Panthera leo
9.	Bear	Ursus arctos
10.	Human	Homo sapines sapines

Acoelomatc: Animals without body cavity or coelom.
Amphibious: The organisms which live on land as well as in water.
Bacteriochlorophyll: A type of chlorophyll unique to photosynthetic bacteria.
Coelenteron: Gastrovascular cavity present in cnidaria or coelenterates.
Conifers: Group of gymnosperms, most of which are evergreen trees.
Cryptogames: Non-flowering, non-seeded plant.
Diploblastic: Body made up of two germ layers-ectoderm and endoderm.
Diatoms: They are soap box shaped and reproduce asexually by fission producing successive generations until size is restored through sexual reproduction by auxospores.
Epiphyte: Plant growing on other plants but do not take food and water from them.
Fauna: All the animal species inhabiting a particular area are called fauna of that area.
Flora: It refers to all the plant species inhabiting a particular area.
Haemocoel: Blood filled body cavity having sinuses and open spaces.
Lichen: A symbiotic combination between an alga and a fungus.
Omnivore: A living organism that consumes both plant and animal food.
Osmoregulation: To keep the salt and water contents constant in the body.
Oviparous: Animals that lay eggs.
Placenta: An intimate connection between the developing foetus and uterine wall of mother.
Rhizoids: Root like structures present in bryophytes.
Viviparous: Animals that give birth to young ones.

9th Class Science Diversity in Living Organisms

Other Topics

Notes - Diversity in Living Organisms