CBSE Class 9 Science Diversity in living Organism Exam Notes

CBSE Class 9 Science Diversity in living Organism Exam Notes. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

CLASSIFICATION

The method of arranging organisms into groups on the basis of similarities & differences is called classification.

TAXONOMY

The taxonomy is the study of diversity & kind of organism & the evolutionary relationship among them.

BASIS OF CLASSIFICATION

Some examples of such characters, used in grouping and sub-grouping of organisms, are as follows :

Cells are prokaryotic or eukaryotic :

Organisms may be grouped into two broad categories on the basis whether they possess prokaryotic cells or eukaryotic cells. In case of prokaryotic cells the nuclei and other organelles are not clearly developed. The eukaryotic cells, on the other hand, have membrane-bound organelles, including a nucleus.

Cells occur singly or in clusters :

Many organisms are unicellular, i.e., made up of only one cell, e.g. Amoeba. Others are multicellular. i.e., cells groups together to form single organism (e.g., insect). In case of multicellular organisms the different groups of cells carry out specialized functions.

Organism is photosynthetic or takes food from outside :  

Green plants perform photosynthesis and synthesise their own food. Animals cannot perform photosynthesis. They get food from outside.           

Organisation of different body parts :

Grouping of organism may be done on the basis of body organization. For example, plants possess stem, root and leaves. Similarly, the animals possess specialized organs to perform different functions. The characteristics based on body design used for classification of plants is quite different then used for classifying animals.

In classification, the organisms that closely resemble one another are placed in a group. These groups are further placed in larger groups on the basis of close similarities. The larger groups are again placed in still larger groups. The various grouping levels or ranks in classification are known as categories. Each category has its specific name. There are seven major categories.

Species
Genus
Family
Order
Class
Phylum (for animals)/division (for plants)
Kingdom

Species :

Species is the lowest category regarded as basic unit of classification. It is a group of similar individuals which resemble with each other in morphology, breed among themselves but not with others and probably descended from a common ancestor.

Genus :

A genus is a group of closely resembling spcies having a common ancestry. All the species in a genus show similarities in broad features of their organization but differ in minor details.

Family :

A family represents a larger group of closely related genera. It is composed of one or more genera. For example, the genus Felis of cats and the genus Panthera of lion, tiger and leopard are placed in the family Felidae because all these animals have retractile claws.

Order :

An order is a group of closely related families. For example, the family Felidae (that includes cats) and the family canidae (that includes dogs) are assigned to the order carnivore because both cats and dogs have large canine teeth and are fleash eaters.

Class :

A class is a group of related order.

Phylum/Division :

Phylum (in case of animals) or Division (in case of plants) is a group of related classes.

Kingdom :

Kingdom is the highest category in biological classification. It is a group in Phyla (in case of animals) or divisions
(in case of plants).

The various categories used in biological classification can be arranged in a hierarchy (i.e.; ranked one above the other). It was introduced by Linnaeus and is, therefore, called Linnaenan hierarchy. The hierarchy indiciates the various levels of Kinship (i.e., relationship by blood). Nearer the categories in hierarchy the greater is the similarity between their organisms. The hierarchy of major categories is given below -
Kindom

Phylum/Division

(for animals) (for plants)

Class

Order

Family

Genus

Species

Ø BINOMIAL NOMENCLATURE

Proposed by Carolus Linnaeus.

According to this system of nomenclature, each animal or plant is given two names : the first one is the generic name and the second one is the name of the species.

Scientific names are always in Latin.

The first letter of the generic name is always capitalized and that of the specific name is written in small letter. For example, the scientific name of frog is Rana tigrina, in which Rana is the generic name and tigrina is the name of the species.

 Two Kingdom Classification :

Father of taxonomy - Carolus Linnaeus. He preposed following kingdoms.

Plantae :

Which included Bacteria, Fungi, Algae, Mosses, Liverworts, Ferns, Conifers and Flowering plants.

Animalia :

Included Protozoan, Sponges, Jelly fishes, Worms, Crabs, Insects, Millipedes, Centipedes, Spiders, Snails, Star fishes, Snakes, Frogs, Birds and Mammals.

 Three Kingdom Classification :

This was suggested by german biologist, Haeckel in 1866.
As some microscopic single celled forms were unlike plants or animals altogether and could not be placed in earlier system, thus three kingdom system was proposed. It includes (1) plantae, (2) Animalia,
(3) Protista ... contained all single celled organisms like protozoans and unicellular algae.

 Four Kingdom Classification :

This was developed by Copeland in 1966.
As prokaryotes (Organisms without true nucleus) were different from eukaryotes (organism with true nucleus), a new group, monera was formed.

 Five Kingdom Classification :

This most favoured scheme was proposed by R.H. Whittaker in 1969. Fungi could not find a suitable place in earlier system of classifications and thus whittaker’s five kingdom theory found favour amongst most biologists.

This classification includes :

(a) Plantae

(b) Animalia

(c) Fungi

(d) Protista

(e) Monera.

 Six Kingdom Classification :

It was proposed by Woese, Kandler and Wealis (1990). They divided monera into Archae bacteria and Eubacteria.

Kingdom : Monera (Gk. Monos – Single)

• Kingdom, Monera includes the most ancient, the smallest, the simplest and the most plentiful prokaryotes. These organisms are most primitive. Monerens are characterized by the following.

• The organisms are mostly unicellular. The cyanobacteria are, however, filamentous.

• They do not have a definite nucleus. The genetic material is a circular, double-stranded, helical DNA (Deoxyribonucleic acid) not enclosed by a nuclear envelope. Such organisms which do not have a definite nucleus are called prokaryotic.

• The cytoplasm of organisms is devoid of membrane bound organelles, i.e., mitochondria, plastids, Golgi apparatus, lysosomes, endoplasmic reticulum, centrosome, etc. are lacking. However, the ribosomes are
present.

• Cell wall is generally present. some of prokaryotes do not have cells wall.

• The mode of nutrition of organisms in this group can be either :

 (i) Autotrophic (i.e., synthesize their own food by photosynthesis) or

 (ii) Heterotrophic (i.e. get their organic food from the environment).

• Single stranded flagella are present in many monerans.

• Kingdom Monera includes true bacteria, actinomycetes, cyanobacteria or blue green algae, mycoplasma and archaebacteria.

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