RBSE Class 9 Science Notes Chapter 7 Diversity in Living Organisms

These comprehensive RBSE Class 9 Science Notes Chapter 7 Diversity in Living Organisms will give a brief overview of all the concepts.

RBSE Class 9 Science Chapter 7 Notes Diversity in Living Organisms

→ Each organism is different from all other organisms.

→ Biodiversity : It means the existence of different plants, animals and microorganisms present on earth. Biological diversity or biodiversity is the occurrence of various forms of living beings which are different from one another in size, colour, appearance, behavior, habitat and structure, etc.

→ Walter G. Rosen coined the term “Biodiversity” in 1986.

→ Classification : It becomes very difficult to study this huge diversity one by one. To make it easier, they need to be classified. Classification is the division of organisms into groups and sub-groups on the basis of their characteristics.

→ Classification by Aristotle : He classified animals as aquatic or terrestrial, according to their living environment. But we find so many animals who can live in water as well as on land, so his classification has limitations.

→ Basis of Classification :

(i) Complexity of cell structure
(ii) Mode of taking food as autotrophic/heterotrophic
(iii) Basic/primary characteristics
(iv). Various level of organisation
Thus, it was decided to classify the organisms on the basis of hierarchy.

→ Classification and Evolution : The process of continual changes from simple life forms to complex life forms is called ” Evolution”., The idea of evolution was first given by Charles Darwin a British scientist (1859) in his book “The Origin of Species”. Organisms evolved earlier have simple and ancient body. designs (primitive) whereas recently evolved young organism have complex body designs (advanced).

→ The branch of science that deals with identification, nomenclature and classification of organisms is called taxonomy.

→ Formation of Kingdom : Biologists Ernst Haeckel, Robert Whittaker and Carl Woese have tried to categorised different organisms into several kingdoms. Carolus linnaeus (in 1758) proposed the two kingdom classification of organisms as plantae and animalia.

→ Further Robert H. Whittaker divided living organisms into five kingdoms :

(i) Monera : It includes unicellular prokaryotic organisms like bacteria, blue-green algae or cyanobacteria, Anabaena, Nostoc and mycoplasma.

(ii) Protista : It includes unicellular eukaryotic organisms like protozoans, diatoms and algae.

(iii) Fungi : These are heterotrophic eukaryotic non-green organisms. These are initially unicellular but can become multicellular in later stages of life. Most of them are decomposers or may be parasitic e.g. Yeast and Mushroom (agaricus), bread mould (Rhizopus), etc.

(iv) Plantae : These are autotrophic eukaryotic organisms. Plants are multicellular. Autotrophs use chlorophyll for photosynthesis. These are made up of cellulose e.g. rice, wheat, flowering plants.

(v) Animalia : These are motile, multicellular eukaryotes without cell walls. Animals are heterotrophic eig. Insects, reptiles.

→ Classification of Kingdom Plantae: It is further classified into two sub-kingdoms –
(i) Cryptogamae and (ii) Phanerogamae.

→ Cryptogamae : It includes plants with hidden reproductive organ not bear seeds or flowers. Cryptogams are further classified into three groups : Thallophyta, Bryophyta and Pteridophyta.

(i) Thallophyta : These plants do not have a well-differentiated body design and distinct components, commonly called “Algae”. These are mostly found in aquatic environment. Examples – Spirogyra, Ulothrix, Cladophora, Ulva, Chara etc.

(ii) Bryophyta: These plants have little differentiated body. The distinct components are present as stem and leaves. These are commonly called “Amphibians of plant kingdom”, because they require both terrestrial and aquatic environment for completion of their life cycle. Examples – Mass (Funaria) and Marchantia.

(iii) Pteridophyta : The plant body is differentiated into roots, stem and leaves.
They possess naked embryos underneath the leaf in the form of spores. Examples – Marsilea, Ferns and horse-tails.

→ Phanerogamae : It includes plants having well developed reproductive organs and plants that develop seeds. These are classified into two subgroups : Gymnosperms and Angiosperms.

(i) Gymnosperms : These are evergreen, woody and perennial plants. They bear naked seeds i.e. seeds are not enclosed inside fruits. Examples – Pines (Pinus), cycas and deodar (Cedrus).

(ii) Angiosperms : These are flowering plants which develop seeds inside an organ which turns into a fruit. Plant embryos in seeds have structures called cotyledons. Angiosperms can be divided into two parts on the basis of the presence of cotyledons –
(a) Monocotyledons or monocots (seeds having single cotyledon)
(b) Dicotyledons or dicots (seeds having two cotyledons)

→ Classification of Kingdom Animalia : On the basis of extent and body type design, they are classified as Non-chordates and Chordates.

→ Non-chordates are :

• Porifera : Examples – Sycon, Spongilla, Euplectella, etc.
• Coelenterata (Cnidaria) Examples – Span (Hydra), Sea anemones (Metridium), Jellyfish (Aurelia).
• Platyhelminthes : Examples – Tapeworm (Taenia solium), Liver Fluke (Fasciola hepatica), Planaria.
• Nematoda (Aschelminthes) : Examples – Ascaris, Wuchereria.
• Annelida : Examples – Earthworms (Pheretima), Leeches (Hirudinaria), Clamworm (Nereis).
• Arthropoda : Examples – Scorpion, Spider, Prawn, Butterfly, Moth, Cockroaches, Housefly, Crab, Shrimp, etc.
• Mollusca : Examples – Snails, Mussels, Octopus, Unio, Chiton, Pila, etc.
• Echinodermata : Examples – Sea-cucumber (Holothuria), Sea-star (Asterias), Sea-urchin (Echinus).

→ Chordates are :

(i) Protochordata : Examples – Balanoglossus, Herdmania and Amphiozus etc.
(ii) Vertebrata : Classes –
(a) Cyclostomata : Examples – Lamprey and Hagfish.
(b) Pisces : Examples – Electric ray, sting ray, dog fish, rohu, sea horse, flying fish etc.
(c) Amphibia : Examples – Frogs, toads and salamanders etc.
(d) Reptilia : Examples – Snakes, turtles, lizards and crocodiles etc.
(e) Aves : Examples – Birds.
(f) Mammalia : Examples – Human, whale, monkey, lion, cat etc.

→ Nomenclature : An organism can have different names in different languages, so it creates confusion in naming them. The scientific name is same in all the languages. Scientific nomenclature system was introduced by Carolus Linnaeus.

It is binomial nomenclature which includes two words – first word denoting name of ‘genus’ (first letter should be capital) and second word denoting ‘species’ (in small letters). Binomial names are printed in italics and underlined when written with hands. Example : Tiger – Panthera tigris.