9th Class Science Diversity in Living Organisms

Diversity in Living Organisms

Category : 9th Class


Diversity in Living Organisms




  • Classification helps us in exploring the diversity of life forms and systematic study of organisms.


  • Robert Whittaker (1959) proposed the '5-kingdom System' based on the cell structure, mode of nutrition and body organisation. The five kingdoms are Monera, Protista, Fungi, Plantae and Animalia.


  • Scheme of classification is:

          Kingdom \[\to \] Phylum (or) Division \[\to \] Class \[\to \]Order\[\to \] Family \[\to \] Genus \[\to \] Species.


  • Monerans do not have a defined nucleus. The mode of nutrition is either autotrophic or heterotrophic. e.g., cyanobacteria, mycoplasma, etc.


  • Protista includes unicellular eukaryotic organisms mode of nutrition is either autotrophic or heterotrophic. e.g., diatoms, protozoan, etc.


  • Fungi are saprophytic eukaryotic organisms. They have -cell walls made up of chitin. e.g., yeast and mushroom. Some fungi lead a symbiotic life with algae. e.g., lichens.


  • Plants that do not have a differentiated plant body belong to thalloptiyta. e.g.,. spirogyra, ulothrix,


  • Plants with a differentiated plant body without a specialized vascular tissue belong to e.g. moss, marchantia, etc.


  • In Pteridophyta the plant body is differentiated into roots, stem and leaves and has specialized vascular tissue, e.g., fern, marsilea, etc.


  • Thallophytes, bryophytes and pteridophytes are together called


  • Plants with well-differentiated reproductive tissues that ultimately bear seeds are called Phanero- gams(Gymnosperms and Angiosperms).


  • Gymnosperms bear naked seeds and are usually perennial/evergreen and woody, e.g., pine, deodar, etc.


  • Angiosperms bear seeds inside the fruit. Plants with seeds having a single cotyledon are called monocots. e.g., paddy


  • Plants having two cotyledons are called e.g., bean.


  • Organisms belonging to animalia are eukaryotic, multicellular, heterotrophic and mobile. They do not have a cell wall.


  • Porifera includes non-mobile animals having pores and are commonly called sponges.


  • Animals belonging to coelenterate show body design differentiation and have a cavity in the body.
  • The body is made up of two layers of cells, e.g., hydra, sea anemones/etc.


  • The body of platyhelminthes is bilaterally symmetrical with no true ceolom. e.g., planarians, liver fluke, etc.


  • The body of nematodes is triploblastic with pseudoceolom. e.g., ascaris, wuchereria, etc.


  • Annelid shave extensive organ differentiation in a segmented form. e.g., earthworms, leeches, Animals belonging to arthropoda have open circulatory system and jointed legs, e.g., prawns, spiders, crabs, etc.


  • In molluscans the ceolomic cavity is reduced, e.g., snails, mussel, etc.


  • Animals of Echinodermata have calcium carbonate in their skeleton and a water-driven tube system, e.g., starfish, sea cucumber, etc.


  • Notochord is replaced by vertebral column in vertebrata. (Pisces, Amphibia, Reptilia, Aves and Mammalia).


  • In pisces, exoskeleton is made up of scales, endoskeleton of bones and cartilage/They respire by means of gills.


  • Amphibians have a three chambered heart, mucous glands in the skin and respire with the help of lungs (gills in larval stage).e.g., frogs, etc.


  • The animals belonging to reptilia are cold blooded, have a three-chambered heart (crocodile-being an exception - has four chambers), e.g., snakes, lizards, etc.


  • Aves (birds) are warm-blooded animals and have a four chambered heart. They lay eggs and their two fore limbs are modified for flight.


  • Mammals are warm-blooded animals with a four-chambered heart. They have mammary glands for production of milk. They are viviparous, e.g. human beings/whales, etc.


  • Duck-billed platypus and echidna are egg-laying mammals. Kangaroos (marsupials) give birth to poorly developed young ones and nurse them in their pouches.

Notes - Diversity in Living Organisms

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