Diversity in Living Organisms
Synopsis
- 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.
