Diversity in living organisms

Diversity in living organisms 

16)                   The main characteristics considered in the five-kingdom scheme of classification are:

i)         Presence of prokaryotic or eukaryotic cells ii)             If eukaryote, whether the organism is unicellular or multicellular.

iii)       Whether the cells possess or lack cell wall and whether they can prepare their own food.

17)                The categories or taxa used in the classification of organisms are kingdom, phylum/division, class, order, family, genus and species. The smallest unit of classification is species whereas the highest unit is kingdom. 

18)                The 5 kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae and Animalia. Carl Woese further divided Monera into Archaebacteria and Eubacteria.

19)                Prokaryotic one-celled organisms such as bacteria, cyanobacteria and mycoplasma are included in Monera.

20)                Monerans show either autotrophic or heterotrophic nutrition. Cell wall may be present or absent.

21)                Unicellular eukaryotic organisms such as protozoans, unicellular algae and diatoms are grouped under Protista. They may be autotrophic or heterotrophic and may use appendages for locomotion.

22)                Fungi, such as yeast and mushrooms, include heterotrophic, eukaryotic organisms, which are normally saprophytes. Their cell walls are composed of chitin.

23)                Lichens are symbiotic associations of certain fungi with blue green algae.

24)                Multicellular, autotrophic eukaryotes possessing cell wall are included under kingdom Plantae.

25)                Classification of plants is done at three levels on the basis of 

i)           Presence or absence of well-differentiated body

ii)         Presence or absence of vascular tissue iii)       Ability to bear seeds, which could be naked or enclosed in fruits.

26)                The important divisions of Plantae are Thallophyta, Bryophyta, Pteridophyta, Gymnospermae and Angiospermae.

27)                Thallophytes, Bryophytes and Pteridophytes possess inconspicuous reproductive organs and are called Cryptogams. Gymnosperms and Angiosperms are grouped under Phanerogamae, since they possess welldifferentiated, seed producing reproductive tissues.

28)                Thallophytes (or algae) are the simplest plants lacking welldifferentiated body design. E.g. – Spirogyra.

29)                Bryophytes, such as moss and Riccia, show differentiated plant body lacking vascular tissue.

30)                Plants grouped under Pteridophyta show well-differentiated plant body with vascular tissues for conduction. E.g. Ferns. 

More >>>