What is Biodiversity?
"Biological diversity is the variety and variability among living organisms and the ecological complexes in which they occur.
Keyword : diversity,variety,living organism,ecological
official meaning[US Congressional Biodiversity Act, HR1268 (1990)]:
Biological diversity means the full range of variety and variability within and among living organisms and the ecological complexes in which they occur, and encompasses ecosystem or community diversity, species diversity, and genetic diversity."
Keyword :
nBiodiversity found on Earth today is the result of 4 billion years of evolution. The origin of life has not been definitely established by science, however some evidence suggests that life may already have been well-established a few hundred million years after the formation of the Earth. Until approximately 600 million years ago, all life consisted of archaea, bacteria, protozoans and similar single-celled organisms.
nThe history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion—a period during which nearly every phylum of multicellular organisms first appeared. Over the next 400 million years or so, global diversity showed little overall trend, but was marked by periodic, massive losses of diversity classified as mass extinction events.
Level classification :
Kingdom
Phylum
Class
Order
Family
Genus
Species
Phylum
Class
Order
Family
Genus
Species
The Five Kingdom System of Classification(whittaker R.H 1869)
This system of classification looks more scientific and natural because of the following considerations:
•Separation of prokaryotes into an independent kingdom is justifiable because they differ from all other organisms in their general organization.
•Grouping of all unicellular eukaryotes under the kingdom Protista has solved many problems, particularly related to the position of organisms like Euglena.
•Elevation of the group fungi to the status of a kingdom is justifiable since fungi totally differ from other primitive eukaryotes like algae and protozoans.
•The kingdoms Metaphyta and Metazoa are now more homogenous groups than they were in the two kingdom classification as it shows the phylogeny of different life styles.
•The five-kingdom classification gives a clear indication of cellular organization and modes of nutrition, the characters which appeared very early in the evolution of life. However, the five-kingdom classification has certain drawbacks also, particularly with reference to the lower forms of life.
• The kingdoms Monera and Protista include diverse, heterogeneous forms of life. In both the kingdoms there are photosynthetic (autotrophic) as well as non-photosynthetic (heterotrophic) organisms
•Both the kingdoms include organisms which have cells with cell wall as well as without cell wall.
•None of the three higher kingdoms include a single ancestor of all its forms. Multicellular lines have originated from protistans several times (polyphyletic).
•Unicellular green algae like Volvox and Chlamydomonas have not been included under Protista because of their resemblance to other green algae.
•Slime moulds differ totally from other members of Protista in their general organization. Viruses have not been given proper place in this system of classification
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