Student to attempt either option (A) or (B). (A) (i) Explain giving three reasons why tropics show greatest levels of species diversity. (ii) Draw a…

$\displaystyle \star$ Tropical latitudes have remained relatively undisturbed for millions of years and thus had a long evolutionary time for species diversification

$\displaystyle \star$ Tropical environments are less seasonal more constant and predictable. Such constant environments promote niche specialisation and lead to a greater species diversity

$\displaystyle \star$ More solar energy is available in the tropics which contributes to higher productivity which leads to greater species diversity.

Alexander von Humboldt

Within a region species richness increased with increasing explored area but only up to a limit.

Habitat loss and fragmentation: Deforestation leads to habitat loss and ultimately causing extinction of animals and plants / When large habitats are broken into small fragments that also leads to population decline / mammals and birds with large territories and certain animals with migratory habits are badly affected.

Overexploitation: Overexploitation of natural resources by humans leads to extinction of many species / For example overexploitation of Steller’s sea cow or passenger pigeon or many marine fishes led to their extinction.

Alien: species invasions, When alien species are introduced unintentionally or deliberately for whatever purpose some of them turn invasive and cause decline or extinction of indigenous species/ For example Parthenium or Lantana or water hyacinth pose threat to indigenous species

Co-extinctions: When a species becomes extinct the plant and animal species associated with it in an obligatory way also became extinct/ For example unique assemblage of parasites and plant pollinator mutualism where extinction of one invariably leads to the extinction of the other

Ex-situ conservation : Threatened animals and plants are taken out from their natural habitat and placed in special setting where they can be protected and given special care.

e.g. : Zoological parks, Botanical gardens, Wildlife safari parks, seed banks, pollen bank