When Nile perch a large predator fish was introduced in lake Victoria, it started feeding on native fish, cichlid fish. As a result, cichlid fish become extinct and Nile perch, not finding any food for itself, died too.

A harmful organism, that is harmful for one/more populations/species, can be made extinct; the food chain should not be affected. For example, the virus causing small pox has been controlled world over.

Ramsar Convention is a global environmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources. It was called convention on wetlands of international Importance.

Many bacteria cannot be cultured under normal conditions in vitro, which creates a problem in studying their morphological and biochemical charateristics.
Morphology and biochemistry along with some other charateristics are used for the assessment of biodiversity of bacteria. Thus, conventional methods are not suitable for the assessment of biodiversity of bacteria.

Gases and ashes from volcanic erruptions; gases from forest fires and decomposition; dust from storms; pollen, spores, cysts, bacteria from living organisms .

(i) d
(ii) a, g
(iii) b, f
(iv) e
(v) c

Ecologist Paul Ehrlich gave 'rivet popper hypothesis' to understand the contribution of the species richness. He compared each species with rivet in the body of an airplane.
(i) This hypothesis explain that ecosystem to be an airplane and the species to be the rivets joining all parts together.
(ii) If every passenger traveling in the airplane start taking rivets home(causing a species to become extinct), initially it may not affect flight safety (proper functioning of ecosystem), but over a period of time the plane become weak and dangerous (Species become endangered and then extinct).

Effects of habitat fragmentation on Biodiversity:
1.Fragmentation creates barriers that limit the potential of species to disperse and colonise new areas.
2. Species get divided into smaller populations which are unable to sustain.
3.Migratory birds lose their seasonal habitats.
4.It Increases edge areas thus making the species more vulnerable to predators as well as wind and fire.
Thus there is loss of biodiversity because a large number of animals, e.g. elephant, lions, bears, and large cats require big territories to move around and live in. Likewise some birds reproduce successfully only in deep forests. 

Environmental pollution may be defined as an undesirable change in the physical, chemical or biological aspects of environment which makes it harmful for humans, for other living organisms, and for cultural assets.

(i) A = Dissolved Oxygen
(ii) B=Biochemical oxygen demand(BOD)