Human activities causing loss of biodiversity in Amazon rainforest are
(i) Many plants are cut for cultivation of soybean.
(ii) Forests are converted to grasslands for raising beef cattle.

Slope of regression represents the changes in the species richness with the area. Species richness decreases with the decrease in area. The value of 'Z' (regression coefficient) lies in between 0.1-0.2, regardless of the taxonomic groups in the region. For very larger areas like continents, the slope of the line becomes much steep with the Z values in the range of 0.6-1.

Biodiversity must be conserved as it plays an important role in many ecosystem services.
(i) Spiritually or philosophically, we have to realise that every species has an intrinsic value, though it may not be of any economic value to us currently.
(ii) Morally, we have a duty to care for the well-being of the species and pass on our biological legacy in good order to future generations.

Biochemical Oxygen Demand (BOD) is the amount of dissolved oxygen required for microbial breakdown of biodegradable organic matter.
Aerobic organisms use a lot of oxygen and as a result, there is a sharp decline in Dissolved Oxygen (DO) in the water body. This can cause a death of fishes and other aquatic species.The relationship between BOD and sewage can be understood from the graph given below:

Determination of BOD is thus an important parameter in suggesting the quality of a water body.The presence of more organic waste increases the microbial activity thus decreasing the DO.BOD is higher in polluted water and lesser in clean water.

Photochemical smog is grey or yellowish brown, opaque smog formed at high temperature over cities and towns due to still air, emission of nitrogen oxides and volatile hydrocarbons from automobile exhausts and solar energy.It contains secondary pollutants. It is having oxidizing environment.

Co-extinction is a phenomenon in which when a species becomes extinct, the plant and animal species associated with it, in an obligatory manner, also become extinct.
e.g. (i) In case of a co-evolved plant and its pollinator, if one of them becomes extinct, invariably the other one becomes extinct.
(ii) If a host fish becomes extinct, the unique parasites depending on it would also become extinct.
The three other causes are:
(i) Habitat loss and fragmentation
(ii) Over-exploitation and
(iii) Invasion of alien species

(i) The Nile perch introduced into Lake Victoria in East Africa caused extinction of more than 200 species of cichlid fish in that lake.
(ii) Partneniurn, Lantana and Eichhornia caused environmental damage and posed threat to many species in our country.
(iii) Illegal introduction of African catfish, Clarias qariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers.

This is may be due to any following reasons:
(i) Fast growing species may compete with less vigorous local species.
(ii) Alien species will proliferate in that area if their natural pests and predators are not present.
(iii) by amensalism i.e. it may vigorously and may form conditions unfavorable for growth of local native species like Eichhornia.

Species-Area Relationship
1. Alexander Von Humboldt has observed that within a region, species richness increases with increased explored area, but only upto a limit.
2. The relationship between species richness and area for a number of taxa like angiospermic plants, freshwater fishes and birds is found to be a rectangular hyperbola.
3. On a log scale, the relationship becomes linear (straight line) and is described by the equation:
log S = log C + Z log A, where
S = Species Richness
Z = Slope of the line (regression coefficient)
A = Area and C = Y - intercept
4. Ecologists have found that the value of Z-line ranges between 0.1 and 0.2 irrespective of the taxonomic group of the region.
5. But in very large areas, like a continent, the Z value ranges between 0.6 and 1.2 and indicate species richness.