It is said that the harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population. Why ?

Rapid increase in population over a short time period is underline("reproductive health") .

Where would the greatest number of endemic species occur and why ? (a) Small volcanic archipelagos, such as the Galapagos Islands, because the abundance of unoccupied habitats favours the adaptive divergence of colonists from nearby mainland populations. (b) Large oceanic island, such as Australia, because the inhabitants have been isolated from mainland populations for a very long time. (c) On rugged landscapes, such as Patagonia, because of the high levels of natural disturbance by glaciers and earthquakes. (d) Temperate woodlands, such as those in southern England, because of the high levels of disturbance by human activity and the history of artificial selection.

Select the correct term for the following definitions (I,ii,iii,iv). (i) The taxon is liable to become extinct if not allowed to realise its full biotic potential by providing protection from exotic species/human exploitation/habitat deterioration/depletion of food. (ii) The taxon has been completely eliminated or died out from earth. e.g Dodo (iii) The taxon is facing a high risk of extinction in the wild in the near future due to decreasein its habitat, excessive predation or poaching. (iv) They are species with naturally small populations, either localised or thinly scattered, which are always at risk from pests/pathogens/predators/exotic species.

Match column I with column II and select the correct option from the given codes {:(,"Column I",,"Column II"),("A.","Multiple allelism","(i)","Tt" xx "tt"),("B.","Back cross","(ii)","Tr" xx "TT"),("C.","Test cross","(iii)","Human blood groups"),("D.","Crossing over","(iv)","Non-parental gene combination"),("E.","Recombination","(v)","Non-sister chromatids"):}