(a)

Alien species are highly invasive and are a threat to indigenous species. Substantiate this statement with the help of any two examples.

(b)

State any two criteria for determining biodiversity hotspots.

The Nile perch introduced into Lake Victoria in East Africa led eventually to the

extinction of an ecologically unique assemblage of more than $\displaystyle 200$ species of Cichlid fish in the lake, the environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium) or Lantana or water hyacinth (Eicchornia),Introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers

High degree of endemism and high levels of species richness