The phenomenon of evolution of different species in a given geographical area starting from a point and spreading to other habitats is called

$A$: During evolution,pouched mammals of Australia survived.
$R$: Due to lack of competition from any other mammal due to continental drift.

What did Darwin conclude after observing the variations in the beaks of birds on the Galapagos Islands?

Describe one example of adaptive radiation.

Assertion : Darwin's finches show a variety of beaks suited for eating large seeds,flying insects and cactus seeds.
Reason : Ancestral seed-eating stock of Darwin's finches radiated out from South American mainland to different geographical areas of the Galapagos Islands,where they found competitor-free new habitats.

Given below are two statements with respect to homologous organs.
Statement $I$: These organs are structurally similar but perform different functions.
Statement $II$: Differences in homologous organs are examples of adaptive radiation.
In the light of the above statements,choose the correct option from the list given below.