Question

A pair of iguanas are washed out to sea on a log during a storm and end up on a large island. They are able to reproduce and after a very long time there are 4 different species of iguanas on the island, one on the coast, one in the forest, one on the volcano rim and one in the meadows. This is an example of _____.

a. allpatric speciation

b. sympatric speciation

c. bottleneck effect

d. adaptive radiation

Answer 1

This is an example of sympatric speciation. In sympatric speciation, geographical area is same but due to sudden mutation in ploidy level, they convert into different species which are reproductively isolated. This speciation phenomenon most commonly occurs through polyploidy, in which an offspring or group of offspring will be produced with twice the normal number of chromosomes.

Allopatric speciation occur due to formation of geographical barrier, like, ocean, mountain, desert, forest, etc. Initally individuals are able to reproduce but after long time they convert into different species. In the above example, The pair of iguanas which were washed out became other species which were reproductively isolated form their original species (from where they were isolated) because these two were separated by geographical barrier (sea). So the two member showed allopatric speciation with rest of the members.

Bottleneck effect is due natural disasters or human activity. In this the small population of species number decreases suddenly and gene pool is sharply reduced.

Adaptive radiation is the evolution of species by diversifying from a common ancestor to different ecological area. For example darwin finches, bird in different area found different type of seeds according to which there beaks were evolved.