Evolution: Key Questions

1.       A. What is adaptive radiation? How does it contribute to biodiversity?

       B. Correlate adaptive radiation with divergent and convergent evolution.

Adaptive radiation is the evolutionary process by which many species originate from one species in an area and radiate to different areas.

Discovery: First observed by Darwin

Darwin traveled to a place called the Galapagos Island. There he observed that there were finches with different types of beaks. So, he concluded that all of these finches radiated on the same island from a single ancestor finch. All of these finches developed beaks according to the kind of food available to them. Hence, they evolved from the conventional seed-eating finches to vegetarian and insectivorous finches. They later came to be known as Darwin’s finches.

Cause: According to evolutionary theory, living organisms change their physical and anatomical structure over a long period of time for better adaptations to the changing environment. The initiation of the point of evolution was when organisms wanted to exploit a niche and they were not able to do so with their existing body design or structural component. Organisms started to split and adopt various versions for better survival.

Adaptive Radiation and Biodiversity

Adaptive radiation explains the reason for biodiversity. Organisms with same parents and origin, grow under same circumstances and moved to different regions for a better opportunity. Now each one of them has their own adaptation according to their lifestyle and place they stay.  Here the lineage splits and radiates different characteristics giving rise to differently adapted organisms. This may lead to formation of new species and hence increase in biodiversity.

Adaptive radiation and divergent evolution: Divergent evolution means development of varied individuals from common ancestral stock; from which a number of species arise. Example development of different Australian Marsupials from a single ancestral stock in the Australian subcontinent. Thus if species from an area migrate to different areas and evolve in different directions (adaptive radiation) it is known as divergent evolution.

Adaptive radiation and convergent evolution: If in a given geographical area, several adaptive radiations take place for various species, leading to development of similar characters in those species; it gives rise to convergent evolution.