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.
