Concept 10: Adaptive Radiation

Success Criteria

I can explain how organisms are able to adapt relatively quickly to fill vacant niches (adaptive radiation).

Key Vocabulary

Adaptive Radiation, Divergence, Physical Barrier, Niche, Divergent Evolution

Adaptive Radiation

The term adaptive radiation is also sometimes used interchangeably with divergent evolution. However, most science textbooks agree that adaptive radiation is focused more on the microevolution of a rapidly reproducing population. Adaptive radiation may lead to divergent evolution over time as the new species become less similar, or diverge, in different directions on the tree of life. While it is a very fast type of speciation, divergent evolution generally takes more time.

Once a species has diverged via adaptive radiation or another microevolutionary process, divergent evolution will occur more quickly if there is some sort of physical barrier or a reproductive or biological difference that keeps the populations from interbreeding once again. Over time, significant differences and adaptations can add up and make it impossible for the populations to ever interbreed again. This may be caused by a change in chromosome number or as simple as incompatible reproduction cycles.

An example of adaptive radiation that led to divergent evolution is Charles Darwin's finches. Even though their overall appearances seemed to be similar and were clearly descendants of the same common ancestor, they did have different beak shapes and were no longer able to interbreed in nature. This lack of interbreeding and the different niches the finches had filled on the Galapagos Islands led the populations to become less and less similar over time.

Comapring/Contrasting Adaptive Radiation with divergent evolution

Similarities Between Adaptive Radiation and Divergent Evolution

Both adaptive radiation and divergent evolution are mechanisms which bring changes to a particular population.
Both adaptive radiation and divergent evolution are involved in the emergence of a new species from pre-existing species depending on the selective environmental pressure.
Adaptive radiation causes divergent evolution over time.

Difference Between Adaptive Radiation and Divergent Evolution

Definition

Adaptive Radiation: Adaptive radiation is the diversification of a group of individuals into forms filling different ecological niches.

Divergent Evolution: Divergent evolution is a process of developing two or more species from a common ancestor over time.

Type of Evolution

Adaptive Radiation: Adaptive radiation is a type of microevolution.

Divergent Evolution: Divergent evolution is a type of macroevolution.

Emerging Characters

Adaptive Radiation: Adaptive radiation brings morphological and ecological changes to a particular population.

Divergent Evolution: Divergent evolution generates a new species that is unable to interbreed with the original species.

Speed

Adaptive Radiation: Adaptive radiation is a rapid process of evolution.

Divergent Evolution: Divergent evolution is a slow process of evolution.

Examples

Adaptive Radiation: Darwin’s finches, Australian marsupials, and cichlid fish are some examples of adaptive radiation.

Divergent Evolution: The forelimb structures of mammals is an example of divergent evolution.

Conclusion

Adaptive radiation and divergent evolution are two evolution processes which are involved in the emergence of a new species due to the selective pressure of the environment. Adaptive radiation is a type of microevolution process, which causes changes in morphological and ecological diversity. Divergent evolution is a type of macroevolution process, which causes the emergence of new species through sexual incompatibility between individuals. The main difference between adaptive radiation and divergent evolution is in the levels of changes which are brought by each mechanism to a particular population.

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