Evolutionary Physiology: Defintion & Examples

Instructor: Fawn Goodberry

Fawn has taught as a brain training instructor with the Learning Rx. In graduate school served as a teaching assistant for Introduction to Evolution and Ecology and Population Genetics. She received her masters degree in biology in 2013.

It is said that form follows function. When thinking of the natural world we can see many examples of this. Different shaped beaks of birds cater to their diet, streamlined shape of aquatic animals allow for swimming. The evolution of their physiology has best equipped them to their lifestyles and environments.

General Terms:

Lets review some general terms that will help you understand some concepts in evolutionary physiology.

  • Evolution: The process by which organisms develop and diversify from earlier forms. The process usually happens over many generations. Many forces help drive evolution, including natural selection, mutations, and environmental pressures.
  • Phenotype: Observable characteristics of an individual. For example blue or brown eyes. Your parents may have different color eyes and they pass on to you a genotype, the expression that we see is your phenotype. Natural selection works on phenotypes.
  • Niche: Where an organism lives and how it interacts with the environment. One bird may live in the tree tops while another may live on the ground. They are occupying different niches.
  • Homologous: To have similar structures or origin. Usually referring to structures of an organism. For example: pine needles and cactus spines. Both are modifications of a leaf with similar structure and place of origin.
  • Adaptation: A change in the structure or function of an organism or any of its parts that results from natural selection. This change usually results in the organism being better suited for its environment. Different beaks in Galapagos Finches are an example. The adapted beak shapes allow the birds to eat different diets.
  • Co-evolution: The process in which two or more species affect each-other's evolution. Hummingbirds have a specialized beak that allows them to drink nectar from flowers, and in turn these flowers are pollinated. The flowers have colors that attract the hummingbirds to ensure this relationship.
  • Natural Selection: Survival and reproduction of individuals due to differences in phenotype, or the outward traits. Natural selection is one factor that drives evolution.



Here are some specific concepts of physiological evolution and examples to help you better understand them.

  • Convergent Evolution: The formation of similar structure in two different species. For example, bats and birds both have wings used to fly. These structures, although similar in use and structure, are not the same. While a bird has a true wing, a bat uses a modified hand, since bats are mammals.


  • Divergent Evolution: The process where a species evolves into two or more descendants. There are many examples of this, like chicken and ravens, being birds with a common ancestor, but two different species.

Case Study in Divergent Evolution.

When Charles Darwin sailed to the Galapagos and observed the many animals there, one species he noticed were the finches. However, what he noticed was that many of them had different beak shapes and sizes. Why would these birds have different beaks shapes and sizes? Think about how form follows function. When there are a lot of one type of bird, competition for food would become very high. In order to survive, the finches needed to lessen competition. This happened by the process of natural selection. Finches began eating different foods to avoid competition. Over time, birds that had beaks that allowed them to eat different foods would survive better, pass on these genes for different beaks, and eventually create new species of finches!

  • Vestigial Structures: These are remnants of structures that were once used by an organism but through evolution have become obsolete. For example humans appendix is said to be a vestigial structure. An interesting example is leg or hip bones in whales. As whales became aquatic organisms, a streamlined body helped them in this environment and thus the legs were not needed. The function of walking was lost so the form of legs were lost as well.

Whale skeleton showing vestigial structure, labeled C

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