From Seed to Seed:
Plant Science for K-8 Educators

Digging Deeper

Why Is Genetic Diversity Important?

First of all, when a population contains a large gene pool-that is, the genetic blueprints of individuals in the population vary significantly-the group has a greater chance of surviving and flourishing than does a population with limited variability.

Why? Because some of the individuals may have inherited traits that make them particularly resistant to disease or tolerant of cold, for example. Or they may possess other traits that increase their chances for survival. In nature, the "fittest" individuals succeed and go on to reproduce. Darwin termed this process "natural selection." Suppose there is an outbreak of a disease that threatens to wipe out an entire species. The more genetic variability there is within that species, the higher the likelihood that at least some of the individuals will be resistant, and will survive.

Genetic diversity also reduces the incidence of unfavorable inherited traits. In a small, isolated population of organisms, individuals may be forced to breed with close relatives. When this happens, the genetic makeup of the individuals becomes more and more uniform. As a result, genetic flaws become increasingly more common. This phenomenon is referred to as inbreeding.

When closely related organisms interbreed, any genetic weaknesses that are hidden in the parents can be multiplied in the offspring. For example, animals can be carriers of a gene for an inherited disease, but not show any symptoms. If one mates with a partner that is also a carrier, then the offspring may exhibit symptoms of the disease. In an inbred population, the chances are greater that carriers will interbreed. Over time, the entire population is weakened.

In summary, genetic diversity strengthens a population by increasing the likelihood that at least some of the individuals will be able to survive major disturbances, and by making the group less susceptible to inherited disorders.

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