How Environmental Changes Impact Evolution

Instructor: Lisa Roundy

Lisa has taught at all levels from kindergarten to college and has a master's degree in human relations.

The process of evolution is pushed forward by an organism's need to adapt to changing situations. This lesson will help you understand how environmental changes can provide this push.

Adaption and Natural Selection

Once there was a island called Atlantis. It was a beautiful tropical paradise. Then, one fateful day, earthquakes began to shake the land and volcanoes began to erupt. Soon flood waters covered the land as Atlantis sunk to the bottom of the ocean. If we assume Atlantis was real and these events took place, what happened to the inhabitants of Atlantis when the catastrophe occurred?

One of two things could have happened. One option is the inhabitants of Atlantis did not survive. The other option is the inhabitants of Atlantis adapted to the changes in their environment. Maybe they became mermaids and are living today in a beautiful underwater city. This idea demonstrates the impact environmental change could have on the process of evolution.

Evolution is the scientific idea that organisms existing today developed from past organisms. This occurs through a process of adaption and natural selection. If an organism adapts, it has the ability to adjust to the changes it faces. Natural selection is a process that decides if some members of a species will survive because they have adapted well, or if the species will perish because it cannot adapt. Environmental changes have a huge impact on this process.

Environmental Changes

An environmental change is the alteration of the ecosystem in which an organism lives. The changes can take place gradually, like the formation of a desert over thousands of years. In this case, the local organisms have a great deal of time to adapt to their changing world. Changes to an environment can also take place rapidly, like when a volcano erupts. In this case, like in our example of Atlantis, the local organisms must also adapt quickly or they may not survive. In both cases, survival forces the organism to evolve or be eliminated.

The blue moon butterfly from the Samoan islands is a good example of adaption to an environmental change. A parasite began attacking the male embryos of the butterfly. Things got so bad that only one percent of the adult butterflies were male at one point, and the blue moon butterfly was in danger of becoming extinct.

Luckily, the one percent of males survived because of a genetic mutation that prevented the parasite from killing them as embryos. Since they were the only males available to mate with, this genetic trait was passed on to new male embryos. Within 10 generations the number of male butterflies increased to approximately 40% of the population. The parasite was still a part of the environment, but it was no longer able to kill the male embryos of the Blue Moon Butterfly. Instead, the butterflies adapted immunity to the parasite through the survival of the immune male embryos.


Environmental change can also be a result of moving an organism to a different environment. Organisms usually fit into their native ecosystem very well. They have a specific role to play and have developed characteristics that fit the part. If the organism is introduced to a new ecosystem, it may have to adapt to fill a different role. This creates a driving force for the process of evolution to take place.

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