Our actions as a human species are inadvertently altering the evolutionary trajectories of countless organisms.
Explain two distinct mechanisms by which human activities exert selection pressures on other species. For each mechanism, provide a specific example of a species affected by this pressure. (4 marks)
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Answers could include two of the following.
Mechanism: urbanisation
- Human activities exert selection pressure on other species through urbanisation. As cities expand, isolated pockets of natural habitat are created, forcing species to adapt to smaller, disconnected areas.
- For example, the San Diego deer mouse has shown rapid evolution in its size and fur colour to better camouflage against urban environments, with urban mice becoming larger and darker than their rural counterparts.
Mechanism: pollution from fossil fuel burning
- Humans exert selection pressure on other species through pollution from fossil fuel burning.
- The emission of sulfur-dioxide from coal-burning power plants has led to acid rain, which changes soil and water pH levels. This has resulted in strong selection pressure on aquatic organisms.
- For instance, in some Scandinavian lakes, the European perch has evolved increased tolerance to acidic conditions in order to survive.
Mechanism: use of pesticides
- Another mechanism is the widespread use of pesticides, which creates strong selection pressures for resistance. In agriculture, the overuse of pesticides has led to the evolution of resistance in many insect pest species.
- A specific example is the green peach aphid, which has developed resistance to multiple classes of insecticides. This adaptation makes it increasingly difficult to control these crop pests without resorting to even more potent chemicals.
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Answers could include two of the following.
Mechanism: urbanisation
- Human activities exert selection pressure on other species through urbanisation. As cities expand, isolated pockets of natural habitat are created, forcing species to adapt to smaller, disconnected areas.
- For example, the San Diego deer mouse has shown rapid evolution in its size and fur colour to better camouflage against urban environments, with urban mice becoming larger and darker than their rural counterparts.
Mechanism: pollution from fossil fuel burning
- Humans exert selection pressure on other species through pollution from fossil fuel burning.
- The emission of sulfur-dioxide from coal-burning power plants has led to acid rain, which changes soil and water pH levels. This has resulted in strong selection pressure on aquatic organisms.
- For instance, in some Scandinavian lakes, the European perch has evolved increased tolerance to acidic conditions in order to survive.
Mechanism: use of pesticides
- Another mechanism is the widespread use of pesticides, which creates strong selection pressures for resistance. In agriculture, the overuse of pesticides has led to the evolution of resistance in many insect pest species.
- A specific example is the green peach aphid, which has developed resistance to multiple classes of insecticides. This adaptation makes it increasingly difficult to control these crop pests without resorting to even more potent chemicals.