Final answer:
Natural selection causes changes in hawksbeard, rat, and junco populations through the process of adaptation. This process leads to the development of traits that help the organisms survive and reproduce in their environment.
Step-by-step explanation:
Natural selection caused changes in the populations of hawksbeard, rat, and junco through the process of adaptation. Adaptation is the process by which organisms develop traits that enable them to survive and reproduce in their environment. In the hawksbeard population, for example, natural selection may have favored individuals with longer beaks, which allowed them to access nectar from deeper flowers. The individuals with longer beaks had a higher chance of surviving and passing on their genes, leading to an increase in the frequency of the longer beak trait in the population over time.
In the rat population, natural selection might have favored individuals with resistance to a certain pesticide. If the pesticide was introduced in the environment, the rats lacking the resistance gene would die off, whereas the rats with the resistance gene would survive and reproduce, passing on their resistance to future generations.
In the junco population, natural selection could have acted on the coloration of the birds. If the environment included areas with light-colored ground and areas with dark-colored ground, the predators would have a difficult time spotting the birds that matched the ground color. Therefore, natural selection would favor birds with coloration that closely matched the surroundings, increasing their chances of survival and reproduction.
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