list the four requirements for natural selection and explain using evidence why natural selection was occiring in one of the following populatons: rock pocket mice, ensatina salamanders, galapagos finches

Answer 1

The four requirements for natural selection are as follows:

1. Variation: There must be variations or differences in traits within a population. This variation can be caused by genetic mutations or genetic recombination during reproduction.

2. Heredity: The traits that contribute to the variation must be passed on to future generations. This occurs through genes being passed from parents to offspring during reproduction.

3. Selection: Certain variations must provide individuals with a higher chance of survival or reproduction. Individuals with these advantageous traits will have higher fitness and are more likely to pass on their genes to the next generation.

4. Time: Natural selection acts over long periods of time, allowing advantageous traits to become more prevalent in a population, while disadvantageous traits become less common.

Now, let's examine how natural selection occurred in the Galapagos finches. These finches are a classic example of adaptive radiation, where a common ancestor colonized different islands, leading to the evolution of various species in response to diverse environmental conditions and available food sources.

The finches on the Galapagos Islands demonstrate variations in beak size and shape. Certain islands have specific food sources that require particular types of beak adaptations for efficient feeding. For example, on islands with mainly large, tough seeds, finches with larger, stronger beaks were more successful at cracking open these seeds and obtaining food. On islands with abundant insect populations, finches with smaller, more pointed beaks were better equipped to catch and eat insects.

This variation in beak size and shape demonstrates the presence of the first requirement for natural selection. These differences are heritable as they are passed down from parents to offspring, meeting the second requirement.

The third requirement, selection, is evident in the finch population as individuals with advantageous beak traits have higher survival rates and reproductive success. Those with beak traits that match the prevalent food source on their respective island are more likely to survive longer, reproduce more, and pass on their beak traits to future generations.

Finally, the process of natural selection requires time, allowing the advantageous traits to become more prevalent in the population. Over time, the finches with the most suitable beak traits for their respective environments will dominate their specific islands. This process has contributed to the formation of multiple finch species, each adapted to the food sources available on their particular island.

In conclusion, the variations in beak size and shape among the Galapagos finches, coupled with the observed correlations between beak traits and specific food sources, provide evidence that natural selection is occurring in this population.