Which scenario is an example of natural selection?
A.) People kill rattlesnakes that rattle when approached by humans, but people do not kill rattlesnakes that remain silent. The quiet snakes survive and breed.
B.) Farmers crossbreed two types of cows to produce a breed of cow that has high quality beef and can tolerate hot climate.
C.) Giraffes that have long necks to survive a dry season by eating leaves from the tops of trees. Those giraffes breed more successfully that year.
D.) Dogs that have a desirable coat color are bred with one another to produce puppies the same coat color
The Correct Answer and Explanation is:
The correct answer is A) People kill rattlesnakes that rattle when approached by humans, but people do not kill rattlesnakes that remain silent. The quiet snakes survive and breed.
Explanation:
This scenario represents natural selection, which is a process in which organisms with traits better suited to their environment are more likely to survive and reproduce. Over time, these advantageous traits become more common in the population. Let’s break down the reasoning behind why option A is an example of natural selection:
- Natural Variation: In this scenario, there is natural variation in the rattlesnake population, where some snakes rattle and some remain silent when approached by humans.
- Survival Advantage: The quiet snakes are less likely to be killed by humans because they do not alert people to their presence. This gives them a survival advantage over the rattling snakes.
- Reproduction: The quiet snakes that survive are more likely to breed, passing on their trait of remaining silent to their offspring.
- Change in Population: Over time, the population of rattlesnakes will increasingly consist of individuals that remain silent because this trait is passed down through generations. This is a direct example of natural selection acting on a specific trait (the ability to remain silent when approached).
In contrast, the other options describe scenarios that are not examples of natural selection:
- B) Farmers crossbreed cows to produce a breed that is more adapted to hot climates and produces better beef. This is an example of artificial selection, where humans selectively breed organisms for specific traits, not a process that occurs naturally in the wild.
- C) Giraffes with long necks surviving a dry season due to their ability to reach food at the tops of trees might seem like natural selection, but the trait (long neck) was already present in the population and was advantageous during that season. The key distinction is that this example focuses on survival based on a pre-existing trait, not a gradual change driven by natural variation and the survival of specific individuals.
- D) Breeding dogs with desirable coat colors is another example of artificial selection, where humans are selecting for a particular trait in a controlled breeding environment, not a natural, survival-based process.
Thus, A best illustrates natural selection, where a trait (silence) provides a survival advantage in the wild.