Question

in a population of giraffes, some have slightly longer necks than others. if the main food source becomes leaves on taller trees, what would be the most likely result for the population over time?
the population of giraffes would immediately stop evolving.
the trait for long necks would become more common in the population.
the giraffes would all learn to stretch their necks longer in their lifetime.
the trait for short necks would become more common in the population.

Explanation:

This question is about the evolution of giraffe neck traits based on natural selection. In a population of giraffes, if the main food source (leaves on taller trees) becomes more accessible to those with longer necks, giraffes with longer necks will have a survival advantage (more likely to get food, reproduce, and pass on the long - neck trait). Over time, through natural selection, the trait for long necks will become more common in the population.

• The first option is incorrect because evolution is a gradual process and giraffes won't immediately stop evolving.
• The third option is incorrect as giraffes' necks don't get longer within a lifetime due to stretching (this is a Lamarckian view which is not supported by modern evolutionary theory; evolution occurs at the population level over generations, not at the individual level within a lifetime).
• The fourth option is incorrect because short - necked giraffes will have less access to the new main food source, so the short - neck trait will become less common, not more.

Answer:

The trait for long necks would become more common in the population.