Consider the following hypothetical scenarie: An ancestral species of duck had-a varied diet that included aquatic plants and terrestrial plants and insects. These ducks spent time on both Land and water. Individuals of this species varied in the amount of webbing in thelr feet, with some individuals having more webbing and some having less. As many years went by, the environment changed such that the aquatic food sources were much more plentiful than those on land. Many generations Iater, almost all ducks had more webbing ‘on their feet. How is this best explained? Ducks with less webbing worked harder than ducks with more webbing to eat aquatic plants. The more they used their feet, the more webbed their feet became, so they got enough food to survive and reproduce. Due to chance mutations, all the ducks’ feet in the next generation had more webbing. They were therefore able to eat aquatic plants and get encugh food to survive and reproduce. Ducks with more webbing were better at eating aquatic plants than ducks with less webbing, so the
The Correct Answer and Explanation is:
Correct Answer:
Ducks with more webbing were better at eating aquatic plants than ducks with less webbing, so they got enough food to survive and reproduce.
Explanation
This scenario illustrates the process of natural selection, a fundamental concept in evolutionary biology proposed by Charles Darwin. In the ancestral duck species, individuals showed variation in the amount of webbing in their feet—a heritable trait. Initially, these ducks consumed both aquatic and terrestrial food sources, and webbing likely had minimal impact on survival.
However, when environmental changes made aquatic food sources more abundant and terrestrial ones scarcer, survival and reproduction increasingly depended on the ducks’ ability to thrive in aquatic environments. Ducks with more webbing had an advantage in this new environment: webbed feet act like paddles, making swimming easier and more efficient. As a result, these ducks were better able to access aquatic plants and other resources in water.
Because they could swim more effectively, ducks with more webbing had better access to food, giving them higher chances of survival and reproduction. Over time, they passed on the genes for more webbing to their offspring. Meanwhile, ducks with less webbing struggled to compete for food and were less likely to survive and reproduce, so their traits became less common in the population.
This gradual change in the population’s traits over generations, driven by differential survival and reproduction, is natural selection. It’s important to note that this change is not due to use or effort (as suggested in the incorrect Lamarckian explanation) or random mutation alone (mutations provide variation, but selection determines which traits persist).
In conclusion, the increased webbing in the modern duck population is best explained by natural selection acting on inherited variation: ducks with more webbing were more successful in the aquatic environment, survived in greater numbers, reproduced more, and passed on their advantageous traits to the next generation.
