Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Directions: Use the information provided and your knowledge of Life Science to answer the following questions. Show all work where necessary.
Commercial fishing has transformed marine ecosystems. Large fish are often targeted because they yield more meat, leading to intense pressure on the biggest and oldest individuals in a population. However, when large fish are consistently removed before reproducing, only smaller, faster-maturing fish pass on their genes.
This phenomenon is known as fisheries-induced evolution. In species like cod, haddock, and salmon, researchers have documented decreases in both average size and age at maturity over decades of fishing. For example, Atlantic cod that once reached reproductive age at seven years now mature as early as four.
Mathematical models help scientists describe this shift. They track the mean size and age distribution of a population, calculate selection differentials, and model how trait frequencies change from generation to generation. The results are clear: when fishing selectively removes large individuals, alleles for smaller body size or earlier reproduction become more common.
Even when fishing stops, populations can take decades to recover. Because these changes are genetic and not just environmental, reversing them requires many generations of natural selection in the opposite direction - favoring larger individuals again.
This example shows how quantitative data can make natural selection visible. Over time, the mean size of fish decreases, the variance narrows, and the proportion of smaller-bodied individuals increases. These mathematical trends reveal how human activity can act as a powerful selection force, shaping evolution within a single human lifetime.
The key lesson is that natural selection doesn’t just happen in the wild — it also occurs wherever environmental or human pressures favor certain traits. In this case, “survival of the smallest” replaces “survival of the fittest,” illustrating evolution in real time.
Graph of Information - Figure 1.
Graph of Information - Figure 2.
Figure 3.
Figure 4.
According to Table 1, in which year did the mean body length of the fish population first drop below
Using Table 1, describe the trend in the percentages of large (
Explain why smaller, faster-maturing fish became more common in the population over decades of commercial fishing.
According to the reading, why do alleles for smaller body size become more common under heavy fishing pressure?
Using Table 2 and Figure 2, describe how the frequency of the large-size allele (L) changes across generations. What mathematical pattern does this decline represent?
Does the data support the claim that human activities can drive evolutionary change in fish populations?
Claim:
Evidence:
Reasoning: