Lake Victoria in East Africa is home to many species of fish called cichlids. In 1954 the predatory Nile perch was introduced to Lake Victoria. The Nile perch became the dominant fish species in the lake by the mid-1980's. The number of cichlid species in the lake decreased as the Nile perch population increased. The perch preyed heavily on cichlid species that fed on algae and debris on the bottom of the lake. Algae in the lake increased, and oxygen levels decreased. The surface area of the gills of some cichlid species has increased in just over 20 years.
Which statement explains the increase in gill surface area seen in some of Lake Victoria's cichlids?
Select one:
a. Increased gill surface area has allowed the cichlids to be camouflaged and avoid being eaten by the Nile perch.
b. Increased gill surface area has allowed the cichlids to better absorb the limited oxygen in the water.
c. Increased gill surface area has allowed the cichlids to leave Lake Victoria and establish population in nearby bodies of water.
d. Increased gill surface area has allowed the cichlids to change their diet and avoid competing with the Nile perch.
note:
"..... oxygen levels decreased ...."
To determine which statement explains the increase in gill surface area seen in some of Lake Victoria's cichlids, we need to analyze the given information and understand the possible reasons for this adaptation.
The introduction of the predatory Nile perch to Lake Victoria led to a decrease in the number of cichlid species in the lake. This occurred because the Nile perch preyed heavily on cichlid species that fed on algae and debris on the bottom of the lake. Consequently, the increase in Nile perch population resulted in an increase in algae and a decrease in oxygen levels in the lake.
Given this information, we can eliminate options C and D. Option C suggests that the increased gill surface area allowed the cichlids to leave Lake Victoria and establish populations in nearby bodies of water, which is not supported by the given information. Option D suggests that the increased gill surface area enabled the cichlids to change their diet and avoid competing with the Nile perch. However, the given information does not mention any change in diet.
Now we are left with options A and B. Option A suggests that the increased gill surface area allowed the cichlids to be camouflaged and avoid being eaten by the Nile perch. However, the given information does not mention anything about camouflage or avoiding predation.
Therefore, the correct answer is option B. The increased gill surface area has likely allowed the cichlids to better absorb the limited oxygen in the water. As the oxygen levels in the lake decreased due to the increase in algae, cichlids with increased gill surface area would have an advantage in extracting as much oxygen as possible, enabling them to survive in the changing conditions of the lake.