1. In a freshwater pond there exists a population of amphipods (aquatic crustace
ID: 259814 • Letter: 1
Question
1.
In a freshwater pond there exists a population of amphipods (aquatic crustaceans). The pond is then stocked with Sunfish, a fish that feeds on amphipods. Sunfish are visual predators and as such tend to eat large-medium sized amphipods. Thus, overtime large-medium sized amphipods become absent from the pond leaving only small sized amphipods.
a. Given that size is a heritable trait in amphipods what kind of selection is occurring (directional, stabilizing, or disruptive? Explain
b. What size amphipods are evolutionarily more fit in this scenario?
2. The Common Mudpuppy is a species of aquatic salamander native to Eastern North America. In a lake there exist two distinct gill phenotypes of Mudpuppies: long gills and short gills. Long gilled Mudpuppies are able to survive in lower oxygen conditions. The phenotypic frequencies of this population are 30% long-gilled 70% short-gilled. The following are 3 different scenarios for the reproduction of this population. Determine whether the following are examples of natural selection or genetic drift. If it is an example of genetic drift, state what process (bottleneck or founder effect) is occurring. Give an explanation for your answers.
a. Unfortunately, the overall water quality of this lake begins to decline due to human activity. This leads to drastic decreases in the oxygen concentration of the lake. Thus, the population of short-gilled mudpuppies begins to decline. The next generation contains 90% long-gilled 10% short-gilled.
b. The company Nestle decides to pump water from the south part of the lake to use for bottled water. This dries up the south side of the lake leading to a massive (and random) kill off of Mudpuppies. Only 15 Mudpuppies remain. 10 are short-gilled and 5 long-gilled. The next generation contains 66% short-gilled 34% long-gilled.
c. Someone decides to randomly capture 20 Mudpuppies from the lake and transfer them into a pond. The new population that has been moved to the pond contains 10 short-gilled and 10 long-gilled Mudpuppies. The next generation (of the new pond population) is 50% short-gilled and 50% longgilled.
3.
The graph below represents the frequency of beak sizes in a population of finches. Draw a new graph representing what the frequency of beak sizes would look like if this population were to go through disruptive selection. (bell-curved graph)
Explanation / Answer
1.a. Since sunfish feeds on large amphipod, the selection is a disruptive one due to which large amphipod population goes down and thus population of small amphipod survives.
1b. Small amphipodand are fit for survival as sunfish have tendency to consume/feed large amphipod.
2a.Since long gilled mudpuppies are able to survive better in a low oxygen condition,population of long gilled increases. This is an example of bottleneck of short gilled population , thus a reduction in genetic variation.
2b . This is an example of a bottleneck of existing population due to human effects . But there is a chance of founder effect of a new population altogether that may survive the effect of dryness in the area. Same percentage of population is maintained in the next generation.
2c. The population is in equilibrium as the ratio of both mudpuppy population is equal. This genetic variation will be maintained in this scenario.
3. Graph not shown in the question. However , finches in case of disruptive dynamics /selection will have one population in excess and selection of say larger sized beaks over smaller one
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.