annotated-Problem%20set%20%231

.pdf

School

University of California, Santa Barbara *

*We aren’t endorsed by this school

Course

Subject

Anthropology

Date

Dec 6, 2023

Type

pdf

Pages

Uploaded by UltraIbexPerson976

Brooke Uehlinger Anthropology 5 Problem Set # 1 Fall 2023 1. To answer these questions you will first need to watch the short video called Evolution of coat color in pocket mice (in Week 2, on the course website). A. As a result of geologic events, what was once a single population of pocket mice now find themselves living in two adjacent but different habitats. Mice in both habitats are often eaten by visually hunting predators. In the face of that predation, what role does coat color (fur color) play in a mouse’s survival? Explain. Mouce’s coat color plays a role in its survival because it helps them camouflage with the background color in their habitat. For example, mice that live in lava rock habitats evolved to have dark fur so predators from above cannot spot them as easily as they would with light fur. B. Can you interpret your answer to 1A as an example of natural selection? Explain. Over time, natural selection may begin to favor mice with a specific coat color. The favored mice will likely be the ones that show higher survival rates in their environment. This natural selection could lead to genetic variations of different fur colors to have a higher chance of avoiding predators. C. Do genes affect coat color in these mice, and does that matter to your answer to 1B? Explain. Fur color is a trait controlled by several genes. Light and dark mice have almost identical genes other than four chemical letters (Mc1r). This does matter to my previous answer because a mouse with these mutations grows dark fur, causing their chances of survival to increase on a dark background. D. Traits change over evolutionary time and thus it is useful to be able to talk about what came first and what (changes) came later. For any given case, the ancestral condition (also called the primitive condition) is what came first. What do you think the ancestral (primitive) coat color was in these mice, and what change came later? What makes you think that was the order? I think the primitive coat color was light for several reasons. I assume their original habitat was sandy and light, which would relate to why their fur started off as light. As geological events happened, like lava flow, the mice had to adapt from light to dark fur to increase their chances of survival on that new background. E. This change (from one coat color to another) happened “convergently” across the desert southwest. “Convergently” means that the same change happened multiple times, in different populations. What is the evidence that it happened multiple times? There are actually two separate kinds of evidence; please mention both.

Once beneficial mutations appear, natural selection can under similar conditions favor almost identical adaptations. Also, the rock pocket mouse is a real life example that evolution does repeat itself and why it’s changes are never ending. Although the mice look almost identical, they were found to have different genes F. All of the mice, regardless of which habitat they live in, have white bellies. Why did they evolve white bellies? A full answer would mention two ideas. The mice evolved white bellies because predators are coming from above meaning the belly has no reason to evolve to be dark. Their dark fur everywhere but on their bellies provides camouflage for them. Also, Mutations causing dark bellies do not occur. 2. Selection changes traits until they reach the optimum (ideal) value. For example, if trait X is too small (given the prevailing environment), selection disfavors any mutations that decrease the size of trait X and favors any mutations that increase the size of trait X, until trait X reaches the optimum. I’m going to suggest that virtually every trait in every species has an optimum and that selection is always pushing towards that optimum; or stabilizing that optimum, once it is reached. A. We said how selection will work when trait X is below the optimum (too small). How will selection work if trait X is above the optimum (too large)? Selection will work if trait X is above the optimum because they will have a higher chance of fitness compared to other individuals. Just like individuals with traits below the optimum, ones above will be more likely to have higher chances of survival and reproduction. Overtime, selection can begin to be disrupted because there will be abnormal amounts of trait distribution of trait values in the population. B. And how will selection work once trait X reaches the optimum? Once trait X reaches the optimum, stabilizing selection will maintain that trait by favoring individuals with traits near the optimum and not with extreme deviations. This helps to keep the traits adaptive fit and not make some individuals over powered. 3. Let’s consider a human trait that could be too big or too small, birth weight (the amount a woman grows her baby before she gives birth to it). Assume that birth weight is influenced by genes (it is, e.g., by genes that affect the flow of nutrients to the fetus during gestation). For questions 3A-C try to answer in terms of conditions during the long phase of human evolution before modern medicine (99.95% of the time our species has existed!). A. What might have been harmful to fitness about being too small at birth? If a human is too small at birth, this can be harmful to fitness because infants born with a low weight have a higher chance of mortality after being born. Also, these babies can

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version