(Mt) – Arizona Christian University Foundations of Biology Exam Practice

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1. DNA methylation plays a major role in gene expression. Read the following article and then answer the following questions: https://www.sciencedaily.com/releases/2019/08/190819105952.htm a) Describe how methylation is related to epigenetics. b) What is the purpose of adding methyl groups to parts of the DNA sequence? c) From a natural selection perspective, what would be an advantage to being able to pass on gene expression to the next generation? 2. Coronavirus is on all of our minds right now. Let’s focus on the science behind it. Start by reading this article: https://www.medrxiv.org/content/10.1101/2020.04.14.20062463v1 a) This study estimates that the actual infection rate could be up to 85-times higher than the current amount of reported cases. How did the study estimate how many people have been infected? How does this differ from how the number of positive tests is normally calculated? b) What do these results mean for how infectious the disease is? c) Why could it be good news that 85-times more people than we thought may have been infected? (hint: why might it be good that more people have had the disease?) d) Look at this graph showing deadliness of diseases and contagiousness: https://informationisbeautiful.net/visualizations/the-microbescope-infectious-diseases-in-context/ Why do you think there aren’t any diseases that are highly contagious AND highly deadly? 3. There is debate over whether dinosaurs were warm-blooded (endotherms) or cold-blooded (ectotherms). a) find and cite an argument for one side of this argument. Why does the article that you found think that their viewpoint is correct? b) Describe (not just list) the main advantages and disadvantages of being endo- or ecto-thermic. c) Humans can have a body temperature between 97-99 (98.6 is not actually the average). Why do we want to maintain a stable body temperature? (hint: think about why we don’t want to be too warm or cold). 4. Parthenogenesis, or “virgin birth”, occurs when offspring are born without fertilization (no sperm necessary). a) Why can’t the eggs or ova of most organisms (like humans) develop without fertilization? What is different about parthenogenic organisms? b) Describe at least one major advantage and disadvantage of this type of reproduction. c) Research (and cite) any animal you can find that has this type of reproduction. For this animal, how might environmental conditions (biotic or abiotic) make parthenogenesis a positive (advantage)? d) If a species suddenly had a mutation that made it parthenogenic, how would this influence the prevalence of X-linked diseases? What about Y-linked diseases? 5. Use the pedigree below to answer the questions. IMPORTANT: only the top row is filled in with the presence or absence of this disease, so we don’t know which of the others (#s 3-10) have the disease a) If this trait was X-linked recessive, which of the children (#4-7) would be most likely to have the disease? Explain how you know. b) If this trait was X-linked recessive, what are the odds of each sex of children being a carrier? Males (5, 7): Females (4,6): Explain how you know: c) If this trait was X-linked recessive, what are the odds (knowing only what you see in the diagram) of the grandson (#10) having this disease (remember we only know about the top row for sure)? Explain your answer. 6. In a sad development, many elephants are being born without tusks. This is not a disease, but rather a result of natural selection. a) Explain how this might be happening. Be sure to address the role of variability in the population, survival rate, and selective pressure. b) IF (assume this is the case) only female elephants were being born without tusks, what might this tell you about what the tusks are used for? c) Look up and describe one example each of an honest signal and a dishonest signal in animal communication. d) Explain how your answer to (c) might relate to sexual selection. 7. Use the following food web to answer the questions below. For each animal, the arrow points to an animal that eats it. a) Based on this diagram, which animal do you think is most likely to be a keystone species? Explain your thinking, and also explain what makes something a keystone species. b) How would you expect Animal B to be affected if Animal D populations went UP? Explain. c) Animal E and B are both at the same trophic level. Which one of these two animals do you think would have a larger impact on the ecosystem if it went extinct? Explain. d) We discussed the value of biodiversity in class. What advantage is there to an ecosystem to have multiple species at the same trophic level (like the food chain on the left-hand side of this diagram)? Explain your answer.

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