University:
The University Of Western Ontario
Course:
2483A | Ecology
Academic year:

2024
Views:

346

Pages:

2
Author:

Kyuwon J.

Biology 2483A Ecology - Darwinian Snails 1. Fill in the blank. Mutation are the only true source of genetic variation in populations. (1 mark) Correct 2. Explain why the following statement is false and write a corrected sentence which describes a key concept from the tutorial. Some snails evolved thicker shells to avoid being eaten by crabs. (2 marks) Answer: Some snails did not evolve. The evolutionary pressure was put on, only the thick shell survived, then reproduced having its hard shell to offspring. Over generations, there will be a population of hard shell. 3. Define genetic drift and explain how it differs from natural selection. (2 marks) Answer: Genetic drift occurs by random events, where none of the selection is done by gene/phenotypical characteristics. Natural selection occurs by gene/phenotypical selection, where only the fittest for the given environment gets to survive. 4. Some plants produce chemicals to deter herbivory. Assuming the concentration of defense chemicals is variable and leads to selective survival against herbivory, briefly explain one experiment to test if natural selection is acting on these plants. Describe how it would prove or disprove the hypothesis. (3 marks) Answer: Grow test to see if this characteristic is heritable or not. If it is heritable, it will prove natural selection is happening on the plant. 5. Explain why a trait must be variable and heritable to contribute to natural selection. (3 marks) Answer: Variable traits will make the population survive (continue on) when selection pressure is given. However, it should also be heritable, since the genotype shall be passed on generation to keep the phenotypical characteristics. 6. After a harsh winter, some of the mountain goats in a fictional population have shorter tails due to frostbite. Cougars have a harder time catching short-tailed goats, so these goats live and produce the next generation. Is natural selection acting on the mountain goat population? Why or why not? (2 marks) 1 Corrected Answer: No, natural selection is not acting on the population because the shorter tails are due to frostbite, not a heritable genetic trait. For natural selection to occur, the trait must be heritable and variable within the population. In this case, short tails are not inherited but rather caused by environmental factors (frostbite), and there is no genetic basis for tail length variability. 7. In a fictional population of cats, a mutation arises which prevents claws from developing. This makes it difficult for the cats to catch their prey. Over time, would the population evolve to have no claws? Why or why not? (2 marks) Answer: No, for cats with this mutation will have disadvantage in survival due to difficulty in catching prey, meaning they are not fit. Therefore, population will not evolve to have claw. 2