Ecology Week 5 Assessment.

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Name: Module 5 Assessment Chapter 9 questions 1. Cheetahs have been hunting gazelles in the savannahs of Africa for hundreds of thousands of years. Over time both gazelles and cheetahs have incrementally increased their speed. Explain a reason this may be occurring. What hypothesis could explain this phenomenon? -The Red Queen concept explains why cheetahs and gazelles run incessantly to survive on the African savannahs. Gazelles increased their speed in response to cheetahs' evolution over hundreds of thousands of years to become faster predators. This arms race between coevolving species reflects their ongoing desire to outpace one another in order to survive. Inspired by Lewis Carroll, the Red Queen's race reflects this dynamic, in which it takes continual progress and adaptability to remain in the same ecological place. 2. A downside of self-fertilizing in hermaphrodites is inbreeding depression. How does inbreeding depression impair fitness? -Hermaphrodites experience inbreeding depression as a result of self-fertilization, which reduces fitness by encouraging the expression of deleterious recessive genes. Because inbred offspring have a greater mortality rate and fewer opportunities to reach reproductive age, this results in reduced viability. In addition to compromising fertility, this results in fewer kids, and weakened immune systems make people more susceptible to illness. The more prominently expressed damaging alleles are, the higher the incidence of genetic diseases. 3. Consider a pathogen that infects a species of tree. Over many decades, how might the presence of the pathogen influence the proportion of individuals in the tree population that reproduce by self-fertilization (asexually) versus the proportion that reproduce by outcrossing (sexually)? Why? - A pathogen that affects a species of tree could change the reproductive strategies used by the population over several decades. At first, the pathogen might prefer those who can reproduce asexually, which could accelerate the spread of resistance genes. This might result in a greater percentage of trees creating through cloning. However, sexual reproduction might return if the pathogen burden decreases or varies. Genetic variety is introduced by sexual reproduction, which is advantageous for climate adaptation. Thus, depending on the dynamics of the environment and selective pressures, the pathogen's long- term effects may lead to an adaptive balance between asexual and sexual reproduction. 4. What characteristics in a species are associated with monogamy? What kinds of animals have a high percentage of species utilizing a monogamous mating strategy? Are these species truly monogamous? -Animals vary greatly in their levels of monogamy, and these differences are frequently correlated with the degree of parental care needed. Swans and eagles are among the birds that often create lifelong pair bonds and share responsibilities such as nest- building and raising chicks. Certain mammals are said to exhibit social bonding and shared

parenting, such as prairie voles, and to be truly monogamous. The phrase "truly monogamous" is complicated, though, because mating practices can be influenced by individual differences and hereditary fidelity. Numerous animals that are classified as monogamous may occasionally participate in extra-pair copulations, highlighting the complex nature of environmental influences and evolutionary pressures in determining the dynamics of relationships in the animal kingdom. 5. When researchers experimentally altered tail lengths of male widow birds ( Euplectes progne ), they found that females chose males with longer tails even when tail length did not correlate with any tangible benefit to a male’s ability to defend territory. What are two possible reasons that females prefer longer tails? -A possible reason would be that in male widow birds, larger tails are an indicator of genetic fitness or overall health. Because features like longer tails indicate that a male has strong genes and is more likely to produce healthy offspring, females may naturally favor partners with exaggerated traits. Another reason can be female-driven sexual selection. Males with longer tails are more likely to breed and transmit the characteristic on to the next generation if females regularly prefer them, which sets up a positive feedback loop. Even if there isn't a clear functional benefit to having a longer tail, this could eventually cause longer tails to evolve and remain in the population. 6. You discover a new species of wasp with females that lay their eggs inside tree branches which protect their eggs from predators. After the eggs hatch, only the females possess the mouthparts needed to chew through the wood and escape. All of the males die in the nest. The young females must obtain the strength necessary for eating their way out of the branch by eating spermatophores (small packets containing sperm and nutrients) that each male releases in the nest. These spermatophores also fertilize the females. Once a male releases his spermatophore, he dies. The more spermatophores a female eats, the more likely it is that she will escape the nest. In this wasp species, would you predict a sex ratio bias? Explain. Would this mating system be classified as promiscuity, polygyny, polyandry, or monogamy? - A sex ratio bias could be anticipated in this species of wasp. Since all the men die in the nest after releasing their spermatophores, and because the females need to eat these spermatophores to get the strength to escape, the amount of spermatophores that are available will probably affect how many females are able to safely exit the nest. A female-biased sex ratio might result from fewer spermatophores being available, which would restrict the number of females that can escape. On the other hand, a more balanced or male-biased sex ratio may arise from an abundance of spermatophores, which would allow more females to successfully emerge. This situation would be considered polyandry in terms of the mating system. A mating system known as polyandry occurs when females mate with numerous males. Chapter 10 questions

7. You discover a small reef fish species in the Great Barrier Reef off the Australian coast. You study its ecology and discover that many midsized and large predatory fish consume the new species. Further, you find that this species consumes the same prey as many other species of similar-sized fish. However, many of those other small species tend to live in large schools, whereas individuals of this newly discovered species live alone. Propose proximate and ultimate causes for this behavior. -Both immediate and long-term factors contribute to the solitary existence of the recently found reef fish in the Great Barrier Reef. The distribution of resources, territorial behavior, and the efficiency of individual foraging all play crucial roles. In areas where prey is dispersed and territorial disputes may arise, fish that live alone are better able to secure resources. In the end, the tendency to isolate oneself could be an evolutionary reaction to the pressure of predators, helping to hide from them. The species may also be able to take use of a distinct ecological niche if it is a tactic to reduce intra- specific competition. To further enhance the overall fitness and adaptability of the species in the dynamic reef habitat, this solitary lifestyle may also be linked to certain mating methods. 8. What is a lek? How is it beneficial? -A lek is a gathering of male animals where they compete with one another to draw in females for mating. Leks are beneficial because they give females the ability to select mates based on their physical attributes, overall health, or genetic suitability. Ensuring that the strongest and most capable genes are passed on to the next generation corresponds to a natural selection party. Thus, leks do play a role in the general well-being and adaptation of the species. 9. Why would evolution favor a social structure that relies on dominance hierarchies rather than individual territories? -For several reasons, evolution could encourage social systems that have dominance hierarchies over individual regions. Dominance hierarchies can minimize the energy required for territorial upkeep by streamlining resource access and defense. Due to its efficiency, energy conservation is encouraged for vital tasks like reproduction. Furthermore, well-defined social structures promote cooperation among group members, which helps to maintain stability and order. Within certain species, individuals in a dominating position may have better reproductive outcomes and hence pass on desirable features. Additionally, the group's learning and social skill transmission are facilitated by the hierarchical structure. In the end, the predilection for dominance hierarchies is a result of an evolutionary tactic that maximizes reproduction and survival in particular ecological circumstances. 10. Why would an individual in a social group of a diploid species help to rear the young of its siblings rather than reproducing itself? Describe the expected relative importance of direct and indirect fitness benefits and explain your answer. - Within social groups of diploid animals, individuals may choose not to reproduce directly, instead helping to raise the offspring of their siblings. The inclusive fitness theory, which considers both direct and indirect fitness advantages, can be used to explain this seemingly altruistic action. Due to environmental

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limitations, the individual might put off reproducing itself in favor of supporting the offspring of its siblings. Benefits are derived indirectly from kin selection, in which the inclusive fitness of the beneficent individual is improved by the 50% genetic relatedness with siblings in diploid animals. This relationship is highlighted by Hamilton's Rule, which states that altruistic actions develop when the benefit to kin multiplied by relatedness is greater than the cost to the altruist. Consequently, individuals indirectly pass on a significant amount of their own genes through helping in the reproduction of closely related relatives. This cooperative method clarifies the evolutionary reasoning behind altruistic behaviors in social contexts by achieving a balance between direct and indirect fitness advantages. 11. What is eusociality? What evidence is there that eusociality likely evolved independently at least several times? -Within a colony, overlapping generations, reproductive work division, and cooperative care of children are all part of the intriguing social structure known as eusociality, which is found in several animal species. The possibility that it independently evolved several times across several taxa is what makes it intriguing. Several insect groups, including termites, ants, bees, and wasps, exhibit this convergence. These groups have different genetic bases for eusociality, suggesting separate evolutionary pathways. Furthermore, the hypothesis of numerous, distinct beginnings of eusociality is further supported by the diversity of behaviors and social structures observed in eusocial organisms, as well as the ecological factors impacting their evolution. It's an amazing illustration of how identical answers to difficult social problems are found by nature in seemingly unrelated organisms. 12. Why does natural selection not favor spiteful behavior? - Natural selection favors traits that increase an individual's chances of successful reproduction. An organism that hurts another, even at its own expense, is said to exhibit spiteful behavior, which is normally discouraged since it comes with high costs and no rewards. Altruism and reciprocity are examples of cooperative behaviors that are more likely to be valued because they help an individual survive and reproduce, particularly in social species. An individual's general fitness may be lowered by spiteful behavior, which can cause social conflict and isolation. Additionally, cooperative behaviors tend to be more enduring in populations throughout time than spiteful ones due to evolutionary stable methods. Although behavior may be influenced by context, natural selection generally favors characteristics and behaviors that increase individual as well as community success.

Ecology Week 5 Assessment.

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