Sexual Selection Flashcards
Why is sexual selection considered a paradox?
A) It only benefits females
B) It can shorten the lifespan of individuals
C) It has no impact on evolution
D) It only occurs in mammals
B- it can shorten the lifespan
What are the two types of sexual selection described by Darwin?
A) Intrasexual and intersexual
B) Natural and artificial
C) Genetic and environmental
D) Male and female
A) Intrasexual and intersexual
Darwin described two types of sexual selection:
Intrasexual selection: This involves competition between individuals of the same sex (usually males) for access to mates. For example, male animals might fight for dominance or territory that attracts females. (LAW OF BATTLE)
Intersexual selection: This involves mate choice, where individuals of one sex (often females) select mates based on certain traits, such as physical appearance, behavior, or other qualities that signal good genes or suitability for reproduction (Sexy son hypothesis .
These two types of sexual selection help explain the development of traits that might not necessarily contribute to survival but increase reproductive success.
What is the primary reason females are choosy about their mating partners?
A) To avoid predators
B) To ensure genetic diversity
C) Due to high parental investment
D) To increase their lifespan
C) Due to high parental investment
Females are generally more choosy about their mating partners because they often invest more in offspring, such as through pregnancy, nursing, or care. This higher investment in reproduction means that females are selective in choosing mates who offer the best genetic material or resources to ensure the survival and success of their offspring. This is why females tend to favor traits in males that signal good genes, health, or the ability to provide resources.
What is the handicap hypothesis proposed by Zahavi?
A) Males develop ornaments to look attractive
B) Males develop ornaments as an impediment to demonstrate survival abilities
C) Females prefer males with no ornaments
D) Ornaments have no impact on mating success
B) Males develop ornaments as an impediment to demonstrate survival abilities
The handicap hypothesis, proposed by Amotz Zahavi, suggests that males develop costly or extravagant traits (such as bright feathers or large antlers) as a way to signal their genetic quality to females. These traits are considered a “handicap” because they are energetically costly and can reduce the male’s ability to survive. However, by successfully displaying and maintaining these traits, the male signals to females that he is strong and genetically superior, capable of surviving despite the handicap. This indicates to females that his genes are of high quality and worth passing on to offspring.
What is Fisher’s runaway selection theory?
A) Females prefer males with shorter tails
B) Females prefer males with exaggerated traits that increase reproductive success
C) Males prefer females with exaggerated traits
D) Traits that are harmful are selected for
B) Females prefer males with exaggerated traits that increase reproductive success
Fisher’s runaway selection theory suggests that females may prefer males with exaggerated traits (such as long tails or bright colors), and this preference can drive the evolution of those traits to extreme levels over time. The idea is that the preference for these traits and the trait itself reinforce each other in a “runaway” feedback loop, where males with more exaggerated traits are more likely to reproduce, and females who prefer these traits are more likely to pass on their preferences to offspring. This process leads to the amplification of these traits, even if they may not necessarily increase survival, but they increase reproductive success due to mate choice.
What is the primary cost of sexual reproduction according to Williams (1975)?
A) The cost of meiosis
B) The cost of producing males
C) The cost of courtship and mating
D) All of the above
D) All of the above
According to Williams (1975), sexual reproduction comes with several costs, including:
The cost of meiosis: Only half of an individual’s genetic material is passed on to offspring, which reduces the potential for gene transmission compared to asexual reproduction, where all genetic material is passed on.
The cost of producing males: In species with separate sexes, producing males can be seen as a cost because males do not directly contribute to reproduction (they do not carry offspring), reducing the number of offspring an individual can produce.
The cost of courtship and mating: The energy, time, and resources invested in attracting and mating with a partner are additional costs in sexual reproduction.
These costs highlight some of the evolutionary trade-offs involved in sexual reproduction.
What is the ratchet effect described by Muller (1964)?
A) Accumulation of harmful mutations in asexual species
B) Faster evolution in sexual species
C) Accumulation of beneficial mutations in asexual species
D) Slower evolution in sexual species
A) Accumulation of harmful mutations in asexual species
The ratchet effect, proposed by Hermann Muller in 1964, refers to the phenomenon where harmful mutations accumulate in asexual species over time. In asexual reproduction, there is no mechanism to remove deleterious mutations from the genome, leading to a gradual decline in fitness. This “ratcheting” effect occurs because once harmful mutations accumulate, they cannot be purged through recombination, as they can in sexual reproduction, which may result in the eventual breakdown of the species.
What is the primary reason for the evolution of male adornments according to Hamilton-Zuk (1982)?
A) To attract predators
B) To demonstrate freedom from parasites
C) To increase lifespan
D) To reduce competition
B) To demonstrate freedom from parasites
According to the Hamilton-Zuk hypothesis (1982), male adornments, such as bright colors or elaborate displays, evolve as signals to females about the male’s health and genetic quality. The hypothesis suggests that these traits are honest signals of the male’s ability to resist parasites or diseases. Since such traits are costly to produce and maintain, only males that are in good health and free from parasites can afford to display them, making them more attractive to females as a sign of high genetic fitness.
What is the primary factor influencing female choice according to Trivers?
A) Physical appearance
B) Parental investment
C) Aggressiveness
D) Social status
B) Parental investment
According to Robert Trivers’ theory of parental investment, the primary factor influencing female choice is the amount of investment a female makes in her offspring. Since females typically invest more in reproduction (e.g., through pregnancy, lactation, or care of offspring), they are more selective in choosing mates. They tend to prefer males who can provide good genetic material, resources, or support to ensure the survival and success of their offspring. This theory helps explain why females are often choosier than males in mating.
What is the primary reason males court females rather than the other way around?
A) Males have more energy
B) Females are less aggressive
C) Males have a larger amount of low-cost sperm
D) Females have more time
C) Males have a larger amount of low-cost sperm
The primary reason males court females, rather than the other way around, is rooted in reproductive investment. Males typically produce a large quantity of sperm at a relatively low cost, so they can afford to mate with multiple females to increase their reproductive success. In contrast, females usually invest more heavily in each offspring (e.g., through gestation, egg production, and nurturing), which leads them to be more selective in choosing a mate. This difference in reproductive investment is a key factor driving courtship behavior, with males often seeking to attract females to maximize their reproductive opportunities.
What is the primary reason for the development of male-male competition?
A) To attract females
B) To increase lifespan
C) To reduce predator attacks
D) To compete for resources
A) To attract females
The primary reason for male-male competition is typically to attract females. In many species, males compete with each other for access to mates. This competition can take various forms, such as physical fights, displays of strength or territory, or other signals of fitness. The goal of these competitive behaviors is to demonstrate to females that the competing male has desirable traits (e.g., strength, genetic quality, or resource control), thereby increasing his chances of mating and passing on his genes.
What is the primary reason for the evolution of female preference?
A) To avoid predators
B) To ensure genetic diversity
C) Due to high parental investment
D) To increase lifespan
C) Due to high parental investment
The primary reason for the evolution of female preference is typically linked to high parental investment. Since females often invest more time and energy into reproduction (e.g., gestation, nursing, or caregiving), they are more selective in choosing mates. They tend to prefer males who display traits that signal good genetic quality, the ability to provide resources, or other factors that would increase the chances of survival for their offspring. This selectivity helps ensure the best possible outcome for their reproductive success.
What is the primary reason for the evolution of sexual reproduction?
A) To increase genetic diversity
B) To reduce competition
C) To increase lifespan
D) To avoid predators
A) To increase genetic diversity
The primary reason for the evolution of sexual reproduction is to increase genetic diversity. Sexual reproduction combines genetic material from two parents, which results in offspring with a unique combination of genes. This diversity is crucial for the adaptability and survival of populations, as it enhances the ability to respond to environmental changes, resist diseases, and reduce the risk of harmful mutations spreading through the population.
What is the primary reason for the evolution of male adornments according to Zahavi (1975)?
A) To attract predators
B) To demonstrate survival abilities
C) To increase lifespan
D) To reduce competition
B) To demonstrate survival abilities
According to Zahavi’s Handicap Hypothesis (1975), male adornments (like bright feathers, large antlers, or elaborate displays) evolve because they act as a “handicap” that demonstrates a male’s ability to survive despite the costly or risky nature of the adornment. These traits signal to females that the male is strong, healthy, and capable of thriving despite the disadvantage posed by such costly traits, thereby making him a more attractive mate as it indicates good genes.
What is the ratchet effect described by Muller (1964)?
A) Accumulation of harmful mutations in asexual species
B) Faster evolution in sexual species
C) Accumulation of beneficial mutations in asexual species
D) Slower evolution in sexual species
A) Accumulation of harmful mutations in asexual species
The ratchet effect, proposed by Hermann Muller in 1964, refers to the accumulation of harmful mutations in asexual species. In asexual reproduction, there’s no mechanism to eliminate these harmful mutations (like recombination in sexual reproduction). Over time, these mutations build up in the population, leading to a decline in fitness. The “ratchet” metaphor illustrates how, once harmful mutations accumulate, they are unlikely to be removed, effectively “locking” the population into a progressively worse genetic state.
