SEXUAL SELECTION

Question 1

§What is intersexual selection?

Answer 1

Intersexual selection occurs when individuals of one sex (usually females) choose mates based on specific traits, such as size, coloration, or display behaviors, leading to the evolution of those traits.

Question 2

What is intrasexual selection?

Answer 2

Intrasexual selection occurs when individuals of the same sex (usually males) compete for access to mates, leading to the evolution of competitive traits.

Question 3

What types of traits are selected in intrasexual selection?

Answer 3

Physical Traits: Size or weaponry.

Physiological Traits: Sperm production.

Behavior: Competitive behaviors that enhance mating success.

Question 4

What is pre-copulation sexual selection?

Answer 4

Pre-copulation sexual selection is the process that occurs before mating, where individuals compete to attract mates through traits, behaviors, or resources.

Question 5

What are the stages in pre-copulation selection?

Answer 5

Mate Competition: Competing with the same sex to show dominance.

Mate Choice: Females select mates based on desirable traits.

Signaling and Displays: Males perform visual or auditory displays to attract females.

Question 6

What are secondary sexual characteristics?

Answer 6

Secondary sexual characteristics are noticeable differences between sexes that evolve to increase mating success, such as elaborate plumage or vocal displays in males.

Question 7

What is post-copulation sexual selection?

Answer 7

Post-copulation sexual selection occurs after mating, where individuals compete to influence which sperm fertilizes the egg, shaping traits and behaviors to enhance reproductive success.

Question 8

What are the processes involved in post-copulation sexual selection?

Answer 8

1. Sperm Competition: Involves competition among sperm from different males to fertilize an egg.
2. Cryptic Female Choice: Females can eject sperm or use hormonal signals to influence which sperm fertilizes their eggs.

Question 9

What are epigamic characters?

Answer 9

Epigamic characters are traits selected for their role in attracting mates, including behaviors and ornamentation that signal fitness or genetic quality.

also known as secondary sexual traits. these are non essential for survival but increase reproductive success and fitness of individual

Question 10

What are the reasons for mate choice?

Answer 10

Direct Benefits: Resources such as food, protection, or parental care.

Honest Signaling: Traits that signal indirect tangible benefits.

Fisher’s Runaway Sexual Selection: Exaggerated traits favored by females lead to a feedback loop enhancing the trait.

Sensory Bias: Preferences based on arbitrary traits linked to sensory systems.

Question 11

What are the basic functions of sex?

Answer 11

Reproduction: Production of offspring.

Sex: Combining and mixing of genes through gamete fusion from different individuals.

Question 12

How has reproduction evolved?

Answer 12

Asexual reproduction is the primitive state, while sexual reproduction evolved despite its costs, such as the two-fold cost of sex and reduced allele transmission in males.

Question 13

Why do males and females often look and behave differently?

Answer 13

Differences arise from sexual selection, a subset of natural selection that describes the evolution of distinct male and female attributes based on their roles and pressures in mating success.

Question 14

How do male and female gametes differ in terms of sexual selection?

Answer 14

Females: Few, large, and costly gametes, limiting their reproductive rate.

Males: Many, small, and inexpensive gametes, allowing them to seek multiple mating opportunities.

Question 15

Q: How does parental investment affect sexual selection?

Answer 15

When parental investment is unequal, the sex with higher investment becomes choosy, while the sex with lower investment becomes competitive, leading to sexual selection dynamics.

Question 16

What are the implications of sexual selection on populations?

Answer 16

Sexual selection can drive the evolution of traits that enhance mating success, potentially leading to speciation, divergence, and greater genetic diversity within populations.

Question 17

fishers runaway sexual selection

Answer 17

It explains how certain traits in males, especially exaggerated or ornamental features, can evolve and become more pronounced over time due to a positive feedback loop driven by mate preference.

• Female Preference Drives Male Trait Evolution:
• ## Genetic Correlation Between Traits and Preferences:

Question 18

how fishers runaway works

Answer 18

How It Works:
Initial Trait Evolution: A male trait arises that is either randomly selected or slightly advantageous. At first, females may prefer this trait for reasons such as it being an honest signal of good genes, health, or vigor, or simply due to a preference for the trait itself.

Female Preference for the Trait: Females who prefer this trait (for any reason) are more likely to mate with males who possess it, resulting in more offspring that carry both the preferred trait and the genetic predisposition to prefer it.

Positive Feedback Loop: As these traits become more pronounced in males, the preference for those traits in females becomes stronger, further selecting for more extreme traits in males.

Exaggeration of Traits: Over generations, the trait in males (e.g., a peacock’s tail feathers or the size of a bird’s plumage) can become exaggerated to extreme levels, even if it has no direct survival advantage, simply because females continue to prefer it.