chapter 11

Question 1

what is genetic load?

Answer 1

1. Genetic load is the burden imposed by the accumulation of deleterious mutations

Question 2

What is female choice, why and when does it occur?

Answer 2

Female choice is when the female chooses the male she wants to mate with. It occurs because the female puts the most energy into reproduction. By choosing the best/strongest mate she gets direct benefits such as food, nest sites, protection, spermatophores, help raising the young and reduced risk. She also receives indirect benefits that affect the genetic quality of the female’s offspring

Question 3

What is runaway sexual selection?

Answer 3

1. Runaway sexual selection occurs when there is a heritable variation in a trait that affects the ability to obtain mates, then variants conductive to success will become more common overtime. Called a runaway mechanism because it can only be stopped when a sexually selected trait starts to become a serious threat to male’s survival.

Question 4

When does sexual selection acts on females?

Answer 4

1. Sexual selection acts on females when the male provides all of the offspring care. In this case, the females will evolve ornaments, be larger and more aggressive than males.

Question 5

When does sexual selection acts on males?

Answer 5

Sexual selection acts on males when the female provides most of the offspring care. The female will often choose the largest, strongest male so the traits are passed down to their offspring

Question 6

is sexual selection stronger on females or on males?

Answer 6

sexual selection is typically stronger on males

Question 7

When can natural and sexual selection collide?

Answer 7

1. When Natural selection and sexual selection collide, something has to give. When sexual selection is strong, natural selection has to work to overcome the sexual selection to allow an individual to survive. On the otherhand, if natural selection is too strong, sexual selection has to work so the individuals are able to attract mates and produce more offspring.

Question 8

Why is female choice common, but male choice rare?

Answer 8

1. Female choice is common because they invest more into raising offspring. In males, the certainty of paternity is low because the female may mate with other males as well. Since the female knows the offspring is hers, she will invest the time to raise and care for it. On the other hand, the males benefit by mating with many different females to ensure the production of some offspring.

Question 9

What is sperm competition and what are examples?

Answer 9

1. Sperm competition is a form of sexual selection that arises after mating when males compete for fertilization of a female egg. For example, seed beetles have sharp spines on their penises. If the female has already mated with another male, the spines allow the male to remove sperm from the earlier male. The longer the spines, the more likely the male will be to fertilize the eggs Additionally, primates have evolved larger testicles to place large amounts of sperm in a female’s reproductive tract. Lastly, in deer mice, the sperm will join together so it can swim faster to fertilize the egg first.

Question 10

Define sexual conflict

Answer 10

Sexual conflict is the evolution of phenotypic characteristics that confer a fitness benefit to one sex, but a fitness cost to another.

Question 11

What are alternative male mating strategies and why do they exist?

Answer 11

1. An alternative male mating strategy is mating with a single female, trying to fight off other males and helping to raise the offspring. This prevents the males from competing for females to mate with and the chance their sperm will not be used after mating.

Question 12

What is the concept of the sneaker male?

Answer 12

1. A sneaker male is a male that pretends to be a female. During the courtship process of a territorial male, the sneaker male interrupts and tries to mate with the female.

Question 13

When is male competition and combat expected?

Answer 13

male competition is expected when the 2 males vying for the female are of about the same size/physical ability

Question 14

paternal investment

Answer 14

the energy and time expended in both constructing and caring for an offspring

Question 15

reproduction

Answer 15

the formation of new individual organisms

Question 16

hermaphrodites

Answer 16

individuals that produce both female and male gametes

Question 17

twofold cost of sex

Answer 17

asexual lineages multiply faster than sexual lineages because all progeny are capable of producing offspring. in sexual lineages, half of the offspring are males who cannot themselves produce offspring. this effectively haves the rate or replication of sexual species.

Question 18

muller’s ratchet

Answer 18

the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner

Question 19

red queen effect

Answer 19

for coevolving populations, to maintain relative witness, each population must constantly adapt to each other. term is used to refer to the biological arms race such as those between parasites and their host

Question 20

anisogamy

Answer 20

sexual reproduction involving the fusion of 2 dissimilar gametes, individuals producing larger gametes are defined as females and the individual producing the smaller gamete as male

Question 21

fecundity

Answer 21

the reproductive capacity of an individual such as the number or quality of egg or sperm. as measures of relative fitness, fecundity refers to the number of offspring produced by an organism

Question 22

certainty of paternity

Answer 22

the probability that a male is the genetic sire of the offspring his mate produces

Question 23

operational sex ratio (OSR)

Answer 23

the ratio of male to female individuals who are available for reproducing at any given time

Question 24

sexual selection

Answer 24

differential reproductive success resulting from the competition for fertilization, which can occur through competition among the same sex or through attraction of the opposite sex

Question 25

sexual dimorphism

Answer 25

a difference in form between males and females of a species, including color, body size, and the presence or absence of structures used in courtship displays or in contests

Question 26

opportunity for selection

Answer 26

the variance in fitness within a population. when there is no variation in fitness, there can be no selection, when there is large variance in fitness, there is a great opportunity for selection. in this sense, the opportunity for selection constrains the intensity of selection that is possible

Question 27

leks

Answer 27

assemblages of rival males who cluster together to perform courtship displays in close proximity

Question 28

monogamy

Answer 28

a mating system in which one male pairs with one female. sexual monogamy is very rare and occurs when each male mates only with one female and vice versa. social monogamy occurs when a male and female form a stable pair bond and cooperate to rear the young, even if either or both partners seek extra-pair copulations. social monogamy occurs in a few fish and mammal species and in almost 90% of bird species.

Question 29

polygyny

Answer 29

a mating system where males mate or attempt to mate with multiple females

Question 30

polyandry

Answer 30

a mating system where females mate or attempt to mate with multiple males