Chapter 9: Evolution of Reproductive Behaviour

Question 1

Sex in animals is based on ____ size

Answer 1

GAMETE size. small gamete= male, large gamete= female

Question 2

according to darwin, the number of genes you leave behind =

Answer 2

is indicative of reproductive success

Question 3

two types of morphological traits that evolved to help with reproductive behavior

Answer 3

1: ornaments: used in mate attraction (ex/ bird of paradise plumage)
2) armaments: used in intrasexual competition (ex/ antlers)

Question 4

T?F sexual selection most often favours the evolution of elaborate traits in one sex and not the otehr

Answer 4

true. the end result is a SEX DIFFERENCE in the TRAIT ITSELF, and also sex differences in associated reproductive behaviors.

Question 5

the unequal partitioning of reproduction within a population or social group is known as ___ ___

Answer 5

reproductive skew.
Males have a higher reprouctive skew: some males in a group have a lot of offspring, others have none. Females have a small reproductive skew; most females mate at least once. This can be seen in the variance in reproductive success of the bower birds.

Question 6

what is the fundamental asymmetry of sex

Answer 6

the idea that eggs are expensive but sperm are cheap to make. There is also an anisogamy between the sexes: difference in size between sperm and egg.

Question 7

anisogramy

Answer 7

difference in size between sperm and egg.

Question 8

small sperm vastly outnumber the large egg, resuting in ___ ___.

Answer 8

sperm competition. there is often wayyyy more sperm than eggs to fertilize, and therefore they must compete to fertilize the limited number of eggs.

Question 9

a males contribution to the next generation is dependent on:

female’s contribution to the next generation is limited to:

Answer 9

a males contribution to the next generation is dependent on HOW MANY SEXUAL PARTNERS HE HAS

female’s contribution to the next generation is limited to; NUMBER OF EGGS THEY CAN PRODUCE and THE QUALITY OF HER PARTNER

Question 10

Bateman’s principle

Answer 10

males tend to have higher reproductive variance because male’s reproductive success is more closely tied to his number of mates.

Question 11

Robert trivers coined parental investment. what is this?

Answer 11

the expenditures of time, energy and risks taken by a parent to help a current offspring that REDUCES a parent’s ability to invest in future offspring.

Question 12

Pros and cons of parental investment

Answer 12

pro: parental investment may increase the likelihood an existing offspring will survive to reproduce
con: parental investment may reduce a parent’s ability to produce future offspring.

Question 13

what is the operational sex ratio

Answer 13

the ratio of SEXUALLY RECEPTIVE MALES to receptive females.

generally, there are way more receptive males than females because once a female has copulated, she doesn’t benefit from copulating again.

Question 14

theory of sex differences

Answer 14

the sexual behavior of males and females differ because there are differences in parental investment that affect the rate at which individuals can produce offspring.

Question 15

when the operational sex ratio is strongly biased, the less abundant sex:

Answer 15

can afford to be choosy. the more abundant sex needs to compete for mates.

Question 16

what is sex role reversal?

Answer 16

behaviors in which females compete for males and males exert greater measures of parental care.

Question 17

explain female behavior in the long-tailed dance fly

Answer 17

long tailed dance flies exhibit sex role reversal. females try to look as large as they can by inflating their abdoment and holding their legs around their body.

Question 18

explain how pipefish exhibit sex role reversal

Answer 18

males carry offspring in a brood pouch, and females are the ones to engage aggressively in courtship. Large males discriminate against SMALL FEMALES: males prefer large ornamented females. therefore, the males are the ones to exert their MATE CHOICE.

Question 19

mate choice is an example of ____ selection and uses _____, where as competition is an example of ___ selection and uses ____

Answer 19

mate choice is an example of INTERSEXUAL selection and uses ORNAMENTS, where as competition is an example of INTRAESEXUAL selection and uses ARMAMENTS.

Question 20

explain how mormon crickets exhibit sex role reversal

Answer 20

male crickets often transfer a nutrient rich gift to females alone with their spermatophore. females compete with each otehr for this gift, and males choose the heavier female because she will produce more eggs.

Question 21

two mechanisms of sexual selection

Answer 21

1) intrasexual selection

2) intersexual selection

Question 22

2 common consequences of intersexual selection (selection for FIGHTING ABILITY)

Answer 22

1) evolution of large body size and thus SEXUAL DIMORPHISM

2) evolution of weaponry.

Question 23

male weaponry has faced ____evolution

Answer 23

CONVERGENT evolution. males of many species have antlers and horns that are used in male-to-male combat.

Question 24

males often compete for mates, however, it is not always immediate access to mates. sometimes male aggression is more about ___ ___ that will pay off down the road with more mates. example?

Answer 24

males often compete for mates, however, it is not always immediate access to mates. sometimes male aggression is more about ESTABLISHING DOMINANCE that will pay off down the road with more mates.

Ex/ savanna babboons. male baboons fight for social status. opponents are willing to fight more up the ladder, and as a result, individual males get bitten about once every six week (injured wayyy more than females).

Question 25

Explain how dominance is linked to mating success in savanna baboons. How do lower ranking males make up for their decreased mating success?

Answer 25

dominant males were copulating the same amount as normal males, but they copulated more often when they were fertile. This is because when the less-dominant males were bitten, it results in temporary sterility.

Lower ranking males may also form PARTNERSHIPS and band together with other lower-ranking males in order to oppose higher ranking males. They also form PARTNERSHIPS WITH FEMALES and help defend females and their offspring. Because of their friendship, she male seek him out when she is in estrous.

Question 26

how to pacific salmon males use “alternative mating tactics”

Answer 26

hook nose males are the most aggressive and dominant males. Jack males are considered “sneakers,” and they fertilize eggs when the dominant male doesn’t see.

If a male salmon is too small, it is forced to use only sneaker tactics. but hook nose males has CONDITIONAL TACTICS. if surrounded by small males, it uses ATTACK TACTICS. If surrounded by larger males, it uses SNEAKER TACTICS.

Question 27

What are conditional mating strategies?

Answer 27

males (primarily) make different choices about development or behaviour based upon condition.

For example, if there are large robust males in the population, and you are a small male, it may be pointless to attempt to challenge these males directly. It may be better to develop an alternative morphology and set of mating tactics in these circumstances.

Question 28

what is an alternative mating tactic in marine iguanas?

Answer 28

small males of the marine iguana must cope with sexual interfernce from larger rivals. they become satellite males and try to sneak copulations. However, when food is scarce, they gain the advantage because they do not require as much food to maintain.

Question 29

principle of energy allocation

Answer 29

males can use their energy to either form more weaponry, or more sperm.

ex/ scarab beetles with large horns have smaller testes. small individuals lose fights with larger horned beetles, but they will try and sneak coputlations. when they do, they transfer large quantities of sperm because they have larger testes, since less energy was used to create a horn.

Question 30

describe alternative mating tactics in scorpion flies and how the quality of male affects mating strategy.

Answer 30

highest quality male: provides nuptual gift to attract female
medium quality male: secretes saliva on leaves and waits for females to consume this nutritional gift.
lowest quality male: forced copulation. occurs when the male cannot provide anything for the female.

Question 31

generally, alternative mating tactics are best explained as ____ strategies. However, some mating strategies are hereditary, and are known as ____ mating strategies.

Answer 31

CONDITIONAL STRATEGIES. different tactics are utilized depending on size and population and competition.

Mating strategies that are hereditary are DISTINCT mating strategies.

Question 32

Outline the distinct mating strategies of male ruffs

Answer 32

three types of male ruffs:

1) territorials (most dominant)
2) satellites on territory
3) female mimics: looks like females and the dominant ruffs allow them on their territory. then they get confused when they see the “two females” copulating.

these male types are considered distinct mating strategies because they are hereditary.

Question 33

outline the distinct mating strategies of bluegill sundish

Answer 33

1) territorial male guards a nest and attracts females to lay their eggs in the nest
2) little sneaker males Hides and waits for an opportunity to slip between a spawning pair, and releases sperm when the territorial male does
3) female colored- sneaker males hovers above a nest before sliping between the territorial male and female. The large male thinks he’s copulating with two females, but the female mimic is actually fertilizing the eggs.

Question 34

when fertilization is internal, the ___ ___ of sperm is favored

Answer 34

swimming speed

Question 35

T/F there is cooperation between sperm

Answer 35

true. even though there is sperm competition, there are cases of cooperation between sperm in the SAME ejaculate.

Question 36

how do male black-winged damselflies engage in sperm competition?

Answer 36

males try to win the sperm wars by physically removing rival gametes from their mate’s body before transferring their own. their penis has lateral horns and spines that enable him to scrub out a female’s sperm storage organ before passing his own sperm to her.

Question 37

methods of sperm competition

Answer 37

1) physically removing rival sperm (damselflies)
2) producing more sperm in general (large testis = larger sperm count
3) sperm cooperativity from the same ejaculate, making them reach the egg faster (deer mouse)
4) producing faster swimming sperm (longer sperm)

Question 38

What is the first-mate advantage?

Answer 38

when the male to first copulate with the female prevents second males from coming in and copulating because the female reproductive tract is temporarily locked.

ex/ male ground squirrels ejaculates sperm and a gelatinous plug. this plug prevents a second males sperm from entering the reproductive tract.

Question 39

what are extra pair copulations

Answer 39

copulations occur outside of a pair-bond in a monogamous species. very common in birds.

Question 40

what is cryptic female choice?

Answer 40

cryptic female choice represents a female-driven bias in fertilization that occurs AFTER mating or the release of male gametes into the system.

females have CONTROL OVER PATERNITY in some species by using their sperm-storage systems to bias male fertilization.

Therefore, copulation success doesn’t necessarily equal fertilization success

Seen in birds. ex/ female chickens eject semen from low-ranking males.
ex/ dropsophila can select preferred sperm after mating with multiple mates.
can also occur after mating: the more attractive the male, the more effort goes into maternal care: female mallards will produce larger eggs

Question 41

In order to combat against cryptic female choice, what do males do?

Answer 41

in order for a male to assure that his sperm fertilizes a females eggs is to make sure she doesn’t mate with anyone else and store their sperm. known as MATE GUARDING.

cons: by spending time guarding a mate, males may miss out on other reproductive opportunities.

Question 42

outline mate guarding in seychelle’s warblers

Answer 42

males can determine fertility based on egg presence in the nest. No egg= possibility she is pregnant. Heavily guarded by mate, low number of EPCs.

egg= not fertile, she just laid her egg. mate doesn’t guard her much. lots of EPC’s occurs, and her eggs get fertilized by other males.

Question 43

name benefits gained from female mate choice and examples

Answer 43

1) paternal care. ex/ red coloration of stickleback male offers cues as to paternal helpfulness. Males with red bellies have fewer parasites and are better able to care for eggs
2) resources. ex/ male dung beetles roll large dung balls (nutrition) for female to lay her eggs in.

ex/ nuptual gifts in hanging flies

Question 44

how do female ospreys choose a good mate?

Answer 44

they pick a male with a good COURTSHIP DISPLAY because it signals the ability of a male to perform as a parent.

male ospreys courtship involves feeding females, which signals the ability to deliver food to the kids.

Question 45

explain female mate choice in hanging flies

Answer 45

females mate with the male that can provide a nuptual gift. males usually provide a moth (RESOURCE), and seretes a pheromone into the air to signal to her that he has a gift for her.

quality of gift is correlated with duration he’s allowed to copulate. TRANSACTIONAL RELATIONSHIP.

Question 46

explain the extreme form of nuptial gifts males give in the redback spiders species

Answer 46

male redbeck spiders jump into the females mouth and give the ultimate nuptial gift– himself. it provides a large nutritional benefit, and there is a very little chance that he’ll find another female anyways because they are hard to find.

this trait is perpetuated because eaten males fertilize 1000 more eggs than the males who do not get eaten. when he jumps into her mouth, he breaks off the petiipalp in the female and leaves it there. this allows for sperm transfer and prevents and other males from mating.

the female engages in sexual cannabalism.

Question 47

3 hypotheses that explains female mate choice and the development of male ornamentation even IF THE MALE HAS NO DIRECT/MATERIAL BENEFIT

Answer 47

1) good genes
2) sexy son hypothesis/ runway hypothesis.
3) chase away selection (male benefits)

Question 48

what is the “good gene hypothesis”

Answer 48

the idea that female choice still occurs (if male has no material benefit for her) because her offspring may inherit advantages of their father, such as good immune systems.

Question 49

what is the “sexy son hypothesis”

Answer 49

the idea that female choice still occurs (if male has no material benefit for her) because mating will allows her sons to inherit the trait that makes them sexually attractive, and daughters inherit the majority mate preference.

Question 50

what is the “chase away selection” hypothesis

Answer 50

the idea that female choice still occurs (if male has no material benefit for her) because the male appeals to HER SENSORY BIASES, but females derive no inherint benefits by being choosy.

Question 51

give an example of the good genes model of sexual selection (female choice)

Answer 51

preferences for certain male ornaments and courtship displays enable females to choose partners whose genes will help their offspring have higher fitness.

ex/ bowerbird females prefer mates with higher cognitive ability. males build elaborate nests for them, which is indicative of cognitive ability.

Question 52

what is a leking species

Answer 52

Lek polygyny is a mating system common in polygynous species of insects and birds in which the male provides no parental care to its offspring.

ex/ bower bird. female is choosy because of good gene model, not because the male has resources/will provide parental care.

Question 53

immunocompetence handicap hypothesis (hamilton and zuk hypothesis)

Answer 53

elaborate plumage or coloration is associated with resistance to parasites or other pathogens, and serves as an indicator of immune system competance.

testosterone is what gives rise to these secondary sex characteristics (plumage), while subsequently depressing the immune system. therefoer, if the male was able to express such elaborate plumage while not getting sick, he must be super healthy.

therefore, plumage in males is an HONEST SIGNAL of health.

Question 54

explain female mate choice based on a physiologically challenging tasks in canaries

Answer 54

females prefered males who could trill at a very wide bandwidth sung at a very fast rate. this is very hard to do and not many males were able to accomplish this task.

this is also considered part of the good-gene hypothesis.

Question 55

outline the runway model of selection and provide an example

Answer 55

when female mating preferences for certain male attributes create a positive feedback loop, favouring both males with these traits and females that prefer them.

ex/ long tailed widow birds. females prefer males with the longest tails. this trait is perpetuated until the trait becomes too costly to maintain.

Question 56

outline the chase-away model of sexual selection and provide and example

Answer 56

an antagonistic coevolutionary relatinoshipbetween males and females in which some mlae traits attract females may not provide any benefit to females, or actually by DISADVANTAGEOUS to them.

ex/ fruitflies.
female fruitflies prefer to mate with larger males. but the chemical that makes males larger is transfered in their semen and it decreases the females lifespan.

Question 57

explain the phenomena with sperm competition in Dunnocks

Answer 57

sperm competition in dunnock species requires FEMALE COOPERATION. the male has to peck at the cloaca of a female, and if she feels like it, she’ll eject a droplet of sperm containing ejaculate that was received by another male.

Question 58

4 ways in which females influence male reproduction

Answer 58

1) egg investment- what materials and how much of them will be placed in an egg
2) mate choice- direct or indirect benefits, or cryptic mate choice
3) egg fertilization (cryptic mate choice)
4) offspring investment.

Question 59

4 ways in which males influence female reproduction

Answer 59

1) resources- can influence egg investment, mate choice, or egg fertilization decision.
2) elaborate courship - can influence mate choice or egg fertilization decisions
3) sexual coercion- seen in low quality scorpion flies
4) infanticide- may overcome female decisions about offspring investment.

Question 60

explain the sexual conflict of infanticide

Answer 60

males will kill infants of females to cause them to be sexually receptive again (lions, langurs, mice).

Question 61

explain sexual conflict of forced copulation

Answer 61

males may force unwilling females to mate (stitchbirds, hangingflies, scorpion flies)

Question 62

explain the chemically-mediated sexual conflict in drosophila.

Answer 62

male fruit flies transfer chemicals along with sperm that increase the delay in remating by their partners. when males copulate with females, they transfer a protein (ACP62F) that boost males fertilization success but shortens the lives of females.

Question 63

t/f the evolution of male traits harmful to females is actually due to sexual selection

Answer 63

true. ex/ female fruit flies prefer male fruitflies, but then they select for acp62F while they’re at it, which harms them

studies show that monogamous drosophila males have less acp62F and females are not as resistant to acp62F

Question 64

explain the sexual conflict in bed bugs

Answer 64

male bed bugs utilize traumatic insemination. male bed bugs stabs the female by his spear penis and ejaculated his sperm directly into the body of the female. the sperm travels in the blood stream.

males cannot differentiate between males and females. he will stab any bed bug. male who was stabbed by another male will transfer both his sperm and his attackers sperm.