Social Influences on Reproduction

Question 1

What is the best way to ensure that your genetics are passed on to the next generation?

Answer 1

breed with the best available mate

Question 2

Sexual selection

Answer 2

competition for mating opportunities, which involves selection both within the members of a sex and between the sexes

Question 3

What is the parental investment of females?

Answer 3

• gestation, lactation, and offspring care

- produce relatively few gametes and require relatively few matings to ensure these are fertilized

Question 4

What is the parental investment of males?

Answer 4

• produce lots of gametes but have little or no involvement in gestation, lactation, and offspring rearing
• capable of fertilizing more than a single female’s eggs

Question 5

What is female reproductive success limited by?

Answer 5

access to resources to develop eggs and raise offspring

Question 6

What is male reproductive success limited by?

Answer 6

access to female eggs

Question 7

What is the difference between the limiting sex and the competing sex?

Answer 7

limiting sex = females b/c while engaged in gestation she is not available form sting

competing sex = males b/c they must compete for limited opportunities to mate

Question 8

Fertility

Answer 8

ability to produce young

Question 9

Fecundity

Answer 9

ability to produce many young

Question 10

When assessing potential mates, a female will look for what?

Answer 10

1. get the best genetics for her offspring
2. best resources for raising offspring
3. avoid exposing herself to disease during the mating process
4. paternal assistance with offspring care

Question 11

How are males chosen by females?

Answer 11

• males advertise for mates

- advertisements can be long or short-range and most are visual or auditory

Question 12

Why must advertisements be costly to produce or maintain?

Answer 12

keeps the signal honest (i.e. it is representing a fit animal who is ready to mate)

Question 13

What is intersexual selection?

Answer 13

• secondary sex characteristics that are designed to attract mates
• they advertise general fitness of the male, his quality, and freedom from diseases

Question 14

What is intrasexual selection?

Answer 14

visual signals between males in establishing a dominance hierarchy for mating purposes

Question 15

What are pheromones?

Answer 15

substances secreted by one individual that give specific physiologic reactions in other individuals of the same species

Question 16

Pheromones are detected by what?

Answer 16

main olfactory system (MOS)

sometimes vomeronasal organ

Question 17

How are pheromones used in mate choice?

Answer 17

they are a mechanism for avoidance of interbreeding

Question 18

How are auditory cues used for mating?

Answer 18

• reinforce olfactory cues when females are sending out a notice of their willingness to mate
• quality of a male’s song to make mate selection
• establish dominance (ex: roaring contests)

Question 19

The Whitten Effect

Answer 19

introduction of a novel male into a group of females that have suppressed cycles

Question 20

How does the Whitten Effect work?

Answer 20

1. introduction of male results in increased gonadotropins which results in increased estrogen secretion
2. increased estrogen induces LH surge and the females ovulate
3. wave of follicle growth occurring increases systemic estrogen levels
4. reduced progesterone and increased estrogen results in premature onset of luteolytic mechanisms and CL is destroyed so new ovulation can occur

Question 21

The Bruce Effect

Answer 21

exposure of an early pregnant female to a different male results in failure of her pregnancy and she returns to estrus

Question 22

What are the two explanations for the Bruce Effect?

Answer 22

1. pheromone in male urine causes an increase in dopamine release from the hypothalamus resulting in suppression of prolactin and the CL regresses
2. testes of male mice secrete estrogen in the urine and it is absorbed in the females via the vomeronasal organ, making the uterus non-receptive

Question 23

The Lee-Boot Effect

Answer 23

females housed in crowded groups have extended estrous cycles by entering a period of pseudopregnancy/extended diestrus

Question 24

The Coolidge Effect

Answer 24

males mated to exhaustion or refusal with one female will recover libido when exposed to another female

Question 25

Explain illegitimate receivers

Answer 25

many signals used by animals as part of intrasexual and intersexual competition are used by their predators and parasites as a means of locating prey or hosts

Question 26

Interceptors

Answer 26

by having their territory near that of the dominant male, they can intercept females that have been attracted to his resources as they pass through

Question 27

Impersonators

Answer 27

subordinate males mate females that are attracted from neighboring groups because they may think they are mating the dominant male

Question 28

Sneaky rutters

Answer 28

immature or weaker males wait at the edge of a harem for the dominant male to be occupied, then they run into breed and run away again