Lecture 18

Question 1

The phenotype. . .

Answer 1

is a combination between both genotype & environment

Question 2

Reproduction is. . .

Answer 2

the means by which a new organism acquires a genotype

Question 3

Asexual vs Sexual females

Answer 3

• asexual females can produce twice as many childbearing offspring (females) as sexual females, so natural selection might be expected to favour asexual reproduction

Question 4

Asexual species are more common in agricultural habitats that are typically. . .

Answer 4

homogenous
perhaps sexual reproduction provides advantages in spatially and temporally variable environments

asexual reproduction - will favour species that don’t require sex in order to deal with the changing environments

Question 5

Define dimorphic

Answer 5

occurring in or representing two distinct forms.

sexual dimorphism = differences between the sexes

Question 6

A signalling explanation why gametes (sperm & eggs) are dimorphic

Answer 6

• prevents the ligands from binding to receptors on its own membrane which may impair intercellular signalling
• producing ligand and receptor in an asymmetric manner resolves this issue

Question 7

1 challenge in sexual reproduction

Answer 7

introduces the challenge of bringing male and female gametes together

signals, indicating location and receptivity, are required to bring sexes (or gametes) together - this can also act as CUES to alert natural enemies

Question 8

Modes of reproduction that remove the hassle with sex

Answer 8

facultative parthenogenesis

hermaphroditism

Question 9

Facultative parthenogenesis

Answer 9

females are able to produce viable eggs irrespective of whether mating has taken place

Question 10

hermaphroditism

Answer 10

organisms have complete or partial reproductive organs and produces gametes normally associated with both male and female sexes

Question 11

What is sexual selection?

Answer 11

when there is competition between members of one sex (typically males) for reproductive opportunities with the other sex (typically females)

signalling
males have evolved armaments that are used in contests & may also signal fighting ability

Question 12

Darwin also suggested that sexual selection shapes “organs of sense”

Answer 12

• chemical signalling (pheromones) and the function of antennae were not discovered until many years later

Question 13

Traps with a single female, which release less pheromone than traps with 2 females,. . .

Answer 13

attract males with larger antennae

Question 14

Reproductive success for a female can be improved by mating with . . .

Answer 14

more than 1 male (polyandry) within their reproductive cycle

Question 15

Reproductive success for males is compromized by. . .

Answer 15

polyandry, and sexual selection favours mechanisms to prevent it

Question 16

How might females benefit from polyandry?

Answer 16

If competitive fertilization success is heritable, females may benefit from polyandry by producing sons that are superior sperm competitors

acquisition of sufficient sperm to fertilise all of a female’s ova

Question 17

Male counter-adaptations to polyandry

Answer 17

• males may physically prevent her from mating
• males of many butterflies protect their paternity with a sphragis (dried seminal fluid that covers the female genital opening, preventing other males from mating)
• interfering with female signalling

female spiders place a pheromone in their webs to attract males - attracted males destroy her web before courtship

Question 18

Polyandry vs polygyny

Answer 18

polyandry - the best outcome for females

polygyny - the best outcome for males

Question 19

The net benefit for the female may not be the same as that for the offspring. Why?

Answer 19

Because the maximal benefit for the offspring may require a higher cost for the mother, which could limit the mother’s ability to survive until the next reproductive season.

Question 20

What is meant by cooperative breeding?

Answer 20

the dependent young receive parental care (food, defense) from their parents as well as other individuals in the group

Question 21

What are the major defining features of eusocial insects?

Answer 21

1) cooperative care of young

2) sterile castes - help in nest maintenance and raising offspring, but cannot themselves reproduce

3) overlapping generations - such that mother, adult offspring and larval offspring are alive at the same time

e.g. wasps, ants, bees

Question 22

Complex societies require the exchange and acquisition of lots of info

Answer 22

• green tree ants cooperate to construct a lead
• scouting worker bees return to the nest and perform a dance, which tells other bees the location, distance, and nature of the food source