sex + reproduction in invertebrates 1

Question 1

getting the sexes together can be difficult in insects because

Answer 1

they’re generally short lived and not very mobile

Question 2

getting the sexes together can be difficult so the male insects usually takes risks/spends most resources on this

Answer 2

if making the signal is costly, males make the signal
if moving to the signaller is costly, males move to the signaller

Question 3

males travel costs

Answer 3

many female moths produce attractive pheromones, male emperor moths can detect these from 8km

Question 4

males travel costs - hue intricate antennae help but how should they behave, a few basic rules apply

Answer 4

if in the odour plume, fly upwind
if not in the odour plume, fly to the left and right across the wind until they find the plume again

Question 5

protandry

Answer 5

males usually emerge into adulthood first

Question 6

if only one sex has wings, what sex is it

Answer 6

male

Question 7

courtship

Answer 7

males of some singing species switch to short range songs when they get close to female
other males do dances with adorned antennae, eye stalks or decorated wings

Question 8

prę zygotic reproductive isolation

Answer 8

making sure species mate with the same species

Question 9

2 hypothesis on how we should view courtship

Answer 9

main evolutionary driver behind courtship is pre-zygotic isolation
main evolutionary driver behind courtship is sexual selection

Question 10

2 hypotheses why females choose an attractive male

Answer 10

fisherman (sexy sons) hypothesis
Zahavi’s handicap hypothesis

Question 11

fisherian hypothesis

Answer 11

‘attractiveness for its own sake’
attractiveness only indicates genes that will help create attractive offspring
involved in runaway sexual selection - females preferences genes become linked to male trait genes

Question 12

Zahavi’s handicap hypothesis

Answer 12

male attractiveness indicates genes for good physical health
males ability to afford spectacular ornaments depends on genetic quality and resource availability

Question 13

Zahavi’s handicap hypothesis - proven in stalk eyed flies

Answer 13

males have a higher relative eye span when fed on high quality food than low quality food, unlike females

Question 14

Hamilton’s + Zuk’s parasite resistance hypothesis

Answer 14

extension of Zahavi’s handicap
how important disease is in terms of natural selection
suggested high quality male ornaments may indicate high disease resistance, which is likely to be heritable

Question 15

nuptial gifts

Answer 15

male animals often give females a nuptial gift (food)

Question 16

what does the male get in nuptial gifts

Answer 16

paternal investment, ensuring paternity, being able to give impressive gift is inherently attractive to a female

Question 17

nuptial gifts - hanging flies

Answer 17

male hanging flies offer food to a female
the larger the food, the longer they copulate for
the longer they copulate for, the more sperm he will transfer to her
after a really large meal, she’ll reject future mates for a few hours

Question 18

nuptial gifts - behaviour and gift

Answer 18

male artic dance flies hunt for mosquitoes
they take a mosquito with them and fly above a landmark in mating swarm
rise towards female and transfer prey to her
pair then fly to suitable resting site and copulate while female feeds

Question 19

nuptial gifts - sexual cannibalism

Answer 19

occurs especially in spiders and mantids
4 explanatory hypotheses - adaptive foraging, aggressive spillover, mate choice, mistaken identity

Question 20

sexual cannibalism - adaptive foraging

Answer 20

female assess male based on benefit of eating him compared to benefit of mating with him
but in several species, female can achieve both, only in some species, she has to make a decision

Question 21

sexual cannibalism - aggressive spillover

Answer 21

females who are more aggressive to potential prey will feed more and thrive but may lose potential mates who will run away from them
non-maximum level of aggressive may be optimal but she may get hungry

Question 22

sexual cannibalism - mate choice

Answer 22

smaller/less aggressive males are often less attractive to females
females eats them instead of mating but only in some species does she have to make a choice

Question 23

sexual cannibalism - mistaken identity

Answer 23

if a female attacks male before he displays some/all mating displays, she may kill him without realising he’s a potential mate
difficult to prove

Question 24

how many predatory mantid species exhibit some cases of sexual cannibalism

Answer 24

90% - but most observations are of captive animals

Question 25

how often does sexual cannibalism occur in european mantis

Answer 25

25-33% of matings and its wild frequency isn't significantly different from its captive frequency

Question 26

sexual cannibalism - Chinese mantids

Answer 26

females engage more in matings and so more cannibalisms of males than they need to gain sufficient sperm for fertilisation seem to be benefitting from all those extra calories and other nutrients at the time of egg creation

Question 27

Herd et al - sexual cannibalism

Answer 27

females ate so many males that the sex ratio changed from 1.45:1 (male:female) to 0.21:1 (male:female)

Question 28

why do males tend to target heavy females in sexual cannibalism

Answer 28

heavier females will lay eggs sooner heavier females have more eggs to lay heavier females produce more sex pheromones heavier females are less likely to eat males