L2

Question 1

Paradoxical Behaviours

Answer 1

Damaging behaviours yet they are still performed

Question 2

Group Selection and Individual Selection: Infanticide in Hanuman langurs

Answer 2

• Live in social groups: one large male , several females and young
  • When a male is displaced infants die - new males are the prime suspects in most cases

Question 3

Why do males kill offspring?

Answer 3

There are large consequences e.g female attacking new male

Question 4

3 hypotheses for why males kill other offspring

Answer 4

Non -adaptive

Favoured by natural selection at the individual level

Favoured by natural selection at the group level

Question 5

Non-adaptive hypothesis of infanticide

Answer 5

Social pathology brought on by overcrowding

Question 6

Favoured by natural selection at the individual level

Answer 6

Infanticide frees females to become pregnant sooner. The male becomes a father sooner and has more offspring before he is himself overthrown by another male

Question 7

Favoured by natural selection at the group level

Answer 7

• Infanticide reduces overcrowding which would cause the group to overexploit its food or other resources

Group selection can theoretically occur but circumstances that favour it are rare

Question 8

The logic of group selection

Answer 8

• Group selection suggests an individual’s behaviours are adaptations that assist the survival of their “group” eg reproducing less to avoid overexploiting resources

Groups with individuals that practise self restraint or do something else beneficial to the group, survive better

This is selected for at the group level

Individuals who don’t show self restraint will prosper, there must be a survival advantage at the group level

Individual selection will usually be stronger.

Individual selection: Advantage to

Question 9

Over time selfish individuals outnumber …

Answer 9

altruistic individuals

Question 10

if resources are limited and two groups are competing?

Answer 10

group selection is more favourable

Question 11

Between group selection: advantage to

Answer 11

• More restraining individuals end up with more resources
  
  • They are selected for through group selection

Red is favoured at individual level, blue is favoured at between group level

Blue only favoured if:

Groups are relatively long lived in relation to individual life span

inter - group competition is important

Question 12

Infanticide

Answer 12

• Often carried out by males as they compete for females
• In jacanas the females compete, so they commit infanticide

Question 13

infanticide in meerkats

Answer 13

• Meerkats live in social groups
  
  • Dominant female and subordinate females who breed
  • Pregnant females will kill the pups of other females (it is more likely if other females are pregnant)
  • If other subordinate females are pregnant then dominant female pup survival decreases
    ○ If no other females are pregnant then subordinate pups survive (less than dominant female though)
  • If other females are pregnant then subordinate pups are less likely to survive

Infanticide is adaptive so they cannot compete with their unborn offspring
Pregnant females increase their fitness
Direct reproductive benefit

Question 14

Aggression in Meerkats

Answer 14

• Special reading Bell MBV
  
  • Suppress subordinate pregnancy
  • Costs to aggressive behaviour

Suppressed breeding in subordinate and looked at dominant behaviour

Question 15

Self-sacrifice in worker honey bees

Answer 15

• Autotomy
  
  • Abdomen is ripped out
  • Death

Barbed sting
* Lodges into flesh of attacking vertebrate
* Easy to go in
* Hard to get out

Sting exhibits complex adaptive behaviour
* Muscles and nerves cause stings stylets to drill into flesh and venom is pumped into victim
* Alarm pheromone is volatile and smells of bananas
* Guides bees to intruder and makes them more prone to stinging
* Highly defensive behaviour
* Most effective when sting is detached

Honeybee workers rarely reproduce. Instead they rear close relatives so their genes are passed on indirectly.
By sacrificing themselves they save their reproductive investment

Question 16

Sex change in anthias fish

Answer 16

• Females change into males when a large dominant male dies and leaves an opening in the population
  
  • Increases fitness when female are small but better to be a large male
  • Pass on more genes

Question 17

Garden Spider: male approaching female

Answer 17

• smaller male wanders around looking for females
  
  • Plucks strands of her web to let her know he is not food
    ○ Not always successful, some are eaten

Tied down female
* Ties female down and traps her
* Copulates with her and leaves her to untangle herself

Question 18

Nuptial Gift

Answer 18

• Food offerings in the form of insects wrapped up in silk
  
  • Female eats gift whilst male copulates

Question 19

Black Widow

Answer 19

• Eats partner following copulation

Question 20

Redback Spider

Answer 20

• Females are much larger than males
  
  • Females longer lived than males
  • Male matures at a younger age
  • Many males per female
  • Multiple mating by females occurs
  • 17% females mated with 2-3 males
  • Male places himself in the females jaws during copulation

Question 21

Redback spider: copulation

Answer 21

• Does not give female resources
  
  • Male must benefit somehow

Question 22

Benefit to first male being cannabilised

Answer 22

• Effect of cannabilised on first males paternity

If female eats first male then 67% next male is rejected

If female doesnt eat first male then 4% next male is rejected

Question 23

Benefit of 2nd male being cannabilised

Answer 23

• Copulation duration increases with paternity
  
  • Longer the male mates the more sperm transferred and more likely to father offspring
  • Non-cannibalised males don’t copulate as long

Redback spider
* In balance

Question 24

Bean Weevil

Answer 24

• Tip of penis covered in spines
  
  • Male tears apart reproductive tract so female does not reproduce again
  • Damage discourages 2nd mating
  • Females kick male to reduce damage to their reproductive tract
  • No difference in fecundity between females with one damaging mating and two damaging matins
  • Damage reduces lifespan
  • Genital damage is only costly to female not female
  System is always in dynamic flux

Question 25

Filial cannabilism

Answer 25

○ Sand goby * Deal N D S sand goby Individuals cannibalise own offspring