E6 Further Studies of Behaviour

Question 1

Describe the social organisation of honey bee colonies

Answer 1

• Bees live and interact together in a community divided into caste system consisting of a queen, drones and workers
  
  • Queens are fertile females who lay eggs, and produces pheromones
  • Drones are fertile males who can mate with the queen
  • Workers are infertile females who gather food

Question 2

Outline how natural selection may act at the level of the colony in the case of social organisms

Answer 2

• Natural selection is a mechanism of evolution that acts on the gene pool of a given population
  
  • Beneficial alleles become more frequent in a population as individuals with those alleles are more likely to achieve reproductive success
  • Many organisms form social clusters as their survival prospects are improved by cooperative group organisation
  • Because colonies are usually comprised of genetically related individuals, behaviours or traits that benefit the colony will improve the reproductive success of the group, even if it does not directly benefit the individual
  • Such characteristics are more likely to be passed on to subsequent generations and hence become more frequent in the gene pool

Question 3

Discuss the evolution of altruistic behaviour using two non-human examples

Answer 3

• Altruistic behaviour is behaviour that benefits other individuals and may be harmful to the self
  
  • It is common in animals with complex social structures
  • It increases survival of the colony or species as a whole, but not of individuals
  • Natural selection works at the level of the population, and normally works against behaviour that reduces the chance of survival and reproduction
  • In a naked mole rat colony, non-breeding animals help to raise offspring
  • Sometimes, individuals care for related individuals who are not their own offspring e.g. vampire bats share regurgitated blood with other unrelated colony members who haven’t fed
  • It is difficult to explain altruism towards unrelated individuals

Question 4

Outline how foraging behaviour optimises food intake, using bluegill fish foraging for Daphnia

Answer 4

• Foraging is the act of searching for, and finding, food
  
  • As the availability and abundance of food sources will vary, animals must adapt their feeding behaviours to account for these changes
  • The bluegill fish feeds on the aquatic crustaceanDaphniaand has been shown to change its foraging behaviour if prey availability is altered
  • If a feeding population is at high density, bluegill fish will predominantly eat largerDaphnia(high energy payoff at low search cost)
  • If a feeding population is at low density, bluegill fish will eat a range ofDaphniasizes (high search cost outweighs benefit of high energy payoff))
  • The bluegill fish has also been shown to demonstrate different foraging behaviour depending on the availability of types of prey

Question 5

Explain how mate selection can lead to exaggerated traits

Answer 5

• The success of an organism is not only measured by the number of offspring left behind, but also by reproductive fitness of the offspring
  
  • Features that improve a male’s chances of successfully competing with other males for the best mate will become more prevalent within the gene pool
  • As exaggerated traits are more likely to attract female attention and consequently promote successful reproduction, these traits will be selected for through sexual selection, even though they may increase predator attention and diminish the survival prospects of the individual
  • E.g. plumage feathers of the peacock

Question 6

State that animals show rhythmical variations in activity

Answer 6

Animals often show behaviours that follow rhythmical variation, including:
• Diurnal (daily) cycles
• Lunar cycles (monthly)
• Seasonal changes

Question 7

Outline the behavour of moonrats as an exmple illustrating the adaptive value of rhythmical behaviour patterns

Answer 7

Moonrats are nocturnal. Their excellent sense of smell helps them to forage at night when much or their prey is active (insects and other invertebrates). They are also less vulnerable to predation at night, and they rest in holes among tree toots or in hollow logs during, where they are unlikely to be discovered.

Question 8

Outline the behavour of red deer as an exmple illustrating the adaptive value of rhythmical behaviour patterns

Answer 8

Reproduction follows an annual cycle in red deer. Males and females are only sexually active during autumn. Males fight to establish dominance over groups of females with whom they mate. The advantage is that if the females start gestation in the autumn, the offspring are born in spring, when most food is available for feeding the offspring.