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Responses to the external environment · Part 5 of 5
12 exam-style questions with model answers, plus 16 quick multi-choice questions — every question on this part of the standard, grouped by the 4 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Describe what is meant by intraspecific competition, and describe two effects of increasing population density on a population.
In a colony of a native seabird, breeding pairs nesting at the crowded centre of the colony fledge fewer chicks than pairs at lower density near the edge, yet birds compete intensely for central sites. Explain how intraspecific competition operates here and why birds nonetheless compete for the crowded centre.
Discuss why intraspecific competition, despite harming individuals, is essential to both population regulation and to evolution by natural selection.
Describe what is meant by territoriality and by a dominance hierarchy, and describe one way each reduces the cost of competition.
A territorial bird defends a territory of 1.5 ha in a season when food is scarce, but only 0.4 ha in a season when food is abundant. Explain how this response occurs and why it provides a selective advantage.
Territoriality and dominance hierarchies both resolve intraspecific competition, but species tend to use one or the other. Discuss what determines which system is used, and evaluate the consequences of each for the individuals involved.
Describe three ways in which living in a group provides protection from predators, and describe one cost of group living.
Pūkeko breed in groups in which several adults share a nest and help to raise chicks. Explain how this cooperative breeding works and why it provides a selective advantage to the individuals involved.
Natural selection acts on individuals, yet cooperative behaviour that appears to benefit others at a cost to the performer is widespread. Discuss how this is possible, and evaluate the conditions under which cooperation is stable.
Describe the difference between intrasexual and intersexual selection, and describe three functions of courtship behaviour.
Male kākāpō gather at a display arena and 'boom' for several weeks, losing considerable body condition. Females travel to the arena, choose a male, mate, and then raise the chick entirely alone. Explain how this system works and why female choice provides a selective advantage.
Discuss why elaborate male displays that reduce a male's own survival can nonetheless spread through a population, and evaluate what limits how extreme such traits become.