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45 exam-style questions with model answers, plus 60 quick multi-choice questions — every question on the site for this standard, grouped by the 15 pages of notes they come from.
Write a full answer before you reveal the model one — that comparison is where the marks come from. Every block links back to the notes that teach it.
Distinguish between an organism's habitat and its ecological niche, and give one example of a biotic and one example of an abiotic factor in the external environment of a forest-floor invertebrate.
A small alpine daisy growing on the Canterbury high country forms a tight, ground-hugging cushion. Explain how this growth response occurs and why it provides a selective advantage in relation to the plant's ecological niche.
The same species of alpine daisy is found growing as a loose, upright plant 30 cm tall in a sheltered gully, and as a tight cushion on an exposed ridge 200 m away. Discuss why one growth response cannot be described as 'better' than the other, linking your answer to selective advantage and ecological niche.
Describe what is meant by a tropism, and describe the response of a shoot placed in one-sided light.
A young rimu seedling on the forest floor receives light only through a small gap in the canopy directly above and to one side. Explain how its phototropic response occurs and why it provides a selective advantage in relation to its ecological niche.
Compare the phototropic response of a shoot with the gravitropic response of a root, and discuss why a plant benefits from having both responses controlled by the same hormone.
Describe the difference between a tropism and a nastic response, and give one example of each.
The flowers of a coastal herb open during daylight and close at night and in heavy cloud. Explain how this response occurs and why it provides a selective advantage in relation to the plant's ecological niche.
A plant shows both a phototropic growth response and a photonastic flower response to the same stimulus — light. Discuss why natural selection has favoured two different mechanisms for responding to one stimulus.
Describe what is meant by a taxis and by a kinesis, and give one example of each.
Freshwater kōura shelter under rocks during the day and emerge to forage at night. In a laboratory tank with a light gradient, they consistently move to the darkest end by the most direct route. Explain how this response occurs and why it provides a selective advantage in relation to the kōura's ecological niche.
Two invertebrate species both end up concentrated in damp leaf litter, but one does so by chemotaxis towards humidity and the other by klinokinesis. Discuss the relative advantages of the two mechanisms, and evaluate under what conditions each would be favoured by natural selection.
Distinguish between homing and migration, and describe two cues an animal may use to orient over long distances.
Longfin eels (tuna) spend decades in New Zealand fresh water, then migrate thousands of kilometres to spawn in the tropical Pacific, breed once and die. Explain why this migration provides a selective advantage, despite its cost.
Migratory birds typically possess several navigation systems — magnetic, solar, stellar and olfactory — rather than one highly accurate system. Discuss why natural selection has favoured redundancy, and evaluate what this implies for migratory species facing environmental change.
Describe the difference between an endogenous and an exogenous rhythm, and describe how an experiment could distinguish between them.
Kiwi are nocturnal, emerging to forage shortly after dusk. Explain how this rhythm is controlled and why it provides a selective advantage in relation to the kiwi's ecological niche.
An internal clock is metabolically costly to build and run, and it must still be corrected daily by an environmental cue. Discuss why natural selection has favoured internal clocks rather than direct responses to the environment, and evaluate when a direct response might be favoured instead.
Describe what is meant by a tidal rhythm and a lunar rhythm, giving the approximate period of each, and describe one response controlled by each.
A bivalve living buried in a mudflat opens its shell to filter feed only when the tide covers it. Explain how this rhythm is controlled and why it provides a selective advantage in relation to the bivalve's ecological niche.
A single shore organism may show both a circadian and a tidal rhythm. Discuss why maintaining two separate clocks could be advantageous, and evaluate the difficulties this creates for the organism.
Describe what is meant by photoperiodism, and describe two annual responses it controls — one in a plant and one in an animal.
A deciduous tree sheds its leaves each autumn, triggered by shortening days rather than by falling temperature. Explain how this response occurs and why it provides a selective advantage in relation to the tree's ecological niche.
Climate change is causing spring temperatures in New Zealand to rise, but day length is unaffected. Discuss the implications for organisms whose annual rhythms are cued by photoperiod, and evaluate which species are most at risk.
Describe what is meant by interspecific competition, and describe the difference between a species' fundamental and realised niche.
Common wasps in South Island beech forest consume most of the honeydew produced by scale insects during late summer. Tūī, korimako and kākā feed on the same honeydew. Explain how this competition affects the native birds, and why the birds' responses to it provide a selective advantage.
Two species that compete for the same resource may end in competitive exclusion or in resource partitioning. Discuss what determines which outcome occurs, and evaluate what this predicts about the impact of introduced species in New Zealand.
Describe what is meant by mutualism, and describe one nutritional and one transport mutualism, stating what each partner gains.
The short-tailed bat (pekapeka) pollinates Dactylanthus, a parasitic plant whose flowers sit at ground level and produce strong scent and large amounts of nectar. Explain how this mutualism works and why it provides a selective advantage to each partner.
Many New Zealand plants depend on native birds for pollination or seed dispersal, and several of those birds are now rare or locally extinct. Discuss the consequences for the plants, and evaluate why obligate mutualisms make both partners more vulnerable than facultative ones.
Describe the three forms of exploitation named in this standard, and describe one adaptation of the exploiting organism and one of the exploited organism in any one of them.
Explain how an evolutionary arms race between a predator and its prey occurs, and explain why it does not result in one species eliminating the other.
Introduced mammalian predators have devastated New Zealand's native birds, while predator–prey relationships that evolved together generally remain stable. Discuss why, and evaluate what this implies for conservation strategy.
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.