Evolution in Action
A population of insects becomes increasingly resistant to a pesticide over several generations. Which statement best explains this change? [1 mark]
A. Individual insects develop resistance because they need to survive.
B. Insects with heritable resistance are more likely to survive and reproduce.
C. All insects develop the same beneficial mutation after pesticide exposure.
D. The pesticide causes insects to acquire characteristics that are inherited by their offspring.
What is B. Insects with heritable resistance are more likely to survive and reproduce.
Which observation provides the strongest evidence that two populations are separate species under the biological species concept? [1 mark]
A. They occupy different geographical regions.
B. Their average body sizes are different.
C. They are reproductively isolated.
D. They have different allele frequencies.
What is C? — The populations are reproductively isolated.
Which human activity is most likely to directly reduce native species biodiversity? [1 mark]
A. Reintroduction of locally extinct native species.
B. Restoration of degraded habitats.
C. Conversion of natural forest into agricultural plantations.
D. Establishment of protected wildlife corridors.
What is C? — Conversion of natural forest into agricultural plantations.
Which of the following is an abiotic factor that may limit the distribution of a plant species? [1 mark]
A. Competition with other plants
B. Soil salinity
C. Herbivory by insects
D. Infection by pathogenic fungi
What is B? — Soil salinity.
Which organism is most likely to be a niche specialist? [1 mark]
A. An animal that consumes many different foods across several habitats.
B. A bacterium capable of surviving in both aerobic and anaerobic conditions.
C. An insect species whose larvae feed on only one species of host plant.
D. A predator that switches prey when its usual prey becomes scarce.
What is C? — An insect whose larvae depend on one host plant.
The forelimbs of humans, whales, and bats contain similar arrangements of bones but perform different functions.
State the term used to describe these structures and explain what their similarity suggests about evolution. [2 marks]
What are Homologous structures? (1); similar underlying anatomy provides evidence of shared ancestry and divergent evolution (1).
Two populations of the same species become separated by the formation of a mountain range.
Outline how this geographical barrier could affect gene flow and allele frequencies in the two populations. [2 marks]
The barrier reduces or prevents gene flow between the populations (1); independent mutation, natural selection, or genetic drift can cause allele frequencies to diverge (1).
The North Island giant moa became extinct after human settlement of New Zealand. [2 marks]
State one likely anthropogenic cause of its extinction and outline how this activity could cause population decline.
Overhunting (1); removal of individuals faster than the population could replace them contributed to decline and eventual extinction (1).
Some mangrove trees have specialized salt glands in their leaves.
Outline how these glands help mangrove trees survive in saline environments. [2 marks]
Salt glands secrete excess salt (1), helping maintain suitable internal ion concentrations and osmotic balance for cellular metabolism (1).
Distinguish between the fundamental niche and the realized niche of a species. [2 marks]
Fundamental niche: the potential range of conditions and resources a species could use in the absence of limiting biotic interactions (1). Realized niche: the actual range occupied, often reduced by competition or other biotic interactions (1).
Sharks and dolphins have independently evolved streamlined bodies that reduce resistance while swimming.
Which statements are correct? [1 mark]
I. Their streamlined body shapes provide evidence of convergent evolution.
II. Similar selection pressures can result in similar adaptations in distantly related organisms.
III. Their streamlined bodies demonstrate that sharks and dolphins share a recent common ancestor.
A. I only
B. I and II only
C. II and III only
D. I, II and III
What is B — I and II only?
A river divides an ancestral primate population. One population experiences frequent food shortages while the other has a relatively stable food supply.
Which outcome is most likely over many generations? [1 mark]
A. Both populations will evolve identical adaptations because they originated from the same species.
B. Different selection pressures may favour different inherited traits in each population.
C. Individuals will develop whichever adaptations they need and pass them directly to offspring.
D. Geographical separation immediately produces two reproductively isolated species.
What is B? — Different selection pressures may favor different inherited traits in each population.
Which statements about conservation are correct? [1 mark]
I. In situ conservation involves protecting species in their natural habitats.
II. Ex situ conservation may involve captive breeding in zoos.
III. Releasing captive-bred organisms into a protected natural habitat can connect ex situ and in situ conservation.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
What is D? — I, II and III.
Marram grass grows on exposed sand dunes where water availability may be limited.
Which adaptation and explanation is most appropriate? [1 mark]
A. Broad, flat leaves increase the surface area available for transpiration.
B. Rolled leaves trap moist air near the stomata, reducing water loss.
C. Increased numbers of exposed stomata increase evaporation and cool the leaf.
D. Thin cuticles allow water to diffuse rapidly into leaf cells.
What is B? — Rolled leaves trap moist air near the stomata, reducing water loss.
Which statements about modes of nutrition are correct? [1 mark]
I. Saprotrophs digest organic matter externally and absorb the resulting products.
II. Mixotrophs can obtain organic compounds through both autotrophic and heterotrophic nutrition.
III. Detritivores typically digest dead organic material externally before absorbing nutrients.
A. I only
B. I and II only
C. II and III only
D. I, II and III
B — I and II only.
(Detritivores ingest dead organic matter and digest it internally, unlike saprotrophs.)
Domestic dogs exhibit considerable variation in body size, coat type, and skull shape.
Explain how selective breeding has produced this variation and why it provides evidence that populations can evolve over generations. [3 marks]
Humans select parents with desirable inherited traits (1); these individuals reproduce and pass on relevant alleles (1); repeated breeding changes the frequencies of inherited traits across generations (1).
A population of small mammals is divided when a large highway is constructed through its habitat.
Explain how prolonged isolation of the two populations could eventually result in speciation. [4 marks]
Highway construction restricts gene flow (1); genetic differences accumulate through mutation, drift and/or selection (1); inherited traits and allele frequencies diverge (1); reproductive isolation may eventually arise, resulting in distinct species (1).
An invasive plant species spreads through a woodland and displaces several native plant species.
Explain how the invasive species could reduce local biodiversity, and suggest one conservation strategy that could address the problem. [4 marks]
The invasive species competes with native species for limited resources such as light, water or nutrients (1); native populations may decline through competitive exclusion (1); reduced survival or local extinction decreases species richness and/or evenness (1); an appropriate conservation intervention, such as targeted invasive-species removal with native habitat restoration (1).
Tropical coral reefs occur mainly in warm, shallow marine environments.
Explain how three abiotic conditions influence whether reef-building corals can thrive in a particular habitat. [3 marks]
Award one mark for each correctly explained condition, up to three: suitable warm water temperature supports coral and symbiont metabolism; shallow, clear water allows sufficient light for photosynthetic symbionts; suitable salinity maintains osmotic balance; suitable alkaline pH supports calcium carbonate skeleton formation. Conditions must be linked to their biological significance.
Two closely related bird species feed on the same insect species in a forest. When they occur separately, both forage throughout the canopy. When they occur together, one feeds mainly in the upper canopy and the other in the lower canopy.
Explain this observation using interspecific competition, fundamental niches, and realized niches. [4 marks]
The birds have overlapping fundamental niches (1); interspecific competition occurs when both exploit the same food or foraging space (1); competitive interactions restrict or alter the habitat use of one or both species (1); they occupy different realized niches in the canopy, reducing overlap and allowing coexistence (1).
The wings of bats and insects perform the same function, yet they have different anatomical origins.
Explain how wings evolved in these organisms, referring to natural selection, analogous structures, and their evolutionary ancestry. [4 marks]
Bat and insect wings have the same function but different anatomical origins (1); they are analogous structures (1); flight adaptations evolved independently in the two lineages through convergent evolution (1); heritable variation and natural selection favored structures that improved survival or reproduction (1).
Chimpanzees and bonobos are thought to have diverged from a common ancestral population following geographical separation associated with the Congo River.
Explain how genetic variation, different selection pressures, and reproductive isolation could have contributed to the formation of these two species. [5 marks]
A common ancestral population became geographically separated (1); reduced gene flow allowed independent genetic divergence (1); mutations and genetic recombination produced heritable variation (1); differing selection pressures changed allele frequencies in the two populations (1); accumulated differences eventually led to reproductive isolation and speciation (1).
Ecologists surveyed two ponds and recorded the following numbers of individuals of four species. [4 marks]
Pond A: Species A: 15, Species B: 3, Species C: 1, Species D: 1
Pond A: Species A: 5, Species B: 5, Species C: 5, Species D: 5
Using the data:
a. State which pond has higher species richness. [1]
b. Deduce which pond has higher species evenness. [1]
c. Predict which pond would have the higher Simpson's reciprocal diversity index and explain your answer. [2]
(a) Both ponds have equal species richness: four species each (1). (b) Pond B has greater evenness (1). (c) Pond B is predicted to have a higher Simpson's reciprocal diversity index (1) because individuals are evenly distributed among species rather than dominated by one species (1).
A species of freshwater fish has the following response to water temperature. [4 marks]
SEE POWERPOINT
a. Identify the optimum temperature from the data. [1]
b. State the approximate observed temperature range within which the species was present. [1]
c. Explain why the abundance decreases as temperature moves away from the optimum, referring to physiological tolerance and limiting factors. [2]
(a) 25°C (1). (b) Approximately 15–35°C in the sampled data (1). (c) Away from the optimum, physiological processes become less efficient or stressful conditions affect metabolism (1); temperature increasingly limits survival, reproduction and/or growth, reducing abundance (1).
An ecosystem contains three microorganisms:
Species A uses sunlight to produce organic molecules but can also ingest other microorganisms.
Species B obtains nutrients by secreting digestive enzymes onto dead organic matter and absorbing the products.
Species C can generate ATP with oxygen present but can also survive and metabolize without oxygen.
Identify the nutritional strategy or oxygen classification of each species, and explain the features that support your classifications. [5 marks]
Species A is a mixotroph (1) because it can both synthesize organic compounds using light and obtain them by ingesting organisms (1). Species B is a saprotroph (1) because it externally digests dead organic matter and absorbs the soluble products (1). Species C is a facultative anaerobe because it can metabolize in both the presence and absence of oxygen (1).