Question 1
A biologist describes a species of warbler as feeding on small insects in the upper canopy, nesting in tree holes and being limited by winter temperature and competition from other insectivorous birds.
What has the biologist described?
A.
The species ecological niche
B.
The species population size
C.
The species trophic level only
D.
The species habitat only
Question 2
Photosynthesis is the mode of nutrition in plants, algae and several groups of photosynthetic prokaryotes.
Which group is not expected to use photosynthesis as its mode of nutrition?
A.
Cyanobacteria
B.
Seaweeds
C.
Flowering plants
D.
Archaea
Question 3
A bacterial species grows in waterlogged mud but stops growing and dies when exposed to oxygen gas.
What is the most appropriate classification of this species?
A.
Obligate anaerobe
B.
Facultative anaerobe
C.
Photosynthetic prokaryote
D.
Obligate aerobe
Question 4
In holozoic nutrition, food is taken into a digestive tract and processed inside the body.
What is the correct sequence of processes after ingestion?
A.
Digestion, assimilation, egestion, absorption
B.
Assimilation, digestion, absorption, egestion
C.
Digestion, absorption, assimilation, egestion
D.
Absorption, digestion, assimilation, egestion
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Question 5
A culture of Euglena grows in the light using carbon dioxide. When kept in darkness it can continue growing if dissolved organic compounds are supplied.
What term best describes this mode of nutrition?
A.
Saprotrophic nutrition
B.
Holozoic nutrition
C.
Facultative mixotrophy
D.
Obligate aerobic nutrition
Question 6
A mould growing on fallen fruit releases enzymes into the fruit tissue and then absorbs soluble digestion products.
What distinguishes this nutrition from holozoic nutrition in animals?
A.
It requires ingestion before digestion
B.
It synthesizes organic carbon compounds from carbon dioxide
C.
It occurs only in animals with a digestive tract
D.
It uses external digestion before absorption
Question 7
A small insectivorous bird feeds mainly on larvae found under loose bark, nests in tree holes and is most abundant in cool, moist woodland.
State what is meant by an ecological niche.
[1]
Explain why the habitat of the bird is only part of its ecological niche.
[2]
Question 8
Cultures of Euglena are grown in two conditions: bright light with few dissolved organic compounds, and darkness with many dissolved organic compounds.
State the term used for an organism that uses both autotrophic and heterotrophic nutrition.
[1]
Explain how facultative mixotrophy could be advantageous to Euglena in these conditions.
[2]
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Question 9
An archaeal species obtains energy for ATP production by oxidizing inorganic chemicals in hydrothermal vent water.
What type of nutrition is shown?
A.
Photosynthetic nutrition
B.
Chemotrophic nutrition
C.
Facultative mixotrophy
D.
Holozoic nutrition
Question 10
A fossil hominid skull has large molars with broad, flat grinding surfaces and a robust jaw. The canines are not prominent.
What diet is best supported by these observations?
A.
Mainly carnivorous, because flat molars are specialized for piercing prey
B.
Strictly saprotrophic, because the jaw indicates external digestion
C.
Obligately mixotrophic, because both plant and animal tissue are required
D.
Mainly herbivorous, because fibrous plant material requires crushing and grinding
Question 11
An insect feeds by inserting long, narrow mouthparts into a leaf vein and sucking out liquid sap.
What adaptation is best matched to this feeding niche?
A.
External digestive enzymes for decomposing leaves
B.
Piercing mouthparts for penetrating plant tissue
C.
Broad grinding molars for crushing seeds
D.
Chewing mouthparts for removing pieces of leaf blade
Question 12
A small fish species forms dense schools when a predatory fish is nearby. Individuals at the edge of the school frequently change position with individuals in the centre.
What type of anti-predator adaptation is this?
A.
Behavioural adaptation that reduces capture risk
B.
Chemical adaptation that poisons the predator
C.
Physical adaptation that increases armour thickness
D.
Saprotrophic adaptation that increases decomposition
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Question 13
A sealed column containing pond water and mud is left in the light. Oxygen concentration is highest near the water surface and decreases with depth.
State the type of organism most likely to be restricted to the deepest anoxic mud.
[1]
Explain the difference between an obligate aerobe and a facultative anaerobe in terms of oxygen tolerance.
[2]
Suggest why the column could contain more than one microbial band.
[1]
Question 14
Photosynthesis and holozoic nutrition are two modes by which organisms obtain materials and energy for growth.
Outline photosynthesis as a mode of nutrition.
[2]
Distinguish photosynthetic nutrition from holozoic nutrition in animals.
[2]
Question 15
Predator and prey species exert selection pressures on each other.
Describe two adaptations of predators for finding, catching or killing prey.
[2]
Describe two adaptations of prey animals for resisting predation.
[2]
Question 16
Ecologists compared two closely related shore crab species living on the same rocky shore. The data show selected niche dimensions for each species.
Species | Shore height / m | Salinity / ppt | Main food source | Feeding time |
|---|---|---|---|---|
Shore crab species 1 | 0.2–0.8 | 18–30 | Small algae and detritus scraped from rock surfaces | Mostly during the day |
Shore crab species 2 | 0.5–1.1 | 22–36 | Small animals such as barnacles and mussels | Mostly at night |
Identify one abiotic factor included in the data.
[1]
Describe how the mode of obtaining food differs between the two crab species.
[2]
Suggest why the two crab species are described as having overlapping but not identical ecological niches.
[1]
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Question 17
A sealed column containing pond mud and water was kept in the light for several weeks. Oxygen concentration and the growth of three bacterial groups were recorded at different depths.
Depth interval / cm | Oxygen concentration / mg dm | Group A growth / a.u. | Group B growth / a.u. | Group C growth / a.u. |
|---|---|---|---|---|
0-1 | 8.0 | 3 | 2 | 0 |
1-2 | 6.0 | 3 | 3 | 0 |
2-3 | 4.0 | 2 | 3 | 0 |
3-4 | 2.0 | 1 | 3 | 0 |
4-5 | 0.0 | 0 | 2 | 1 |
5-6 | 0.0 | 0 | 1 | 3 |
Identify the bacterial group most likely to be facultatively anaerobic.
[1]
Explain the distribution of the obligate anaerobe in the column.
[2]
Suggest the likely effect of stirring the column so that oxygen reaches the deepest mud.
[1]
Question 18
A plant species produces a toxic secondary compound in its leaves. Two leaf-eating insect species were placed on plants with different toxin concentrations.
Identify the insect species most likely to have chewing mouthparts.
[1]
Describe the effect of increasing toxin concentration on the feeding of the two insects.
[2]
Suggest an adaptation that could allow insect Y to feed on leaves containing the toxin.
[1]
Question 19
A woody plant germinates on the forest floor and climbs the trunks of other trees, using them for support while growing towards brighter light. It does not obtain food from the supporting trees.
What plant form is described?
A.
Epiphyte
B.
Strangler epiphyte
C.
Shade-tolerant herb
D.
Liana
Question 20
Two species of barnacle can each occupy upper and lower shore zones when grown separately. When they occur together, species X remains only in the upper zone and species Y remains only in the lower zone.
What is the best interpretation?
A.
Competition has restricted both species to part of their fundamental niches
B.
Abiotic tolerance alone determines the realized niche of each species
C.
Both species have identical realized niches in the same shore zone
D.
Species X has been eliminated by competitive exclusion
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Question 21
Two hominid skulls are compared to infer diet from dentition.
Identify two dentition features that would support an inference of a mainly herbivorous diet.
[2]
Explain why diet inferred from the skull remains a deduction rather than a direct observation.
[2]
Question 22
Archaea are one of the three domains of life and are found in many environments.
State one cellular feature of archaea that places them outside Eukarya.
[1]
Outline the diversity of nutrition in archaea.
[2]
Question 23
A plant species produces toxic secondary compounds in its leaves. A specialist insect herbivore feeding on this plant has enzyme pathways that detoxify the toxin.
Explain how the toxin can reduce herbivory.
[2]
Explain how detoxification can produce both an advantage and a limitation for the specialist insect.
[2]
Question 24
Different plant forms in a tropical forest harvest light in different ways.
State one advantage to a liana of using another plant for support.
[1]
Explain one advantage and one disadvantage of being an epiphyte.
[2]
Suggest why shade-tolerant herbs can persist on the forest floor despite competition for light.
[1]
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Question 25
Four unicellular organisms were cultured under different combinations of light and available organic carbon. Growth was measured after five days.
Organism | Light, IC only | Dark, IC only | Light, IC+OC | Dark, IC+OC |
|---|---|---|---|---|
A | 8 | 0 | 0 | 0 |
B | 0 | 0 | 6 | 6 |
C | 7 | 0 | 8 | 5 |
D | 0 | 0 | 5 | 0 |
Identify the organism with photosynthesis as its only observed mode of nutrition in these conditions.
[1]
Distinguish the evidence for heterotrophic nutrition from the evidence for photosynthetic nutrition in the data.
[2]
Explain why one organism can be classified as a facultative mixotroph.
[2]
Question 26
Measurements were made from digital skull models of three members of the family Hominidae. The likely diet was inferred using observations from living mammals.
Skull model | Molar/premolar crown shape | Average grinding surface area / mm | Mandible depth at M1 / mm |
|---|---|---|---|
A | broad, slightly rounded | 265 | 15.0 |
B | very broad, flat | 425 | 22.5 |
C | moderately broad, rounded | 305 | 17.2 |
State the dentition feature that gives the strongest evidence for a plant-rich diet.
[1]
Infer which skull belonged to the most herbivorous hominid, using evidence from the data.
[2]
Suggest one reason why dentition alone cannot prove the exact diet of an extinct hominid.
[1]
Question 27
Light intensity and plant forms were surveyed in a tropical forest from the forest floor to the canopy.
Identify the plant form that grows on another plant without obtaining food from it.
[1]
Compare the light-harvesting strategy of a canopy tree with that of a liana.
[2]
Explain why shade-tolerant herbs can occupy the forest floor.
[2]
Question 28
The distribution of a freshwater snail species was measured along a water-depth gradient. The snail was studied alone and when a competing snail species was present.
Identify which curve represents the fundamental niche and give a reason.
[2]
Explain how competition changes the realized niche of the focal snail.
[2]
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Question 29
Two unicellular species were cultured using the same limiting food resource. Their population sizes were measured when each species was grown alone and when both species were grown together.
State the ecological process shown when one species disappears in the mixed culture.
[1]
Explain why the species that disappears could grow when cultured alone but not when cultured with the other species.
[2]
Suggest one way two species with overlapping fundamental niches could coexist in the same ecosystem.
[1]
Question 30
Some species are highly specialized for a narrow resource, whereas others are generalists able to use a wider range of resources.
Explain one advantage of specialization in an ecological niche.
[2]
Evaluate one disadvantage of specialization compared with versatility.
[2]
Question 31
A freshwater snail was grown in experimental channels across a gradient of water depth. In one treatment it was grown alone. In a second treatment it was grown with a competing snail species.
State which treatment gives the best estimate of the focal snail's fundamental niche.
[1]
Using the data, calculate the reduction in the depth range occupied by the focal snail when the competitor is present.
[2]
Explain why the distribution with the competitor present represents the realized niche rather than the fundamental niche.
[2]
Question 32
Two species of freshwater protist were cultured separately and together in identical microcosms with a single limiting bacterial food source.
Identify the outcome of competition shown in the mixed culture.
[1]
Explain how the separate cultures support the conclusion that disappearance in the mixed culture was due to competition.
[2]
Evaluate whether the data prove that the two protist species have identical niches.
[2]
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Question 33
A predator fish hunts small crustaceans. Researchers measured capture success under different environmental conditions and prey behaviours.
Identify one predator adaptation for finding prey that is supported by the data.
[1]
Describe two prey adaptations shown to reduce capture success.
[2]
Discuss how these results illustrate reciprocal adaptation between predators and prey.
[2]
Question 34
Three archaeal isolates were grown in media that differed in available energy sources. ATP production was measured after incubation.
Condition | Isolate A / arbitrary units | Isolate B / arbitrary units | Isolate C / arbitrary units |
|---|---|---|---|
Light only | 90 | 5 | 4 |
Inorganic chemicals only | 5 | 92 | 6 |
Organic carbon only | 4 | 6 | 91 |
No added energy source | 1 | 1 | 1 |
Identify the archaeal isolate that is phototrophic.
[1]
Distinguish the energy source of the chemotrophic archaeon from that of the heterotrophic archaeon.
[2]
State the feature of archaea illustrated by the data.
[1]
Question 35
Two species of shore crab live on the same rocky shore. Species A is usually found under stones high on the shore and feeds mainly on small algae. Species B is usually found in lower pools and feeds on small molluscs and dead animal material.
I.
State why the ecological niche of a crab species is more than its habitat.
[1]
II.
Distinguish between one biotic factor and one abiotic factor affecting the niche of species A.
[2]
Explain how the mode of nutrition of species B contributes to its ecological niche.
[2]
Discuss one advantage of specialization and one advantage of versatility for organisms living on a variable rocky shore.
[2]
Question 36
A sealed glass column contains pond water above pond mud. After several weeks in light, coloured bands of microorganisms form at different depths. Oxygen is highest near the surface and absent in deeper mud.
I.
State the region of the column where obligate aerobes would be expected to grow best.
[1]
II.
Explain the expected distribution of obligate anaerobes and facultative anaerobes in the column.
[2]
Compare the ecological consequences of being an obligate aerobe, an obligate anaerobe and a facultative anaerobe.
[3]
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Question 37
A palaeontologist compares two hominid skulls. Skull X has large molars with broad grinding surfaces and a robust jaw. Skull Y has smaller molars, incisors suited to biting and moderately developed canines.
I.
Explain the relationship between molar form and herbivorous diets in members of the family Hominidae.
[2]
II.
Suggest the likely diet of skull Y, giving evidence from dentition.
[2]
Evaluate the use of dentition alone to deduce the diet of an extinct hominid.
[3]
Question 38
Two protist species were cultured under combinations of light and prey availability. Growth rate was measured to classify their nutritional strategies.
Culture condition | Species P growth rate / | Species Q growth rate / |
|---|---|---|
Light + prey | 1.6 | 1.1 |
Light only | 0.9 | 0.0 |
Prey only | 0.8 | 0.0 |
Neither light nor prey | 0.0 | 0.0 |
Identify which protist is a facultative mixotroph.
[1]
Explain the evidence that species Q is an obligate mixotroph.
[2]
Suggest one ecological advantage and one disadvantage of facultative mixotrophy compared with obligate mixotrophy.
[2]
Question 39
Two insectivorous bird species forage in the same woodland. Their prey size and foraging height were recorded before and after one species was experimentally excluded from half of the plots.
Describe the evidence that the two bird species have different realized niches when both are present.
[2]
Explain why the change in species R after removal of species S suggests competition had restricted its realized niche.
[2]
Evaluate whether these data support the idea that coexisting species have unique ecological niches.
[1]
Question 40
A freshwater pond contains duckweed, unicellular algae, Euglena, small crustaceans and decomposer bacteria growing on dead leaves.
I.
Explain photosynthesis as a mode of nutrition in duckweed and algae.
[2]
II.
Distinguish between holozoic nutrition in small crustaceans and saprotrophic nutrition in decomposer bacteria.
[2]
Explain why Euglena may be difficult to classify as only a producer or only a consumer.
[2]
Compare the inputs, processes and outputs of photosynthetic and saprotrophic nutrition in this pond.
[2]
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Question 41
Two insects feed on the same shrub. Insect A removes pieces of leaf tissue. Insect B inserts a narrow tube into vascular tissue and sucks sap. The shrub has tough leaves, thorns and toxic secondary compounds in its seeds.
I.
Compare how the mouthparts of insect A and insect B are adapted to different feeding niches.
[2]
II.
Explain how two plant features in the shrub resist herbivory.
[2]
Discuss how metabolic detoxification by an insect can affect its specificity and versatility as a herbivore.
[3]
Question 42
A small fish is hunted by a larger predatory fish. The predator has forward-facing eyes, rapid acceleration and sharp teeth. The small fish forms schools, has a silvery body surface and responds to alarm chemicals released when skin is damaged.
I.
Classify two adaptations of the predator as helping to find, catch or kill prey.
[2]
II.
Explain how two adaptations of the small fish reduce predation.
[2]
Explain why predator and prey adaptations can be considered selection pressures on each other.
[2]
Evaluate the statement: “The small fish forms schools because it needs to adapt to predators.”
[2]
Question 43
A tropical forest contains canopy trees, lianas, epiphytes on tree branches, strangler epiphytes and shade-tolerant herbs on the forest floor.
I.
Explain how lianas and epiphytes differ in their strategy for harvesting light.
[2]
II.
State one cost of the epiphyte strategy.
[1]
Compare canopy trees with shade-tolerant forest-floor herbs as adaptations for light harvesting.
[2]
Discuss how differences in plant form can reduce direct competition for light in the forest.
[2]
Question 44
Microbial communities occur in hot springs, salt lakes and sediments. Some archaeal species use light as an energy source, some oxidize inorganic chemicals and others oxidize carbon compounds from organic material.
I.
Compare phototrophic, chemotrophic and heterotrophic archaeal nutrition in terms of energy source.
[2]
II.
State the domain to which archaea belong in relation to the three-domain classification.
[1]
Discuss why the nutritional diversity of archaea supports the idea that light is not essential for all life.
[3]
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Question 45
Two species of aquatic plant can grow across a range of water depths. In separate tanks each species grows over a broad depth range. In mixed tanks, species P is mostly found in shallow water and species Q is mostly found in deeper water.
I.
Distinguish between the fundamental niche and realized niche of species P.
[2]
II.
Use the results to infer the effect of competition on the realized niches of the two species.
[2]
Explain why the realized niche is often smaller than the fundamental niche.
[2]
Evaluate whether the data provide evidence for competitive exclusion.
[2]
Question 46
Two species of seed-eating finch live on an island. Their beak sizes and preferred seed sizes overlap. During a drought, only a narrow range of hard seeds remains abundant.
Measure | Finch 1 | Finch 2 | Island seeds |
|---|---|---|---|
Beak depth range / mm | 8.4–9.6 | 8.9–10.5 | — |
Preferred seed size range before drought / mm | 4–7 | 5–8 | — |
Seed size range available during drought / mm | — | — | 7–8 |
Seed abundance before drought / index | — | — | 100 |
Seed abundance during drought / index | — | — | 20 |
Relative abundance before drought / index | 100 | 100 | — |
Relative abundance during drought / index | 35 | 60 | — |
I.
Explain why competition between the two finch species is expected to increase during drought.
[2]
II.
Predict two possible ecological outcomes if competition continues for many generations.
[2]
Discuss why long-term coexistence of the two finches would support the idea that ecological niches are unique.
[2]
Evaluate whether beak size alone is enough to define the niche of a finch species.
[2]
Question 47
A planktonic protist can photosynthesize in bright water but can also ingest small bacteria. A related protist requires both light and bacterial prey for maximum growth.
I.
Distinguish between facultative mixotrophy and obligate mixotrophy.
[2]
II.
Use the information to identify which protist has the more versatile niche, giving a reason.
[2]
Compare the inputs and processes used by a mixotroph during autotrophic and heterotrophic nutrition.
[2]
Evaluate the trade-off between specificity and versatility using the two protists as examples.
[2]
Question 48
An introduced snail and a native snail graze on the same algae in a lake. Laboratory tests show that both species can survive across similar temperature and oxygen ranges. Field surveys show that the native snail is now found mainly in shaded shallows, while the introduced snail dominates open shallows.
Measure | Native snail | Introduced snail |
|---|---|---|
Temperature survival range () | 8–28 | 9–29 |
Dissolved oxygen survival range (mg L) | 3.0–11.0 | 2.5–11.5 |
Field records in shaded shallows (n) | 26 | 7 |
Field records in open shallows (n) | 4 | 23 |
I.
Explain why the laboratory data estimate the fundamental niches of the two snails.
[2]
II.
Explain why the field distribution of the native snail is evidence of a realized niche.
[2]
Discuss whether the introduced snail has caused competitive exclusion of the native snail.
[2]
Evaluate one management action that could help conserve the native snail, using niche concepts.
[2]
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