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Ecology and Environment

Ecology and Environment — Free MYP5 Biology Practice Questions

1QuestionImportance of Biodiversity in EcosystemsConcept Practice

2 marks~3 minCriterion D

Chytridiomycosis, caused by the fungus Batrachochytrium dendrobatidis, has driven multiple frog species to extinction. Conservation biologists have proposed inserting disease-resistance genes directly into the genomes of critically endangered frog populations to improve their survival prospects in the wild.

Identify and outline this application of genetic modification in conservation biology. [1]

Describe one ethical issue that arises specifically from releasing these genetically modified frogs into wild ecosystems. [1]

Solutions

2QuestionThreats to Biodiversity: Habitat Loss, Pollution, Climate ChangeConcept Practice

2 marks~3 minCriterion A

The diagram shows primary succession on a volcanic island across four stages: Stage 1 — bare rock colonised by lichens; Stage 2 — grasses and small herbs; Stage 3 — shrubs; Stage 4 — forest.

Identify the pioneer species in Stage 1 and explain how it contributes to soil formation. [1]

Describe the directional sequence of succession shown in the diagram and identify the climax community, explaining why it is considered stable. [1]

Solutions

3QuestionSustainable Practices and Renewable EnergyConcept Practice

2 marks~3 minCriterion B

Students monitored bird species diversity across three habitats over five years. Their counts are recorded below.

Forest — Year 1	12	Year 2: 14	Year 3: 15	Year 4: 17	Year 5: 18
Grassland — Year 1	8	Year 2: 9	Year 3: 10	Year 4: 10	Year 5: 11
Wetland — Year 1	20	Year 2: 18	Year 3: 16	Year 4: 14	Year 5: 12

Identify the trend in bird species count for the wetland habitat over the five-year period. [1]

Deduce the expected number of bird species in the wetland in Year 6, using the trend you identified. [1]

Solutions

4QuestionGreenhouse Gases and Global WarmingConcept Practice

2 marks~3 minCriterion D

Rice paddies flooded continuously produce methane (

\text{CH}_4

), a potent greenhouse gas, through anaerobic decomposition by methanogenic bacteria in waterlogged soil. Researchers are trialling mid-season drainage as a mitigation strategy. Studies show this can reduce

\text{CH}_4

emissions by up to 40%, but the practice requires additional labour and alters soil conditions during a critical growth phase.

Explain how mid-season drainage reduces methane emissions from rice paddies. [1]

Identify one ethical issue that arises from requiring farmers — particularly in low-income, rice-dependent regions — to adopt this drainage practice. [1]

Solutions

5QuestionCarbon Cycle and Human DisruptionConcept Practice

2 marks~3 minCriterion A

The diagram below shows a simplified carbon cycle. Arrows A, B, C, and D connect the atmosphere (

\text{CO}_2

), plants, animals, dead organic matter, and fossil fuels. Arrow A points from the atmosphere to plants. Arrow B points from plants to animals. Arrow C points from dead organic matter to the atmosphere. Arrow D points from fossil fuels to the atmosphere.

(a) Identify the process represented by arrow A, and name the organelle in plant cells where this process occurs. [2]

Solutions

6QuestionBiomass Pyramids and Energy PyramidsConcept Practice

3 marks~5 minCriterion A

A grassland ecosystem contains the following food chain with measured energy values:

Grass (producer)	10	000 kJ
Grasshopper (primary consumer)	1	000 kJ

Mouse (secondary consumer): 100 kJ
Hawk (tertiary consumer): 10 kJ

Show that the percentage of energy transferred from grass to grasshopper is 10%. [1]

Explain two distinct biological reasons why only a small percentage of energy passes from one trophic level to the next. [2]

Solutions

7QuestionBiomass Pyramids and Energy PyramidsConcept Practice

2 marks~3 minCriterion A

A biomass pyramid for a coastal kelp forest ecosystem contains four trophic levels. The dry mass values recorded are:

Trophic level 1 (base): 10 000 kg per hectare
Trophic level 2: 1 000 kg per hectare
Trophic level 3: 100 kg per hectare
Trophic level 4 (apex): 10 kg per hectare

State the correct biological name for each trophic level, from base to apex. [1]

Explain why biomass decreases at each successive trophic level in this pyramid. [1]

Solutions

8QuestionAdaptations to Environmental ConditionsConcept Practice

2 marks~3 minCriterion A

Water lilies (Nymphaea sp.) grow rooted in pond sediment, with leaves that rest on the water surface. Their leaves have four key structural features: a broad, flat shape; a waxy cuticle on the upper surface; stomata positioned on the upper epidermis; and large internal air spaces (aerenchyma).

State one structural feature of a water lily leaf that helps it float on the water surface. [1]

Explain how the position of stomata on the upper epidermis allows the water lily leaf to carry out gas exchange effectively in an aquatic environment. [1]

Solutions

9QuestionBioaccumulation and ToxinsConcept Practice

2 marks~3 minCriterion A

A lake ecosystem contains the following food chain:

algae → small fish → large fish → bird

A persistent chemical toxin enters the lake and is absorbed by algae. Data collected from tissue samples show that toxin concentration increases at each successive trophic level, reaching its highest level in the bird.

State the term for the process by which toxin concentration increases progressively through the trophic levels of a food chain. [1]

Explain why the bird accumulates a higher concentration of toxin in its tissues than the large fish. [1]

Solutions

10QuestionConservation Strategies and Protected AreasAssessment Practice

2 marks~3 minCriterion B

A study recorded the number of key bird species across three zones of a national park over five years.

Core zone (Year 1–5)	45	48	52	55	58
Buffer zone (Year 1–5)	32	35	37	40	42
Transition zone (Year 1–5)	18	20	19	21	22

Analyse the data to identify the pattern in species richness across the three zones over the five years. [1]

Using your analysis, formulate a general rule to explain which zone best supports biodiversity and why. [1]

Solutions

11QuestionConservation Strategies and Protected AreasAssessment Practice

4 marks~6 minCriterion D

The diagram below shows a rectangular nature reserve bisected by a river running from left to right, with farmland surrounding the reserve on all sides.

Explain how the rectangular shape of this reserve increases edge effects and reduces the area of interior habitat available to wildlife. [2]

Explain how the river further reduces the conservation value of the reserve by affecting population connectivity. [2]

Solutions

12QuestionEndangered Species and ExtinctionAssessment Practice

3 marks~5 minCriterion C

The bar graph below shows the number of endangered species recorded across five habitat types.

Habitat — Endangered species (approximate)
Tropical rainforest: 950
Coral reef: 830
Wetland: 500
Grassland: 300
Tundra: 100

Describe the trend shown in the graph. [1]

Identify the habitat with the highest number of endangered species and explain why this habitat supports such a disproportionately large number of threatened species. [1]

A conservation biologist argues that protecting a single large tropical rainforest reserve will conserve more species than protecting several smaller reserves of equivalent total area across other habitats. Evaluate this argument using evidence from the graph and your biological knowledge. [1]

Solutions

13QuestionConservation Strategies and Protected AreasAssessment Practice

3 marks~5 minCriterion A

A survey of four tropical forest reserves recorded the following data:

Protected area size (ha)	100	1 000	10 000	100 000
Number of species recorded	48	97	201	398

The relationship between area and species richness follows the species–area relationship.

Describe the trend shown by the data above. [1]

Explain how greater habitat diversity in larger reserves accounts for the higher species richness observed. [1]

Analyse why a single large reserve may be more effective at preventing local species extinction than several small reserves of equivalent total area. [1]

Solutions

14QuestionConservation Strategies and Protected AreasAssessment Practice

6 marks~9 minCriterion D

The Javan rhino (Rhinoceros sondaicus) survives as a single wild population of approximately 70 individuals in Ujung Kulon National Park, Indonesia. The population faces threats from poaching, volcanic eruption risk, and invasive Arenga palms that reduce carrying capacity. A conservation agency must allocate limited funding to either a captive breeding programme (ex-situ) or expansion and active management of protected habitat (in-situ).

Explain one ethical advantage of establishing a captive breeding programme for the Javan rhino. [2]

Analyse one ecological limitation of relying solely on in-situ conservation for a population of this size. [2]

Evaluate which conservation strategy is more justified for the Javan rhino, using biological evidence from the scenario. [2]

Solutions

15QuestionConservation Strategies and Protected AreasAssessment Practice

6 marks~9 minCriterion C

A five-year study monitored bird species richness across three coastal zones: a fully protected marine protected area (MPA), a partially protected zone (fishing permitted with restrictions), and an unprotected zone (no restrictions). The graph shows the average number of bird species recorded per survey in each zone from 2019 to 2023.

MPA (solid line): increases from 18 species (2019) to 26 species (2023).
Partially protected (dashed line): increases from 16 species (2019) to 20 species (2023).
Unprotected (dotted line): decreases from 15 species (2019) to 12 species (2023).

Identify the trend in bird species richness for each of the three zones between 2019 and 2023. [2]

Using data from the graph, analyse the relationship between the degree of protection and bird species richness. [2]

Evaluate the hypothesis that fully protected marine areas are more effective in conserving bird species richness than partially protected or unprotected areas, identifying one limitation of the evidence. [2]

Solutions

16QuestionDeforestation, Urbanization, and Land UseAssessment Practice

8 marks~12 minCriterion D

A proposal has been made to convert a 50-year-old secondary forest in Costa Rica into a palm oil plantation. The site supports over 200 bird species, stores an estimated 300 tonnes of carbon per hectare above ground, and serves as the dry-season water source for the Indigenous Bribri community. The developer argues that satellite imagery showing canopy gaps across more than 30% of the area proves the forest is 'degraded', and that the plantation will create 500 local jobs and reduce palm oil imports from deforested regions in Southeast Asia.

Identify TWO environmental impacts of replacing this forest with a palm oil plantation. For each impact, refer to a specific ecological concept. [2]

Identify TWO societal impacts on the Bribri community, linking each impact to their specific dependence on the forest. [2]

Evaluate the developer's use of satellite imagery alone to classify the forest as 'degraded'. In your response, discuss at least TWO limitations of relying solely on remote-sensing data for this environmental impact assessment. [4]

Solutions

17QuestionClimate Action and Global CitizenshipAssessment Practice

3 marks~5 minCriterion C

The graph below shows global atmospheric

\text{CO}_2

concentration (ppm) and global average surface temperature anomaly (°C) from 1950 to 2020.

Describe the relationship between atmospheric

\text{CO}_2

concentration and global average surface temperature shown in the graph. [1]

Explain how

\text{CO}_2

acts as a greenhouse gas to trap heat in the atmosphere. [1]

Analyse why a continued rise in atmospheric

\text{CO}_2

concentration is likely to accelerate, rather than simply maintain, the rate of global temperature increase. [1]

Solutions

18QuestionGreenhouse Gases and Global WarmingAssessment Practice

5 marks~8 minCriterion C

A diagram of the global carbon cycle shows enteric fermentation in ruminants as a source of atmospheric

\text{CH}_4

. According to the diagram, livestock account for approximately 14.5% of global anthropogenic methane emissions; fossil fuel extraction and use contribute approximately 33%.

A student claims: "Cattle farming has a negligible impact on atmospheric methane levels compared to fossil fuels."

Identify the biological process by which cattle produce

\text{CH}_4

, and explain the role of microorganisms in this process. [2]

Using the data from the diagram, interpret the relative contributions of livestock and fossil fuels to anthropogenic methane emissions. [1]

Evaluate the student's claim, using the diagram data and your knowledge of methane as a greenhouse gas. [2]

Solutions

19QuestionCarbon Cycle and Human DisruptionAssessment Practice

3 marks~5 minCriterion D

The diagram below shows a simplified carbon cycle. Arrow X represents the movement of carbon dioxide from the atmosphere into a tree.

Identify the biological process represented by arrow X. [1]

Explain how deforestation reduces the rate of the process shown by arrow X, and state the effect this has on atmospheric CO₂ concentration. [1]

Evaluate the claim that deforestation has a greater impact on atmospheric CO₂ than the burning of fossil fuels, using your knowledge of the carbon cycle. [1]

Solutions

20QuestionCarbon Cycle and Human DisruptionAssessment Practice

4 marks~6 minCriterion A

The simplified carbon cycle diagram below shows four reservoirs — atmosphere, oceans, fossil fuels, and biomass — connected by labelled flux arrows.

- Arrow A: atmosphere → biomass
- Arrow B: biomass → atmosphere
- Arrow C: fossil fuels → atmosphere

Identify the process represented by each arrow and describe the role of the organisms involved. [2]

Explain how increasing the flux represented by Arrow C, without a corresponding increase in Arrow A, disrupts the balance between carbon reservoirs. Use evidence from the diagram in your answer. [2]

Solutions

21QuestionDefinition and Components of an EcosystemAssessment Practice

2 marks~3 minCriterion B

The table below lists biotic and abiotic components for five ecosystems.

Pond — Biotic: fish, algae, frogs, insects	Abiotic: water, sunlight, soil, rocks
Forest — Biotic: trees, deer, birds, fungi	Abiotic: sunlight, soil, air, water
Grassland — Biotic: grasses, rabbits, snakes, insects	Abiotic: sunlight, soil, air, water
Desert — Biotic: cacti, lizards, insects, snakes	Abiotic: sunlight, sand, air, water
Coral reef — Biotic: coral, fish, algae, sea turtles	Abiotic: sunlight, saltwater, rocks, sand

Identify one pattern in how biotic and abiotic components are represented across all five ecosystems, and explain what this suggests about the completeness of the table. [1]

A deep-ocean hydrothermal vent is proposed as a sixth ecosystem. Deduce one biotic component and one abiotic component that would likely appear in this ecosystem's entry, justifying your choices with reference to both the ecological conditions of a hydrothermal vent and the pattern identified in part (a). [1]

Solutions

22QuestionDefinition and Components of an EcosystemAssessment Practice

3 marks~5 minCriterion D

The bar graph below shows the energy available at each trophic level in a grassland ecosystem.

Producers:

20\,000 \ \text{kJ/m}^2\text{/year}

Primary consumers:

2\,000 \ \text{kJ/m}^2\text{/year}

Secondary consumers:

200 \ \text{kJ/m}^2\text{/year}

Tertiary consumers:

20 \ \text{kJ/m}^2\text{/year}

Describe the trend in energy availability across the four trophic levels shown. [1]

Explain why energy decreases between trophic levels, referring to at least two processes responsible for energy loss. [1]

A fifth trophic level (quaternary consumers) is proposed for this ecosystem. Analyse whether this ecosystem could realistically support it, using the data to justify your reasoning. [1]

Solutions

23QuestionDefinition and Components of an EcosystemAssessment Practice

5 marks~8 minCriterion C

A researcher sets up 12 identical mesocosms (enclosed experimental ecosystems), each containing grass, soil, and 20 grasshoppers. The mesocosms are divided into four treatment groups with different nitrogen and light conditions. After 8 weeks, the final grasshopper populations are recorded.

Treatment Group	A	B	C	D
Nitrogen level (mg/kg)	10	50	10	50
Light level (hours/day)	6	6	12	12
Final grasshopper population	35	82	68	91

The researcher claims: "Nitrogen is the only limiting factor in this ecosystem."

Describe the effect of increasing nitrogen level on grasshopper population at each light level. [1]

Analyse the effect of increasing light level on grasshopper population at each nitrogen level, and explain what this reveals about the researcher's hypothesis. [2]

Evaluate the researcher's hypothesis using quantitative evidence from all four treatment groups, and justify which abiotic factor appears to be the primary limiting factor. [2]

Solutions

24QuestionDefinition and Components of an EcosystemAssessment Practice

4 marks~6 minCriterion A

The diagram shows a pond ecosystem. Biotic components include algae, lily pads, and fish. Abiotic components include sunlight, water, and rocks.

Identify one biotic–abiotic interaction and one biotic–biotic interaction visible in this pond ecosystem. [2]

Explain how energy flows from sunlight through two trophic levels in this ecosystem, using the terms producer and consumer. [1]

Evaluate how the removal of algae from this pond ecosystem would affect both energy flow and nutrient cycling. [1]

Solutions

25QuestionLimiting Factors and Ecosystem StabilityAssessment Practice

5 marks~8 minCriterion C

A student sets up three mesocosms, each containing 10 L of filtered lake water with naturally occurring phytoplankton. All mesocosms receive 12 hours of light per day at constant intensity and temperature. Sodium nitrate is added to give initial concentrations of 0.5 mg/L (Mesocosm A), 2.0 mg/L (Mesocosm B), and 8.0 mg/L (Mesocosm C). Algal biomass is measured every two days as chlorophyll

a

concentration (

\mu

g/L). Results are shown in the graph.

Two hypotheses are proposed:

Hypothesis 1: Nitrate is the primary limiting factor for algal growth.
Hypothesis 2: Light is the primary limiting factor for algal growth.

Identify the trend in chlorophyll

a

concentration for each mesocosm over the 10-day period. [1]

Explain how the data from the three mesocosms support Hypothesis 1 rather than Hypothesis 2. [2]

Evaluate the conclusion that nitrate depletion, rather than light limitation, causes the plateau observed in Mesocosms B and C. [2]

Solutions

26QuestionBiomass Pyramids and Energy PyramidsAssessment Practice

8 marks~12 minCriterion D

A company proposes converting 50,000 hectares of Indonesian tropical rainforest into a palm oil plantation to produce biodiesel. An ecological survey records that forest producers store

20{,}000 \ \text{kJ m}^{-2} \text{year}^{-1}

. Energy transfer efficiency between trophic levels is 10%. The plantation would yield

8{,}000 \ \text{kJ m}^{-2} \text{year}^{-1}

in palm fruits, all harvested for fuel.

Calculate the energy available to primary, secondary, and tertiary consumers in the natural forest. [2]

Using your results from (a), compare the ability of the natural forest and the plantation to support higher trophic levels. [2]

Evaluate the long-term societal and environmental impacts of this proposal, and discuss the limitations of energy pyramids as a tool for predicting real-world outcomes of such a conversion. [4]

Solutions

27QuestionAdaptations to Environmental ConditionsAssessment Practice

6 marks~9 minCriterion C

The diagram shows a polar bear and a fennec fox. The polar bear lives in the Arctic and has thick fur, a subcutaneous blubber layer, and small ears. The fennec fox lives in the Sahara Desert and has large ears, thin fur, and a slender body.

Describe how the polar bear's thick fur and blubber layer each help it survive in the Arctic. [2]

Explain how the fennec fox's large ears help it lose heat in the desert. [2]

A student claims that the polar bear's small ears and the fennec fox's large ears are both adaptations to the same underlying physiological principle. Evaluate this claim. [2]

Solutions

28QuestionHow Biotic Factors Influence Population SizeAssessment Practice

5 marks~8 minCriterion B

A 20-year study tracked snowshoe hare and Canadian lynx populations in a boreal forest.

Year	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
Hare population (thousands)	20	30	40	80	60	50	40	20	25	70	75	85	80	70	60	20	20	30	40	90
Lynx population (thousands)	4	6	8	10	20	18	16	12	6	8	10	20	18	16	14	6	6	8	10	18

A biologist hypothesises that lynx population size is controlled solely by hare availability.

Describe the relationship between the hare and lynx populations, using specific values from the data. [2]

Identify the time lag in the lynx population's response to changes in hare population size, and explain what biological process this lag reflects. [1]

Evaluate the biologist's hypothesis using the concept of time-delayed density dependence. [2]

Solutions

29QuestionAdaptations to Environmental ConditionsAssessment Practice

3 marks~5 minCriterion D

The diagram shows a cross-section of a cactus stem. Structure X is labelled on the outermost layer of the stem.

Identify structure X. [1]

State how structure X forms a barrier that limits water movement out of the stem. [1]

A cactus growing in a desert experiences daytime air temperatures of 45 °C and very low humidity. Explain why the properties of structure X are more critical to the cactus's survival under these conditions than they would be for a plant growing in a tropical rainforest. [1]

Solutions

30QuestionDefinition and Examples of Abiotic FactorAssessment Practice

4 marks~6 minCriterion D

A farmer applies nitrogen-rich fertiliser to a wheat field to increase yield. During heavy rainfall, excess nitrates leach into a nearby river, triggering a rapid algal bloom. When the algae die, aerobic decomposers break down the organic matter, consuming large quantities of dissolved oxygen and causing fish kills.

Explain how excess nitrates entering the river lead to a decrease in dissolved oxygen concentration. [2]

Discuss the ethical conflict between the farmer's goal of increasing food production and the ecological impact of nutrient runoff on the river ecosystem. [2]

Solutions

31QuestionDefinition and Examples of Abiotic FactorAssessment Practice

5 marks~8 minCriterion C

A group of students investigates how light intensity affects bean plant growth. Fifteen identical seedlings are divided into three groups of five, each receiving a different light intensity. Soil type, daily water volume (50 mL), and temperature (22°C) are kept constant throughout the four-week experiment. Results are recorded below.

Light intensity (lux)	50	150	450
Average height (cm)	8	14	18
Average number of leaves	4	7	9

The students hypothesise that light intensity is the primary abiotic factor limiting plant growth in this setup.

Identify the independent variable in this experiment. [1]

Describe the trends shown in the data, referring to specific values for both growth measures. [2]

Evaluate whether the evidence supports the students' hypothesis, and discuss two limitations of the experimental design. [2]

Solutions

32QuestionDefinition and Examples of Abiotic FactorAssessment Practice

3 marks~5 minCriterion C

The graph below shows how earthworm population density (number per

\text{m}^2

) changes with soil moisture (%) in a grassland ecosystem.

Describe the relationship between soil moisture and earthworm population density shown in the graph. [1]

Identify the optimal soil moisture range for earthworm survival and explain how this range supports maximum population density. [1]

Analyse why both extremely dry conditions (below ~20% soil moisture) and extremely wet conditions (above ~85% soil moisture) are detrimental to earthworm survival. [1]

Solutions

33QuestionEcosystem Changes Due to Natural and Human CausesAssessment Practice

4 marks~6 minCriterion A

The diagram below shows four stages of primary succession following a volcanic eruption: bare volcanic rock → pioneer species (lichens and mosses) → small grasses and shrubs → climax forest.

Identify TWO ways in which pioneer species contribute to the formation of soil on bare volcanic rock. [2]

Explain how the soil formed by pioneer species enables shrubs and trees to colonise the area in later successional stages. [2]

Solutions

34QuestionConstructing and Analyzing Food WebsAssessment Practice

6 marks~9 minCriterion B

Population data for four species in a coastal ecosystem:

Year: 2019 / 2020 / 2021 / 2022 / 2023
Kelp (thousands): 120 / 90 / 60 / 80 / 110
Sea urchins (thousands): 10 / 25 / 40 / 20 / 12
Sea otters (thousands): 4 / 2 / 1 / 3 / 5
Orcas (thousands): 1 / 1 / 2 / 3 / 4

Identify the predator–prey relationships in this food web, listing each pair as predator → prey. [2]

Describe the relationship between sea urchin and kelp populations from 2019 to 2021, using data to support your answer. [2]

Analyse how the data from 2021 to 2023 support the conclusion that orcas act as a keystone predator in this ecosystem. [2]

Solutions

35QuestionBioaccumulation and ToxinsAssessment Practice

6 marks~9 minCriterion D

A small coastal community depends on a lake for food and income. Agricultural runoff containing DDT has entered the lake's food web: phytoplankton → zooplankton → small fish → large fish → humans. DDT is a persistent, fat-soluble toxin. Monitoring data show DDT concentrations rising from 0.000 003 mg/kg in phytoplankton to 0.5 mg/kg in large fish.

Explain why DDT concentration increases from phytoplankton to large fish, using the concepts of bioaccumulation and biomagnification. [2]

Discuss the ethical dilemma the government faces in deciding whether to restrict fishing, considering both the health risks to the community and the economic consequences of a ban. [2]

Evaluate the limitations of the scientific data available to the government when making this decision, considering uncertainties in measuring DDT levels and in predicting long-term health effects. [2]

Solutions

36QuestionConstructing and Analyzing Food WebsAssessment Practice

2 marks~3 minCriterion C

A conservation biologist constructs a food web for a mangrove ecosystem following the introduction of an invasive predator. The food web reveals that the invasive predator shares prey species with two native predators and feeds directly on three herbivore species, each of which supports a distinct set of primary producers.

Explain how the food web enables the biologist to predict which native species will be most severely affected by the invasive predator's introduction. [1]

Identify one limitation of using this food web when making such predictions. [1]

Solutions

37QuestionConstructing and Analyzing Food WebsAssessment Practice

3 marks~5 minCriterion A

The diagram below shows a food web in a grassland ecosystem.

Grass → Rabbit → Fox → Hawk

Identify the trophic level of the fox. [1]

Explain why the fox population has more energy available to it than the hawk population, using the concept of energy transfer efficiency between trophic levels. [1]

A disease eliminates 80% of the rabbit population. Analyse how this would affect energy availability at the fox and hawk trophic levels, and predict which population would be more severely impacted. [1]

Solutions

38QuestionBioaccumulation and ToxinsAssessment Practice

2 marks~3 minCriterion D

Industrial discharge releases mercury into coastal waters off Japan's Minamata Bay. Phytoplankton absorb dissolved mercury; small fish consume large quantities of phytoplankton; apex predators such as tuna consume many small fish.

Identify one ethical issue arising from mercury bioaccumulation in this marine food chain. [1]

Explain how the structure of this food chain causes mercury to reach dangerous concentrations in tuna, and discuss why resolving the ethical issue you identified in (a) is difficult in practice. [1]

Solutions

39QuestionBioaccumulation and ToxinsAssessment Practice

3 marks~5 minCriterion D

A bar graph shows DDT concentration (ppm) in a lake food chain:

Phytoplankton: 0.04 ppm
Zooplankton: 0.16 ppm
Small fish: 0.80 ppm
Large fish: 3.20 ppm
Osprey: 12.80 ppm

Describe the trend in DDT concentration across the five trophic levels shown in the graph. [1]

Explain why DDT concentration increases at each successive trophic level, naming the process responsible. [1]

The osprey population in this lake has shown declining reproductive success. Using the data and your knowledge of biomagnification, discuss whether the osprey's trophic position makes it more vulnerable to DDT toxicity than the large fish. [1]

Solutions

40QuestionEcological Efficiency and Energy FlowAssessment Practice

6 marks~9 minCriterion C

A grassland ecosystem has the following energy values measured at each trophic level:

Grass	20	000 kJ m $^{-2}$ yr $^{-1}$
Grasshopper	2	000 kJ m $^{-2}$ yr $^{-1}$

Mouse: 200 kJ m

^{-2}

^{-1}

Hawk: 20 kJ m

^{-2}

^{-1}

Calculate the percentage of energy transferred from grass to grasshopper. [1]

Deduce whether the data follow the ten percent law at every trophic level. Support your answer with calculations. [2]

A student states: "Only 0.1% of the sun's energy reaches the hawk." Evaluate this claim using the data provided and your knowledge of energy capture by producers. [3]

Solutions