Ecology

State two resources for which plants in the same habitat may compete.

A flowering plant is the main food of an insect and depends on that insect for pollination. Explain how a large fall in the insect population could affect the community.

Two bird species use the same nesting sites and eat the same seeds. A third bird species eats insects and nests in tree holes. Explain which pair is most likely to compete strongly and predict one possible long-term effect on the community.

State two abiotic factors in soil that can affect a plant community.

After warm weather, the dissolved oxygen concentration in a pond falls and some fish die. Explain how this abiotic change affects the fish population.

A plant is abundant in open grassland but rare beneath dense trees. Soil moisture and mineral content are similar in both places. Use the information to suggest and explain the most likely abiotic cause of the distribution.

State two biotic factors that can affect a community.

A new predator enters an island and feeds mainly on a native lizard. Explain two ways the lizard population may change.

Species A and B eat the same food. A new pathogen kills many individuals of species A, after which species B increases. Explain the changes using biotic factors.

Name the three categories of adaptation specified for organisms.

A desert animal rests underground during the hottest part of the day and produces very concentrated urine. Classify and explain both adaptations.

A bacterium is found growing beside a deep-sea vent at very high temperature and pressure. Explain why it is described as an extremophile and why finding it there alone does not identify a particular structural adaptation.

In the food chain grass, rabbit, fox, state the producer and the primary consumer.

A student records a plant count of $3$, $5$, $4$, $2$ and $6$ in five equal quadrats. Calculate the mean count per quadrat.

Describe how to investigate the effect of distance from a hedge on the distribution of a small plant species, and state how the results should be processed.

Name the process by which plants remove carbon dioxide from the atmosphere.

Explain two roles of decomposing microorganisms in cycling materials through an ecosystem.

A woodland receives no rain for several months and many plants die. Explain how the water and carbon cycles connect this change to other organisms in the ecosystem.

State three environmental factors that affect the rate of decay of biological material.

The pH of fresh milk falls from $6.8$ to $5.6$ in $4\,\mathrm{h}$. Calculate the mean rate of pH decrease.

A gardener compares a warm, moist, regularly turned compost heap with a cold, dry, compacted heap. Explain why the first heap should decay faster and give one useful product of decay in each of aerobic composting and anaerobic biogas generation.

Higher tier: state two environmental changes that can affect the distribution of a species.

Higher tier: a plant species spreads northwards during a period of rising average temperature. Explain how the environmental change could cause the altered distribution.

Higher tier: a wetland bird declines after drainage reduces water availability, but its predator also arrives in the same year. Evaluate whether drainage caused the bird's decline.

What is meant by biodiversity in an ecosystem?

Explain why an ecosystem with many species may be more stable than one with very few species.

Habitat X contains $12$ species with fairly even populations. Habitat Y contains $5$ species but many more individual organisms. Compare their biodiversity and explain why organism count alone is insufficient.

Give one source of water pollution and one source of air pollution.

Explain why economic development and population growth can increase pollution.

A factory's waste enters a river and the number of plant and animal species downstream falls. Explain why this is evidence of reduced biodiversity and outline one limitation of the evidence.

State two human land uses that reduce habitat area.

Explain two environmental consequences of removing peat from a bog for garden compost.

Evaluate a proposal to drain a peatland so that crops can be grown and inexpensive compost can be sold.

State two reasons for large-scale tropical deforestation.

Explain how clearing a tropical forest for cattle can reduce biodiversity.

A company argues that clearing forest to grow biofuel crops will always reduce atmospheric carbon dioxide. Evaluate this claim.

Name two atmospheric gases whose increasing levels contribute to global warming.

Describe three possible biological consequences of global warming.

A commentator says that uncertainty in one regional climate prediction means there is no scientific consensus on global warming. Evaluate this reasoning.

State two measures used to maintain biodiversity.

Explain how reintroducing hedgerows and field margins on a farm can help maintain biodiversity.

A government can protect a rare wetland or permit development that creates jobs. Evaluate the decision from the information given.

In the food chain alga, snail, fish, heron, state the trophic level of the fish.

Describe how a decomposer obtains nutrients from dead plant material.

A bird eats both caterpillars that feed on leaves and spiders that eat those caterpillars. Explain why the bird cannot be assigned one trophic level without specifying its food.

State which trophic level is placed at the bottom of a pyramid of biomass.

A food chain has producer biomass $800\,\mathrm{g}$, primary-consumer biomass $160\,\mathrm{g}$ and secondary-consumer biomass $40\,\mathrm{g}$. Describe how to construct an accurate pyramid of biomass.

A student draws three equal-width bars for trophic levels containing $600\,\mathrm{g}$, $90\,\mathrm{g}$ and $15\,\mathrm{g}$ of biomass. Evaluate the diagram and state how it should be corrected.

Approximately what percentage of biomass is transferred from one trophic level to the next?

A herbivore population contains $240\,\mathrm{kg}$ of biomass and its predators gain $18\,\mathrm{kg}$. Calculate the efficiency of biomass transfer.

Explain why a field can support many herbivorous insects but only a few insect-eating birds at the next trophic level.

Define food security.

Explain how a new crop pathogen and a failed rainy season could combine to reduce food security.

A country produces more food than five years ago, but its population has grown faster and fertiliser prices have risen. Evaluate what this information suggests about its food security.

State two ways farmers can reduce energy transfer from food animals to the environment.

Explain why limiting an animal's movement and controlling its environmental temperature can improve food-production efficiency.

Evaluate the intensive rearing of animals in temperature-controlled housing with restricted movement and high-protein feed.

State two controls used to conserve fish stocks.

Explain how increasing the mesh size of fishing nets can help a depleted fish stock recover.

A fishery introduces larger net meshes but no catch quota. Evaluate whether this is sufficient to make the fishery sustainable.

Name the fungus used to produce mycoprotein and state the gas condition needed during its growth.

Describe how mycoprotein is produced using biotechnology.

Explain how genetically modified microorganisms and crops can help meet demands from a growing human population, using two named examples.