Question 1: Define a food web and explain how it differs from a food chain.

Answer: A food web is a network of interconnected food chains showing how different organisms in an ecosystem are related by feeding relationships. Unlike a food chain, which follows a single pathway, a food web illustrates multiple feeding relationships and energy flows between species.

Question 2: Describe the role of primary consumers in an ecosystem's food web.

Answer: Primary consumers are herbivores that feed on producers like plants or algae. They transfer energy from autotrophs to higher trophic levels within the food web.

Question 3: Explain the concept of energy transfer efficiency in a food web and why it is usually around 10%.

Answer: Energy transfer efficiency refers to the percentage of energy passed from one trophic level to the next. It is usually around 10% because much energy is lost as heat, used in metabolic processes, or remains as waste, making transfer inefficient.

Question 1: If a producer has an energy content of 5000 kJ and a primary consumer receives 10% of this energy, how much energy does the primary consumer gain? Show your working.

Answer: Energy gained = 10% of 5000 kJ = 0.10 × 5000 kJ = 500 kJ

Question 2: A secondary consumer receives 50 kJ of energy from the primary consumer. If the energy transfer efficiency between primary and secondary consumers is 10%, what was the original energy content of the primary consumer? Show your working.

Answer: Original energy = 50 kJ ÷ 0.10 = 500 kJ

Question 1: Outline a safe procedure for collecting samples of insects in a woodland to study their role in the food web.

Answer: First, wear appropriate protective clothing and use insect nets to collect samples from different areas of the woodland. Handle insects carefully with forceps to avoid injury. Use labelled containers to store specimens and wash hands after handling. Ensure all equipment is sterilised to prevent contamination. Follow local wildlife regulations and obtain necessary permissions.

Question 2: Identify three variables that should be controlled during an experiment to investigate the effect of plant abundance on herbivore populations.

Answer: Variables to control include soil type, amount of sunlight, and water availability.

Question 1: In an ecosystem, the energy content of producers is 6000 kJ, herbivores is 600 kJ, and carnivores is 60 kJ. Calculate the energy transfer efficiency between each level and comment on the overall energy loss.

Answer: Efficiency from producers to herbivores = (600/6000) × 100 = 10%. From herbivores to carnivores = (60/600) × 100 = 10%. Overall, the energy decreases significantly at each level, showing about 90% energy loss, mainly as heat and waste.

Question 1: Explain how food webs illustrate the complexity of energy flow in an ecosystem, including examples of how the removal of one species can impact the entire system.

Answer: Food webs demonstrate the interconnectedness of organisms within an ecosystem, showing multiple feeding relationships rather than a single pathway. For example, removing a top predator like a fox can lead to an increase in herbivore populations, which may overconsume plants, disrupting the entire balance. This illustrates the fragile stability of ecosystems and the importance of biodiversity for maintaining energy flow.

Question 1: Describe how understanding food webs can assist in managing pest populations in agriculture.

Answer: Understanding food webs helps identify natural predators of pests, allowing farmers to promote beneficial species and reduce pesticide use. This integrated pest management supports sustainable agriculture by maintaining ecological balance.

Question 2: Discuss how food web analysis can contribute to conservation efforts, particularly in protecting endangered species.

Answer: Food web analysis helps identify key species that support ecosystem stability. Protecting these species ensures the integrity of the food web, supporting endangered species indirectly. It also highlights critical interactions that need safeguarding to prevent ecosystem collapse.