Question 1: Define biotic factors and give two examples within a forest ecosystem.

Answer: Biotic factors are living components of an ecosystem, such as trees and animals.

Question 2: Explain how abiotic factors like temperature and rainfall can affect the distribution of plants in a grassland.

Answer: Temperature and rainfall influence plant growth; for example, low rainfall limits water availability, restricting plant types that can survive.

Question 1: A lake has a pH level of 6.2. If the pH scale is logarithmic, calculate the hydrogen ion concentration in moles per litre. (Formula: pH = -log[H+])

Answer: [H+] = 10^(-pH) mol/L

Question 1: Describe an experiment to investigate how soil moisture affects plant growth. Include variables to be controlled and safety precautions.

Answer: Students could set up pots with identical soil and plant species, vary soil moisture levels, control light and temperature, and record plant growth. Safety precautions include handling equipment properly and avoiding spillage.

Question 1: In a study, the average temperature in a pond during summer is 24°C, and the fish diversity index is 8. During winter, the temperature drops to 8°C, and the diversity index drops to 3. Explain the possible relationship between temperature and fish diversity.

Answer: Lower temperatures during winter may reduce oxygen levels and metabolic activity, leading to a decrease in fish diversity. This suggests temperature influences fish survival and diversity.

Question 1: Describe how the presence of a predator (biotic factor) can influence the abiotic conditions, such as water quality, in an aquatic ecosystem. (6 marks)

Answer: Predators can reduce prey populations, which may lead to decreased waste and organic matter in the water, improving water quality. Alternatively, predator activity can disturb sediments, affecting oxygen levels. This interaction demonstrates how biotic factors indirectly influence abiotic conditions.

Question 1: How can knowledge of abiotic factors be used to improve agricultural practices? Provide two examples.

Answer: By adjusting irrigation to account for rainfall patterns and selecting crop varieties suited to soil pH and temperature, farmers can optimise growth and yields.