Question 1: Define biotic factors in an ecosystem.

Answer: Biotic factors are the living components of an ecosystem, such as plants, animals, fungi, and bacteria.

Question 2: Explain how abiotic factors influence the distribution of organisms within an ecosystem.

Answer: Abiotic factors like temperature, light, water, and soil pH affect where organisms can survive and thrive by creating suitable or unsuitable conditions.

Question 1: Calculate the rate of photosynthesis if a plant produces 200 units of oxygen in 4 hours. Express your answer in units per hour.

Answer: Rate = Total units / Time (hours); Rate = 200 units / 4 hours = 50 units/hour

Question 2: A pond has a temperature of 15°C. If the optimal temperature for a certain algae species is 20°C, by what percentage is the pond's temperature below the optimum? (Show your working.)

Answer: Percentage below = ((20 - 15) / 20) × 100 = (5 / 20) × 100 = 25%

Question 1: Describe a simple experiment to test the effect of soil pH on plant growth, including variables and safety precautions.

Answer: Select different soil samples with varying pH levels, plant identical seedlings in each, control variables like water and light, measure growth over time. Safety precautions include wearing gloves when handling soil samples and ensuring proper disposal of chemicals used to alter pH.

Question 2: Identify the independent, dependent, and control variables in a study investigating the effect of light intensity on the rate of photosynthesis.

Answer: Independent variable: light intensity; Dependent variable: rate of photosynthesis; Control variables: type of plant, temperature, water amount.

Question 1: A freshwater lake shows decreased oxygen levels during summer months. Explain how high water temperature (an abiotic factor) could contribute to this observation.

Answer: Higher water temperatures reduce oxygen solubility, leading to lower oxygen levels, which can stress aquatic organisms and reduce biodiversity.

Question 2: Discuss how understanding abiotic factors can benefit industries such as agriculture or environmental management.

Answer: Knowledge of abiotic factors allows industries to optimise conditions for crop growth, manage water resources effectively, and develop strategies to mitigate environmental impacts, ensuring sustainable practices and ecosystem health.

Question 1: Describe how changes in soil pH can affect plant growth and the broader ecosystem.

Answer: Alterations in soil pH can affect nutrient availability, microbial activity, and root health, which in turn impacts plant growth. Changes can cascade through the food chain, affecting animal populations and overall ecosystem stability.

Question 2: Calculate the decrease in photosynthetic rate if light intensity drops from 1500 lux to 600 lux, assuming a linear relationship where at 1500 lux the rate is 100 units and at 600 lux the rate is proportionally lower.

Answer: Proportional decrease = (600 / 1500) × 100 units = 0.4 × 100 = 40 units; decrease = 100 - 40 = 60 units.