Question 1: Explain the difference between genetic and environmental sex determination.

Answer: Genetic sex determination involves chromosomes (such as XX or XY), whereas environmental sex determination depends on environmental factors like temperature during development.

Question 2: Name two environmental factors that can influence sex determination in certain species.

Answer: Temperature and pH levels.

Question 1: What is the typical sex ratio in a population where sex is determined by environmental temperature?

Answer: It can be skewed towards one sex depending on the temperature range, often leading to more females or males.

Question 2: Describe how temperature-dependent sex determination (TSD) works in reptiles such as crocodiles.

Answer: In TSD, the temperature during a critical period of egg incubation influences the development of either male or female sex organs, with specific temperature ranges favouring one sex over the other.

Question 1: If 100 crocodile eggs are incubated at a temperature that produces 75 females and 25 males, what is the sex ratio of females to males? Express your answer as a ratio.

Answer: Females:Males = 75:25 or 3:1

Question 2: Calculate the percentage of females in this population.

Answer: 75%

Question 1: Outline a basic experimental setup to test the effect of temperature on sex determination in reptile eggs.

Answer: Collect fertilised eggs and incubate groups at different controlled temperatures. Record the number of male and female hatchlings to determine the influence of temperature. Ensure safety measures such as wearing gloves and using appropriate incubators. Variables include temperature (independent), sex ratio (dependent), and incubation duration (controlled).

Question 2: Identify two variables that should be kept constant in this experiment and explain why.

Answer: Incubation duration and humidity levels, to ensure that temperature is the only variable affecting sex determination.

Question 1: In a study, a bird species shows a skewed sex ratio in environments with high pollutant levels. The sex ratio shifts towards females. Propose a possible environmental factor causing this shift and explain how it might affect sex determination.

Answer: Pollutants such as endocrine disruptors may interfere with hormonal pathways, leading to a bias towards female development. This environmental factor can alter the normal genetic or environmental cues that determine sex.

Question 1: Explain how environmental factors can influence the sex ratio of a population. Include examples and potential ecological impacts in your answer. (6 marks)

Answer: Environmental factors such as temperature, pH, or pollutants can bias the sex ratio by affecting developmental pathways during critical periods. For example, higher incubation temperatures can lead to more females in some reptiles. Ecologically, skewed sex ratios can reduce reproductive success and threaten population stability, impacting biodiversity and ecosystem balance.

Question 1: How might climate change impact sex ratios in species with temperature-dependent sex determination?

Answer: Climate change can alter temperatures during incubation, potentially leading to overly skewed sex ratios, such as too many females or males, which can threaten population viability.

Question 2: Suggest one way in which conservationists could mitigate skewed sex ratios caused by environmental changes.

Answer: Conservationists could manage incubation temperatures artificially or protect habitats to maintain natural environmental conditions.