IB MYP Integrated Sciences e-Assessment : Habitat and ecosystems Exam Style Practice Questions - New Syllabus
Question (15 marks)
Daphnia are fresh-water organisms between 1–5 mm in length. They are found all around the world in water temperatures up to 40°C. Daphnia are transparent organisms, and their feeding, egg production, and heart rates are easily observed. They mature and breed very rapidly. In the wild, Daphnia are an important source of food for pond organisms. Most Daphnia will be eaten soon after hatching.
Question a (12 marks)
Design a scientific investigation to observe Daphnia’s response to varying water temperature within the range of its natural environment. In your answer, you should include:
- a list of suitable equipment
- the independent, dependent, and control variables
- how you will manipulate the variables
- how you will collect sufficient data
- a description of the method
- any relevant safety or ethical considerations.
▶️Answer/Explanation
Answer: We will investigate different groups of Daphnia in different water pools of different temperatures. We will need Daphnia, 5 different pools of river water of different temperatures large enough to hold 5 Daphnia each, and a microscope to observe them in the pools. The independent variable will be the temperature of the water they are in, the dependent variables will be how many were born and how many died as well as the way they behave in the water, and the control being the amount initially in the pond and the time they have been in the environment (5 days). They will need to be checked on regularly to see how the numbers are fluctuating, and we will see how the temperature affects their habits and reproductive cycle by observing their heart rate and their mating speed in each temperature. As time goes on, we will see the different changes in them as the newer generations are born into the environment of a different temperature.
Detailed Solution: The investigation involves setting up controlled environments with varying temperatures and observing Daphnia’s behavior, reproduction, and survival rates. Ethical considerations include ensuring the Daphnia are not harmed unnecessarily and are returned to their natural habitat after the experiment.
Question b (3 marks)
A student suggested that Daphnia’s response to increasing temperature is a useful model to understand human responses to temperature. Discuss whether or not this conclusion is valid.
▶️Answer/Explanation
Answer: I think it is a rather valid conclusion as all organisms react to temperature and react to the changes they are subject to. Though we are extremely different from Daphnia, we will also as humans change the way we behave based on the environment we are in. For example, humans who were born into a cold environment and had parents who were resistant to the cold will have a strong resistance to cold and thus will be able to perform better in colder temperatures because of their conditioning and genetic background. This is true for all organisms as temperature has an effect on everything to a certain degree.
Detailed Solution: While Daphnia’s response to temperature can provide insights into how organisms adapt to environmental changes, humans have more complex physiological and behavioral responses. Therefore, while the conclusion is partially valid, it cannot be directly applied to humans without further research.