OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

How do simple animals typically respond to light stimuli?

1. They move towards the light

2. They move away from the light

3. They remain stationary

4. They exhibit erratic movements

The correct answer is: They move away from the light

Simple animals often exhibit behaviors in response to environmental stimuli, and their reactions can provide insights into their survival strategies. One common behavior of many simple organisms, such as certain types of single-celled organisms and invertebrates, is phototropism. In some cases, moving towards or away from light can be crucial for their survival, affecting processes such as feeding, reproduction, and protection from predators. Simple animals that move away from light help avoid exposure to harmful conditions, as bright light may signal danger or indicate a hostile environment. For example, many worms and some marine organisms tend to migrate to darker areas to stay safe from harmful UV radiation and reduce the chance of desiccation. This behavior can be advantageous as it allows simple animals to navigate their habitats more safely. The tendency to move away from light rather than towards it helps them find food sources or shelter while avoiding potential threats. Thus, this response aligns with their biological needs and environmental adaptations.