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

What defines a response in biological terms?

1. The sum of all behaviors

2. Actions or behavior caused by a stimulus

3. A series of learned behaviors

4. The initial perception of a stimulus

The correct answer is: Actions or behavior caused by a stimulus

A response in biological terms is defined specifically as actions or behaviors that occur as a result of a stimulus. This means that when an organism detects a change in its environment, it reacts in a certain way, which constitutes its response. This process involves sensory receptors detecting the stimulus, subsequent processing in the nervous system, and then executing an appropriate behavior. This definition captures the essence of how organisms interact with their surroundings and emphasizes the importance of external stimuli in initiating a response. For instance, a plant bending towards a light source (phototropism) or an animal fleeing from a perceived threat are both examples of responses dictated by stimuli present in their environment. The other choices do not strictly relate to the definition of a response. The concept of 'the sum of all behaviors' encompasses more than just responses to stimuli, while 'a series of learned behaviors' implies that all responses are based on prior experiences, which is not always the case as some responses can be instinctual. Additionally, 'the initial perception of a stimulus' refers to the detection process rather than the reaction itself, which further distinguishes it from the definition of a biological response.