How do endotherms and ectotherms differ?

a) Endotherms are warm-blooded and ectotherms are cold-blooded.
b) Endotherms and ectotherms differ in the means by which they regulate their body temperature.
c) Endotherms are regulators and ectotherms are conformers.

The correct answer is b) Endotherms and ectotherms differ in the means by which they regulate their body temperature.

To understand the difference between endotherms and ectotherms, you need to know how they regulate their body temperature. Here's how you can get to the answer:

1. Define what endotherms and ectotherms are:
- Endotherms are organisms that can generate heat internally to regulate their body temperature, typically maintaining a constant body temperature regardless of the external environment.
- Ectotherms, on the other hand, rely on external sources such as the environment to regulate their body temperature. They do not produce as much internal heat and their body temperature fluctuates with the surrounding conditions.

2. Compare how endotherms and ectotherms regulate their body temperature:
- Endotherms have the ability to generate and control their body heat internally. They can adjust their metabolic rate to produce heat or cool down by increasing or reducing their heat production.
- Ectotherms lack the ability to internally regulate their body temperature. Instead, they rely on behaviors such as basking in the sun, seeking shade, or burrowing to adjust their temperature according to the environment.

3. Evaluate the answer choices:
- Option a) states that endotherms are warm-blooded and ectotherms are cold-blooded. While it is true that endotherms are warm-blooded due to their internal heat production, the term "cold-blooded" is not entirely accurate for ectotherms.
- Option c) suggests that endotherms are regulators and ectotherms are conformers. While it captures the general idea about their temperature regulation, it does not specifically address the means by which they control their body temperature.

Based on the comparison between endotherms and ectotherms in how they regulate body temperature, option b) is the correct answer.