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What do we mean by Allen's rule?

1. Mammals from colder climates generally have shorter ears and limbs to minimise heat loss.
2. Desert lizards lack the physiological ability that mammals have to deal with the high temperatures of their habitat.
3. Some plants have no leaves; they are reduced to spines, and the photosynthetic function is taken over by the flattened stems.
4. The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding affinity of haemoglobin and by increasing the breathing rate.

Correct answer: Mammals from colder climates generally have shorter ears and limbs to minimise heat loss.

Solution

Allen's rule states that endothermic animals in colder climates tend to have shorter extremities such as ears, tails, and limbs. This reduces surface area and helps conserve body heat. Hence, the option about shorter ears and limbs is correct.

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