AP Biology All living organisms on earth need energy to grow

AP Biology: All living organisms on earth need energy to grow, reproduce, and carry out cellular functions; however, these energy requirements are not equal for all cells. Neither are they equal for different species.

Discuss the biological evidence that shows that larger animals require a lower metabolic rate than smaller animals. Discuss the effect of energy on reproduction for K-strategists and R-strategists.

Solution

Larger animals require a lower metabolic rate than smaller animals. Kleiber\'s Law states that an animals metabolic rate scales to the 3/4 power of the animal\'s mass. A small animal has more surface area than the large animal. Animals need to exchange their body heat with the environment for their bodily functions. So a small animal will lose more heat to the environment and faster than the large animals due to its more surface area. This means small animals would need more energy and a higher metabolic rate to maintain its constant body temperature. Eg. a gram of mouse tissue metabolizes 10 times faster than a gram of elephant tissue.

R-selected organisms have short life spans, are generally small, quick to mature and waste a lot of energy. Their ability is to reproduce rapidly ie. exponentially at an early age using low energys. eg insects. K-selected organisms are long lived, large, have slow maturation and are more energy efficient. They have a reproductive stratergy to grow slowly using high energys. eg humans