Chapter 6, Problem 51A

Summary Introduction

To write:

How reproductive strategies differ.

Introduction:

The study of human population size, density, distribution, movement, and birth and death rates is demography. For many years, environmental conditions kept the size of the human population at a relatively constant number below the environment's carrying capacity. Population growth rate is an important characteristic of any population. It explains how fast a given population grows. Some populations tend to remain the same size from year to year while other populations vary in size depending on their environmental conditions.

Explanation of Solution

Species of organisms vary in the number of births per reproduction cycle, in the age that reproduction begins, and in their lifespan. Both plants and animals are placed into groups called r-strategists. The rate strategist or r-strategists is an adaptation for living in an environment where biotic or abiotic fluctuations occur. These fluctuating factors might be availability of food or temperature changes. An r-strategist is generally a small organism such as a fruit fly, a mouse, or a locust. They generally have a short lifespan and produce many offspring. An r-strategist's reproductive strategy is to produce as many offspring as possible in a short span of time. Usually they invest little to no energy in raising their young and are regulated by independent density factors. They usually do not maintain a population near the carrying capacity. The k-strategist or carrying capacity strategy, is an adaptation for living in a more stable environment. A k-strategist is usually a larger organism that has a longer lifespan, produces fewer offspring and whose population reaches equilibrium at the carrying capacity. The reproductive strategy of a k-strategist is to produce only a few offspring who have a better chance of surviving to reproductive age due to the energy, time and resources spent in caring for the young. K-strategist populations are regulated by density-dependent factors.

Conclusion

An r-strategist's reproductive strategy is to produce as many offspring as possible in a short span of time. The reproductive strategy of a k-strategist is to produce only a few offspring who have a better chance of surviving to reproductive age.