tailieunhanh - Linzey - Vertebrate Biology - Chapter 10

C H A P T E R 1 0 Population Dynamics Reproductive (Biotic) Potential The maximum number of young that a population can produce under ideal conditions during a particular time period is referred to as the reproductive (biotic) potential of that population. | Linzey Vertebrate Biology 10. Population Dynamics I Text The McGraw-Hill Companies 2003 CHAPTER 10 Population Dynamics INTRODUCTION Animal populations which are dynamic and constantly changing depend on successful reproduction to maintain their existence. Other important factors in maintaining viable populations include an adequate food supply sufficient home sites and the effects of dispersal immigration emigration climate predation disease and parasites. The impact of some of these factors is density-dependent that is the effect varies according to the population density for others the impact is density-independent that is unrelated to population size. POPULATION DENSITY Population density is an important variable that can influence the level of competition for scarce resources. Every habitat has a theoretical maximum number of individuals of a given species that it can support for an extended period of time. This level is known as the carrying capacity Fig. and is determined by environmental resistance factors acting on the reproductive biotic potential of a population. It is primarily determined by the availability of food and shelter. Vertebrates exhibit three basic types of population growth. Once many species reach the environmental carrying capacity of their range they maintain relatively stable populations Fig. . This is especially true of species inhabiting some tropical regions where temperature and rainfall show little variability. Some species that normally maintain relatively stable populations experience sharp population increases at irregular intervals. Such irruptions which cause the population to exceed its carrying capacity may be the result of such transient factors as a reduction in predators an increase in food a favorable change in the weather or any combination of these. Still other species experience sharp increases in their population sizes at regular intervals followed by crashes. Species exhibiting regular cyclic population .