tailieunhanh - From Individuals to Ecosystems 4th Edition - Chapter 5

Chapter 5 Intraspecific Competition Introduction Organisms grow, reproduce and die (Chapter 4). They are affected by the conditions in which they live (Chapter 2), and by the resources that they obtain (Chapter 3). But no organism lives in isolation. | Chapter 5 Intraspecific Competition a definition of competition Introduction Organisms grow reproduce and die Chapter 4 . They are affected by the conditions in which they live Chapter 2 and by the resources that they obtain Chapter 3 . But no organism lives in isolation. Each for at least part of its life is a member of a population composed of individuals of its own species. Individuals of the same species have very similar requirements for survival growth and reproduction but their combined demand for a resource may exceed the immediate supply. The individuals then compete for the resource and not surprisingly at least some of them become deprived. This chapter is concerned with the nature of such intraspecific competition its effects on the competing individuals and on populations of competing individuals. We begin with a working definition competition is an interaction between individuals brought about by a shared requirement for a resource and leading to a reduction in the survivorship growth and or reproduction of at least some of the competing individuals concerned . We can now look more closely at competition. Consider initially a simple hypothetical community a thriving population of grasshoppers all of one species feeding on a field of grass also of one species . To provide themselves with energy and material for growth and reproduction grasshoppers eat grass but in order to find and consume that grass they must use energy. Any grasshopper might find itself at a spot where there is no grass because some other grasshopper has eaten it. The grasshopper must then move on and expend more energy before it takes in food. The more grasshoppers there are the more often this will happen. An increased energy expenditure and a decreased rate of food intake may all decrease a grasshopper s chances of survival and also leave less energy available for development and reproduction. Survival and reproduction determine a grasshopper s contribution to the next .