1. Population Dynamics and Carrying Capacity
A. Populations change in size, density, and age distribution; most members of populations live together in clumps or groups. 1. Three general patterns of population distribution occur in a habitat: clumping, uniform distribution, and random dispersion. Most species live in clumps or groups. a. Availability of resources varies from place to place. b. Living in groups offers better protection from predators. c. Some predator species live in packs to better have a chance to get a meal. d. Temporary groups may form for mating and caring for young. 2. Uniform pattern distribution may occur where a resource, such as water, is scarce. B. Four variables influence/govern population size: births, deaths, immigration, and emigration. 1. Increase in population occurs by birth and immigration. 2. Decrease in population occurs by death and emigration. 3. Age structure of a population is usually described as the pre-reproductive stage, the reproductive stage and the post-reproductive stage. A population with a large reproductive stage is likely to increase, while a population with a large post-reproductive stage is likely to decrease. C. No population can grow indefinitely due to limited resources such as light, water, and nutrients and also due to competitors and/or predators. 1. The biotic potential is the population’s capacity for growth. 2. The intrinsic rate of increase (r) is the rate of population growth with unlimited resources. 3. Rapidly growing populations have four characteristics. a. Individuals in the population reproduce early in life. b. Individuals have short periods between generations. c. Individuals have long reproductive lives.
d. Individuals produce multiple offspring each time they reproduce. D. Environmental resistance consists of factors that limit population growth. 1. Carrying capacity (K) is determined by biotic potential and environmental resistance. This is the number of a species’ individuals that can be sustained indefinitely in a specific space. 2. As a population reaches its carrying capacity, its growth rate will decrease because resources become more scarce. E. A population can grow rapidly with ample resources.
1. With few resource limitations...