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Ecology of Populations Chapter 46 Mader: Biology 8th Ed. Outline • • • • • • • • Scope of Ecology Population Density and Distribution Population Growth Models Survivorship Curves Age Distributions Regulation of Population Size Life History Patterns Human Population Growth – Environmental Impact Mader: Biology 8th Ed. Scope of Ecology • Ecology - Study of the interactions of organisms with other organisms and the physical environment. – Habitat - Place where an organism lives. – Population - All the organisms within an area belonging to the same species. – Community - All various populations interacting at same locale. – Ecosystem - Community of populations. Mader: Biology 8th Ed. Ecological Levels Mader: Biology 8th Ed. Density and Distribution of Populations • • Population Density - Number of individuals per unit area or volume. Population Distribution - Pattern of dispersal of individuals within the area of interest. – Ecologists want to analyze and discover what causes the spatial and temporal “patchiness” of organisms. Limiting Factors are factors that particularly determine whether an organism lives in an area. Mader: Biology 8th Ed. Uniform Distribution Mader: Biology 8th Ed. Random Distribution Mader: Biology 8th Ed. Clumped Distribution Mader: Biology 8th Ed. Characteristics of Populations • Intrinsic Rate of Natural Increase (r) – If immigration (+) and emigration (-) cancel each other out, then population growth can simply be modeled by birth rate minus the death rate. Mader: Biology 8th Ed. Population Growth Models • Exponential Growth – Number of individuals added each generation increases as the total number of females increases. Biotic Potential - Maximum population growth that can possibly occur under ideal circumstances. Environmental Resistance - All environmental conditions that prevent populations from achieving biotic potential. Mader: Biology 8th Ed. Exponential Growth Curve Mader: Biology 8th Ed. Exponential Growth Equation Mader: Biology 8th Ed. Logistic Growth • Logistic growth occurs when environmental resistance comes into play and retards exponential growth. – Living populations must eventually come under the control of environmental resistance. Mader: Biology 8th Ed. Logistic Growth Mader: Biology 8th Ed. Logistic Growth Mader: Biology 8th Ed. Carrying Capacity • Carrying Capacity is the maximum number of individuals of a given species the environment can support. – The closer the population to the carrying capacity, the greater the environmental resistance. Biotic potential is having full effect and birthrate is a maximum during exponential growth. Mader: Biology 8th Ed. Mortality Patterns • A cohort is composed of all the members of a population born at the same time. – Survivorship is the probability of newborn individuals of a cohort surviving to particular ages. Survivorship Curves Mader: Biology 8th Ed. Survivorship Curves Mader: Biology 8th Ed. Survivorship Curves Mader: Biology 8th Ed. Age Distributions • Populations differ according to what proportion of the population falls in each age category. – At least three structures possible. Increasing Stable Decreasing Mader: Biology 8th Ed. U.S. Age Distributions Mader: Biology 8th Ed. Regulation of Population Size • • Density - Dependent Factors – Number of organisms present influences the effect of the factor. Competition Predation Density - Independent Factors – Number of organisms present does not influence the effect of the factor. Natural Disasters Mader: Biology 8th Ed. Life History Patterns • r - Strategists (Opportunistic) – Produce large numbers of offspring. – Small body size. – Early maturity – No parental care. – Density independent controls. – Good dispersers and colonizers. Mader: Biology 8th Ed. Life History Patterns • k - Strategists (Equilibrium) – Produce small numbers of offspring. – Large body size. – Late maturity – Significant parental care. – Density dependent controls. – Specialists Mader: Biology 8th Ed. Human Population Growth • • Human population has an exponential growth pattern. – Doubling time currently estimated at 53 years. Population Size – 1800 1 Billion – 1930 2 Billion – 1960 3 Billion – 2000 6 Billion Mader: Biology 8th Ed. World Population Growth Mader: Biology 8th Ed. Country Development • • More-Developed Countries (MDCs) – Slow population growth. – High standard of living. – Completed Demographic Transition. North America and Europe Less-Developed Countries (LDCs) – Rapid population growth. – Low standard of living. Latin America Africa and Asia Mader: Biology 8th Ed. Age Distributions • Age Structure Diagrams divide populations into three age groups. – Pre-Reproductive – Reproductive – Post-Reproductive Mader: Biology 8th Ed. More-Developed Countries Mader: Biology 8th Ed. Less-Developed Countries Mader: Biology 8th Ed. Environmental Impact • Environmental impact of a population is measured in terms of: – Population Size – Resource Consumption Per Capita – Resultant Pollution Mader: Biology 8th Ed. Environmental Impact Mader: Biology 8th Ed. Review • • • • • • • • Scope of Ecology Population Density and Distribution Population Growth Models Survivorship Curves Age Distributions Regulation of Population Size Life History Patterns Human Population Growth – Environmental Impact Mader: Biology 8th Ed. Mader: Biology 8th Ed.