Fig Organismal ecology Population ecology Community ecology Ecosystem ecology Landscape ecology Global ecology

Introduction to Ecology Populations Population ecology – Abundance – Dynamics Density, dispersion, demographics, interrelationships with other populations

Population density The number of individuals per unit area or volume

Fig. 52-1a, p (a) Random dispersion Pattern of dispersion Refers to how individuals are spaced relative to one another

Fig. 52-1b, p (b) Clumped dispersion Pattern of dispersion Patchiness in resources Family groups Reduce risk of predation

Fig. 52-1c, p (c) Uniform dispersion Pattern of dispersion Aggressive interactions Competition

Population dynamics 4 primary factors that influence population size – Births – Deaths – Immigration – Emigration How do these factors affect the rate at which populations change?

Fig Births Births and immigration add individuals to a population. Immigration Deaths and emigration remove individuals from a population. Deaths Emigration

Fig Births Births and immigration add individuals to a population. Immigration Deaths and emigration remove individuals from a population. Deaths Emigration

– The age at which reproduction begins – How often the organism reproduces – How many offspring are produced during each reproductive cycle evolutionary outcomes reflected in the development, physiology, and behavior of an organism – based on trade-offs Life History

Age (years) , Number of survivors (log scale) Males Females A survivorship curve is a graphic way of representing the data in a life table relatively constant death rate

Fig , II III Percentage of maximum life span Number of survivors (log scale) I

Fig (a) Dandelion (b) Coconut palm

Fig. 52-2, p Number of bacteria (N) Hours Dynamics - Population growth r = unchecked population growth

Fig , p : 6.5 billion Human population (billions) Black Death Time (years)

Fig. 52-3, p Carrying capacity of the environment (K) Number of individuals (N) Time

The Logistic Model and Life Histories Life history traits favored by natural selection may vary with population density and environmental conditions K-selection, or density-dependent selection, selects for life history traits that are sensitive to population density r-selection, or density-independent selection, selects for life history traits that maximize reproduction

Density-dependent – Density of population alters the affect of an environmental condition Density-independent – Effect of an environmental factor is not affected by the density of a population Factors influencing population size

Density-dependent factors

Competition – interaction in which individuals try to use the same resource – Intraspecific – Interspecific Density-dependent factors

Density-independent factors

Metapopulations Environments are heterogeneous – Resources are patchy – Several small populations rather than 1 large Not all patches are equal – Less desirable may result in lower b or higher d – More productive may lead to higher b and lower d

Fig , p. 1138