PACKET #31 CHAPTER #14 Population Ecology

Introduction & Review Population  Group consisting of members of the same species that live together in a prescribed area at the same time. Population Ecology  The study of numbers of individuals of a particular species, at a given time and location, and the interactions of that population with other populations and the environment Population dynamics  Study of changes in populations

IMPORTANT FEATURES OF POPULATIONS Population Ecology

Population Density  This is how population size is expressed  The number of individuals of a species per unit space

Dispersion  Describes the spacing of individuals and there are three types.

Types of Dispersion Uniform Dispersion  Individuals are evenly distributed Clumped (Aggregated) Dispersion  Most common type  Individuals are concentrated in specific parts of the habitat  Patchiness Occurs as a result of distribution of resources or by asexual reproduction Random dispersion  Occurs when individuals of a population are spaced throughout an area in a manner that is unrelated to the presence of others  Least common; hardest to observe  Results from a lack of interaction between individuals or a homogenous environment

MATHEMATICAL MODELS Population Ecology

TYPES OF GROWTH RATES Population Ecology

Exponential Growth  Population growth is at a rapid pace  Humans have exhibited this growth pattern for centuries—but can it last?

Exponential Growth & The Human Population II Not all countries have the same growth rate  Higher in developing countries  India  South Asia  Africa Age structure of a country can be used to predict future population growth  Shows the percentages of population at different ages  A broader base to the age structure indicates a growing population while a narrower base indicates a stable or shrinking population.

Logistic Growth  Exponential growth with environmental resistance (carry capacity of the environment = K) incorporated into the equation  Exhibited by most natural populations.

FACTORS INFLUENCING POPULATION SIZE Population Ecology

Dispersal  Movement of individuals among populations  Immigration  Migration of individuals into the population  Emigration  Migration of individuals out of the population Dispersal Immigration Movement into population Emigration Movement out of population Movement among populations

Density Dependent Factors II Predation Disease  Increases when contact with toxic waste, produced by population itself, increases with population size. Competition  Intraspecific  Competition between members of the same species  Interspecific  Competition between members of different species

Density Independent Factors Climatic factors  Sunlight  Rainfall  Temperature  All have impacts no matter what the population size  Climatic and seasonal factors, monsoon season for example, can severely decrease populations

LIFE “HISTORY” TRAITS OF POPULATIONS Population Ecology

Introduction Life history traits, products of natural selection, are traits that affect an organism’s schedule of reproduction and survival.  Birth  Reproduction  Death

Semelparous vs. Iteroparous Species Semelparous Species  Expend their energy in a single, immense reproductive effort  Pacific salmon  Agave Iteroparous Species  Exhibit repeated reproductive cycles  Most vertebrates  Most shrubs  Most trees

r Strategists r strategists  Have traits that contribute to a high population growth rate.  High r  Small size  Large numbers of offspring  May live in unpredictable habitats Weeds Pests Roaches

K Strategists K strategists  Maximize the chance of surviving in an environment where the number of individuals (N) is near the carrying capacity (K) of the environment.  Population size near K  Larger body size  Long life span  Late reproduction and slow development  Have fewer offspring  May care for their young African elephants Humans

Review

Students are encouraged to place their own questions and charts on following slides.