Population Ecology

Ecology ecology environment components biotic abiotic

Ecology Hierarchy of Ecology biosphere ecosystem community population individual

Population Ecology 2 characteristics of a population: density dispersion

Density we measure density by sampling mark and recapture method line intercept method point count method

Population Distribution distribution patterns clumped uniform random

Age Distribution distribution of males and females in each age group of a population used to predict future population growth

Survivorship mirrors mortality expressed in survivorship curves plots surviving individuals at different age groups

Survivorship three types of survivorship curves late loss (Type I) constant loss (Type II) early loss (Type III)

Changes in a Population 3 factors determine population changes births deaths migration immigration emigration

Population Dynamics measures optimal population growth J curve exponential growth measures optimal population growth rmax = intrinsic rate of increase

Population Growth example: 10,000 birds in a population 1500 births and 500 deaths per year 1500/10,000 - 500/10,000 = .10 or 10% expressed by saying there is a 10% increase per bird per year

Population Dynamics size of a population is limited to: intrinsic rate of increase environmental resistance includes limitations the environment imposes on birth rate and death rate in a population food space predation parasitism

Population Growth and Regulation carrying capacity (K) determined by renewable resources like water, nutrients, and light nonrenewable resources such as space

Carrying Capacity logistic population growth r decreases as N increases K-N tells us # of individuals population can accommodate S curve

Population Growth Models K selected equilibrial populations live at density near limit imposed by resources r selected opportunistic populations live in environments where little competition is present

Density Influence on Birth and Death Rates 2 mechanisms density independent density dependent

Density Independent Factors unrelated to population size most important: weather climate

Density Dependent Factors increase effectiveness as population density increases especially affects long lived organisms include predation parasitism competition

Human Population Growth J curve growth grows at a rate of about 80 million yearly (r=1.3%) Why doesn’t environmental resistance take effect?

Human Population Growth altering their environment technological advances the cultural revolution the agricultural revolution the industrial-medical revolution