EQ: How do we measure populations? Population Ecology EQ: How do we measure populations?

Population Dynamics Population: All the individuals of a species that live together in an area Demography: The statistical study of populations, allows predictions to be made about how a population will change Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations: Size Size: number of individuals in an area Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations: Size Growth Rate: Birth Rate (natality) - Death Rate (mortality) How many individuals are born vs. how many die Birth rate (b) − death rate (d) = rate of natural increase (r) Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Three Key Features of Populations: Density Density: measurement of population per unit area or unit volume Pop. Density = # of individuals ÷ unit of space Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

How Do You Affect Density? Immigration: movement of individuals into a population Into Emigration: movement of individuals out of a population Exits Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites) Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)

Factors That Affect Future Population Growth Don’t copy this slide Factors That Affect Future Population Growth Immigration + + - Population Mortality Natality - Emigration

Three Key Features of Populations: Dispersion Dispersion: describes the spacing of organisms relative to each other Clumped Uniform Random Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Population Dispersion

How Are Populations Measured? Count all the individuals in a population Estimate by sampling Mark-Recapture Method

How Do Populations Grow? Exponential Growth – when individuals in a population reproduce at a constant rate Under ideal conditions with unlimited resources, a population will grow exponentially

How Do Populations Grow? Logistic Growth – when a population’s growth rate slows or stops flowing a period of exponential growth - Happens when resources become less available

Carrying Capacity (k): The maximum population size that can be supported by the available resources Although several species may share a habitat they each have their own niche. A niche is a very narrow range where a species fits within a habitat.

Factors Limiting Growth Rate Declining birth rate or increasing death rate are caused by several factors including: Limited food supply The buildup of toxic wastes Increased disease Predation

“Booms” and “Busts”

History of the Human Population

Human Population Growth Grows at a rate of about 80 million yearly Why doesn’t environmental resistance take effect? Altering their environment Technological advances The cultural revolution The agricultural revolution The industrial-medical revolution