Populations. Chapter 19. Populations. Is a groups of organisms that belong to the same species and live in a particular place at the same time. Properties of Populations. Populations Size Population Density Dispersion Random Uniform Clumped. Population Density.
Populations Chapter 19
Populations Is a groups of organisms that belong to the same species and live in a particular place at the same time.
Properties of Populations • Populations Size • Population Density • Dispersion • Random • Uniform • Clumped
Population Density • The number of individuals of a species per unit area or volume • Density is determined by sampling and extrapolating • # red oak / km2 • # of earthworms / m3
Dispersion Patterns • clumped: most common-due to clumping of resources • examples: • fungus growing on a rotting log • schools of fish
Dispersion Patterns • uniform: evenly spaced • examples: • shore birds (gannets and king penguins) • plants secrete chemicals to decrease competition
Dispersion Patterns • random: unpredictable spacing, no pattern • example: • dandelions due to windblown seed distribution
Population Dynamics Birth Rate Death Rate Mortality rate- the number of deaths in period of time • The number of births occurring in a period of time
Survivorship Curves Life Tables track survivorship in populations. Insurance companies use them for human life expectancy.
Survivorship Curves • Show the probability that members of a population will survive to a certain age. • Type I • Likelihood of dying is small until late in life • Type II • The probability of dying does not change throughout life • Type III • Likely to die when young
Population Growth Rate BIRTH RATE – DEATH RATE = GROWTH RATE The amount by which a population’s size changes in a given time.
LIMITING FACTORS Any factor that limits or restrains the growth of a population BIOTIC VS ABIOTIC
Limiting Factors Density-Independent Density Dependent An individual’s chance of surviving or reproducing depends on the number of individuals Resources limitations • Reduce the population by the same proportion • Weather • Flood • Fires