Biology Populations and Sustainability

Population

group of individuals of the same species that live in the same area

3 dispersal types in populations

clumped, uniform, and random

clumped dispersion

most common, clumped resources/example: can provide protection/warmth

uniform dispersion

individuals/resources are evenly distributed, territoriality

random dispersion

random spacing of individuals of the same species within an area/example: plants via wind (pollen/seeds)

survivorship curves

type 1, 2, and 3

type 1 survivorship curve

high death rate late in life (humans)

type 2 survivorship curve

constant death rate (ground squirrels)

type 3 survivorship curve

high death rate early in life (sea turtles)

2 population curves

exponential growth and logistic growth

exponential growth curve

can't go on forever because of growth limits (space, food, diseases, natural disasters, etc.)

logistic growth curve

starts with exponential, then population is slowed and finally brought to a standstill by limiting factors

density dependent factors

limiting factor that depends on population size/
examples: competition, predation, disease, stress from overcrowding, war, food

density independent factors

limiting factors whose influence is not affected by population density/examples: natural disasters, storms, drought

human population

exponentially increasing, but our rate of growth is decreasing

demographic transition

as a country becomes industrialized, death rates go down, and birth rates go down

demographic transition: death rates go down because...

increased sanitation, healthcare, increase in food resources, clean water

demographic transition: birth rates go down because...

fewer kids to work, loose fewer kids, women get educated about birth control

growth pyramids

analyze number of people in different age groups in a population: can determine if a pop is growing rapidly or slowly

logisitcal growth

exponential growth

mark-recapture method

boom and bust cycle