group of individuals of same species living in same area

(size, density, distribution/dispersion)

Populations

Habitat vs. Niche

Habitat vs. Niche

type of area an organism lives in vs. role in ecosystem

competition for resources

age structure (rapid growth vs. declining vs. stable populations)

Populations

POPULATION GROWTH

1. Density-dependent limiting factors: competition for resources, parasites and diseases, waste products, stress, predation
2. density independent limiting factors: climate = temperature and rainfall, natural disaster
3. exponential growth (J-shaped, unlimited) vs. logistic growth curve (S-shaped, limited)
4. carrying capacity = maximum population supported by habitat
5. populations can cycle

population ability to respond to changes in the environment is affected by genetic diversity

species and populations w/ little genetic diversity are at risk for extinction

COMMUNITIES

measured and described in terms of species composition and species diversity

symbiosis = species interaction

MUTUALISM +/+ 

COMMENSALISM +/0 (egrets/cattle)

PARASITISM +/- (tapeworm/cow)

PREDATION +/- (carnivores/herbivores)

COMPETITION

ECOSYSTEMS

free energy

1. reproduction and rearing of offspring require free energy beyond that used for maintenance and growth; different organisms use various reproductive strategies in response to energy availability
2. relationship exists b/w metabolic rate per unit body mass and size of multicellular organisms - generally, smaller organism → higher the metabolic rate
3. excess acquired free energy vs required free energy expenditure results in energy storage or growth
4. insufficient acquired free energy vs required free energy expenditure results in loss of mass and ultimately, death of an organism

ECOSYSTEMS

energy flow/production = energy flows through

90% lost at each level; 10% transferred to next level

1. TROPHIC levels = primary producers, primary consumers, secondary consumers, tertiary consumers, detrivores and decomposer
2. ecological pyramids (of energy, biomass, numbers)
3. food chains and food webs
4. biotic and abiotic factors can both cause disruption and collapse of ecosystems