Biology3 ecology exam2

the study of interactions between organism and environment

a group of organisms of the same species who live in a specific location and breed with one another

a type of organism

the number of organisms of a particular population in a given area

mean number of individuals in a population

(births - deaths) + (immigrants - emigrants) = change in population size

r (growth rate) = b (births) - d (deaths)

• maximum number of individuals an environment can hold
• S-shaped growth curve stabilizes at carrying capacity

• density: number of individuals per given area
• * independent: environmental factors that have nothing to do with population size (weather, temperature, etc.)
• * dependent: environmental factors due to population size (predation, competition, etc.)

• how organisms are arranged in a population
• clumped
• uniform
• random

a group of populations living close enough to potentially interact

• all the factors that affect or are affected by an organism
• the role of a species in its community

a species that plays a larger role in a community (starfish/muscles or beavers/dams)

harmless animals may evolve to resemble poisonous ones

two unpalatable and harmful organisms resemble eachother

• two organisms live together
• commensalism: one species benefits and the other is unaffected
• mutualism: both benefit
• parasitism: one species benefits and the other is harmed

two species in the same area with same niche will compete for limited resources and one will out compete the other

similar species in same area will usually occupy some slight differences in their niches (allows them to coexist)

• a gradual change in a community in which one array of species replaces another
• primary: ecological succession occurs in an area where there was previously no soil
• secondary: ecological succession occurs in an area where a community previously existed and soil remains

energy enters ecosystem from sun, flows through it as food and exits as heat

• CO₂ in the atmosphere
• taken in by plants during photosynthesis
• consumed by herbivore => consumed by carnivore
• carbon returns to atmosphere via organism's aerobic respiration
• decomposition of wastes and the dead bring carbon to soil
• soil bacteria and detritus feeders perform respiration
• carbon diffuses between the atmosphere and the ocean
• over time, sediments become carbon-rich rocks => fossil fuels

• nitrogen in the atmosphere
• nitrogen-fixing bacteria in legume roots and soil
• they break N₂ bonds and use nitrogen atoms to form ammonia => dissolves to form ammonium ions (NH_4⁺)
• plant roots take up ammonium which gets eaten by consumers and used in metabolic reactions
• also, decomposers break down waste and remains to produce ammonium
• bacteria convert ammonia to nitrates (nitrification) which plants can use
• ecosystems lose nitrogen by denitrification, denitrifying bacteria use nitrate and give off nitrogen gas back to the atmosphere