Ecology Unit Review Topics
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II.
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Ecology
a. Study of interactions between organisms and organisms, and organisms and their
environment
b. Abiotic Factors- non-living
i. Moisture
ii. Wind/air currents
iii. Light
iv. Soil
v. Temperature
c. Botic factors- living
d. Levels of organization in ecology
i. Organism
ii. Population- made up of one species
iii. Community- many populations living in one area
iv. Ecosystem- all organisms in a particular area with non-living
v. Biome- group of ecosystems that have similar climate and similar dominant
communities
vi. Biosphere- all of planet where life exists
e. Habitat v. niche
i. Habitat- where organisms live
ii. Niche- organisms role in its environment
f. Community interactions
i. Competition- occurs due to limited resources
1. Competitive exclusion principle- no two species can occupy the same
niche in the same habitat at the same time
ii. Predation- organism captures and feeds on another organism
iii. Symbiosis- relationship where two species live closely together
1. Mutualism- both benefit
2. Commensalism- one benefits, one is not harmed
3. Parasitism- one benefits, one is harmed
Energy Flow- from autotrophs to heterotrophs
a. Producers- autotrophs, make food from their environment
i. Photosynthesis- from sun
ii. Chemosynthesis- without light
b. Consumers- heterotrophs
i. Herbivores- eat only plants
ii. Carnivores- eat animals
iii. Omnivores- eat both plants and animals
iv. Detritivores (decomposers)- eat dead matter
c. Energy flows in ONE DIRECTION from sun, to autotrophs, to heterotrophs, to
decomposers
i. Food chain- series of steps energy is transferred by eating or being eaten
ii. Food web- network of feeding relationships
iii. Trophic levels- each step in a food web/chain
1. Each level depends on the one below for energy
2. Only 10% is transferred from one trophic level to the next- 90% lost as
heat
Biogeochemical cycles- matter is recycled through an ecosystem
a. Hydrologic (Water) Cycle
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V.
VI.
i. Precipitationpercolationwater flowevaporation/transpiration
condensation
b. Carbon cycle
i. Carbon dioxide in atmosphere
1. Released by combustion, respiration, decomposition
2. Removed by photosynthesis
ii. Sediments (fossils/fossil fuels) are main reservoir
c. Nitrogen cycle
i. Used in amino acids and nucleic acids
ii. Main reservoir is nitrogen gas in atmosphere
iii. Decomposers convert nitrogen into usable form for plants (nitrogen fixation) and
add back to atmosphere (denitrification)
d. Phosphorus cycle
i. Used for phospholipids and nucleotides
ii. Cycle exists in earth’s crust- not in atmosphere
iii. Added to soil from living organisms by waste products
Communities
a. All the populations that live in a habitat- structure determined by type of habitat
b. Limiting factors
i. Food
ii. Predators
iii. Temperature
c. Changes to a community- ecological succession
i. Primary- no preexisting soil, usually after volcano eruption, earthquake
ii. Secondary- preexisting soil, usually after natural disaster (fire, flood)
iii. Pioneer species- those that colonize barren habitats (i.e. lichens)
iv. Climax community- stable community that remains unchanged over time
v. Pioneer stage    Climax Community
Biogeography- study of distribution of organisms and factors that contribute to distribution
a. Geologic history
b. Topography
c. Climate (average weather in a region)
d. Soil characteristics
e. Species interactions
Population ecology
a. Sampling- to get best estimate of population size
i. Random
ii. Non-random
b. Factors that affect population size
i. Birth, death
ii. Immigration
iii. Emigration
c. Population growth
i. Exponential- no limits, “J” curve
ii. Logistic- limits (carrying capacity), “S” curve
d. Environmental limits on populations
i. Density-dependent: disease, food, parasitism, predation, competition
ii. Density-independent: temperature, storms, floods, drought, habitat disruption
e. Human population growth (Demography)
i. Reached exponential because of industrial revolution
ii. Age structure pyramids- compare age structure of populations of different
countries