Unit 1- Ecology
 The role of abiotic factors in the formation of biomes.
o Abiotic factors are non-living components of the environment. They
can determine the type/amount of communities and populations in a
biome. Some abiotic factors include: amount of light, temperature,
precipitation, and amount of water.
 How biotic and abiotic factors affect distribution of biomes
o The distribution of biomes is determined by abiotic factors like
climate, latitude, and altitude. Biotic factors are dependent on the
abiotic factors.
 How changes in these factors may alter ecosystems
o Changes in abiotic factors- may reduce a population by pushing it out
of its tolerance range for a specific factor (amount of light, water
availability) or increasing a population by pushing towards its
optimum range for a specific factor
o Changes in biotic factors- come in forms of competition, food
availability, disease, etc. May change the species through extinction,
or select members better adapted to lead to creation of a subspecies.
 How density, dispersion, and demographics can describe a population
o Demographics- statistical study of population that include density,
distribution, and rate of growth
o Population density- number of individuals in a unit area
o Population distribution- clumped, random, or uniform
 Determined by resources and limiting factors
 The differences between exponential and logistic models of population
growth
o Exponential- the number of individuals increases rapidly, J-shaped
and has two phases: Lag (slow due to small population) and
exponential (accelerated growth
o Logistic- occurs when population is below carrying capacity, Sshaped and has 4 phases: Lag, exponential, Deceleration (growth
slows as carrying capacity is neared), and stable equilibrium (little to
no growth)
 How density-independent and density-dependent factors can control
population growth
o Density dependent- operates in populations living at a density near the
limit imposed by their resources where competition is stronger among
individuals
o Density independent- occurs in populations well below carrying
capacity
 How a change in matter or energy will affect the population or community
o Less energy leads to a lower population
o All living things require energy
o Changes in amounts of producers affects all organisms
 The effect of age distributions and fecundity on human populations as
presented in age-structure pyramids
o Pre-reproductive numbers being the highest results in a higher
birthrate than death rate. More individuals entering reproductive stage
then leaving, results in population growth.
o Population stabilize when all stages are relatively equal in number,
with post-reproductive being slightly smaller.
o Post reproductive having largest numbers results in higher death rate,
more individuals leave reproductive phase than enter, creates
population decay
o Higher fecundity= higher fertility rates, results in more offspring and
therefore either greater growth or smaller decay
 The difference between a fundamental niche and a realized niche
o Fundamental- where a species can survive
o Realized- where a species actually survives when biotic conditions are
present
 The role of competitive exclusion in interspecific competition
o No two species can occupy the same niche at the same time. Through
interspecific competition, when different species try to use the same
resources, there is competitive exclusion so only 1 species will be
involved in that niche.
 The symbiotic relationships of parasitism, mutualism, and commensalism
o Parasitism- one organism benefits at the expense of the other
o Mutualism- both participants benefit
o One organism benefits, one is neither helped nor harmed
 The impact of keystone species on community structure
o Keystone species- activities significantly affect community structure
o Grizzly bears in northwestern US- disperse seeds, keep smaller hoofed
animal populations under control, move soil when they dig up roots
 The difference between primary and secondary succession
o Primary- formation of soil from exposed rock due to wind, water, etc.
Occurs where there is no base soil. Ex- volcano, glacial retreat
o Secondary- disturbance based on progressive change from grasses to
shrubs to trees. Occurs where soil is already present. Ex- cultivated
field returning to normal state
 How energy flows through the ecosystem in relations to food webs and food
chains
o Food webs- diagrams that describes trophic (feeding) relationships,
Shows various interconnecting paths, Grazing begins with a producer
o Food chain- show a single path of energy flow in an ecosystem
o Shows trophic relationships
 The difference between gross primary productivity and net primary
productivity
o Gross primary productivity- total amount of energy harvested by
producers
o Net primary productivity- total amount of energy harvested by
producers minus amount they use to produce energy.
 The carbon and nitrogen biogeochemical cycles
 How biogeochemical cycles impact individual organisms and/or populations
and ecosystems
o Water- necessary for life
o Carbon- necessary for photosynthetic organisms
o Nitrogen- limiting plant nutrient
o Phosphorus-mineral component in bones and teeth
 The value of biodiversity and the major human threats to it
o Biodiversity insures survival of species. Biodiversity is greatest where
sunlight is the most abundant and water availability is high.
o Threats include burning of fossil fuels and woods, deforestation, oil
spills, mining activities, dumping of waste, overexploitation
 How human actions are changing the Earth
o Population growth- Depleting resources, CO2 emissions
o Pollution
o Depletion of freshwater
o Eutrophication
o Acid deposition
o Greenhouse effect- climate change and global warming
 How to predict consequences on both local and global ecosystems of
specific human activities
o Habitat loss- moving, building, deforestation, overhunting, bringing in
disease, exotic pets, pollution