Concepts In Ecology

Rocco Cieri

Medford High School

Population Ecology

Size of population (N) Density (total number per area) Dispersion (distribution of individuals) Age Structure (abundance of individuals at each

age) Survivorship (mortality of individuals) r-selected – no parental care, lots of offspring, high

death rate K-selected – extensive parental care, few offspring,

low death rate

Population Growth

Exponential– idealized

population in an unlimited environment

Logarithmic– maximum population

size that a particular environment can support (S-curve)

Limiting Factors to Growth

Density-dependent factor– Competition for a shared food resource, water,

sunlight, essential life ingredients, or space – Predation– stress/crowding– waste accumulation

Density-independent factor– weather/climate (droughts, cold snaps)– periodic disturbances

Human Population Growth

How many humans can Earth support?– Consider:

Increases in food supply Reduction in disease Reduction in human wastes (water purification) Expansion of habitat

There is no consensus among scientists as to the carrying capacity of Earth.

Community Ecology

Competitive Exclusion 2 species with similar needs for the same limiting resources cannot coexist in the same place

Resource Partitioning sympatric species consume slightly different foods or use other resources in slightly different

ways Character Displacement (niche shift)

sympatric species tend to diverge in those characteristics that overlap (Darwin’s Finches) Predation

– Kills and eats another animal Symbiosis

Two species that live together in close contact during a portion (or all) of their lives. – Mutualism – both species benefit– Commensalism – one species benefits, other is neither helped nor harmed– Parasitism – one benefits, the other is harmed

Ecological Succession

Ecological succession– transition in species composition over ecological

time Primary

– begun in lifeless area; no soil, perhaps volcanic activity or retreating glacier

Secondary– an existing community has been cleared by some

disturbance that leaves the soil intact

Coevolution

Cryptic (camouflage) coloration

Aposematic (warning) coloration

Mimicry – a superficial resemblance to another species– Batesian

palatable/ harmless species mimics an unpalatable/ harmful model

– Müllerian 2 or more unpalatable, aposematically colored species

resemble each other

Biogeochemical Cycles

Biogeochemical cycles are the movements of matter from one organism to the next and through the environment.

Water– Carbon– Nitrogen– Phosphorus

Matter Recycles

Water Cycle– Transpiration– Evaporation– Precipitation

Carbon– Biological processes of carbon = respiration,

photosynthesis, decomposition– Geochemical processes of carbon = volcanic activity

and storage within earth's crust– Human activities = burning fossil fuels, cutting and/or

burning wood

Matter Recycles (II)

Nitrogen– Nitrogen fixation = when the atmosphere or bacteria take

atmospheric nitrogen and convert it into Ammonia, Nitrates and Nitrites

– Denitrification = when bacteria take nitrates and nitrites and convert them into atmospheric nitrogen

Phosphorus– Phosphorus is essential to living organisms becuase it forms

an important part of DNA, RNA, and ATP.– Phosphorus is released through erosion of rocks and

sediments.– Phosphates (useful phosphorus compounds) are taken in by

organisms in water. Usually it is a Limiting Nutrient, when too much is in water it can be harmful.