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.