Keystone

Ecology Review

Levels of Organization

• Ecosystem—biotic & abiotic

• Community—all biotic factors

• Pollution—only one group (species) of organisms

Comparing Biotic and Abiotic FactorsBiotic—all living or once living organismsAbiotic—all non living factors

Food Chain in an Antarctic Ecosystem• A food chain shows ONE possible feeding pathway.• The arrow always goes into the mouth of the eater

Food Web in an Antarctic Ecosystem• A food web shows all possible feeding relationships in a

ecosystem

Energy Transfer Through Trophic Levels• Only 10% of energy from each level is available to be

passed on to the next level. • Most of it gets used or lost as heat. That’s why more

organisms on bottom than top

Energy Pyramid

Symbiosis—close, long term relationship b/w to organisms (at least one benefits

Parasitism, mutualism, commensalism

Parasitism

The parasite benefits while the host is hurt

Mutualism

• Both organisms benefit

Commensalism• One benefits while the other is neither hurt nor

helped

Recycling Matter through the Ecosystem

Water Cycle

• Key processes are– Evaporation– Transpiration– Precipitation

Carbon CyclePhotosynthesis & Respiration are the two main steps

Nitrogen Cycle• Nitrogen fixing bacteria change nitrogen gas into a useable

form for nitrogen for plants (& then animals) • Denitrification puts nitrogen gas back into the atmosphere

Phosphorus Cycle

Phosphorous moves from phosphate deposited in rocks , to the soil, to living organisms and finally to the ocean

Succession—gradual sequential regrowth of a community of a species in a area

Two Types:Primary

Secondary

Primary SuccessionOccurs where the land has not supported any prior life, bare rock, newly formed islands (soil lacks nutrients or any life left behind)

Secondary SuccessionOccurs where soil has previously existed and some life is still left behind.

Ecological Succession at Glacier Bay

• Carrying capacity— number of individuals the environment can sustain

• Limiting factor— any factor the restrains the growth of a population (space, sunlight, food, water, mates)

Carrying Capacity of Reindeer in Pribilof Islands