Keystone
Ecology Review
Levels of Organization
• Ecosystem—biotic &
abiotic
• Community—all biotic
factors
• Pollution—only one
group (species) of
organisms
Comparing Biotic and Abiotic Factors
Biotic—all living or once living organisms
Abiotic—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 Cycle
Photosynthesis & 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 Succession
Occurs where the land has not supported any prior life, bare
rock, newly formed islands (soil lacks nutrients or any life left
behind)
Secondary Succession
Occurs 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