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Ecological Relationships
ECOLOGY
▸ Community= Interactions between species
Review
▸ Abiotic vs. biotic factors
▸ Habitat vs. niche
INTERSPECIFIC INTERACTIONS
▸ Parasitism +/-
▸ Mutualism +/+
▸ Commensalism +/0
▸ Predation +/-
▸ Competition +/-
▸ Herbivory +/-
▸ Facilitation +/+ or +/0
COMPETITIVE EXCLUSION PRINCIPLE
▸ No two organisms can occupy the exact same niche
▸ The two will compete and one will either change, move or die
P. CAUDATUM VS. P. AURELIA
RESOURCE PARTITIONING
▸ Allows similar species to coexist in same community
▸ Differentiates the niche
▸ Can be done with space or time
Ecological Adaptations
CRYPTIC COLORATION▸ Camouflage
▸ Makes prey tough to see
APOSEMATIC COLORATION
▸ Bright warning coloration
▸ Often exhibited by animals with chemical defense
MIMICRY
▸ Batesian
▸ One harmless organism resembles another “bad”
▸ Mullarian
▸ 2 or more harmful organisms resemble each other
▸ “Safety in numbers”
Ecological Stability
SPECIES DIVERSITY
▸ Variety of organisms in community
▸ Includes species richness= number of different species and relative abundance= proportion of each species in whole community
▸ Impacted by disturbances
▸ Greater diversity usually means more stability
ECOLOGICAL FITNESS
▸ Ability of an organism to reproduce and pass its genes on to the next generation
**Evolution!
▸ More viable offspring = greater fitness
▸ In theory, all energy is directed toward increasing fitness
ECOLOGICAL FITNESS
Energy in Ecosystems
Biomass: Stored organic matter ‣ Created through photosynthesis
‣ Solar energy creates chemical compounds (sugars)
‣ Autotrophs only organisms able to add biomass to ecosystem
REVIEW
ENERGY TRANSFER
▸ Gross Primary Production (GPP)
▸ Total amount of photosynthesis (or chemo-)
▸ Total amount of sugar produced = carbon fixed
▸ Remember- some of this is used, not all stored
ENERGY TRANSFER
▸ Net Primary Production (NPP)
▸ Total photosynthesis minus CR (by autotrophs)
▸ What’s left after autotrophs use some for own survival
▸ What’s available to consumers in the ecosystem
Energetic hypothesis: Length of food chain limited by inefficiency of energy transfer
Dynamic stability hypothesis: Long food chains are less stable. Population fluctuations at lower levels greatly affect higher levels.
ENERGETIC HYPOTHESIS VS. DYNAMIC STABILITY HYPOTHESIS
▸ Possible explanations for size of food chains
TEXT
OPTIMAL FORAGING THEORY
▸ How do animals “know” how to spend their time?
▸ Risk vs. reward
▸ Amount of food taken in will be in proportion to the amount of energy spent
▸ What is the relationship to fitness?
Impacts on Ecosystems
IMPORTANT SPECIES
▸ Keystone
▸ Not numerous
▸ Play critical role
▸ Dominant
▸ Most numerous or highest biomass
GREAT LAKES KEYSTONE SPECIES
BIOMAGNIFICATION/BIOACCUMULATION
▸ Amplification of toxins through a food chain
▸ Caused when toxins are fat-soluble, but not water soluble
‣ Non-native species introduced to an area
‣ Exponential growth—> no natural predators
‣ Great lakes —> brought through ballast water
INVASIVE SPECIES
QUESTION
▸ What is the purpose of the goldenrod gall?
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