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?