Population Ecology

Biotic potential:-maximum possible growth rate for a species-depends on: -age at maturity

-clutch size-how often and how long can

reproduce-how well and how

many offspring survive-never attained in nature!

Why?

Limiting Factors:-space, light, water, food, nutrients, etc.

Density-dependent factors-have an increasing effect as population density

rises

Density-independent factors-population size does not influence effect

Growth Rate: r = births-death

N

Patterns of GrowthExponential -rapid growth

-frequent doubling-results in J curve

*Occurs when: new habitat, new food source, decrease in predators, etc.

Stabilization phase - # deaths = # births -S (sigmoid) curve

*Carrying capacity: max. # of individuals a habitat can sustain

Population cycles -lynx and snowshoe hare

-gypsy moths

r strategists-many offspring small, mature quickly-little or no parental care-often in unpredictable environments- “opportunists”

k strategists-small # of large, slow maturing offspring-lengthy parental care-adapted to stable environments

Interactions between species(community ecology)

Competition “Interspecific competition” – between members of different species; for limited resources

Competitive Exclusion Principle-when 2 species compete for 1 limited resource 1 wins, the other is eliminated-only 1 species per niche

Realized niche

-actual niche

Fundamental niche

-theoretical

-larger

-could be occupied by a species if no competitors present

Predator-PreyComplex, dynamic interactions

Co-evolution: 2 species evolve in response to each other

1. Plant structural defenses -thorns, spines, hairs, silica, sticky substances

2. Secondary compounds in plants-toxic to herbivores-therefore, plants are avoided eg. mustard oils, tannins, nicotine, poison ivy toxin

3. Cryptic coloration

4. Aposematic (warning) coloration

-conspicuous coloration

-predators learn to avoid

5. Mimicry

-1 or more species evolves to

resemble another

Batesian mimicry- unprotected

species mimics protected species

Muellerian mimicry- many

protected species share a color pattern

Symbiosis-Parasitismbotfly video

-Commensalism

which is this?

-Mutualism

Ecosystem DynamicsEnergy – does it cycle? NO! it flows through ecosystems, gradually lost as heat

Matter – (nutrients) do not leave ecosystem, they cycle

Biogeochemical cycles:-water cycle-carbon cycle – CO2 based-phosphorous cycle-nitrogen cycle

-78% of air is N2

but most organisms can not use N2

Biogeochemical cycles (Nitrogen)

3 sources of useable N in ecosystems:

1. lightning - N2 NO3-

2. Decomposition in soil

3. N-fixing bacteria - N2 NH4+

Nitrogen fixation – without it there would be virtually no life!*free living bacteria – in soil*symbiotic bacteria - in root nodules of

legumes

Nitrification – bacteria in soilNH4

+ NO2

–

NO2 -NO 3

- (nitrate)

(plants take in through roots and use)

Dentrification – bacteriaNO3

- N2

*N is often THE limiting factor in ecosystems

Where does each get its N from? (and in what form?)

Animals Plants Bacteria Atmosphere

500 bushels of wheat1 cow

What should they do to survive the longest?

A. Eat the cow and then the wheat

B. Drink the cow’s milk, then eat the wheat

C. Don’t feed the cow but drink the milk, eat the cow when the milk stops, then eat the wheat

D. Feed the wheat to the cow and drink the milk

E. Feed the wheat to the cow, drink the milk, then eat the cow

F. Eat the wheat, then the cow