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Ecosystems- Part 2 -

Habitable Planet Unit 4CIS Environmental Studies

PLHS SiteD. Blanck, M.S.

Population

Population:individuals of aspecies that livetogether andnaturallyreproduce.

Population Features

# of individuals in apop. is its size.

# of individuals livingin an area is thedensity.

The arrangement ofindividuals in a pop. isits dispersion.

Population Features

Population Growth

Populations growexponentially.

Population anenvironment cansustain is itscarryingcapacity.(K)

Population Growth

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Population Growth Models

Growth Rate (akaReproductive Rate) R = birthrate - deathrate

Exponential*

Population GrowthFormula Nt = Rt•N0

* Logistical Growth is limitedby the Carrying Capacity (K)

Growth Pyramids

Population Control

Density dependentfactors Food Water

Population Control

Densityindependent factorsinclude Rainfall Temperature

Life History Strategy

An organism'sallocation of energythroughout itslifetime amongthree competinggoals: growing,surviving, andreproducing.

Life History Strategies

Rapid populationgrowth in goodconditions (r-selected)

Slow growth (K-selected)

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Lemmings as an r-selected species

The lemming is the smallest mammal in the Arctic. It is a main source of foodfor predators such as owls. Lemming populations rise and fall dramatically,peaking about every 4 yrs and then dropping to near extinction.

Wolves as a K-selected species

Hunted to near extinction acrossthe northern hemisphere, therange of the Timber or Gray Wolfis now Canada, MN, WI and theUP. Wolves are also found inIdaho and have been successfullyre-introduced in Yellowstone NP.

Yellowstone Wolf Video

Symbiosis

Parasitism

A long termrelationship betweentwo species

One organism feedson (and usuallylives in or on)another. The hostis harmed.

Mutualism

Commensalism

Both species benefit

One organismbenefits. The otheris neither helped norharmed

Niche/Habitat

A niche is the“role” that a speciesplays in theircommunity.

A habitat is theplace where anorganism lives outits life.

Keystone Species

A species thatoccupies a vitalecological niche.

Eg: black-tailedprairie dogs impactthe prairieecosystem inmultiple ways:

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Their burrows act as homes to othercreatures, including burrowing owls, badgers,rabbits, black-footed ferrets, snakes,salamanders, and insects.

Their burrowing activity works to loosen andchurn up the soil, increasing its ability tosustain plant life.

Their foraging and feeding practices enable amore nutritious, diverse and nitrogen-richmixture of grasses and forbs (broad-leafedvegetation) to grow, in turn attracting anamazing array of wildlife.

Black-tailed prairie dogs play an integralrole in the prairie food chain; they are acritical food source for such animals as theendangered black-footed ferret, swift fox,coyotes, hawks, eagles and badgers.

Fundamental and Realized Niches

Fundamental niche: the full range ofenvironmental conditions (biotic andabiotic) under which an organism couldexist.

Realized niche: the ecological role anorganism plays when constrained by thepresence of other competing species.

Competitive exclusion principle

If twocompetitors tryto occupy thesame niche, onespecies will bemore successfuland exclude theother.

Succession

Predictableprogression ofspeciesreplacement.

Primary: NewHabitat

Secondary:Disturbed Habitat

Forest Succession

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Lake Succession

Small “kettle” lakeswill naturallytransition fromOligotrophic toEutrophic andeventually to boggymeadows over time