Ecological Population

Dynamics

Biotic potential

• The maximum number of offspring an

organism can produce is its biotic

potential.

• What keeps organisms from reaching

their full biotic potential?

• Environmental limits (not enough food,

water, shelter or things like disease,

predation). These limits are called

environmental resistance.

Population Growth Models

Exponential model • idealized

• Called “r populations” (J-curve)

Logistic model• realized

• Called “K populations”

(S-curve)

Which one happens most often? Why?

Strategies to increase biotic

potential

• r-selected (opportunistic)

• Short maturation &

lifespan

• Many (smaller)

offspring

• No/little parental care

• High death rate

• EX:?

• K-selected (equilibrial)

• Long maturation &

lifespan

• Few (larger)offspring;

• Extensive parental care

• Low death rate

• EX:?

Population limiting factors-

Environmental resistance!• Density-dependent

factors: • limited food water, shelter •predation • disease

• Density-independent factors •weather/climate

• These factors lead to K*

• (*K=The max number of individuals an area can sustain/Carrying capacity)

• Biotic potential vsEnvironmental resistance! (All life must deal with this)

• Leads to adaptation

More ways to increase success is to

partake in Symbiosis. (2 unrelated

organisms living close together.)

Mutualism

+/+ both species benefit

Commensalism

+/o one species benefits, the other is unaffected

Parasitism

+/- one species benefits, the other is harmed

Neutralism

o/o Neither organism benefits or is hurt

Types of competition:• Intra-specific competition: occurs

among organisms belonging to the

same species.

• Inter-specific competition: occurs

between organisms from different

species (predator-prey)

Competition reduction• Resource partitioning~

species consume slightly

different foods or use other

resources in slightly different

ways (Develop niches)

• Character displacement~

sympatric species tend to

diverge in those

characteristics that overlap

Ex: Anolis lizard sp. perching sites in

the Dominican Republic

Ex: Darwin’s finch beak size on the

Galapagos Islands

Predator/ Prey relationships-

special competition

5 Types of specific coloration

adaptations:

• Aposematic coloration – Stay away color

• Batesian mimicry – copy cat, only 1 bad

• Mullerian mimicry – 2 poisonous resemble

one another

• Camouflage – blend in

• Disruptive coloring – obscures size or shape

of organisms body.

All organisms characteristics

and behaviors lead to

increased survival.

We can measure those

outcomes….

Survivorship curve – plot of numbers that

still alive at each age

• Type 1 –Death

more likely at old

age

Type 2 –Death

equally likely at

all ages

• Type 3 –Death

more likely at

young age

Where would you place k selected and r

selected populations?

Big Changes in the system• Primary

succession- going

from nothing (no

soil)to pioneering

community to

climax

community.

• Why would there

be nothing???

– Melting glaciers

– Volcanic

eruptions

– Landslides

– Strip mines

• Secondary Succession - Re-establish an

ecosystem after a disturbance

• What could be a possible disturbance?

– Flood

– Fire

• Population dispersion refers to how a population is spread in an area. (Density)

Geographic dispersion of a

population shows how individuals

in a population are spaced.

Clumped

dispersion

Uniform

dispersion

Random

dispersion

Random Sampling• Take the area you are

analyzing. Divide it into

equal quadrants.

• Randomly select a specific

number of subdivided

quadrants, count all

organisms in those areas.

• Add up all organisms

counted, divide by # of

quadrants than X by total

quadrants.

• 8/4=2 X16=32

• Actual = 26

• PROBLEMS?

Capture mark-recapture

(Lincoln-Petersen index)

• In a given area, capture a specific number of

organisms, mark them and release them back into

the wild

• Over a set amount of time, recapture a preset

number of organisms and keep track of how many

have already been captured. (They have marks)

• Use math to estimate total population in an area.

• Problems?