Honors Honors BiologyBiology Ch. 4 Ch. 4

PopulationPopulationBiologyBiology

ChCh.. 44 PopulationPopulation

BiologyBiologyChCh.. 44 PopulationPopulation

BiologyBiologyI.I. Population DynamicsPopulation Dynamics

Constant Population: Birth rate = Death rate

Biotic Potential vs.Environmental

Resistance

Biotic Potential vs.Environmental

Resistance

A. Biotic Potential vs. Environmental Resistance

A. Biotic Potential vs. Environmental Resistance

1.1. Biotic Potential:Biotic Potential:- factors that increase

population level

a.Birth rate:a.Birth rate:- number of births, eggs laid,

seeds or sporesb.b.Recruitment:Recruitment:

- becoming part of breeding

pop. - Salmon: high birth rate, low

recruitment - Humans: low birth rate, high

recruitment

Short vs. Long Life History

Short vs. Long Life History

c. Migrationc. Migration

d.d. Adaptibility, Defense, Adaptibility, Defense, ResistanceResistance- if all conditions arefavorable, a populationexplosion (rare) could occur

a.a.Abiotic factors:Abiotic factors:- temperature, water, fire, etc.

b.b.Biotic factors:Biotic factors:- predators, parasites, disease, food- constantly readjusting(dynamic)

2.Environmental Resistance:

2.Environmental Resistance:

3.Exponential Growth

3.Exponential Growth

3.Exponential Growth

3.Exponential Growth- population growth pattern

showing an increasing growth rate

- can result in a population explosion

3.3. Exponential Exponential GrowthGrowth3.3. Exponential Exponential GrowthGrowth

(i) Reproductive Age 4(ii) Reproductive Age 6

4.Carrying Capacity4.Carrying Capacity

(biotic(bioticpotential)potential)

Carrying CapacityCarrying Capacity

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TimeTime

ExponentialExponentialGrowthGrowth

EquilibriumEquilibrium

(environmental resistance)(environmental resistance)

4.Carrying Capacity4.Carrying Capacity- the number of organisms of

a species that a particular habitat can support

Boom-and-bust Population Boom-and-bust Population CycleCycle

Conditions good: Boom; Conditions bad: Bust

Annual lake algal bloom

Effects of Exceeding Carrying Effects of Exceeding Carrying CapacityCapacity

1911 - 25 reindeer introduced

1938 - 2000 reindeer

1950 - 8 reindeer survived

St. Paul Island, Pribilof, Alaska

Lemming Population Lemming Population CyclesCycles

5.5. Density Dependent Density Dependent Factors:Factors:- environmental resistance

increases as population increases- predators, disease, parasites,

competition

6.6.Density Independent Density Independent Factors:Factors:- drought, fire, tsunami,

floods, volcanoes, salinity- affect a population

regardless of its density

B.B.Mechanisms of Mechanisms of Population BalancePopulation Balance1. Predator/Prey

- lynx vs.hare- lynx vs.hare

2.2. Host/Parasite:Host/Parasite:- similar- more common- provides more stability

2.Host/Parasite: weevil vs. wasp

3. Principle of Ecosystem Stability:

- Species diversity provides ecosystem stability

- Species diversity provides ecosystem stability

- Natural enemies provide balance- Evolved together- Introduced species create imbalances

3.Principle of Ecosystem Stability:

3.Principle of Ecosystem Stability:

- Species diversity provides ecosystem stability

- Natural enemies provide

balance- Evolved together- Introduced species create

imbalances

II. Human Population Growth

II. Human Population Growth

A. Human Population Explosion

A.A.Human Population Human Population ExplosionExplosion

A. Human Population Explosion

A. Human Population Explosion- started around 1830- 1 billion added every 12 years- How many can the biosphere support?

B. DemographyB. Demography

- the study of human population growth

Pop. Growth Rates:Developed & Developing Countries

DevelopingDevelopingCountriesCountries

Developed CountriesDeveloped Countries

Age-Structure DiagramsAge-Structure Diagrams

Post-ReproductivePost-Reproductive(46-100 y old)(46-100 y old)

Reproductive(15-45 y old)

Pre-Reproductive(0-14 y old)

ExpandingExpanding StableStable ContractingContracting

Age Structures Developed Country

Age Structures Developing Country

The The EndEnd