Chapter 4Chapter 4

Population BiologyPopulation Biology

How do Populations How do Populations Grow???Grow??? Any population, when given Any population, when given

unlimited amounts of resources unlimited amounts of resources will grow will grow exponentiallyexponentially. .

Types of GrowthTypes of Growth

Logistics growth: Flattened S-Logistics growth: Flattened S-shaped curveshaped curve

Exponential Growth: J-shaped Exponential Growth: J-shaped curvecurve

Predator-Prey: Zig-ZagPredator-Prey: Zig-Zag

Exponential GrowthExponential Growth

Begins slowly, then increases rapidly Begins slowly, then increases rapidly over a short amount of time.over a short amount of time.

Logistic Growth CurveLogistic Growth Curve

Begins Begins slowly, then slowly, then grows grows exponentiallexponentially for a time, y for a time, then begins then begins to level out.to level out.

Flattened S Flattened S shapeshape

What Keeps What Keeps Populations under Populations under control???control???

Limiting Factors !!Limiting Factors !!

2-Types2-Types

Density Dependent Density Dependent Limiting FactorsLimiting Factors Factors that have an increasing Factors that have an increasing

effect as the population effect as the population increases.increases.

Ex: Disease, parasites, predators, Ex: Disease, parasites, predators, competition for food…competition for food…

Density Independent Density Independent FactorsFactors Factors that Factors that

affect affect populations populations regardless of regardless of their density. their density. (abiotic)(abiotic)

Ex: hurricanes, Ex: hurricanes, floods, drought, floods, drought, fire…fire…

Predator-Prey RelationshipPredator-Prey Relationship

Predators and their prey experience cycles in Predators and their prey experience cycles in population growth.population growth.

Carrying CapacityCarrying Capacity

The maximum The maximum number of number of individuals an individuals an area can sustain.area can sustain.

The blue dotted The blue dotted line represents line represents the carrying the carrying capacity.capacity.

2-Life History Patterns2-Life History Patterns

1. Rapid1. Rapid 2. Slow2. Slow

Rapid Life HistoryRapid Life History

Small body sizeSmall body size Mature rapidlyMature rapidly Reproduce earlyReproduce early Short life spansShort life spans

Slow Life HistorySlow Life History

Large body sizeLarge body size Mature slowlyMature slowly Reproduce slowlyReproduce slowly Longer life spansLonger life spans

Three patterns of dispersal are Three patterns of dispersal are randomrandom, , clumpedclumped, and , and uniformuniform..

Density factors and population growthDensity factors and population growth

Random Clumped Uniform

Human Population Human Population GrowthGrowth

DemographyDemography: the study of human : the study of human population sizepopulation size, , density and density and

distributiondistribution, , movementmovement, and its , and its birth birth and death ratesand death rates..

Human Population Human Population Growth…Growth…

Age Structure for Age Structure for Human Population Human Population GrowthGrowth

Population Distribution Per Age Range for Several Countries

Stable growth Rapid growth Slow growth

Population (percent of total for each country)

Male

Female

Reproductive years

Age