Biology Chapter 4 Population Biology Population Limiting factor

Biology Chapter 4 - Population Biology Population Limiting factor Exponential growth Carrying capacity Life-history patterns Density R strategy K strategy Competition

More Vocabulary • • Stress Crowding Demography Birthrate Deathrate Doubling time Age structure

Population Growth • J Curve • http: //cauchy. math. colostate. edu/Applets/E xponential. Growth/exponentialgrowth. htm • Limits to growth (Limiting Factors y’all) – Biotic and abiotic • Carrying Capacity • Exponential growth • Page 94 growth graph and explaination

More graphing • Add carrying capacity • http: //cauchy. math. colostate. edu/Applets/L ogistic. Growth/logisticgrowth. htm

Life History patterns • Rapid Life history • Slow life history • K reproduction strategy (but intrinsic, not conscious) • R reproduction strategy • http: //www. sumanasinc. com/webcontent/a nimations/content/tradeoffs. html

Population Density Patterns – Random – Clumped – Uniform Limiting Factors • Density-dependent – Disease – Competition • Density-independent – Usually abiotic

Organism interactions • Predation – Graph p 98 • Interspecies competition • Intraspecies competition • Effects of crowding

Addendum • An S shaped curve is logistic growth • This is the more common representation of population growth

Basic Characteristics of Populations • The suitability of habitats influences the geographic distribution of a species. • Insights can be gained by studying the spatial distributions of populations within habitats.

Population Age Structure • Differences in environmental conditions and past history may cause populations to differ in their age distributions. • The future growth of a population depends on its current age distribution.

Density-Independent Population Growth • Simple models describe how idealized populations would grow in an infinite environment. • In these models, populations increase to infinity or decrease to zero. • Continuous Model – Reproduction occurs in the population at all times. • Discrete Model

Density-Dependent Population Growth • In density dependent population growth, the per capita growth rate decreases as the population approaches a carrying capacity. • When population growth rate depends on current population size, the population smoothly approaches carrying capacity.

Dynamics of Lagged Logistic Growth Models • As growth rate increases, populations overshoot carrying capacity (K). • Further increases cause the population to cycle.

Human Population Growth • Human population growth does not currently show density effects that typically characterize natural populations. • In natural populations, per capita population growth rate decreases with population size, whereas global human population growth rate has a positive relationship. • Human population growth rate has been growing more than exponentially. • Limited resources eventually will cause

Density-Dependent and Density. Independent Effects on Populations • In many habitats, the forces that limit population sizes are independent of population density. For example, extreme weather events may decrease populations. • For most species, density-dependent factors limit birth rates or increase death rates at least some of the time. This type of population determination often is referred to as “regulation. ” • Disease outbreaks and starvation are two

r-selected Reproductive Strategy • r-selected Species: – have high reproductive rates – tend to occur in unpredictable environments – typically have type III survivorship curves

K-selected Reproductive Strategy • K-selected Species: – occur near carrying capacity – experience effects of population density – have low reproductive rates, high parental care – have type I survivorship

Populations • Groups of organisms of the same species that live within a given area • Key characteristics: Ostriches are nomadic, wandering in small groups. – Dispersion patterns – Population density – Growth rate Aspen trees are quick to pioneer areas that have been disturbed by fire. Bio. Ed Online

Dispersion Patterns Within Populations Three common patterns of population distribution are: Bio. Ed Online

Population Density • Population density is total population size per unit of area. • Population densities depend on: – Interactions within the environment – Quality of habitat – Density dependent factors – Density independent factors • Carrying capacity is the maximum number of organisms that can be supported in a given habitat. Bio. Ed Online

Population Growth Exponential vs. Logistical Growth Bio. Ed Online

Survivorship in Populations Bio. Ed Online

Reproductive Strategies • r- Selected (maximum growth rate, below carrying capacity) – – Early reproduction Short life span High mortality rate Little or no parental care – Large investment in producing large numbers of offspring – Below carrying capacity Bio. Ed Online • K-Selected (maximizes population size near carrying capacity) – – Late reproduction Long life span Low mortality rate Extensive parental care – Greater investment in maintenance and survival of adults – At or near carrying capacity

Limits on Population Growth • Density Dependent Limits – Food – Water – Shelter – Disease Water and shelter are critical limiting factors in the desert. • Density Independent Limits – Weather – Climate Bio. Ed Online Fire is an example of a Density independent Limiting factor.