Population Ecology Scientists study the dynamics of population, change, and the factors that affect distribution/abundance of organisms

Characteristics of populations  The following characteristics can be used to predict the future dynamics of a population  Population Size  Population Density  Population Distribution  Random, Uniform, Clumped  Age Structure/ Sex Ratios  Birth and Death Rates, Growth rate

Factors that influence population growth  Limiting factors will prevent a population from growing forever  Populations rise sharply at first, but them begin to level off as limiting factors become stronger and stabilizes the population  Take a second to sketch a graph of this type of curve

Demography/Human Populations Demography is studying the statistical changes of human populations Can be used to predict populations and potential environmental impacts of populations

How did we get here?  7B+ humans  Exponential growth  Global growth rate peaked in the 1960’s and has declined since then  Currently grows at 1.2% (this seems small)

Is this a problem?  Food production has balanced rapid growth in recent decades  Can we maintain quality of life for all people?  How do the views of Asian governments differ from those of European governments on this topic?

Studying Human Populations  Population Size  Doesn’t really tell us the entire story, need other factors  Density/distribution of population  Human populations tend to be clumped  Age structure of population  Rates of birth, death, immigration, emigration

Under 15: Pre reproductive stage 15 – 65: Reproductive stage 65: Post reproductive stage

Interpreting age structure diagrams  Interpret the following graphs:

Demographic transitions Life Expectancy change due to living conditions (healthcare, sanitation, food supplies, need for labor) that can be linked to demographic transitions  Pre-industrial stage  High death and birth rates  Relatively stable population  Industrialization  Low death, high birth rates  Industrial Stage  Low death, falling birth rates  Post-Industrial Stage  Low birth and death rates  Population may be impacted by immigration

Demographics are linked to society  Fertility Rates  Total fertility rate: number of children an average woman has in her lifetime, should not fall below 2.1  Empowered woman  Fertility rates drop when woman have access to birth control and education  Population policies  Most countries do not have a firm policy at this point, but encourage reproductive rates at or below 2.1  Poverty  99% of the next billion people will be born in developing nations  More than 82% of people live in developing nations

Demographics are linked to society  Some regions still have increasing death rates  HIV/AIDS  Overwhelming challenges faced by countries including  Losing young and productive members of society to disease  Educating  Wars and conflicts

Birth & Death Rates  Birth (natality) rate = the number of live births in a population over a specific unit of time.

Birth & Death Rates  Death (mortality) rate = the number of deaths in a population over a specific unit of time.

Changes in Populations  Population growth:  If the birth rate is greater than the death rate  Increased Immigration (moving into an area)

Changes in Populations  Population decline:  If the birth rate is less than the death rate  Increased Emigration (moving out of an area )

Survivorship Curves  Shows the proportion of individual likely to survive to each age.

Typical Population Growth Curve Lag phase: Slow population growth

Typical Population Growth Curve Exponential growth phase: accelerated growth birth > death

Typical Population Growth Curve Stable Equilibrium phase: no growth birth = death

Carrying capacity  The max. number of individuals that can be sustained or supported in an area.

Carrying capacity  Not all organisms reach a carrying capacity bc. of limiting factors

Humans Population revisited  Increasing human population growth rate is an increase in medical care  Human population will ultimately reach a carrying capacity and stabilize.

What is our carrying capacity?  Have we reached it?  Warning signs??

Reproductive Strategies  K Strategist  Large organisms  Long-lived  Produce few offspring  Provide substantial parental care

Reproductive Strategies  K Strategist  Usually occupy relatively stable environments.  Reproductive strategy is to invest in a few, quality offspring.  Rely on learning  Elephants, humans, cougar  Lower population growth

Reproductive Strategies  r Strategist  Small organisms  Short-lived  Produce many offspring  Little if any parental care

Reproductive Strategies  r Strategist  Exploit unstable environments.  Reproductive strategy is to produce large numbers of offspring to overcome high mortality.

Reproductive Strategies  r Strategist  Insects, fish, frogs  Short lives  High reproductive rate  Rely on instinct