Warm Up to……Ecology

Using Pa forests provide an example/describe of * Species•Population•Community•Ecosystem•What might be limiting factors for this species?•What does carrying capacity mean?•Explain diff between density dependent and density independent limiting factors

What to Do?

• You are a population ecologist studying white-tailed deer populations in your state.Populations have been growing exponentially for some time and food is becoming a limiting factor. Many deer are dying of starvation, and others are in bad health. What do you recommend to state officials? Should people intervene and try to limit through hunting or relocation? Let the population regulate itself? Why

Understanding Understanding PopulationsPopulations

Population – group of the sameSpecies that live and interact in t

the same region.

What influences Population Growth Rates?

Population Growth Rate determined by 4 Factors:

•Birth Rate Natality #/1000

•Death Rate Mortality #/1000

•Immigration Incoming individuals

•Emigration Outgoing individuals

•Migration – seasonal movement

•Growth Rate

Measures changes in population size;

Births – Deaths = Growth Rate

Reproductive Strategies

Reproductive (Biotic) Potential – The maximum number of offspring that a population can produce in ideal conditions.

Influencing factors:

Gestation time – pregnancy period

Generation time – time to reach

sexual maturity

Number of offspring born

Two evolutionary strategies:K-strategists r- strategists

r- Strategists

• Small organism

• Many offspring

• Little to no care of offspring

• Live in unstable environments

• Early maturity

• Short life expectancy

• Ex. Insects, bacteria

K-strategists

• Larger organism

• Few offspring

• Later sexual maturity, often prolonged care by parents

• Long life expectancy

• Often reproduce more than once

• Ex. Elephants

Populations Can’t Grow Forever

How does the environment affect a population?

Carrying Capacity – The maximum population that the environment can support for a long period of time

What happens when thepopulation size exceedsthe carrying capacity?

The carrying capacity is generally set by a…Limiting Factor – A resource needed by a population whose availability limits its continual growth; Ex. food, water mates, sunlight

What are the limiting factors of a deer population?

Limiting Factors

• Characteristics of the environment that limit population growth.

Can be biotic or abiotic..

The number and type of limiting factors in the environment determine a population’s carrying capacity.

Limiting Factors

.

Density Dependent – High population density increases competition for resources such as food, water, mates

Factors influence changes with

population density – more

crowded population willhave less resources to shareAND attracts more predators

Limiting Factors

Density Independent –Factors that affect population size but are not affected by population density.Ex: Natural disasters & Extreme weather

Let’s Review…What have you learned in this unit?

1.Are humans r or K strategists?

2.Are stink bugs r or K strategists?

3.Is starvation density dependent

4.Is disease density dependent

5.Is a flood density dependent

6.Is mating success density dep.

7. Describe what happens whena population exceeds its carryingcapacity. Why?

OUR PLANETOUR PLANET

Unit 1-4bUnit 1-4b

Human PopulationsHuman Populations

Human History

Demography – The study of human populations

The history of our human population was fairly stable until the 1800s when humans experienced…

Exponential Growth –A growth rate thatcontinues to increaseeach year

Demographerspredict a worldpopulation of 8 billionby the year 2025.

Forecasting Populations

Four factors affect population predictions…

1.Age Structure – The distribution of age in a population

• Countries with high growth rates have more young people than old people…why?

• Countries with slow

growth rates have even

distribution of ages

Which country has the highest growth rate? Lowest?

Forecasting Populations

• 2. Survivorship – Percentageof a population that areexpected to survive to thenext age level

– Type 1: Humans (offspring cared for immensely, long life span)

– Type 2: Rodents (equal chance of death throughout lifespan)

– Type 3:Sea Turtles (lots of offspring, most of which don’t survive)

Which curve would humans in developed countries follow?What about developing countries?

Forecasting Populations

3. Fertility Rates – The number of babies born per 1,000 women. It’s an average.

Most countrieshave a fertilityrate less than 3.

Yet an averagewomen in Africamay have asmany as 6 kids.

What would the fertility rate be if it was replacement level?

4. Migration – Immigration & emigration between countries

Which has increased in developed countries, immigration or emigration rates?

The End Of Death?

Recently, life expectancies (the average age a person dies) has increased dramatically due to…

• Medicine

• More Food

• Clean Water

• Safe Waste Disposal

The average lifespanhas increased from40 years to over 80 years for many developed countries.

More successful births and less deaths = larger population

How Long Can This Continue?

Do these graphs look similar?

Where have we seen the graph on the right before?

What is the carrying capacity for our human population?

10 Billion people???

But Human Populations Are Different!

Demographic Transition – A model that describes the four stages of human populations

Stage 1 Population is low;Birth & death rates are high

Stage 2 Because of education,Births stabilize and death ratesdecrease as the population grows

Stage 3 Large population;Low birth and death rates

Stage 4 Population begins to decrease

So Maybe There’s Hope

If developed countries can spread education and wealth across the globe, there’s a chance we’ll

be just fine

Let’s Review…What have you learned in this unit?

1. Besides people, what otherorganisms grow exponentially?

2. Describe the age structurefor the people living in your home.

3. List one factor that affectswomen’s fertility rates.

4. What factors have allowedour life expectancy to increase?

5. Because our population isstable, at which stage is the U.S.in demographic transition?