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 Populations Population – group of the same Species 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 the population size exceeds the 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 will have less resources to share AND 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 when a population exceeds its carrying capacity. Why?

OUR PLANET Unit 1-4b Human 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 that continues to increase each year Demographers predict a world population of 8 billion by 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 – Percentage of a population that are expected to survive to the next 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 countries have a fertility rate less than 3. Yet an average women in Africa may have as many 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 lifespan has increased from 40 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 rates decrease 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 other organisms grow exponentially? 2. Describe the age structure for the people living in your home. 3. List one factor that affects women’s fertility rates. 4. What factors have allowed our life expectancy to increase? 5. Because our population is stable, at which stage is the U.S. in demographic transition?