Ecology

1. Ecology Populations Communities Biodiversity and Conservation

2. Population Ecology: Population Characteristics Population Characteristics • Population Density: • The number of organisms per unit area • Spatial Distribution: • Dispersion: The pattern of spacing a population within an area • 3 main types of dispersion • Clumped • Uniform • Random • The primary cause of dispersion is resource availability

3. Population Ecology: Population Characteristics Population Limiting Factors • Population growth rate • How fast a given population grows • Factors that influence this are: • Natality (____ rate) • Mortality (_____ rate) • Emigration (the number of individuals moving _________ a population) • Immigration (the number of individuals _________ a population) birth death away from moving to

4. Population Ecology: Density-independent factors Population Limiting Factors • Density-independent factors • Factors that limit population size, regardless of population density. • These are usually abiotic factors • They include natural phenomena, such as weather events • Drought, flooding, extreme heat or cold, tornadoes, hurricanes, fires, etc.

5. Population Ecology: Density-dependent factors Population Limiting Factors • Density-dependent factors • Any factor in the environment that depends on the number of members in a population per unit area • Usually biotic factors • These include • Predation • Disease • Parasites • Competition

6. Understanding Exponentials Population Ecology: Population Growth Rate • Think about this: • An employer offers you two equal jobs for one hour each day for fourteen days. • The first pays $10 an hour. • The second pays only 1 cent a day, but the rate doubles each day. • Which job will you accept?

7. Population Ecology: Population Growth Rate Understanding Exponentials Now, how much would your employer owe you if you stayed at this job for another 2 weeks? Job 2 lags for a long time before exponential growth kicks in! What would happen if this type of growth took place within a population?

8. Population Ecology: Population Growth Rate Population Limiting Factors • Population growth models • Exponential growth model • Also called geometric growth or J-shaped growth. • First growth phase is slow and called the lag phase • Second growth phase is rapid and called the exponential growth phase • Bacteria can grow at this rate, so why aren’t we up to our ears in bacterial cells?

9. Population Limiting Factors Population Ecology: Population Growth Rate • Population growth models • Limits to exponential growth • Population Density (the number of individuals per unit of land area or water volume) increases as well • Competition follows as nutrients and resources are used up • The limit to population size that a particular environment can support is called carrying capacity (k)

10. Population Ecology: Population Growth Rate What population do you think this is?

11. So, what do you think is going to happen to the human population? • We will probably reach our carrying capacity. • Our growth rate will start to look like most organisms, which is the Logistic Growth Model Carrying Capacity (k) What letter does this curve kind-of look like?

12. Population Limiting Factors Population Ecology: Population Growth Models • Population growth models • Logistic Growth Model • Often called the S-shaped growth curve • Occurs when a population’s growth slows or stops following exponential growth. • Growth stops at the population’s carrying capacity • Populations stop increasing when: • Birth rate is less than death rate(Birth rate < Death rate) • Emigration exceeds Immigration (Emigration > Immigration)

13. Population Limiting Factors Population Ecology: Population Growth Models • Population growth models • Logistic Growth Model The S-curve is not as pretty as the image looks • Carrying capacity can be raised or lowered. How? Example 1: Artificial fertilizers have raised k Example 2: Decreased habitat can lower k • Populations don’t reach k as smoothly as in the logistic graph. • Boom-and-Bust Cycles • Predator-Prey Cycles

14. Community Ecology: Communities Communities • Review: • A community is a group of interacting populations that occupy the same area at the same time.

15. Community Ecology: Communities Communities • Limiting Factors • Any abiotic or biotic factor that restricts the numbers, reproduction, or distribution of organisms.

16. Community Ecology: Communities Communities • Range of Tolerance • The limits within which an organism can exist.

17. Community Ecology: Ecological Succession Ecological Succession • Ecological Succession • The change in an ecosystem that happens when one community replaces another as a result of changing biotic and abiotic factors

18. Community Ecology: Ecological Succession Ecological Succession • Ecological Succession • Consists of 2 types: • Primary Succession • Secondary Succession

19. Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The establishment of a community in an area of exposed rock that does not have topsoil is called Primary Succession. • It occurs very slowly at first

20. Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The first organisms to arrive are usually lichens or mosses, which are called pioneer species. • They secrete acids that can break down rock • Their dead, decaying organic materials, along with bits of sediment from the rock make up soil.

21. Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • Small weedy plants and other organisms become established. • As these organisms die, additional soil is created

22. Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • Seeds brought in by animals, water and wind begin to grow in the soil. • Eventually enough soil is present for shrubs and trees to grow.

23. Community Ecology: Ecological Succession: Primary Succession Ecological Succession • Ecological Succession: Primary • The stable, mature community that eventually develops from bare rock is called a climax community.

24. Community Ecology: Ecological Succession: Secondary Succession Ecological Succession • Ecological Succession: Secondary • Disturbances (fire, flood, windstorms) can disrupt a community. • After a disturbance, new species of plants and animals might occupy the habitat.

25. Community Ecology: Ecological Succession: Secondary Succession Ecological Succession • Ecological Succession: Secondary • Pioneer species in secondary succession are usually plants that begin to grow in the disturbed area. • This is much fasterthan primarysuccession

26. Community Ecology: Ecological Succession Ecological Succession • Ecological Succession: End point? • Cannot be predicted • Different rates of growth &human involvementmake it impossible toknow if a true climaxcommunity has beenreached.

27. Biodiversity and Conservation: Introduction On the left side of your IntNB, address the following: • What would happen if all of the jackrabbits in a food web died suddenly? • Is the disappearance of one species from Earth important, or will another species fill its niche?

28. Biodiversity and Conservation: What is biodiversity? Biodiversity • What is Biodiversity? The variety of life in an area that is determined by the number of different species in that area. • There are 2 main types: Genetic Diversity Species Diversity

29. Biodiversity and Conservation: Why is biodiversity important? Biodiversity Penicillin: Derived from bread mold Teosinte: A distant relative of corn Domestic corn plant Madagascar Periwinkle: Used to treat childhood forms of leukemia

30. Biodiversity and Conservation: Extinctions Extinction Rates • The gradual process of becoming extinct is known as background extinction. • Mass extinctions: When a large percentage of all living species become extinct in a relatively short period of time. • 250 MYA: Over90% of species died

31. Biodiversity and Conservation: Extinctions Estimated number of Extinctions since 1600

32. Biodiversity and Conservation: Extinctions Five Most Recent Mass Extinctions Cretaceous Period (65 MYA) Triassic Period (200 MYA) Permian Period (250 MYA) Devonian Period (360 MYA) Ordovician Period (444 MYA)

33. Activity: Understanding Geological Time • Working in your groups, you will get the following supplies: • A meter stick • A roll of 5 meters of paper • Colored pencils • Using the worksheet, plot out the dates. • 1 million years is a millimeter • 1 billion years is a meter