Ecology

1. Ecology Part 4. Populations Part 5. Communities Part 6. 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 • Put your pens down for a minute & 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 What population do you think this is? What letter does this curve resemble?

9. The USCB estimates that the world population exceeded 7 billion on March 12, 2012

10. Population growth models • Exponential growth model • Also calledgeometric 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?

11. Population Limiting Factors • 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)

12. 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 http://en.wikipedia.org/wiki/Overpopulation Carrying Capacity (k) What letter does this curve kind of look like?

13. Population Limiting Factors • 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)

14. 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

16. r and K strategists • A logistic equation can describe the self-limiting growth of a biological population. • where r is the maximum growth rate of the population (N), and K is the carrying capacity of its local environmental setting, d stands for derivative, and t for time. In r/K selection theory, selective pressures drive evolution in one of two generalized directions: r- or K-selection

17. r and K strategists • Traits that are thought to be characteristic of r-selection include: • high fecundity • small body size • early maturity onset • short generation time • ability to disperse offspring widely • Traits that are thought to be characteristic of K-selection include: large body size • long life expectancy • production of fewer offspring • extensive parental care until they mature Evolved to take advantage in unstable environment, density independent Evolved to take advantage in stable environment, densitydependent interactions

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

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

20. Community Ecology: Communities Communities • Range of Tolerance • The limits within which an organism can exist. Think: Effects of global warming/climate change?

21. 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

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

23. 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

24. Community Ecology: Ecological Succession: Primary 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.

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

26. 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.

27. 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.

28. 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.

29. 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

30. 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.

31. Biodiversity and Conservation: Introduction • 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?

32. 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

33. 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

34. 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. • Ex: 250 MYA: Over90% of species died

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

36. 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)