Ecology

1. Examine factors such as carrying capacity, fecundity, density and predation that can cause fluctuations in populations. Determine through computer simulations the characteristics of population growth of two different populations (looking at the predator prey cycles. Ecology

2. REVIEW 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

3. 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.

4. 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

5. Determine whether the following are density independent or density dependent factors: A flash flood destroys a field of corn A puffin cannot find a nesting site because of nesting seagulls A tomato plant is killed by an early frost A deer population is prey for a wolf family West Nile Virus spread faster in the crows in Southern Ontario Passenger pigeons are extinct because their numbers dropped below 50,000 birds Painted turtles often dig up the nests of other painted turtles. Density Independent Density Dependent Density Independent Density Dependent Density Dependent Density Dependent Density Dependent

6. Density dependent factors: A: Competition – Interspecific vs intraspecific Interspecific = Between different species Intra specific= Between the same species As the population density increases, there is more competition so that growth rate slows. B: Predation Keeps the population numbers down since predators often select the: Weaker Slower Younger Survival of the fittest

7. Density dependent factors: C. Disease Pathogens spread more easily when populations are overcrowded D. The Allee Effect (named after Warder Allee) When populations are below a critical level they cannot bounce back • Because limited reproductive potential • Usually with low fecundity (reproductive potential)

8. 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?

9. 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?

10. 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?

11. 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)

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

13. 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?

14. 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)

15. 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. Sinusoidal patter can result from seasonal changes or predator /prey relationships also

17. Predator prey relationships Introduction – what does a typical predator-prey cycle look like? What factors does it depend on?

18. http://www.sims.scienceinstruction.org/predprey/index.html (start around 5,1,8) In our first model the following factors were important: Predator birth rate Predator aggression Predator dependency. In this model carrying capacity could be reached for both populations. “Predator dependency” reflected alternative resourses for the predator in the ecosystem. Predator aggression, birthrate and dependency could be directly affected by….. Competition in the ecosystem. Both intra and interspecies competition.

19. http://www.leinweb.com/snackbar/wator/ Ecosystem size would also be relevant to the dynamics of predator/prey cycles. http://www.xjtek.com/anylogic/demo_models/12/ Ecosystem health and distribution of resources can also be directly affected by A single species….

20. Summary from our simulations on predator/prey relationships • Predator prey relationships can result in cyclic populations. The nature of these are dependent upon: • Birth rate (of predator and prey) • Predator aggression • Predator dependency (availability of other resources) • Intra and interspecies competition • Habitat size • . The elephant simulation demonstrated that : An individual species can have an large overall effect on the distribution of resources for other species. Who is the elephant in the room??

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

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

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

24. 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

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

26. 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

27. 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. Why did the fungus marry the Algae? They took a Lichen to each other!!

28. 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

29. 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.

30. 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.

31. 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.

32. 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

33. 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.

35. Biodiversity and Conservation: Introduction FOOD WEB • 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?

36. 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

37. 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

38. 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

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

40. 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)