Population Ecology

1. organism population community ecosystem biosphere Population Ecology

2. April 26, 2012 • BellRinger Quiz • List at least 3 factors that can affect the size of a population • Objective • Use an interactive model to describe how resource availability can affect population size • Homework • Complete analysis questions and deer handout • Chp 54 notes due tomorrow

3. Life takes place in populations • Population • group of individuals of same species in same area at same time • rely on same resources • interact • interbreed Population Ecology: What factors affect a population?

4. Factors that affect Population Size • Abiotic factors • sunlight & temperature • precipitation / water • soil / nutrients • Biotic factors • other living organisms • prey (food) • competitors • predators, parasites, disease • Intrinsic factors • adaptations

5. 1970 1966 1960 1964 1965 1943 1951 1961 Equator 1958 1937 1956 Immigration from Africa ~1900 1970 Characterizing a Population • Describing a population • population range • pattern of spacing • density • size of population range density

6. Population Range • Geographical limitations • abiotic & biotic factors • temperature, rainfall, food, predators, etc. • habitat adaptations topolar biome adaptations torainforest biome

7. Populations activity

8. April 27, 2012 • BellRinger • Extend your graph from yesterday, make a prediction how the population would grow under ideal circumstances • Objective • describe how resource availability can affect population size • Homework • Chp 55 notes (sec 1-3)

9. Population Size • Changes to population size • adding & removing individuals from a population • birth • death • immigration • emigration

10. Population growth change in population = births – deaths Exponential model (ideal conditions) dN = riN dt growth increasing at constant rate N = # of individuals r = rate of growth ri = intrinsic rate t = time d = rate of change every pair has 4 offspring every pair has 3 offspring intrinsic rate= maximum rate of growth

11. Exponential growth rate • Characteristic of populations without limiting factors • introduced to a new environment or rebounding from a catastrophe Whooping crane coming back from near extinction African elephant protected from hunting

12. Logistic rate of growth • Can populations continue to grow exponentially? Of course not! no natural controls K =carryingcapacity effect of natural controls What happens as N approaches K?

13. 10 8 Number of breeding male fur seals (thousands) 6 4 2 0 1915 1925 1935 1945 Time (years) 500 400 Number of cladocerans (per 200 ml) 300 200 100 0 0 10 20 30 40 50 60 Time (days) Carrying capacity • Maximum population size that environment can support with no degradation of habitat • varies with changes in resources What’s going on with the plankton?

14. Changes in Carrying Capacity • Population cycles • predator – prey interactions At what population level is thecarrying capacity? K K

15. Regulation of population size marking territory= competition • Limiting factors • density dependent • competition: food, mates, nesting sites • predators, parasites, pathogens • density independent • abiotic factors • sunlight (energy) • temperature • rainfall swarming locusts competition for nesting sites

16. Population growth rates • Factors affecting population growth rate • sex ratio • how many females vs. males? • generation time • at what age do females reproduce? • age structure • how females at reproductive age in cohort?

17. Sex Ratio • Graphic representation of life table The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. Belding ground squirrel

18. 1000 Human (type I) Hydra (type II) 100 Survival per thousand Oyster (type III) 10 1 0 25 50 75 100 Percent of maximum life span Survivorship curves What do these graphs tell about survival & strategy of a species? • Generalized strategies I. High death rate in post-reproductive years II. Constant mortality rate throughout life span III. Very high early mortality but the few survivors then live long (stay reproductive)

19. Age structure • Relative number of individuals of each age What do these data imply about population growth in these countries?

20. Trade-offs: survival vs. reproduction • The cost of reproduction • increase reproduction may decrease survival • age at first reproduction • investment per offspring • number of reproductive cycles per lifetime Natural selection favors a life history that maximizes lifetime reproductive success

21. Natural selection for Reproductive strategies • K-selected • Favorable when pops at high density, close to carrying capacity • late reproduction • few offspring • invest a lot in raising offspring • primates • coconut • r-selected • Favorable when pop density is low • early reproduction • many offspring • little parental care • insects • many plants K-selected r-selected

22. Learning Check • How does k-selected and r-selected reproductive strategies relate to the survivorship curves?

23. 1000 Human (type I) Hydra (type II) 100 Survival per thousand Oyster (type III) 10 1 0 25 50 75 100 Percent of maximum life span Life strategies & survivorship curves K-selection r-selection

24. Population of… China: 1.3 billion India: 1.1 billion Significant advances in medicine through science and technology Industrial Revolution Human population growth adding 82 million/year ~ 200,000 per day! What factors have contributed to this exponential growth pattern? 20056 billion Is the human population reachingcarrying capacity? Bubonic plague "Black Death" 1650500 million

25. USA 30.2 Germany 15.6 Brazil 6.4 Indonesia 3.7 Nigeria 3.2 India 2.6 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 Acres Amount of land required to support an individual at standard of living of population Ecological Footprint over-population or over-consumption? uneven distribution: wealthiest 20% of world: 86% consumption of resources 53% of CO2 emissions

26. Ecological Footprint deficit surplus Based on land & water area used to produce allresourceseach country consumes & to absorb allwastesit generates

27. AnyQuestions?