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Population ecology 2014
- 2. AP Biology Why Population Ecology? Scientific goal understanding the factors that influence the size of populations general principles specific cases Practical goal management of populations increase population size endangered species decrease population size pests maintain population size fisheries management maintain & maximize sustained yield
- 3. AP Biology Life takes place in populations Population group of individuals of same species in same area at same time rely on same resources interact interbreed rely on same resources interact interbreed Population Ecology: What factors affect a population?Population Ecology: What factors affect a population?
- 4. AP Biology Abiotic factors sunlight & temperature precipitation / water soil / nutrients Biotic factors other living organisms prey (food) competitors predators, parasites, disease Intrinsic factors adaptations Factors that affect Population Size
- 5. AP Biology Characterizing a Population Describing a population population range pattern of Dispersion Density of population #individuals per unit area 1937 1943 1951 1958 1961 1960 19651964 1966 1970 1970 1956 Immigration from Africa ~1900 Equator range
- 6. AP Biology Population Range Geographical limitations abiotic & biotic factors temperature, rainfall, food, predators, etc. habitat adaptations to polar biome adaptations to polar biome adaptations to rainforest biome adaptations to rainforest biome
- 7. AP Biology Population Dispersion Spacing patterns within a population uniform random clumped Provides insight into the environmental associations & social interactions of individuals in population Provides insight into the environmental associations & social interactions of individuals in population Why uniform? Why clump? Why random?
- 8. AP Biology Population Size Changes to population size can occur by:
- 9. AP Biology 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 #females at reproductive age in cohort?
- 10. AP Biology Life tableLife table Demography Study of a populations vital statistics and how they change over time Life tables, Age Structure Diagrams and Survivorship Graphs Why do teenage boys pay high car insurance rates?Why do teenage boys pay high car insurance rates? females males What adaptations have led to this difference in male vs. female mortality?
- 11. AP Biology Age structure Relative number of individuals of each age What do these data imply about population growth in these countries?
- 12. AP Biology Survivorship curves Graphic representation of life table Belding ground squirrel The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females. The relatively straight lines of the plots indicate relatively constant rates of death; however, males have a lower survival rate overall than females.
- 13. AP Biology Survivorship curves Generalized strategies What do these graphs tell about survival & strategy of a species? What do these graphs tell about survival & strategy of a species? 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand I. High death rate in post-reproductive years I. High death rate in post-reproductive years II. Constant mortality rate throughout life span II. Constant mortality rate throughout life span III. Very high early mortality but the few survivors then live long (stay reproductive) III. Very high early mortality but the few survivors then live long (stay reproductive)
- 14. AP Biology Trade-offs: survival vs. reproduction The cost of reproduction To increase reproduction may decrease survival: (think about…) age at first reproduction investment per offspring number of reproductive cycles per lifetime parents not equally invested offspring mutations Life History determined by costs and benefits of all adaptations. Natural selection favors a life history that maximizes lifetime reproductive success Natural selection favors a life history that maximizes lifetime reproductive success
- 15. AP Biology Reproductive strategies K-selected late reproduction few offspring invest a lot in raising offspring primates coconut r-selected early reproduction many offspring little parental care insects many plants K-selected r-selected
- 16. AP Biology Trade offs Number & size of offspring vs. Survival of offspring or parent Number & size of offspring vs. Survival of offspring or parent r-selected K-selected “Of course, long before you mature, most of you will be eaten.”
- 17. AP Biology Survivorship Curves with Reproductive Strategy 0 25 1000 100 Human (type I) Hydra (type II) Oyster (type III) 10 1 50 Percent of maximum life span 10075 Survivalperthousand K-selection r-selection
- 18. AP Biology Population Growth Rate Models Exponential growth Rapid growth No constraints Logistic growth Environmental constraints Limited growth
- 19. AP Biology Population Growth Math Change in population = Births – Deaths Per capita birth rate = b Per capita death rate = d # of individuals = N Rate of population growth (r) = b – d Survivorship = % surviving Ex: If there are 50 deer in a population, 13 die and 27 are born the next month. What is the population size the following month? (Answer: 27-13 = 14, so new population is 64) Ex: What is the birth rate for the deer? #Births/N = b Answer: 27/50 = .54 Death rate (d) = 13/50 = .26 Ex: What is the rate of growth for the deer? r = .54 -.26 = .28
- 20. AP Biology Exponential Growth (ideal conditions) No environmental barriers Growth is at maximum rate dN/dt = rmaxN N = # individuals Rmax = growth rate
- 21. AP Biology African elephant protected from hunting Whooping crane coming back from near extinction Exponential Growth Characteristic of populations without limiting factors introduced to a new environment or rebounding from a catastrophe
- 22. AP Biology K = carrying capacity K = carrying capacity Logistic rate of growth Can populations continue to grow exponentially? Of course not!Of course not! effect of natural controls effect of natural controls no natural controlsno natural controls What happens as N approaches K?
- 23. AP Biology Logistic Growth Equation dN/dt = rmaxN(K-N)/K K = carrying capacity of population Ex: If a population has a carrying capacity of 900 and the rmax is 1, what is the population growth when the population is 435? 1 x 435 (900-435)/900 = 224 What if the population is at 850? What if it is at 1010? Explain the results of each problem.
- 24. AP Biology 500 400 300 200 100 0 200 10 30 5040 60 Time (days) Numberofcladocerans (per200ml) Maximum population size that environment can support with no degradation of habitat varies with changes in resources Time (years) 1915 1925 1935 1945 10 8 6 4 2 0 Numberofbreedingmale furseals(thousands) Carrying capacity What’s going on with the plankton?
- 25. AP Biology Changes in Carrying Capacity Population cycles predator – prey interactions KK KK
- 26. AP Biology Regulation of population size Limiting factors density dependent competition: food, mates, nesting sites predators, parasites, pathogens density independent abiotic factors sunlight (energy) temperature rainfall swarming locusts marking territory = competition competition for nesting sites
- 27. AP Biology Introduced species Non-native species (INVASIVE) transplanted populations grow exponentially in new area out-compete native species reduce diversity examples African honeybee gypsy moth kudzu gypsy moth
- 28. AP Biology Zebra musselssel ecological & economic damage ~2 months reduces diversity loss of food & nesting sites for animals economic damage reduces diversity loss of food & nesting sites for animals economic damage
- 29. AP Biology Purple loosestrife 19681968 19781978 reduces diversity loss of food & nesting sites for animals reduces diversity loss of food & nesting sites for animals
Notes de l'éditeur
- Within a population’s geographic range, local densities may vary substantially. Variations in local density are among the most important characteristics that a population ecologist might study, since they provide insight into the environmental associations and social interactions of individuals in the population. Environmental differences—even at a local level—contribute to variation in population density; some habitat patches are simply more suitable for a species than are others. Social interactions between members of the population, which may maintain patterns of spacing between individuals, can also contribute to variation in population density.
- A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
- A Type I curve is flat at the start, reflecting low death rates during early and middle life, then drops steeply as death rates increase among older age groups. Humans and many other large mammals that produce few offspring but provide them with good care often exhibit this kind of curve. In contrast, a Type III curve drops sharply at the start, reflecting very high death rates for the young, but then flattens out as death rates decline for those few individuals that have survived to a certain critical age. This type of curve is usually associated with organisms that produce very large numbers of offspring but provide little or no care, such as long–lived plants, many fishes, and marine invertebrates. An oyster, for example, may release millions of eggs, but most offspring die as larvae from predation or other causes. Those few that survive long enough to attach to a suitable substrate and begin growing a hard shell will probably survive for a relatively long time. Type II curves are intermediate, with a constant death rate over the organism’s life span. This kind of survivorship occurs in Belding’s ground squirrels and some other rodents, various invertebrates, some lizards, and some annual plants.
- The J–shaped curve of exponential growth is characteristic of some populations that are introduced into a new or unfilled environment or whose numbers have been drastically reduced by a catastrophic event and are rebounding. The graph illustrates the exponential population growth that occurred in the population of elephants in Kruger National Park, South Africa, after they were protected from hunting. After approximately 60 years of exponential growth, the large number of elephants had caused enough damage to the park vegetation that a collapse in the elephant food supply was likely, leading to an end to population growth through starvation. To protect other species and the park ecosystem before that happened, park managers began limiting the elephant population by using birth control and exporting elephants to other countries.
- Decrease rate of growth as N reaches K