1 / 54

Chapter 53 Population Ecology

Chapter 53 Population Ecology. Population Ecology. Study of the factors that affect population size and composition. Individuals of a single species that occupy the same area. Population. Important Characteristics. 1. Density 2. Dispersion. Density.

wesley-stout
Download Presentation

Chapter 53 Population Ecology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 53 Population Ecology

  2. Population Ecology • Study of the factors that affect population size and composition.

  3. Individuals of a single species that occupy the same area. Population

  4. Important Characteristics 1. Density 2. Dispersion

  5. Density • Number of individuals per unit area or volume. • Ex: • Diatoms - 5 million/m3 • Trees - 5,000/km2 • Deer - 4/km2

  6. Dispersion • Pattern of spacing among individuals. • Types: 1. Clumped 2. Uniform 3. Random

  7. Clumped Dispersion • May result form a patchy environment. • May increase chances for survival. • Ex: • Schooling behavior • Flocks of birds

  8. Uniform Dispersion • Often the result of antagonistic interactions between individuals. • Ex: • Territories • Spacing between desert plants

  9. Random Dispersion • Often the result of the absence of strong attractions or repulsions between individuals. • Not a common pattern.

  10. Demography • The study of the vital statistics that affect population size. • Ex: Birth and Death rates

  11. Demographic Factors • Age structure of the population. • Birth and Death rates. • Generation time. • Sex ratio and reproductive behavior.

  12. Life Tables • Mortality summary for a cohort of individuals. • First developed from life insurance studies.

  13. Life Tables Show • Mortality rate per year. • Life span of the organism. • Fecundity (birth rate).

  14. Survivorship Curve • Plot of the numbers of a cohort still alive over time. • Curve Types: • Type I • Type II • Type III

  15. Type I • Low early deaths. • High late deaths. • Ex: • Humans • Other large mammals

  16. Type II • Constant death rate. • Ex: • Annual plants • Many invertebrates

  17. Type III • High early deaths. • Low late deaths. • Ex: • Trees • Oysters

  18. Comment • Curve type may change between young and adults. • Ex: Nestlings - Type III Adult Birds- Type II

  19. Life History Strategies 1. "r" or Opportunistic species 2. "k" or Equilibrial species

  20. "r" Species • Increase fitness by producing as many offspring as possible. • Do this by: • Early maturation • Many reproductive events • Many offspring

  21. Result • Maximize reproduction so that at least a few offspring survive to the next generation. • Most offspring die (Type III curve).

  22. "k" Species • Increase fitness by having most offspring survive. • Do this by: • High parental care • Late maturation • Few reproduction events • Few offspring.

  23. Result • Maximize survivorship of each offspring. • Few offspring, but most survive (Type I curve).

  24. What is the strategy • For a weed? • For an endangered species? • For Garden Pests?

  25. Population Growth • DN/Dt = b - d • Where: • N= population size • t = time • b = birth rate • d = death rate

  26. Rate of Increase • r = difference between birth rate and death rate. • r = b - d

  27. Equation: • DN/Dt = rN • N = population size • t = time • r = rate of increase

  28. From Calculus • The equation DN/Dt = rN becomes: • dN/dt = rmax N • rmax = intrinsic rate of increase

  29. Exponential Growth • dN/dt = rmax N • Characteristic of "r" species. • Produces a “J-shaped” growth curve. • Only holds for ideal conditions and unlimited resources.

  30. Logistic Growth • dN/dt = rmax N K-N K • K = carrying capacity

  31. Result • “S-shaped” growth curve. • Characteristic of “k" species. • Common when resources are limited.

  32. Comment • K is not a constant value. • Populations often oscillate around “K” as the environment changes.

  33. Additional Comments • Populations often overshoot “K”, then drop back to or below “K”. • AP Exam rarely asks you to work the equations, but you should be able to give them.

  34. Regulation of Population Size 1. Density- Dependent Factors 2. Density- Independent Factors

  35. Density-Dependent • Affect is related to N. • As N increases, mortality increases. • Ex: Food, nesting space, disease

  36. Density-Independent • Affect is not related to N. • Mortality not related to population size. • Ex: Weather and climate

  37. Population Cycles • Cyclic changes in N over time. • Often seen in predator/prey cycles. • Ex: Snowshoe Hare - Lynx

  38. Causes • Density dependent factors. • Chemical cycles. • Saturation strategy to confuse predators.

  39. Age Structure Diagrams • Show the percent of a population in different age categories . • Method to get data similar to a Life Table, but at one point in time.

  40. Importances • Can be used to predict future population growth trends, especially for long lived species.

  41. Exponential Growth • Produces age structures that are a triangle or pyramid shape.

More Related