1 / 29

POPULATION ECOLOGY

POPULATION ECOLOGY. Chapter 53. Density and Dispersion. What is the density of a population? The number of individuals per unit area What are the three patterns of dispersion?. Clumped. Clumped dispersion has population occurring in patches

aggie
Download Presentation

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. POPULATION ECOLOGY Chapter 53

  2. Density and Dispersion • What is the density of a population? • The number of individuals per unit area • What are the three patterns of dispersion?

  3. Clumped • Clumped dispersion has population occurring in patches • Increased concentration of resources leads to clumping • Defense against predators • e.g. schools of fish, sea stars grouping together where food is abundant

  4. Uniform • Even spacing of individuals within the population • Diminishes competition • Often seen with plants, they secrete chemicals that prevent germination and growth of individuals that may compete for resources. • King penguins exhibit uniform spacing due to aggressive interactions between neighbors

  5. Random • Spacing is varied and unpredictable • Occurs in the absence of strong attraction (concentrated resources) or strong repulsion (avoidance of competition) between individuals. • Dandelions grow where seeds randomly land

  6. Estimating Population Size • Mark re-capture method. • You capture 200 grasshoppers, mark them all and then release them back into the wild. A few days later you capture 100 grasshoppers and 50 of them were marked. How many grasshoppers do you estimate are in this population? • N = # marked x total captured second time number marked recaptures • 200 x 100/50 = 400

  7. Demography • What is demography? • Study of vital statistics that affects population size

  8. Survivorship Curves • What is a survivorship curve? • Plot of the numbers of a cohort that are alive at each age. • Survivorship curves are generally classified into three types

  9. Characteristics of The Three Types Seen in Survivorship Curves: • Type I : Low death rate in early years. • Small clutch sizes and good care for young • Type II: constant mortality throughout life • Type III: large clutch size, little care for young high mortality rate early on in life.

  10. Life Histories • What is the life history of an organism? • Traits that affect time of reproduction and death. 1. Clutch size 2. Number of reproductive episodes per lifetime 3. Age at first reproduction

  11. Birds with high probability of dying have larger clutch sizes

  12. Number of reproductive episodes: • Large clutch sizes mean one reproductive episode per life. • Small clutch sizes means more than one reproductive episode • Age at first reproduction is younger in large clutch size reproducers, they invest less energy in their own growth and development.

  13. Exponential Growth • J shaped curve • Unlimited population growth, due to unlimited resources. • r selected populations favor the exponential growth curve. Seen in areas with little competition • Opportunistic species display this pattern, grasses, insects… • But all populations eventually have a limit placed on their growth...

  14. Logistic Growth • Limiting factors will affect the size of a population • K = carrying capacity, never changes

  15. Examples of logistic growth K selected species - likely to be living at carrying capacity, seen in areas with competition

  16. r selected • short maturation time • short life-span • high death rate • many offspring/reproduction • one reproductive event • reproduces early in life • small size to offspring • no parental care K selected • long maturation time • long lifespan • low death rate • few offspring/reproduction • several reproductive episodes • reproduces later in life • large sized offspring • parental care for young

  17. Population Limiting Factors • Density dependent factors • Intensifies as population grows • Density independent factors • Affects same number of individuals regardless of population size. • A predator is which sort of limiting factor? • Density dependent • A hurricane is which sort of limiting factor? • Density independent

  18. What sort of limiting factor is seen here?

  19. Density dependent!

  20. What sort of limiting factor is seen here?

  21. Density independent

  22. Usually more than 1 limiting factor is at work

  23. Fluctuations in sheep population due to weather Cold, wet winters weakens sheep and decreases food availability leading to a decrease in the size of the population

  24. Moose population collapse coincided with a peak in the wolf population from 1975-1980 Second moose population collapse in 1995 coincided with harsh winter weather which increased the energy needs of the animals and made it harder for the moose to find food

  25. Describe the population shifts of snowshoe hare and lynx

  26. Human Population • Global population is still growing but the rate of growth is slowing down • Age structures - relative numbers of individuals at each age. Used to tell if a population is increasing, decreasing or staying the same • birthrate, death rate, generation time and sex ratios, all affect interpretation of age structures

More Related