1 / 15

Population properties What is a population?

Population properties What is a population?. Distribution and Range. distribution geographic range – total extent (red maple) to N, -40 degrees C limit it to W, dry conditions limit it to S, ocean and wetlands limit it. Distribution patterns different at different scales

hea
Download Presentation

Population properties What is a population?

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 properties What is a population?

  2. Distribution and Range • distribution • geographic range – total extent (red maple) • to N, -40 degrees C limit it • to W, dry conditions limit it • to S, ocean and wetlands limit it

  3. Distribution patterns different at different scales • Moss (Tetraphissp.) • Microhabitat : • temperature • humidity • pH • stream banks with conifer stumps in one area provide these

  4. Abundance = total number of individuals in a population, no. red dots • Density = number of individuals per unit area • Spatial distributions, and causes

  5. Uniform, desert shrubs; Clumped, caterpillars patterns may indicate important ecological processes how and why hypotheses generated

  6. Estimating population size. • Population size (number of individuals) • 2 components: • density, the number of individuals per unit area • areaoccupied • Density  area occupied = population size.

  7. Measuring density • A total count may be possible: • if individuals can be distinctively marked • larger endangered species • For sessile organisms, local density may be determined in plots, then extrapolated to entire area occupied.

  8. Mark-Recapture Method • Mark-recapture - used with animal populations: • initial sample, mark individuals • Release marked animals, allowed to mix • second sample, tally marked and unmarked ones

  9. Computations • M = initial marked sample • n = size of second sample • x = number of marked animals in second sample • What is N (population size): N (Est. popln. size) = nM/x • M = 20 fish are captured, marked, and returned • n = 50 (x = 5 marked fish) • .

  10. Populations have age structure

  11. Aging organisms

  12. Most species have a dispersal stage • Sponges planula larvae • Corals, jellyfish ciliated larvae • parasitic flatworms ciliated larvae • clams veligers • barnacles small larvae • plants wind-dispersed seeds • plants animal dispersed fruits • Passive versus active/directed dispersal

  13. Why disperse? • Reduce competition from parents, siblings • Find more food, other needed resources • Locate needed microclimate • emigration – moving out of a subpopulation • immigration – moving into a subpopulation • these movements affect population sizes and gene flows • (gene flow homogenizes gene pools) • Risks of dispersal • unknowns of new area, increased predation

  14. Migration • a round-trip • May be local or global • Zooplankton, through a water column • Some invertebrates, mammals and birds migrate • Zooplankton daily migrate in water column, light • Earthworms overwinter deep in soil to avoid frost • Caribou migrate to arctic tundra winter, lichens • Waterfowl and shorebirds • migrate to rich northern breeding grounds, food • Conservation issues and migration • one species may need habitats in 3 different countries!

  15. Distributions and density change over space and time – e.g., European gypsy moth

More Related