Characteristics%20of%20Populations - PowerPoint PPT Presentation

About This Presentation
Title:

Characteristics%20of%20Populations

Description:

CHARACTERISTICS of POPULATIONS Habitat: the place where an organism lives Species: organisms that resemble one another in appearance, behaviour, chemistry and genetic ... – PowerPoint PPT presentation

Number of Views:148
Avg rating:3.0/5.0
Slides: 25
Provided by: emma108
Category:

less

Transcript and Presenter's Notes

Title: Characteristics%20of%20Populations


1
Characteristics of Populations
2
CHARACTERISTICS of POPULATIONS
  • Habitat the place where an organism lives
  • Species organisms that resemble one another in
    appearance, behaviour, chemistry and genetic
    makeup and that have the ability to interbreed
    with each other under natural conditions (produce
    viable offspring).

3
  • Population Size the number of individuals of a
    species occupying a given area at a given time
    (ex. 700 Wood ducks in Elevator Bay)
  • What is the population of humans in Canada? In
    Ontario? In Toronto? In this grade 12 biology
    class?

4
POPULATION DENSITY
  • Population Density (D) is calculated by dividing
    the population size or number of individuals (N)
    by the space occupied by that population (S).

D N S
5
Population DensityChina vs. Canada
6
  • Usually smaller organisms have much greater
    population densities than larger organisms. (Ex.
    350 field mice per hectare in Algonquin Park vs.
    0.8 moose per hectare)

7
TYPES of DENSITY
  • Crude Density number of individuals of the same
    species per total unit area or volume.
  • Ecological Density number of individuals of the
    same species per useable unit area or volume.

D N S or useable S
8
Sample Problem
  • If 480 moose live in a 600 hectare section of
    Algonquin Park, what is their crude density?

9
Solution
  • If 480 moose live in a 600 hectare section of
    Algonquin Park, what is their crude density?
  • of moose N 480
  • Area of space 600 ha
  • Crude density N/S
  • 480 moose / 600 ha
  • 0.8 moose / ha
  • Therefore the crude density is 0.8 moose /ha or
    approximately 1 moose/ha.

10
  • What is their ecological density if that section
    of the park includes 800 000 m2 of open water
    which the moose do not use?
  • (1ha 10,000 m2)

11
Solution
  • What is their ecological density if that section
    of the park includes 800 000 m2 of open water
    which the moose do not use? (1ha 10,000 m2)
  • N 480
  • Unuseable Space Area of open water, convert m2
    to ha
  • 800 000 m2 x 1 ha
  • 10 000m2
  • 80 ha of unusable space
  • Useable Space 600 ha 80 ha
  • 520 ha
  • D N/S
  • 480 moose / 520 ha
  • 0.92 moose / ha
  • Therefore the ecological density is 0.92 moose/ha
    or approximately 1 moose/ha.

12
POPULATION DISPERSION
  • Population Dispersion is the pattern in which
    individuals are dispersed throughout a specific
    area. There are 3 general types

13
POPULATION DISPERSION
  • Clumped Dispersion organisms are densely
    populated in areas of the habitat with favourable
    conditions for survival, usually around resources
    (most populations exhibit this...cattails growing
    at the edges of ponds, fish swimming in
    schools...)

14
POPULATION DISPERSION continued...
  • Uniform Dispersion individuals are evenly
    distributed throughout the habitat. Occurs when
    individuals set up territories (ie Penguins).

15
POPULATION DISPERSION continued...
  • Random Dispersion occurs when the habitat is
    particularly uniform and interactions with other
    members of the same species do not affect
    distribution. This is fairly rare in nature,
    ex. some tropical trees.

16
SAMPLING TECHNIQUES
  • It is rare that biologists can take an exact
    count of all the members in a population due to
    the size and/or range over which the population
    lives.
  • Instead biologists count a sample of the
    population and estimate the population size from
    this sample.

17
QUADRAT SAMPLING
  • A common sampling technique for stationary
    populations is quadrat sampling.
  • A quadrat, or sampling frame, is placed in a
    region within the habitat and each member of the
    population of the species in question that
    appears in the frame is counted.

18
  • The more quadrats used the more accurate the
    population density and population size
    measurements.

19
Equations
  • Average sample density total number of
    individuals counted in sample/ total sample area
  • Estimated population size average sample
    density X total size of study area.

ASD sample N sample Area
Estimated N total ASD x total area
20
MARK-RECAPTURE SAMPLING
  • A common sampling technique for mobile or
    dangerous populations is mark-recapture.
  • Biologists trap/tranquilize/catch a number of
    individuals of a population, mark them and then
    release them back into their habitat. A short
    time later they catch a second sample of the
    population and use the ratio of the marked
    recaptures to the unmarked captures to estimate
    the population size.

21
Example
22
MARK-RECAPTURE formula
  • Total marked (M) of recaptures (m)
  • population size (N) 2nd sample size (n)
  • Rearrange to solve for population size
  • N Mn
  • m

M m N n
Solving for
23
  • The marking must not
  • harm the individual,
  • prevent it from going about daily activities or
  • make it more easily caught a second time.

24
  • The accuracy of the mark-recapture method depends
    on certain assumptions
  • every organism in the population has an equal
    chance of being captured,
  • during the time between captures the proportion
    of marked to unmarked remains unchanged,
  • and, the population size does not increase or
    decrease during the sampling study.
Write a Comment
User Comments (0)
About PowerShow.com