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DEMOGRAPHY

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Title: PowerPoint Presentation Author: Jennifer Templeton Last modified by: jtemplet Created Date: 11/3/2011 11:46:45 PM Document presentation format – PowerPoint PPT presentation

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Title: DEMOGRAPHY


1
DEMOGRAPHY
The study of birth and death processes that
determine growth and age structure of a
population.
2
Each age class of a population has an expected
Mortality rate
Fecundity rate
3
Demographic characteristics can be represented in
  • Life Tables
  • summarize deaths and/or births
  • in different age classes of a population
  1. Conventional life table

4
Cactus
5
Demographic characteristics can be represented in
  • Life Tables
  • summarize deaths and/or births
  • in different age classes of a population
  1. Conventional life table
  2. Diagrammatic life table (flow diagram)

6
Diagrammatic Life Table
in each age class
Fecundity
Probability of survival
(Assumes 50-50 sex ratio)
7
2) Survivorship Curves
1,000
I
100
II
Number of survivors (log scale)
10
III
1
0
50
100
Percentage of maximum life span
Fig. 53-6
8
Imagine that a species of fish used to be a
broadcast spawner (producing many eggs that then
get no subsequent parental care) but has evolved
to be a mouth brooder (holding the eggs in the
parents mouth until they hatch and then caring
for the young for a while). We would expect the
survivorship curve of this species to shift
  • A) from Type I to Type II or III.
  • B) from Type II to Type I.
  • C) from Type III to Type I or II.
  • D) from Type II to Type III.
  • E) The survivorship type would vary unpredictably.

9
POPULATION DENSITY
10
Population Dynamics
11
Population Density (Abundance) of individuals
of the same species that occur in a given area.
Knowing the population density of a particular
species is important for conservation and
management decisions.
12
White Abalone
13
Bald Eagles
14
White-tailed deer
15
Density Estimation (Sampling) Techniques
  1. Census (direct counts)
  2. Indirect counts
  3. Sample plots or transects
  4. Mark-recapture

16
  • Mark-recapture Technique
  • capture and mark several, then release all
  • soon after, capture more, SOME of which
  • have marks (recaptured)

17
Reasoning Proportion of 2nd capture that
are recaptured individuals represents
the proportion marked in entire population...
R/C M/N
M caught and Marked in first trapping session
C Caught in second trapping session
R marked individuals Recaptured
N estimated Number in entire population
18
R/C M/N
So, N M / (R/C)
N (M x C) / R
19
Assumptions of mark-recapture technique
  • closed population (no immigration or emigration)
  • no births or deaths (in sampling period)
  • marked and unmarked individuals
  • equally likely to be caught in second trapping
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