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Population Parameters - Ecology - Lecture Notes, Study notes of Ecology and Environment

National Institute of Industrial EngineeringEcology and Environment

Population Parameters, Particular Geographic Area, Age Distributions, Sampling Populations, Estimate of Population Size, Lincoln-Peterson Index, Demography Vital Statistics are the key points of lecture notes of Ecology.

Typology: Study notes

2012/2013

Uploaded on 01/02/2013

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Ecology 1
Population Parameters
I. What is a population?
A. A group of individuals of one species that live in a particular geographic area within a specific
period of time.
1. All populations share several characteristics.
a) Dispersion (distribution)
b) Density.
c) Age distributions
d) Birth rates
e) Death rates
B. Sampling populations.
1. Mark and recapture.
a. Simplest estimate of population size (Lincoln-Peterson Index):
N = # marked # in 2 nd sample
# recaptured marks
b. Example: catch, mark and release 50. Second sample contains 100, with 10 marked.
c. Estimated population size is
N = 50 100
10 = 500
.
II. Demography – vital statistics.
A. Primary population parameters.
1. Births, b.Deaths,c. Immigration, Emigration.
2. Summation of these four processes results in changes in population size.
B. Introduction to Life Tables.
1. There are 3 types of life tables.
a. Survivorship directly observed – this is a cohort life table. This is where a large cohort –
all born at the same time- are followed throughout their lives.
b. Age at death observed – this is a static life table and represents the type of data that you
will collect for your cemetery demography lab.
c. Age structure directly observed. This method involves determining the ages of the living
members of a population. Also produces a static life table.
• Examining the annular rings on fish scales or
• Coring trees and counting the number of tree rings.
2. Major assumptions of developing and using a static life table is that the population is stable. (a
stationary age distribution).
• it is neither growing or declining,
• it is not receiving new members from outside nor is it losing members.
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Ecology 1

Population Parameters

I. What is a population? A. A group of individuals of one species that live in a particular geographic area within a specific period of time.

  1. All populations share several characteristics. a) Dispersion (distribution) b) Density. c) Age distributions d) Birth rates e) Death rates

B. Sampling populations.

  1. Mark and recapture. a. Simplest estimate of population size (Lincoln-Peterson Index): N =

marked # in 2 nd sample

recaptured marks

b. Example: catch, mark and release 50. Second sample contains 100, with 10 marked.

c. Estimated population size is

N (^) =

50 100 10 = 500 . II. Demography – vital statistics. A. Primary population parameters_._

  1. Births, b.Deaths,c. Immigration, Emigration.
  2. Summation of these four processes results in changes in population size. B. Introduction to Life Tables.
  3. There are 3 types of life tables. a. Survivorship directly observed – this is a cohort life table. This is where a large cohort – all born at the same time- are followed throughout their lives. b. Age at death observed – this is a static life table and represents the type of data that you will collect for your cemetery demography lab. c. Age structure directly observed. This method involves determining the ages of the living members of a population. Also produces a static life table.
  • Examining the annular rings on fish scales or
  • Coring trees and counting the number of tree rings.
  1. Major assumptions of developing and using a static life table is that the population is stable. (a stationary age distribution).
  • it is neither growing or declining,
  • it is not receiving new members from outside nor is it losing members.

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C. Parts of a Life Table.

  1. Life table summarizes the mortality and fecundity of a population. a. The columns in a life table are just different ways of summarizing the same thing: how mortality varies with age over a time period that corresponds to the maximum lifespan.
  2. ( x ) is the age interval or age class.
  3. ( nx ) is the number of survivors at the beginning of age interval x.
  4. ( lx ) is the proportion of organisms surviving to the beginning of the age interval x.
  5. ( dx ) is the number dying between the age interval x and the beginning of age interval x + 1.
  6. ( qx ) is the rate of mortality between the age interval x and the beginning of age interval x + 1.
  7. ( ex ) is the average life expectancy of an individual at age x.

D. Survivorship Curves.

  1. Survivorship curves are plotted logarithmically on the y-axis for two reasons: a. A very tall graph is avoided (Y-axis doesn’t go to a 1,000, or more.) b. The numbers surviving are expressed in constant proportions. i. Constant proportion means that a flat line indicates no mortality. ii. Rates of mortality can be compared among populations of different sizes.

Data from a population in which half the population dies each year.

Year Starting population No. Dying Final Population 0 1000 500 500 1 500 250 250 2 250 125 125

Log(1000) – log (500) = log (500) – log (250) 3.00 - 2.70 = 2.70 - 2.40 = 0.

  1. There are three general types of survivorship. a. Type I: Organisms that usually live out their physiological. Environmental factors not as important as genetic factors affecting lifespan. b. Type III: Organisms that have high mortality rates early in life. Usually from high predation, and inexperience in foraging, or lack of disease resistance. c. Type II curve is linear; typical of organisms with a constant mortality rate. Mortality is associated with environment since mortality rate is equal among all size classes.
  2. Much variation in survivorship curves is dependent upon the environment – even humans.
  3. Survivorship curves most important value is their theoretical use. They help explain the actual patterns of survivorship that are measured in populations.

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