Chapter 10 Population Dynamics
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Transcript of Chapter 10 Population Dynamics
![Page 1: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/1.jpg)
Chapter 10 Population Dynamics
![Page 2: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/2.jpg)
Estimating Patterns of Survival• Three main ways of estimating patterns of survival within a
population:
– Identify a large number of individuals that are born about the same time (=cohort) and keep records of them from birth to death ---> cohort life table
– Record the age at death of a large number of individuals ---> static life table
– Determine patterns of survival for the population from the age distribution
![Page 3: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/3.jpg)
Static Life Tables and Survivorship Curves
Plotting number of survivors against age produces a survivorship curve
Example: Survival pattern of Dall sheep
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Types of Survivorship Curves
Type I Survivorship Curve
• A pattern in which most of the individuals of the population survive to maturity• Or, most individuals of the population do not die until they reach some genetically programmed uniform age
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Types of Survivorship Curves cont.
Type II Survivorship Curve
• Relatively constant death rates with age • Equal probability that an individual will die at any particular age
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Types of Survivorship Curves cont.
Type III Survivorship Curve
• A pattern in which their is an extremely steep juvenile mortality and a relatively high survivorship afterward• Most offspring die before they reach reproductive age
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Age Distribution
• Age distribution can tell you a lot about a population – periods of successful reproduction; periods of high and low survival; whether older individuals are being replaced; whether a population is growing, declining, etc.
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Age Distribution and Stable Populations
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Age Distribution and Declining Populations
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A Dynamic Population in a Variable Climate
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Rates of Population Change: Combining a Cohort Life Table
with a Fecundity Schedule • Fecundity schedule - the tabulation of birth rates (the number
of young born per female per unit time) for females of different ages in a population
• By combining the information in a fecundity schedule with data from a life table, we can estimate several important characteristics of a population
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Example: A Population with Discrete Generations• nx, the number of individuals in the
population surviving to each age interval
• lx, survivorship, the proportion of the population surviving to each age x
• mx,average number of progeny produced by each individual in each age interval
• lx mx, the product of l and m
• Net reproductive rate, R0
R0 = lx mx
• To calculate the number of progeny produced by a population in a given time interval, multiply R0 by the initial number of individuals in the population.
Example: 2.4177 x 996 plants = 2408
![Page 13: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/13.jpg)
Geometric Rate of Increase • The ratio of population increase at two points in time:
= Nt+1
n– Where, Nt+1 is the size of the population at a later time, and Nt is the size
of the population at an earlier time
Example:
= 2408 = 2.4177 996
![Page 14: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/14.jpg)
More on net reproductive rate:
• R0 is an indication of the expected number of female offspring which a newly born female will produce during her life span
• It’s an indication of whether a female replaces herself in the population
– R < 1, the population will decline
– R = 1, the population will remain constant
– R > 1, population will increase (more offspring produced than needed to replace the female)
![Page 15: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/15.jpg)
Mean Generation Time (T)
T = [∑ (x lx mx ] / Ro
where x is age
Example from the common mud turtle:
These turtles have an average generation time of 10.6 years:
= 6.4/0.601 = 10.6
![Page 16: Chapter 10 Population Dynamics](https://reader033.fdocuments.in/reader033/viewer/2022051315/56812c32550346895d90b57d/html5/thumbnails/16.jpg)
per capita rate of increase (r)
r = ln Ro / T
Turtle example:
r = ln (0.601) / 10.6
r = -0.05