BIOL205Ecology Lab 7

Analysis of population

(age structure and rates of population change)

Dr. Erik D. Davenport

Introduction of this lab exercise

This lab exercise is corresponding to the lecture 10 – population dynamics.

Since lecture 10 (population dynamics) includes some difficult concepts and equations, we will first go through a detailed review of these concepts.

Concepts in population dynamics

Life table (we will only talk about cohort life table) survivorship curve

age distribution Birth rate fecundity schedule

– net reproductive rate (R0)– per capita rate of increase (r)– generation time (T).

Life table

life table lists both the survival and the death (or mortality) in the population to describe the survival pattern.

The cohort life table lists the survival and the death a group a individuals that were born at the same time.

Survival Death

Do you need both survivalAnd death columns???

survivorship curve

A survivorship curve summarizes (visualize) the pattern of survival (and death) in a population.

Survivorship curve represents the same thing as a life table, it is just a visualization of a life table.

You need the information in life table to draw survivorship curve!!!!

7Be careful the Y-axis of the curve, it is in log scale!!!!

Survivorship Curves

Type I: Majority of mortality occurs among older individuals. – Dall Sheep

Type II: Constant rate of survival throughout lifetime.– American Robins

Type III: High mortality among young, followed by high survivorship.– Sea Turtles

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Survivorship Curves

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Age Distribution (structure)

Age distribution (structure) of a population gives the information such as how many of the individuals are young, how many are old…

It reflects its history of survival, reproduction, and growth potential.

Don’t get confused for age distribution and survivorship curve!!!!

The difference!!!

Survivorship curve is from life table, all individuals are born at the same time. As the time pass by, the number of individuals decreases because of death.

Age distribution (structure) is a snapshot of the age information of the current population – how many are young, how many in mid age, and how many are old.

So they represent totally different information!!!! Age distribution reflects its history of survival,

reproduction, and growth potential

Age Distribution

Miller published data on age distribution of white oak (Quercus alba).

– Age distribution biased towards young trees.– Sufficient reproduction for replacement.– Stable or growing population

Age Distribution

Rio Grande Cottonwood populations (Populus deltoides wislizenii) are declining.– Old trees not being replaced.

Input the stateName here

Click this link

This is the data you need!

age population

Under 5 years 353,393

5 to 9 years 391,318

10 to 14 years 392,135

15 to 19 years 356,119

20 to 24 years 314,129

25 to 34 years 748,521

35 to 44 years 916,156

45 to 54 years 755,032

55 to 59 years 268,647

60 to 64 years 201,729

65 to 74 years 321,285

75 to 84 years 211,120

85 years and over 66,902

What kind of conclusion you will get from this age distribution?Would you say the populations are stable, declining or dynamic? Explain the reason. (You should give a reasonable and detailed explanation).

Rates of Population Change

Birth Rate: Number of young born per female.

Fecundity Schedule it is a table that lists the birth rates for females of different ages.

So, both life table and Fecundity schedule are tables!!!

Any same column for fecundity schedule and life table?

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life table lists the survival (and death) of a population at different ages.

Fecundity schedule lists the birth at different age. The age column is in both the life table and fecundity

schedule!!! Life table combines with a fecundity schedule can be

used to estimate some important parameters about population dynamics: net reproductive rate (R0) and per capita rate of increase (r), and generation time (T).

– Ro = Net reproductive rate: Average number of offspring produced by a female in a population during its lifetime.

Ro=∑lxmx

– X= Age interval.– lx = % pop. surviving to each age (x).– mx= Average number seeds produced by each

individual in each age category.

Generation time (T): average lifespan for individual in a population.

T = ∑ xlxmx / Ro

Per Capita Rate of Increase (r): normalized population growth rate

r = ln Ro / T

– ln = Base natural logarithms

How get this column??

Survival, from life table Brith, from fecundity schedule