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Mon. Tues. Wed. Thurs. Fri.Week ofOct. 20

Week ofOct. 27

Independent project set-up

Week ofNov. 3

Forest ecology lab – dress for weather

Exam 2T lab switch?

Week ofNov. 10

Independent project analysis

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What do we measure?

Total population size = number of indivduals

How they are arranged in space

How many are in each age or size class

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Figure 13.5

There is a simple statistical test to test for distribution

Mechanisms?

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What do we measure?

Total population size = number of indivduals

How they are arranged in space

How many are in each age or size class

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Outline

Introduction

How are populations defined and measured?

How do populations grow?

How does population size change through time and space?

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Growth = births – deaths + immigration – emigration

When calculating growth rate, usually just seeing change in numbers over time

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Populations grow by multiplication ratherthan by addition

Just like interest in the bank

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Figure 14.3

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Exponential growth

-new individuals are added (born) to population continuously

r = per capita growth rate = contribution of each individual in population

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dN/dt = rN

Rate at which individuals are added = growth

rate on a per individual basis x population size

= derivative of exponential equation

= slope of line

Exponential growth

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Figure 14.4

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Exponential vs. Geometric Growth

Exponential – continuous reproduction- growth is smooth curve

Geometric – discrete breeding seasons- calculate growth at discrete

intervals

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Geometric growth

Growth rate = = population size at one time point/ size

at previous time point

N (t+1) = N(t)

N(t) = N(0) t

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Geometric growth: N(t) = N(0) t

Exponential growth: N(t) = N(0) ert

= er

Ln = r

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Figure 14.5

Exponential

Per capita growth rate = constantRate of increase= dN/dt, increases with N

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Figure 14.6

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Age structure (# of individuals in each age class) of a population affects

population growth

Why??

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Figure 14.8

Stable Fast growth

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Age structure of a population affects population growth

Life table = a summary by age of the survivorship and fecundity of individuals in a population

Shows differences in birth and death rate for different parts of population

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21

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Table 14.3

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Figure 14.7

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Stable age distribution – the proportion of individuals in various age classes in a population that has been growing at a constant rate

- only happens if age-specific birth and death rates are constant over time

- each age class grows at same rate

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What parameters affect growth rate?

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More common to see this patternWhat’s going on?

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Some metric of population sizeSo

me

fact

or

that

aff

ects

gro

wth

rat

eDensity dependence

Lots of examples in bookCommon in nature

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Figure 14.19

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Some metric of population sizeSo

me

fact

or

that

aff

ects

gro

wth

rat

eDensity independence

Very few examples in bookCommon in nature

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Figure 14.27

Population Size

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r = ro(1-N/K)

r = intrinsic growth rate at small N x the

reduction in growth rate due to crowding

K = carrying capacity of population

Logistic growth

R changes as N changes such that

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dN/dt = roN (1-N/K)

Change in N with time = intrinsic growth rate at

small N x population size x the reduction in

growth rate due to crowding

Logistic growth

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Figure 14.17

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Figure 14.16

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If I give you an equation and a value for K and/orr or , I expect that you can sketch the graph.

I expect that you will understand what the terms in the equations mean.

I expect that you understand the assumptions of each model and the differences between them.

I expect that you know what is in a life table and what parameters affect growth rate and what a life table can be used for.