Ecology Test #2 Study Guide
I. Population Ecology
a. What is a population?
i. Individuals of a certain species within a prescribed area. 1. Boundaries may be imposed by geographical limits
(ie. Viable habitat for living) or defined by someone
conducting a study on the population.
i. The study of age or stage based patterns of mortality and reproduction w/in a population
c. Growth of Populations
i. One must understand how a population grows/behaves through the demographic processes of birth, death,
immigration, and emigration to see how viable the Don't forget about the age old question of What are the labels or names used to identify an element?
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population is for the future.
ii. Changes in population can be quantified by the following equation:
1. Nt+1 = Nt (1+b-d+i-e)
a. Nt=population density (# of individuals of the
b. Nt+1= population density one time frame in
c. b=birth rate
d. d=death rate
e. i=immigration rate
f. e=emigration rate
i. (b&I increase the population; d&e We also discuss several other topics like Chlorination is a process of?
decrease the population)
iii. Effects of Births and Deaths on Population Growth
1. Average and Finite Population Growth Rate
a. (Note: system is not affected by resources,
predation, disease, and size; birth and death
rates are constant)
b. Equation: Nt+1=Nt (1+ba-da)
i. ba=average annual death rate
ii. da=average annual birth rate
iii. ra=average annual growth rate (ba-da)
c. Equation: finite growth rate=annual
reproductive rate (geometric scale) or lambda,
i. λ = Nt+1/Nt = 1 + ba - da, or
ii. λ = 1+ ra
d. Understand the Geometric Growth Curve
i. Also, The Instantaneous Per Capita Rate of Increase and the Exponential Growth Model If you want to learn more check out When did computer networks begin allowing computers to talk to each other?
ii. ra = 1 (net gain of 100
iii. gross average growth rate = 100 individuals per year = slope of solid line
iv. x equals the amount of time elapsed between consecutive measurements
v. The per capita instantaneous growth rate, ri, can be obtained by dividing dN/dt by N at a given instant
d N d t
The gross instantaneous growth (dN/dt) = the instantaneous
contribution of each individual to
population growth, ri, multiplied by
the number of individuals in the
iv. Lots of equations and modeling on this test.
Understand how they work and how they apply to
real-life situations and populations.
Calculations of Growth Rate
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r (exponential or
r = binstant – dinstant b = # or births/# of individuals
d=# of deaths/# of individuals
r = ln(λ)
r = ln(Nt+x) –
ln(Nt) / x
λ (geometric or
λ = er
λ = Nt+1/Nt or
d. Effects of Age Structure on Population Growth
i. What is age/stage structure?
1. Proportion of individuals in a population in
different age classes.
a. Populations with significant age
structure is said to have unequal
proportions of individuals among age
classes. Such unequal proportions result
from age-related differences in birth and