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Ecology (Chapter 9: Population Growth and Population)
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Terms in this set (41)
What is a life table?
can be based on age, size, or life cycle stage
provides summary of how survival and reproductive rates vary with the age of organisms
a summary of AGE SPECIFIC survival probabilities (from one year to the next) and fecundity rates
_______ may determine reproductive rate, not age.
size
important in plants and reptiles, and other species where growth continues throughout life
What is a cohort life table?
follow group of organisms born at same time (cohort) until death
best for
shorter lived sessile organisms
What is a static life table
sample different cohorts during one specific time period
must be able to age individuals or group into stages
better for
long lived or mobile organisms
What is the difference between survivorship and survival?
survivorship
is the proportion of individuals that survive from birth to age x.
survival
is the change that and individual of age x will survive to age x+1
How can survivorship vary among groups?
among populations
between sexes
among cohorts
Know the different types of survivorship curves
When will cohort life tables be identical to static life tables?
if abiotic/biotic environmental factors haven't/ don't change
How can a static life table become more accurate?
assume environment and thus survival/birth rates have remained constant during entire time individuals have been alive
Know how to calculate Ix, Sx, Ro
Ix(Survivorship)=how many of original are alive
Sx( survival probability)= probability it takes to survive from current to age x
Ro(net productive rate)= mean # of offspring produced per female over her lifetime (add up all year [survivorship*fecundity]. If <1 its negative growth rate and vice versa
In a cohort LT, the survivorship probability for 1 yr olds is ____ for 2 yr olds
usually higher, sometimes the same as
can never have lower probability
Know the different age structure graphs
slide 32
What are the two things needed to predict future population size?
1) # surviving to next time period
2) # of newborns the survivors produce in next time period
Know how to calculate how many newborns in the next population
Count survivors and multiply by fecundity
Add all of these up
Know how to calculate proportion in each class
What happens to the proportion in each age class for the 1st few years?
It fluctuates alot for the 1st few years
What is stable age distribution?
proportion in each age class begins to stablize after a few years

proportion
in each age class remains the same from year to year
What is geometric population growth rate (lambda λ)?
rate at which population
size
changes over a period of time
must be greater than 0
if λ is less than 1, N is negative and decreasing
fluctuates but then reaches stable age distribution
can only be used to predict
geometric growth
What are discrete generations?
nonoverlapping
individuals breed at same time (ex. spring)
You collected 3000 beetles on month ago. Since then you recorded 400 births and 150 deaths. What will N be in 6 months from your original starting date
Read ecological toolkit 9.1
shows how changes in agespecific birth/death rates affect pop growth
slide 6 part 2
What is the difference between discrete and continuous population growth?
Also the same as geometric growth VS exponential growth
Why do both discrete and continuous growth have Jshaped curves?
 (change in N individuals) is a
constant proportion
between generations
How do you predict the future size of populations growing exponentially?
r= birth rate (b)  death rate (d)
b= how many births per current individuals
d= how many deaths per current individuals
r is not dimensionless like lambda
Explain how population growth rates (λ and r) affect population size
Herd size = 50 cows
r = 0.365 cows/ (cow*year)
What will the herd size be after 1 year?
If the human population in 1993 was 5.4 billion and the doubling time was estimated to be 50 years.
A. What is r?
B. What is the population size projection for the year 2020?
What factors regulate population growth?
1) densitydependent factors
2) densityindependent factors
What is densitydependent population regulation?
change in population size (N) causes change in birth/death rates
EX) >N = intraspecific competition for resources = <resources/individual
greater densities = lower birth rate, increased death rate, increased emigration
What is densityindependent population regulation?
changes in the environment
alter birth and death rates (and thus lambda or r)
irrespective of the population size
EX) temp, precipitation, natural disasters, abiotic factors
What does logistic growth model?
densitydependent population growth
Population growth rate depends on how close N (number of individuals) is to
K (carrying capacity)
geo/expo growth changes by a
constant
proportion
If N exceeds K, the population growth rate is
negative
When is population growth at the maximum rate?
when N is 1/2 its max
(1/2 of K)
When is population growth increasing?
when N is below 1/2 K
When is population growth decreasing?
when N is above 1/2 K
When is population growth stopped?
when N=K
Logistic growth assumes what?
that resources are constant
but if resource availability changes then K changes too
How do you calculate logistic growth
How do you calculate exponential growth?
What is the difference between lambda and r?
lambda calculates change in population size
r calculates per capita rate of increase (births  deaths)
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