Population Ecology I Flashcards
Lesson 16
What is a population?
group of individuals of a single species living in the same general area
What is population ecology?
the study of population sin relation to environment, including environmental influences on density and distribution, age structure, and population size.
What is population size and density & what are they influenced by?
Population Size: # of individuals
Population Density: the # of individuals per unit are or volume
Both are influenced by births, deaths, immigration, and emigration
What is demography?
the study of the vital statistics of populations and how they change over time
What are life tables?
age-specific summaries of the survival patterns of populations, summarize some of the vital statistics
How are life tables built?
Determining the number of individuals that die in each age-group and by calculating the proportion of individuals surviving from one age class to the next
What is survivorship?
proportion of newborns (age = 0) surviving to age (x)
What is mortality or death rates?
proportion of individuals of age (x) dying by age (x+1)
What is survival rate?
proportion of individuals alive at age (x) surviving to age (x+1)
What can age structure do?
The relative number of individuals at each in the population predicts a population’s growth trends and can illuminate social conditions
(AP HuG Charts of different countries)
What are two key factors that determine changes in population size (w/o immigration or emigration)?
Survivorship and reproductive rates
What is a survivorship curve?
Age against log survivorship, is a graphic way of representing the data in a life table
* relative constant rate of death
What are the different types of survivorship curves?
Type I: Parental care, few offspring, territoriality, large body size (humans)
Type II: Some parental care, more offspring, smaller body size (Muskrat)
Type III: No parental care, many offspring, very small body size (Mulleks)
What is tracked for reproductive rates?
Only females, key parameters are number of breeding females and age of reproductive females
What is a reproductive table?
age-specific summary of the reproductive rates in a population. Reproductive tables vary between populating and species
What was Thomas Malthus Theory?
Population growth will always outrun the food supply, and there will be a point of crisis
How to calculate the change in population size?
Change in population size = Births + immigrants entering population - Deaths - Emigrants leaving population
How to calculate the per capita increase if immigration and emigration is ignored?
N/t = (B-D)
N= change of population size
t= time interval
B= births
D= deaths
How can births and deaths be expressed as the average number of births and deaths pre individuals during a specific time (annual) interval?
B=bN
D=mN
b is the annual per capita birth rate
m is the annual per capita death rate
N is population size
How can one rewrite the growth equation?
[(Delta N)/ (Delta t)] = (b-m) N
How can the per capita rate of increase (r) be defined?
r= b-m
when r > 0, population grows
when r < 0, population shrink
How can change of population size be written?
(Delta N)/(Delta t) = rN
How can instantaneous growth rate be expressed?
(dN/dT) = r(instantaneous) N
r(instantaneous) is the instantaneous per capita rate of increase
What is exponential population growth?
population increase under idealized conditions. rate of increase is at its maximum
(dN/dT) = r(max) N
What does discrete growth mean?
the factor that a population increase or decrease each year by a constant proportion
What is Lambda?
finite rate of increase,
Lambda = e^r
Lambda = N(t+1)/N(t)
Population grows when lambda >1
Population shrink when lambda <1
What are some assumptions of the Exponential Model?
- birth and death rates are constant over time and resources are abundant
- no age or size structure, and no difference in birth and death rates among individuals
- no emigration/immigration
- no time lags (for continuous model)
- no genetic structure
What is an issue with exponential population growth?
Not sustainable, eventually will outrun resources
How to know whether to use the continuous or discrete model?
If there are overlapping generations, must use continuous model
What is the equation for continuous growth?
N(t) = N(0) * e^rt
where t is in years
What is equation for discrete growth?
N(t) = (lambda^t) * N(0)
where t is in generations
Where might the exponential model apply?
apply in cases where limits to growth do not exist or have been removed, such as in the lab or an invasive species
