Population Growth And Limits Flashcards
Grew as humans expanded into new territories, grew over 1 million years
Pre-agricultural period
Increased food production and improved sanitation, nutrition, and medical care
Population grew rapidly within 3 centuries
Industrial period
Stimulated population growth
Population grew more rapidly over 7,000 yrs
Agricultural period
When were European starlings introduced to the USA
1890
What changes a population?
Birth, immigration, emigration, and death
How to find change in population?
N=B+I-D-E
What is used for populations with continuous reproduction and/or overlapping generations
Exponential (logistic) growth
What is used for populations with reproduction occurring at discrete intervals
Geometric growth
Formula for rate of change in population
dN/dt = rN
(N is the number of people in the population)
What is “r”
The growth rate ( difference between births and deaths
What happens when all the resources are done?
The population cannot increase, it must fall.
What happens as GPD increases
The birth rate decreases
What does higher birthrate among women do?
It shortens generation time.
What does higher birth rates among younger women lead to?
Shortened generation time
More children growing and reproducing
higher population growth rates.
If we know about specific survival and fecundity what can we project?
Age structure and population size
A group of people in the same age class is a what?
Cohort
What does a life table do?
Summarizes age specific schedules of survival and fecundity ( age, #alive, probability of survival between age classes, mortality rate, and fecundity)
Exponential model of growth assumptions
- essential resources are unlimited
- environment is constant
Can populations increase forever?
No
The number of individuals that the environment can indefinitely support
(K) aka carrying capacity
Carrying capacity formula
dN/dT=rN (1- N/K)
What does (1- N/K) do?
It reduces population growth as size approaches carrying capacity
Can the population exceed carrying capacity?
Yes, but humans don’t know what K is.
What would happen?
The resources would decrease and the population would have too as well.
What factors control population size?
Density dependent factors and density independent factors.
Factors that influence population growth in accordance with population size
Density dependent factors
Factors that affect population regardless of population size
Density independent factors
What are density dependent factors ?
-Resource availability
- competition
- disease
What are density independent factors?
-temperature
- precipitation
- catastrophic disturbances
Tendency of a population to decrease in size when above “K” and increase in size when below that is what?
Regulation
Is regulation density dependent?
Yes
What can populations only be regulated by?
Density dependent factors
