Card Set Information
What is a population?
All the individuals of a species that interact with one another within a given area at a particular time
Why have humans been interested in understanding species abundance?
To increase populations of species that provide resources and food and to conserve species for ethical and aesthetic reasons and to decrease the abundance of crop pests, pathogens, etc.
What is population density?
Number of individuals per unit area or volume
What is population size?
The total number of individuals in a population
What is a geographic range?
The region in which a species is found
What is a habitat?
The specific environments within a range a species is restricted to.
What are habitat patches?
'islands' of suitable habitat separated by areas of unsuitable habitat.
Population densities are dynamic. What does this mean?
That they change over time
Finish the statement populations are ____ in space and ____ over time
Population size changes over time. What does it depend on?
The births and deaths over a given time.
What is the formula for the BD model?
N(t+1) = N(t) + B D
What is a limiting factor to population growth?
Availability of resources
How is the population change over time estimated?
Delta N = N(t-1) - N = B-D
What is the per capita birth rate? (b)
The number of offpring an average individual produces
What is the per capita death rate? (d)
The average individual's CHANCE of dying
What is the per capita growth rate?
Average individual's contribution to tal population growth rate.
What is the FORMULA for per capita growth rate. R?
R = b - d, therefore, DN/DT = rN
If b > d, what does this say about population and r?
R > 0 and population grows
If b < d, what happens to r and population?
R < 0 and population shrinks.
If b = d, what happens to r and population?
r= 0 and population doesnt change
Wht is life history?
It refers to the time course of growth and development, reproduction, and death during an average individual's life.
Finish the statement: life histories are ____ descriptions of _____
Quantitative; life cycles
What is a life table?
It shows ages at which individuals make life cycle transitions and how many individuals do so successfully
What kind of information do life tables provide?
Survivorship, and fecundity
What is survivorship?
A fraction of individuals that survive from birth to different life stages or ages
What is fecundity?
The average number of offspring each individual produces at those stages or ages.
What do individual organisms need to survive?
Materials and energy (resources) and physical conditions they can tolerate
How does the rate at which an organism can acquire resources change?
It increases with the availability of the resource
What is the principle of allocation?
A principle that states that once an organism has acquired a unit of some resource, it can be used for only one function at a time: maintenance, foraging, growth, defense, or reproduction.
How are resources allocated when the individual is under stressful conditions?
They go to maintaining homeostasis before anything else; once it has more than it needs for maintenance, it can allocate the rest to other functions
What happens when the average individuals in a population acquire more resources?
Average fecundity, survivorship, and per capita growth rate increase
What is a life-history tradeoff?
Negative relationships among growth, reproduction and survival
Why would life history tradeoffs be necessary?
If there are high mortality rates.
What aspect of species reflect the effects of environment on per capita growth rates?
Population growth is multiplicative. What does this mean?
An larger number of individuals is added in each successive time period
What is additive growth?
When a constant number (not a constant mutiple) is added each time period.
What drive natural selection and adaptation?
The ecological struggle for existence which is fueled by multiplicative growth
Multiplicative growth has a constant doubling time: what does this mean?
Time it takes a population to double in size
How can doubling time be calculated?
It can be calculated if r is known
Do populations grow multiplicatively for long?
No, their growth slows and reaches a steady size
R is density dependent. What does this mean?
That r decreases at the population becomes more crowded.
What happens to birth and death rates as population grows and becomes more crowded?
The birth rates tend to decrease and death rates increase
What happens to population size when r=0?
It stops changing, the population reaches carrying capacity
What is carrying capacity (K)?
The equilibrium size
What is something that can lead to variation of the carrying capacity?
Spatial variation in environmental factors; i.e. temporal variation
How has technology influenced carrying capacity?
It has raised it by increasing food production and improving health
Who pointed out that human population grows multiplicatively?
What did Thomas Malthus say about the food supply growth?
It grows additively; he predicted that shortages would limit population growth.
Why is it believed that humans have overshot the carrying capacity?
Technological advances depend on fossil fuels which is a finite resource & the global climate and ecosystem is degrading because of the 20th century population expansion.
The population is thought to have exceeded its carrying capacity. What could happen and how can it be fixed?
The population will decrease. And it can be fixed by reducing the per capita birth rate
What are metapopulations?
Regional populations that live in habitat patches where individuals are moving in and out
What does the BIDE model of population growth do?
Adds the number of immigrants (I) and the number of Emigrants (E) to the BD growth model: N(t+1) = Nt + B + I D E
What happens if a small subpopulation in a habitat patch is too vulnerable and goes through too many disturbances?
It can go extinct.
What can subpopulations do if dispersal is possible?
They can recolonize
How do conservation plans begin?
By taking inventories of habitats and potential risks to the habitat; largest patches having higher priority
What are the second and third steps to conserve a patch?
Quality (carrying capacity) is evaluated and then they develop ways to restore or maintain the quality.
Sometimes, a corridor is needed for some species. What does a corridor do?
It connects subpopulations and allows dispersal
What are some examples of corridors?
Vegetation along roads, fences or streams, building bridges or underpasses that allow individuals to avoid roads.