Topic 11 - Population Growth Flashcards
Population
All of the individuals of a given species that live
and reproduce in a particular place
Population size
number of individuals
alive at a particular time in a particular place
What is population size influenced by
births deaths immigration and emigration (we ignore migration)
When does the exponential model of population growth occur
under ideal conditions - assuming unlimited resources
explain the exponential model of population growth
Under ideal conditions
1. per capita growth rate (r) will be at a maximum
2. rmax is always constant and positive
3. rmax varies by species
what is r max
the intrinsic rate of increase
In the exponential growth model, when will the population reach a maximum?
exponential growth curve never reaches a maxima
What factors limit population growth
Temperature, precipitation, predators, disease, food availability, etc
What is carrying capacity (K)
most environments can only support a certain population size
factors that limit population growth combine to determine K
How close the population size is to the carrying capacity can change
as N goes to K, the growth rate will decreases (less resouces/individual available)
In logistic population growth, what is the predicted effect of N on r
As N (population size) increases, r (per capita population growth) decreases
In the logistic model, how does population size change over time
as populations grow, death rates increase, birth rates decrease
r decreases as N increases towards k
What density-dependent factors is population growth influenced by?
Biotic factors - food availability, shelter, mates, predation, disease
What effect do density-dependent factors have on population growth
they have an increasing affect as N becomes large
how do density-dependent factors influence reproduction
as you increase density, reproduction decreases
How does crowding affect growth rate
higher density means slower increase in body mass over time
What do (crowing) density dependent factors influence
growth rate, adult size, survival
How does crowding affect adult size
mass decreases as number of plants increases
how does crowding affect survival
lower density, live longer
What are density-independent factors
abiotic
Temperature
Precipitation
Light
Disturbances (hurricanes, landslides, fires)
Do density independent factors have an affect on any population size?
yes
how do density independent factors influence population growth
population may increase during certain seasons
How does r-strategy influence population growth
Live in environments
with disturbance
* Go through
boom/bust cycles of
population
growth/collapse
* Be individually
smaller in size
* Be early mating
* Stay near the bottom
of the curve
