ENVS Quiz 2 lecture 4
B.I.D.E.
(Births + Immigration) = (Deaths + Emigration)
population equilibrium equation
(Births + Immigration) = (Deaths + Emigration)
characteristics of k-strategists
- high energy per offspring - lower biotic potential - high recruitment - long lived - mature slowly - slow production - logistic population growth - live in stable environments
characteristics of r-strategists
- low energy used per offspring - high biotic potential - low recruitment - short life span/ mature quickly - rapid reproduction - short life span - opportunistic - exponentially growing population
factors hypothesized to decrease recruitment
- pollution - habitat alterations - predation - pathogens
if a population falls below its critical number
- surviving members become more vulnerable - breeding fails - extinction is almost inevitable
ecologists use population growth curves to determine:
1. how fast a population could grow 2. the population size now and in the future
K
Carrying Capacity
K-strategists survivorship
Type I
Population growth
a change in population size
constant population growth
adding a constant number of individuals over each time period - simplest type - not generally found in nature
Population growth rate
amount the population has changed DIVIDED by the time it had to change
density-dependent factor
any factor that increases with increased population density and decreases with decreased population density
density independent factor
any factor that is independent of population density
a population size depends on its
biotic potential and environmental resistance
reproductive strategies fall on a
continuum
top-down regulation
control of a population (species) by predation
bottom-up regulation
control of a population occurs as a result of scarcity of a resource
Population explosion
could occur under unlimited conditions, when organisms with a high r have rapid population growth (j-curve)
examples of density-dependent factors
disease, predation, food shortages
as population density decreases
environmental resistance decreases (population increase)
as population density increases
environmental resistance increases (population growth stops or decreases)
J-curve
exponential growth curve
exponential growth
growth at a constant RATE of increase doubling time remains constant
type I survivorship
high survivorship throughout life, especially early life
examples of type 1 survivors
humans
type II survivorship
intermediate survivorship throughout life
in the absence of environmental resistance you would get a
j-shaped curve
S-curve
logistic growth curve
environmental resistance can lower reproduction via
loss of habitat, pollution, changed animal migration patterns
type III survivorship
low survivor ship throughout life, especially early life
Carrying Capacity
maximum population of a species that a given habitat can support without being degraded over the long term
population density
number of individuals per area
example of r- strategists
ooysters
example of type III survivorship
ooysters
r-strategists react to change by becoming
pests
examples of BIOTIC environmental resistance
predators, parasites, competitors, lack of food
k-strategists
produce few young, but young are nurtured
r-strategists
produce lots of young, but leave their survival to nature
the two reproductive strategies are:
r and k
k-strategists react to change by becoming
rare or extinct
environmental resistance probably has greatest effects by affecting
recruitment
decreasing population
recruitment < replacement
constant population
recruitment = replacement
increasing population
recruitment > replacement
logistic growth
some processes slows growth so it levels off near carrying capacity
examples of density Independent factors
spring freeze, fire, pollution
example of type II survivorship
squirrels, birds
Recruitment
survival through early growth stages to become part of the breeding population
survivorship curves
survivorship curves are used to visualize how the number of individuals in a population decrease with time
environmental resistance
the combination of all biotic and abiotic factors that limit a population's increase
biotic potential (r)
the maximum number of offspring that can be produced under ideal conditions
r-max
the maximum rate at which members of a species can reproduce when conditions are unlimited
critical number
the minimum population base allowing the survival and recovery of a population
r-strategists survivorship
type III
abiotic and biotic factors cause mortality which prevents
unlimited population growth
examples of ABIOTIC environmental resistance
unusual temperatures, moisture, light, salinity, pH, lack of nutrients, fire, toxicants
