population Ecology Flashcards
Ecology
- How organism interact with each other and their environment
- 5 levels:
1) Organismal ecology
2) population ecology
3) community ecology
4) ecosystem ecology
5) global ecology
organismal ecology
how individuals interact with each other and their environment
population ecology
population: a group of individuals of the same species inhabiting a specific area at the same time
- population ecologists focus on how population size changes with time and location
distribution
where organisms are found
abundance
how many organisms are found in a given area
factors that affect abundance and distribution
1) dispersal ability(physical + climatic barriers_
- bodies of water, mountain ranges, etc
- organism can only tolerate certain temperatures + conditions
2) biotic factors: (living AND once-living)
- tree coverage
-food requirements
- predators
competitors
3) abiotic factors: (non-lining)
- light intensity
- temperature
- water availability
- geographical structures
niche
an organisms range of tolerance to abiotic conditions
limits of tolerance
the upper and lower limits to a range of particular factors (temperature, salinity, light intensity, etc) within which an organism can survive
population size
number of individuals in a population
population density
number of individuals in a defined area or volume
estimating population size using Lincoln-Peterson Method (eqt)
N=(Mn)/m
N= total population size m= number of marked individuals in recapture (2nd sample) n= total individuals in recapture (2nd sample) M= number of marked individuals in 1st sample
assumptions of Peterson method
1) population is closed (N is constant)
- no births, deaths, movement of individual in and out
2) all individuals in the population have the same chance of being caught in the first sample
3) marking individuals does not affect their catchability
4) individuals do not lose marks between the two sampling periods
range of tolerance
range of conditions within which an organism can survive
how to determine per capita births and deaths
b= per capita birth rate, B= births, N= total population, d= per capita death rate, D=deaths
b=B/N
d=D/N
per capita growth rate (r)
r=b-d
what are the two models of population growth?
exponential growth model
logistic growth model
exponential growth
- J-shaped curve dN/dt=rN - 'r' is constant population size/density r/growth reate= DENSITY-INDEPENDANT - as the number of individuals added to a population gets larger the population size (N) get larger - the amount added depends on r
when does exponential growth occur
- when a FEW INDIVIDUALS found a new population in a new habitat and resources are plentiful
- population goes through a bottleneck and is starting to recover with a FEW surviving individuals and resources are plentiful
logistic growth
- s shaped curve
- more realistic
growth rate levels off to a carrying capacity (K) - at K, growth rate= 0
-DENSITY-DEPENDANT
dN/dt = rN((K-N)/K)
trend:
- initially growth in exponential
- over time, N increases to the point where competition for resources or other density-dependent factors begins to occur = growth rate declines
- population is at the habitat’s carrying capacity, growth rate = 0
carrying capacity (K)
- the max population size that a particular environment can support over a period of time
- not constant (depends on food, space, water, nesting sites, etc)
- can change with time and location
what are two factors that prevent populations from growing indefinitely?
1) density-dependent factors: changes in intensity as a function of population size and they are usually biotic
ie,
- intraspecific competition for the same limited resources=less energy for reproduction=decrease reproductive success= decrease per capita birth rate and increase the death rate
- predation
- toxic wastes
- disease and paratism
2) density-independent factors: alter birth and death rates regardless of the # individually in the population. involve changes in the abiotic environment
ie, hurricanes, volcanoes, floods, cold snaps
life history traits
an organism’s life history refers to the quantification of stages it goes through in its lifetime:
birth-> growth-> reproduction
-> death
ex:
- age specific survivorship
- age @ first reproduction
- fecundity
- size of offspring
- growth rate
- reproductive lifespan
- sex ratio of offspring
what is a life table?
summarizes the probability that an individual will survive and reproduce in any given time interval over the course of its lifetime
age class
group of individuals of a specific age
cohort
group of individuals of the same age that can be followed through time
survivorship
the proportion of offspring that can survive to a particular age
survivorship curves
graph depicting the % of a population that survives to different ages
Types of survivorship curves
I : survivorship is high then drops dramatically in old age
- ie: humans
II: linear, species where individuals have about the same probability of dying in each year
- ie: blackbirds
III: high death rates earlier in life but then high survival rat later in life
- ie: larvae
what are fitness trade-offs?
resources are limited-
natural selection can not maximize all the life history traits simultaneously
ie: an animal that gives birth to many offspring will not likely be able to provide a lot of parental care due to limited resources (energy, nutrients) thus cannot devote that same energy towards her own survivorship
clutch size
egg laid
fecundity
avg # of female offspring produces by a single female I the course of her lifetime
net reproductive rate
the growth rate of a population per generation
- indicates whether a pop is increasing or decreasing
the general relationship between fecundity and survivorship
1) low fecundity -> high survivorship (invest resources in traits that aid their own survival
- few, expensive offspring
- K selected
2) high fecundity -> low survivorship
- many cheap offspring
- r selected
K-selected organisms are…
adapted to stable environments, where competition is high populations tend to hover near “K”
ie: elephants whales
K-selected life history traits
- longer-lived species often type 1 survivorship reach sexual maturity more slowly - few, large offspring well cared for (more parental care) - larger body size at birth - often. extensive parental care -multiple reproductive events Good competitors
r-selected organisms are…
adapted to unstable/unpredictable environments
ie: dandelion, frogs, salmon, insects
r-selected life history traits
- short lifespan
- type 3 survivorship
- reach sexual maturity quickly
- typically reproduce only once
produce large numbers of SMALL offspring (so some survive) - provide little care (quantity over quality)
maximize “r” (growth rate) - little to no parental care
- ## poor competitors
in reality organism demonstare …(k-selected/r-selcted)
NEITHER! it’s an intermediate between the two
population size equation
birth-deaths+immmigrants-emmigrants
