lecture 21 Flashcards
populations
groups of interbreeding individuals of the same species living in the same general area
population ecology
the study of births deaths and dynamic forces that regulate a population
what are the two ways to describe populations
spatial and temporal
density
the number of individuals per unit area on volume
dispersion
pattern of spacing within population boundaries
how to measure density
you can count individuals in a small area or count the signs of individuals (tracks, feces)
how to measure animals that move
mark recapture methods , 1. capture 2. mark. 3.recapture 4. do math
formula for CMR
number of animals marked on day one times the number of animals captured at day two all divided by the number of marked found in the second capture
question: captured 10 gerbils and second day you get 1000 and only five are marked , calculate
(10x1000)/5
what are the three main dispersion patterns
clumped, random, uniform
clumped
social patterns or resource distribution (common)
random
wind dispersion (less common)
uniform
allelopathy (plants secret toxins), competition, territoriality
temporal populations
pop changes over time, birth and death rates
demography
study of process that influence birth, death, population growth rates.
life history
traits that make up schedule of reproduction (age at first reproduction, frequency and duration, total of offspring)
life history trade offs
cannot invest in all traits simultaneously
principal of allocation
resources need to be directed among competing life functions
what resource has to be met first prior to everything else (in typical conditions, normal resources)
maintenance
how are resources divided in typical conditions and abundant resources
more resources are gained and more are available after maintenance needs are met
how are resources divided in stressful conditions and normal resources
this means more resources must be expended on maintenance and fewer are available for other purposes
semelparous species
they expend their energy inn a single immense reproductive effort (many insects, and annual plants do this)
iteroparous species
they exhibit repeated reproductive cycles
what are the three main patterns of survivorship
type 1 (humans) type 2 (birds) type 3 (trees)
type 1
they have more offspring surviving in the beginning of their lives but they decline as time pass by (they dont live over 90) graph is exponential but backwards
type 2
they have decent survivorship and many grow old so graph is linear
type 3
less off spring survive but they live til forever opposite of type 1 graph
BD model
birth death model, population at future time depends on current population size plus births and deaths in that time interval
BD equation
change in population size over change in time equals B-D
per capita population growth is
expressed on a per individual basis
per capita birth rate is
b= avg number of offspring produced
per capita death rate is
d= avg individual chance of dying
birth rate and death rate equation
B= b times N or b=B/N and D= d times N or d= D/N
per capita rate of increase
r= b-d so r > 0 is increasing and r < 0 is decreasing
the exponential model
describes population growth in an idealized environment (ex. unlimited resources, no competition)
what term are we using when resources are unlimited
r max
what shape does the exponential growth graph show
j shaped
