topic 9 Flashcards
population structure and what are the related topic
the defining patterns in a pop
survivorship
age dst
sex ratio
dispersal
what is a survivorship curve
the pattern of survival in a population. use to determine if mortality rates change with age
type 1- high young survive
type 2 - the constant negative relationship of survival
type 3 - high mortality at young
expressed ona. log scale
what are the 4 types of tables used to st survival pattern
life table
cohort life table
static life table
age distribution
life table
records the age spec survival and death rate in a [o[
cohort table
identify indivs form at the same time and records are kept from birth. death age is recorded
hard collection for long-lived or mobile species
static life table
record age of death of many individuals over a narrow range
not the most accurate method as generation can vary and relise on estimation
age distribution
calc the diff in the proportion of indivs in each age class, assuming a closed population
difficult bc many populations are actually closed
what is a closed pop
a pop with no borth, death, emigration or immigration during study period
what type of life table do we use
a cohort life table
which cohort parameter reveals the survivorship curve
the Ix. this represent the number of survivors found at each stage reality to the starting number at birth
what is dx
the proportion that have died moving from one stag to the next
lx-lx+1
what is qx
the prob a dying at each stage (dx/Ix)
amount died/ the survivorship at each stage
what is sx
the prob of surviving to the next stage
which type of org is each survivorship curve most commonly observed
type 1= large vertebrates (deer, sheep, buffalo and humans)
2= birds
3= common in r selected species (fish, plants, prawns)
what does the age distirubtion of a pop reflect
its history of survival, reprod and potential for future growth
we are able to see periods of success, high or low survivals, if the population is increasing or decreasing (the future determination of a pop)
what is the sex ratio
the frequiency of each sex type in a pop
often in a 1:1
note that of this proportion varies or the population is very large, the fitness of the associated genotype with the sex in increases in efforts to outcompete others
if there is abundant female, the males fitness will increase and vice versa
why may a population size change
birth
death
immigration
emigration
what is the change in the population equation
Nt+1= Nt+B+I-D-E
note that Nt+1 reflects a future population size
what is the chnage in population for per capita rates
this takes into account the ecological process by the number of indivs in a pop to allow for a better comparison between populations of diff sizes
Nt+1= Nt +Nt(b+i-d-e)
b=B/Nt
i= I/Nt
d= D/Nt
e= E/Nt
what is a density dependant factor that changes pop size
commonly biotic factors such as competitors, predator or diseases
the outcome may vary depending on the initial pop size. how many animals survived the decline in food? if the pop was small to being with, the per capita would have survived more than a large pop with limited food source
what is a density independant factor that changes pop size
commonly abiotic factors such as weather or climate
in many cases the influence the effect will hold will act the same regardless of the starting population size. a wildfire will kill all trees in a forest, whether there is 10 or 100 to start
how can we estimate reproductive rates
combining a life table with a fecundity (birth by females) schedule
this will also est the generation ship and per captia rate of inc
what is mx
eggs/Nx
the avg # of offsrping procuded at each age interval
what is lxmx
the avg number of offspring produced by indies by age x
what si the net reproductive rate
the sum of lxmx of a pop
Ro=sum of lxmx
the avg # of offspring proceed by an indive in its life span
Ro<1 then declining
Ro> then growing
Ro=1 then stable
what type of species result in generation overlap
iteroparous (more than one birth period)
what is generation time
the avergae age within a population that female sgive birth (may be able to at 1 year, but wont until 2 on avg)
this number will be larger than the first report age if she have multiple report events
T=sum of x(lxmx)/Ro
what is the per capita rate of increase
the percapita birth rate- death rate (b-d)
r= ln(Ro)/T
r>0 then inc
r<0 then decline
r=1 then stable
