Part 6: Struggle For Existence Flashcards
Most important differences among individuals are
sex and age
Age structures model deal with sex in simpler way, how?
keep track of females only, ignore males
Why do age structures ignore males?
Females = only able to reduce, they only propulsive force for population maintenance
Poplation growth rates and generation times, acceptable to see males
as numerically inconsequential collective source fo sperm (not in short supply)
Sex ratios close to 1;1, do math on females and just multiple by 2 = estimate total population of both sexes. T or F
T
Population size steady if average female =
1 daughter in lifetime
Assign individuals in population to classes based other age using x (subscript) for age
T
Time span of an age class interval?
we want enough age classes to capture birth snd death aspects vary through females life
Life tables for humans, age class how long?
5 yrs long each = 20 classes enough for human lifespan
1st age class denoted by _ N=? N0=? N1=? N2=? sum up nx values over all ages (x) =?
1st age class denoted by 0 N=Total population N0=newborns N1= 1years old N2=2 year old sum up nx values over all ages (x) = TOTAL POPULATION SIZE
Capital stigma indicates
sum up following variables over all possible age classes
What is age structure of population looking at
set of nx values (n0,n1,n2,n3,n4)
Age pyramid
horizontal bar graph (represent age structure)
Survivorship scheduled lx
age-specific risks of mortality
lx = survivorship at age x =?
probability that an individual is still alive at age x
Lx values are probabilities =
range from 0 to 1
Lo=1, what does this mean?
Newborns are alive at birth
Lx values must ALWAYS ____________ as x increase, the probability of being alive always declines with age
Decrease
Lx values must decrease as x increases, why?
The probability of being alive always declines with age (eventually everyone dies)
For life table to be useful, include what of enough?
enough age classes for the last Lx value to be zero
Shape of survivor ship schedule, graph, what is comparing
(graph of Lx vs. x)
species produce huge tiny offspring but they have few defences anise environmental stresses, graph look like
survivorship curve initial drops steeply (little ones Mosley die early, few survive = grow large enough to survive life and survivorship evens off)
Species produce few offsprings but have resources invested in them = larger offspring, survivorship graph look?
larger offspring have resources and resiliency to handle environmental stresses = graph initially defends more gradually
Senescene
die off from generalized breakdown of old organism, not environmental stresses
Exponential Decline
CONSTANT HALF LIFE
probability of dying I constant across all ages
- external accidents rather from intrinsic biological
characteristics (mortality or senescence)
- Radioactive decay of unstable isotopes or expected lifespan of wineglasses in restaurant
Type II survivorship (graph of Lx vs. x)
curves declines steeply but gradually approaches zero as an asymptote (r<0)
Type II decline
log of survivorship (loglx vs. x = straight line with -ve slope)
types of lines
Type I=?
Type II= ?
Type III=?
1) convex curves (low early mortality)
2) Straight lines
3) Concave curves (much early death)
