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)
bx=
not probabilities = ?
average number of daughters produced by females in her xth year
not probabilities = exceed 1.0
b0 = 0 (babies can’t give birth)
unless age class intervals to be inappropriately wide (newborn need pass through period of resource acquit ion and growth after broth before they give birth themselves)
Age of first reproduction
total # of offspring produce & waiting period before reproduction can begin
Why do these model lack density dependance?
fecundity and survivorship secludes as constants
Calcite population wide rates of increase, consider how __________ and __________ interact with each other
fecundity and survivorship
Life time output of average female, discount her potential reproduction at a particular age by likelihood that she dies before reaching that age, formula?
1)
(bxa)(its lxa) = answer a
(bxb)(lxb) = answer b
(bxc)(lxc) = answer c
(for all age classes x)
2) answer 1 +answer2 + answer3 = expected number of daughters a female produce in her lifetime (net reproductive rate)
net reproductive rate
expected # of daughters a female will produce in her lifetime
net reproductive rate (Ro)=∑lxbx
Ro= act similarity to finite rate increase λ
expected # of daughters a female will produce in her lifetime
Ro=1
each females exactly replaces herself and population size remain content
Ro>1
population increase geometrically without limit
Ro<1
population slides toward extinction
How Ro and λ differ is in time scale which they measure?
Ro= amount of growth occurs over one generation λ = amount of growth occurs over one unit of time
If you know number of females on each class at starting t = assumptions?
- fecundity and survivorship values fixed
-all deaths and births occur during a time interval take place at last possible instant before next interval begins (several mothers host enter a time interval = all survive to end of interval (one second before midnight on last night of year for ex) all babies according to bx schedule
some mothers die at midnight accorindgt o lx
-surviving mothers ad no one gave class older
-babies all small age (x=0)
POPULATION GROW OR SHRINK as a step function
Evolutionary ecology considers
the ecological circumstances that drive selection for such life shots characteristic (lifespan, age of first reproduction and number and timing fo offspring)
Size-number tradeoff
allocation of limited resources (plant with fixes amount fo energy and nutrients) (production of offspring)
Early vs late reproduction
newborn organisms undergo pre-reproductive period of growth and resource acquisition before they can birth their own.
Early production = favoured by natural selection (individuals organisms that produce offspring earlier = will dominate population )
Early vs late reproduction (Proviso - all else being equal)
organism that reduce earlier = do not have as long a period to get resources = candy male as many offspring as those who what longer to start
Cost of reproduction
offspring take energy and nutrients that adult could use for other purposes (extend their own life span or saving to make other offspring in future)
Cost of reproduction (higher animals)
1) parental survival can be reduced
2) parental resources for reproduction can be depleted (offspring production is delayed and diminish) HIGH bx early in life = reduces bx late in life
cost of reproduction extend beyond brith, they give parental care to kids
(lactation = need material resources)
R. A Fisher introduced
reproductive value as another aspect of life history (function of survivorship and fecundity schedules)
Reproductive value Vx defined as
expected umber of daughters to be produced by a female of age x, now (xth) and for the rest of her life
Any offspring produced before age x is irrelevant to Vx
reproductive value only looks forward in time
Graph of Vx vs x gives humped shape
reaching was somewhere between youth and old age ( reductive value decline later in life)
(humped graph of Vx vs. x). We know reproductive value declines later in life, why should a newborn with allure life ahead of her, have a lower future value than older female with only part of her life left?
Newborn must get through pre-reproductive, resource acquisition phase before she can reproduce and encounter risk of dying at that time period
(vx of newborn lower than females successfully passed through early life risks)
Relative reproductive
Vx/Vo
Relative reproductive of newborn
1.0
lasting pair bonds between mates
- fairly strong selection for males to refer females with high reproductive values
- tendency for treats associated with consent reductive age to become associated with sexual attractiveness
High Vx values (juveniles driven out of natal territories by dispute with parents)
individuals would have best chance of establishing successful new colony where males more likely to be the lines that disperse
Semelparity (animals)
plants and animals, some species are genetically programs to reproduce once in their lifetimes and die
iteroparity (animals)
plants and animals, some species are genetically programs to reproduce once in their lifetimes and die
Iteroparous (plants) usually called perennials
genetically programs to reproduce once in their lifetimes and die
Semelparous (plants) get names depending on how long they live
genetically programs to reproduce once in their lifetimes and die
Semelparous (plants) get names depending on how long they live but all called monocarpic (making fruit once)
genetically programs to reproduce once in their lifetimes and die
- 1 season live = annuals
Biennials
programmes to grow vegetatively for one year and the flower and die in 2nd year (stressful condition, take some extra years fo growth to get enough resources to flower)
Monocarpic perennials
live longer than 2 years before flowering and then die
Dormancy
small, fast maturing plant that compresses all its active growth into the brief wet season and produce seeds that spend the dry season
Weeds
Fugitive Species
solid disturbance allows a brief period for small annual plants to occur an ungrounded bare site before pushed out by taller perennials (better competitors)
- Fugitive species: KEEP DISCOVERING new bare patches
Desert and weedy annuals adapted to take advantage of brief windows of time, rapid growth possible by milder conditions
- large proportion of population under soil and have long lasting seed banks in soil
Desert: these seeds on germinates only after heavy rains have leached out the inhibitors, plants start growth when water available
Weedy: germinated only when stuck by sunlight (get started right after soil disturbance that brings them to surface - most remain in seed bank)
Crop plants
1) RIce
2) Maize
3) Wheat
perennials
AI through human to max seed output and allow regular cultivation of soil
how long lived semelparous perennially can be an advantageous statergy?
Animal pollinators so such ants may hav been disproportionally striated to visit the plants with largest inflorescences (display) = could confer reproductive advantages on plants that waited longer to flower = store up more resources = produce showier displays
how long lived semelparous perennially can be an advantageous statergy?
Animal pollinators of such plants may have been disproportionally attracted to visit the plants with largest inflorescences (display) = could confer reproductive advantages on plants that waited longer to flower = store up more resources = produce showier displays
