LECTURE 4 - LIFE CYCLES AND POPULATION Flashcards
Population
A group of individuals in from one species
->boundries determined geographically or purposely for simplification
What drives population change?
Birth, death, migration, immigration and emigration
Individuals
Unitary individual -> have a set predictable look and development (ex// us)
Modular -> Have set parts or modules that will develop, but not perfectly predictable (ex// a tree)
How can you tell a modular individual?
Check the RENET (off branches that could look like a different individual ) if its GENET (genetically the same)
How to calculate a population?
Capture, recapture method
marked/total pop = recap. marked/ total recap.
if random density, count a sub-area then multiply by total area
Iteroparous Species
breeds repeatedly ex// humans
semelparous species
expends all energy into a single reproductive moment ex// some flowering plants
Seed banks
After plant releases their seeds, they form a seed bank. Often these do not begin to grow till conditions are favourable (avoider species)
Anual life cycles
One full generation per year, from birth to death ex//trillium
perennial life cycles
individuals have generations that cross over each other
-> life cycle lasts a while
biennial life cycles
takes two years to go through an entire life cycle
ex// Salmon with their long reproductive cycle
cohort life table
Looks at the survivorship and fecundity of a cohort as they grow from birth to death
Static life table
looks at individuals at different ages to determined fecundity and survivorship
Survival rate
Determines if the population will inc or dec
- > Ro > 1, pop inc
- > Ro < 1, pop dec
- > Ro = 1, rate of basic growth (just replaces itself)
measure the survival rate?
E lx * Mx(reproduction of individuals) = Ro
lx (survival of individuals)= ax/total pop
Types of survivorship curves
type 1 -> Mortality inc as the individual gets older
ex//humans
type 2 -> morality constant throughout live ex// birds
type 3 -> morality highest at birth ex//plants
Dispersal patterns
can be random, regular (uniformed) or argrigated (in groups)
Calculate density
total pop/ total area of habitat
What determines abuncance?
If density high then resources decrease (& vice versa)
Then it’s determined by intraspecific competition
The carrying capacity (k)
determined when the birth and death rates become equal
-> max population that can be supported by their recourses
Types of population growth
rate of natural inc (r) -> shows exponential growth (tends to dec as k is approached) Logistic growth (k) -> shows an s curve as it chills by carrying capacity
r vs k species
r -> Reproduce fast with many offsprings. Good for changing env. lives in the “r” phase
k -> few large offsprings. intense competition for resources. Likes in the “k” phase
Cohort
Individuals in a population born in a certain period
