Lecture 6: Population ecology Flashcards
What is the allee effect?
It is the negative effects of low density, arising from social benefits.
populations fluctuate between lower limit and upper limit
if population goes below lower limit, then the specie goes extinct.
hence, meerkats need minimum size of population density to grow.
What is fecundity?
How many offsprings an individual has.
what is survivourship?
Chances that an individual will survive and not die.
What do both fecundity and survivourship depend upon?
Age
Why do different species have different ages that fecundity and survivorship depend on?
Because of Life history: The sequence of events in an species life.
What is a typical life history for many plants and animals?
1) Start life at small size
2) Grow for a period without reproduction (Accumulate resources)
3) Reproduce (use those resources to reproduce)
What is a life history of elephant?
Low fucundity
Late first-birth
Long life span
How is time measured?
IN age-class intervals,
Arbitrary units of time chosen to give a reasonable number of age class.
What does life tables show?
Data that is statistically expected for average individual of specified age.
What is senescence?
Getting old and dying
What is reproduction period often preceded by?
Resource accumulation phase
What is the cost of reproduction?
If fecundity increases, survivorship decreases
what is fecundity-survivorship tradeoffs?
What is Mx ?
Number of daughters a female has in x to x+1 interval
What is R0?
Net reproductive rate
average number of children a female has in her life time.
How is Ro calculated?
sum of all fecundity in that age group*probability to survive in that age group.
= sum(Mx*Lx)
What is T?
Average age a female gives at, or Generation time.
T = sum of age in that age class* probability of survivourship*fecundity divided by Generation time
T = sum (XLxMx)/Ro
How does r, lambda and Ro related?
r = (ln(Ro) /T) = lambda
The difference is time difference
Ro : difference in time in generations
r: difference in change in very small units
lambda: difference at one time step
Organisms with higher growth rate have higher fecundity, then why arent all plants annuals and all mammals mice?
Because of Trade-offs and constraints
Reproduction is costly. Waiting can accumulate resources, hence waiting is good.
What is iteroparity? and semelparity?
Reproducing in multiple years in life is called iteroparity
Waiting till end to reproduce is called semelparity
Is fecundify schedules genetically or phenotypically determined?
Genetically
Write the plant life history
Semelparous (monocarpic) usually live for a year: if one season of reproduction: annual
two: bienniel
more than two: monocarpic perrineal
While iteroparous are called: Perennials
What is an example of obligate semelparity plant example?
The century plant
Why is semelparity good?
When reproductive output is increased by accumulating resources longer
Reproductive output strongly depends on size
What is satiate seed predators?
