apes unit 3 Flashcards
(36 cards)
r-selected - “quantity”
Many offspring, little to no parental
care
May reproduce only once, but
generally reproduce many times
throughout lifespan
Ex: insects, fish, plants
Shorter lifespan, quick to sexual
maturity = high biotic potential = high
population growth rate
More likely to be invasive
Better suited for rapidly changing
environmental conditions
K-selected - “quality”
Few offspring, heavy parental
care to protect them
Generally have fewer
reproductive events than
r-strategists
Ex: most mammals, birds
Long lifespan, long time to
sexual maturity = low biotic
potential = slow population
growth rate
More likely to be disrupted
by environmental change or
invasive species
k selected usually live in habitats…
Usually live in habitats with
higher competition for resources
Populations that reach carrying
capacity (K) usually remain at
stable size, near K
Hence, K-selected or
K-strategist
r selected usually live in habitats….
Usually live in habitats with lower
competition for resources
Population are more likely to fluctuate
above and below carrying capacity
(overshoot and die-off)
“r” is the variable used to
represent maximum reproductive
rate in ecology
Hence, r-selected or r-strategist
Type 1(K selected)
High survivorship early in life
due to high parental care
High survivorship in mid life due
to large size & defensive
behavior
Rapid decrease in survivorship in
late life as old age sets in
Ex: humans
Type 2 (between K and R selected)
Steadily decreasing survivorship
Type 3 (mostly r-selected)
High mortality (low survivorship)
early in life due to little to no parental
care
Few make it to midlife; slow, steady
decline in survivorship in mid life
Even fewer make it to adulthood; slow
decline in survivorship in old age
Ex: insects, fish, plants
Carrying Capacity (K):
the max. Number
of individuals in a pop. that an ecosystem can
support (based on limiting resources)
Overshoot:
when a population briefly
exceeds carrying capacity
Ex: deer breed in fall, give birth all at
once in spring; sudden spike in pop. =
overshoot
Consequence of overshoot:
resource
depletion ex: overgrazing in deer
Die-off Example
Reindeer of St. Paul Island
25 introduced in 1910
Growth was gradual (10’-30’),
then exponential (30’-37’)
Carrying capacity was
overshot
Sharp die-off lead to pop. crash
as food resource (lichen) were
severely depleted
Real pops. don’t always fluctuate
around carrying capacity. If resource
depletion is severe enough, total pop.
crash can occur
Die-off:
sharp decrease in pop. size
when resource depletion
(overshoot) leads to many
individuals dying
Ex: many deer starve with too
many new fawns feeding in
spring
Predator-Prey example
Hare pop. increase due to
low predator pop. (lynx)
Lynx pop. increase due to
increase in food (hare)
Increasing lynx pop.
limits hare pop; leads to
die-off
Hare die-off decreases
lynx food source, leading
to die-off
Hare pop. increase due to
low predator pop. (lynx)
Size (N):
total # of individuals in a given
area at a given time
Larger = safer from population decline
Density:
of individuals/area
Ex: (12 panthers/km2)
High density = higher competition,
possibility for disease outbreak,
possibility of depleting food source
Distribution:
how individuals in population
are spaced out compared to each other
Random (trees)
Uniform (territorial animals)
Clumped (herd/group animals)
Sex Ratio:
ratio of males to females.
Closer to 50:50, the more ideal for
breeding (usually)
Die-off or bottleneck effect can lead
to skewed sex ratio (not enough
females) limiting pop. growth
Density-Dependent Factors:
factors that
influence population growth based on
size:
Ex: food, competition for habitat,
water, light, even disease
All of these things limit pop. growth
based on their size; aka - small pop.
don’t experience these, large do
Density-Independent Factors:
factors that influence population
growth independent of their size
Ex: natural disasters (flood,
hurricane, tornado, fire)
It doesn’t matter how big or
small a pop. is, natural
disasters limit them both
Ex. of Density-Dependent Factor
Food is a density dependent factor.
(also a limiting resource)
When twice as much food was
added to the dish, both species
increased carrying capacity
by about 2x
Biotic potential
= exponential
growth (like a /)
Logistic growth
= initial rapid
growth, then
limiting factors
limit pop. to K ( like in precalc)
intrinsic rate of
increase
maximum potential growth rate, with
no limiting resources
Calculating Population Change
Population Size = (Immigrations + births) - (immigrations + deaths)
Ex: An elk pop. of 52 elk has 19 births and 6 deaths in a season, and 5
new elk immigrate to the herd and 0 elk emigrate from the herd
(19+5) - (6+0) = +18 elk
52 + 18 = 70 elk
