APES Unit 3: Populations

Mod 15: Generalists & Specialists Species, R & r-selected Species & Survivorship Curves

Generalists

species that exist under a broad range of conditions

• wide variety of diet & habitat

ex: racoons, bobcats, coyotes

* might end up as an invaisve species

Specialists

species that exist under a narrow range of conditions

• specialized diet

ex:

koalas - eucalyptus tree

canada lynx - snowshoe hare

pandas - bamboo

* more likely to become endangered/threatened

Ecological Niche 

wide range of tolerance/environmental conditions

Population Growth Rate (Intrinsic)

the # of offspring an individual can produce in a given time pd, minus the deaths of the individual or its offspring during the same pd

Biotic Potential

maximum potential for a pop to grow under ideal conditions

K-selected

species that tend to remain around the carrying capacity of a pop, which means they abide by the resources around them

* provide care for their offsprings

* K - Cares & are type 1 + 2 survivorships

Traits:

• long life-span

• longtime to reproduce maturity

• few # of reproductive events

• few # of offspring

• tend to be larger sizes of offpsring

• present in parental care

• slow pop growth rate

• density dependent on pop regulation

• stable, near carryng capacity pop dynamics

• relatively high compt for resources

• generally high impact of invasive species

r-selected

species that tend to live by their biotic potential, meaning they don’t abide by their resources & try to have as much offspring as possible

* don’t take care of their offsprings & just try to reproduce as much as they can

* r - runs & are type 3 surviviorships 

Traits:

• short life span

• short time to reproduce maturity

• many (although in some cases 1) # of reproductive events

• many # of offspring

• small size of offspring

• absent parental care

• fast pop growth rate

• density independent pop regulation

• highly variable pop dynamics

• low compt for resources

• low impact of invasive species 

Overshoot & Dieback

r-selected pops tend to grow large & fast, and then many die, only to grow & die again

Survivorship Curve

survival patterns that can be represented in a graph that shows the survival of a species as a function of age

Type 1 Survivorship

shows high survival over time * large #”s of death in old age

Type 2 Survivorship

shows there is relatively constant decline over the entire lfie span

Type 3 Survivorship

shows a high death early in life w/few individuals teaching adulthood

Mod 16: Carrying Capacity, Population Growth & Resource Availability

Carrying Capacity

when a population exceeds … overshoot occurs 

* can be denoted as K

• impacts of pop overshoot - resource depletion 

IMPACT ON ECOSYSTEMS: 

• dieback of the pop bc the lack of available resources leads to famine, disease +/or conflict

Density-dependent

factors influence the probability of survival depending on the size of the population

ex: disease transmission, territory size (habitat), food availability, access to clean air + water

Density-independent

factors have the same effect on the probability of survival, regardless of the population size

ex: storms, fires, heat waves, drought

Population Growth Models

mathematical equations that can be used to predict op size at a moment in time

• pops can grow rapidly when not limited, like an r-selected species leading to a higher biotic potential/a growth rate of r

• these species have higher fecundity

• species like this tend to fall on the exponential growth model, which is a typical J-shaped curve

* pops growing exponentially r doubling in size over = increments of time

Fecundity

ability to produce offspring

Logistic Growth Model

describes a pop whose growth is initially exponential, but slows at the pop approaches carrying capacity

S-shaped curve

growth begins to slow abt halfway up the curve, + when carrying capacity is reached, growth falls to zero

Population Oscillation

pops ted to go above carrying capacity, then fall back only to rise again

Predator Prey Relationships

• hare populations increase due to low predator pops (lynx)

• lynx pops 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)