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)

Mod 17: Age Structure Diagrams & Total Fertility Rates

Crude Birth Rate (CBR)

# of live births per 1k ppl in a pop during a specific yr

* CBR = (# of live births in a yr/total mid-yr pop) x 1000

• High: lead to rapid pop growth, which may strain healthcare/education

• Low: lead to an aging pop/labor shortages, but better access to fam planning

Crude Death Rate (CDR)

(total # of deaths in a pop over a yr/mid-yr pop) x 1000

Growth Rate

* immigration + emigration need to be taken into account

National pop growth rate % = (CBR + immigration) - (CDR + emigration)/10

Net Migration Rate

the difference btwn immigration + emigration in a given yr per 1k ppl in a country

Life Expectancy

avg # of yrs an infant born in a particular yr in that country can be expected to live, given the current avg life span + death rate

Infant Mortality Rate

# of deaths of children under 1 yr of age per 1k live births

Child Mortality

# of deaths of children under age 5 per 1k live births 

Environmental Justice

the disproportionate exposure of environmental hazards experienced by ppl of color, recent immigrants + ppl of lower socio-econ backgrounds

Age Structure Diagram

visually represents the # of individuals w/in specific age groups for a country, typically expressed separately for males + females

Population Pyramid

country w/many more younger ppl than older ppl tends to have a wide base + is indicative of a developing nation

* tend to have more pop momentum

Developed Nation

a country that is more top-heavy, is considered an older pop

or 

a country that is more middle-heavy is typically slowing down in growth

Population Momentum

age-structure diagrams that r widest at the bottom will continue to grow even if growth reduction measures r implemented

Total Fertility Rate (TFR)

estimate of the avg # of children that each woman in a pop will have throught her childbearing yrs (15-49)

• age at which a woman has her 1st child can influence __ in a nation

• delaying having a 1st child will lower the __ as it decreases the remaining time to have further children

• the pursuit of education/careers by woman correlates w/delayed child bearing

Family Planning

more access to birth control, choice of partners, etc

Replacement-Level Fertility 

the TFR required to offset the avg # of deaths in a pop in order to maintain the current pop size

• slightly more than 2 children (this way parents can be replaced by their children)

• in many developed nations usually 2 or 2.1, w/many higher income nations dropping as low as 1.6

* developing nations tend to have higher RLF + will cont to grow

Mod 18: HUman Population Dynamics & the Demographic Transition

Factors that contribute to pop growth

• high CBR

• high TFR

• low infant mortality

• early marriage

• lack of access to fam planning

• access to adequate nutrition (developing countries)

• low overall death rate

Factors that contribute to pop decline

• low CBR

• low TFR

• high infant mortality

• postponement of marriage

• access to fam planning

• access to adequate nutrition (developed countries) 

• high overall death rate

Theory of Demographic Transition

tracks how a country moves from high to lower birth + death rates as development occurs + the country moves from a preindustrial to an industrialized econ system

Stage 1

* preindustrial: slow pop growth

• CBR = CDR + both high

• life expectancy is short

• infant + child mortality is high

• children r needed for the workforce + to care for the elderly

Stage 2

* industrializing: rapid pop growth 

• continued high birth rates w/a dropping death rate

• sanitation, clean drinking water, food access improves

• med care improves (vaccinations)

• educational systems + birth controls r slow to form, so birth rates tend to stay high 

Stage 3

* industrialized: stable pop growth

• higher fam incomes, less need for children

• education becomes more of a priority, so TFR begins to drop

• birth + death rates begin to equalize again 

Stage 4

* postindustrial: declining pop growth

• higher affluence + econ prosperity 

• children may become an undesired financial burden

• women choose to remain in school + the workforce longer before child-bearing

• there r more older ppl than younger ppl in the pop

IPAT Equation

show that the increase in these factors will increase the impact of a pop

impact = pop x affluence x tech

* as they increase, the overall impact increases