APES Test 3 Populations Flashcards
Generalist species
live in a variety of environments, eat a variety of foods, broad ecological tolerance for environmental conditions, have an advantage when the environment changes
specialist species
require a specific habitat
limited diet
narrow ecological tolerance for environmental conditions
have an advantage in constant habitats
K selected species
tend to be large
have few offspring/reproduction event
expend significant energy for each offspring
mature after many years of parental care; have long life spans
reproduce more than once in their life
live in stable environments
r selected species
tend to be small
have many offspring
expend or invest minimal energy for each offspring
mature early; have short life spans
may reproduce only once in their lifetime
are able to thrive in disturbed environments
r and k species, general rules
r = generalist, k = specialist
Specialists typically live in areas where there is less competition and it makes sense to put extra energy into offspring; but this is a rule of thumb at best
many are in between, or lean towards one rather than being alll the way to one side
Carrying Capacity
Defined broadly as the number of organisms that an ecosystem can support of any one particular species
Eg. the theoretical maximum population size
Biotic Potential
The reproductive potential of a population- eg. how quickly can a population grow, when left unchecked?
Overshoot
Population exceeds carrying capacity- usually followed by correction (collapse)- decrease in births, increase in deaths
Reaching Carrying Capacity- K (Population Equilibrium)
Population Equilibrium defined as Birth Rate= Death Rate
No population growth or decline
In a functional ecosystem, population equilibrium is reached at carrying capacity
Limiting/Regulating Factors (Biological Resistance Factors)
Density Dependent
Typically (but not exclusively) biotic
Food
Water
Shelter
Nest Sites
Interspecific Relationships
Nutrients
Limiting/Regulating Factors (Biological Resistance Factors)
Density Independent
Typically abiotic or human caused
Volcanoes or other natural disasters
Pollution
Extreme Weather Events
Climatic Shifts
Carrying capacity can change
environment can change, degrading carryign capcaity
ex. carrying capcity of moose was decreased because of increased presence of ticks because of warmer temperatures
Survivorship Curves
Depict death in a population as a function of age
Lifespan is more complex than a mean/median, as many organisms experience steep die offs early in life with several long lived individuals
Survivorship Curves: Type I
Most individuals survive to advanced age
Typically K species
Survivorship Curves: Type II
Relatively constant rate of death over time; death is relatively age independent
Could be r or K species
Survivorship Curves: Type III
Significant early die off, with a few individuals making it to advanced (and reproductive) age
Typically r selected species
(Crude) death rate:
Deaths/population (x 1,000)
(Crude) birth rate:
Births/population (x 1,000)
Population Growth Rate:
Birth Rate- Death Rate
Future Population
Population x Annual Growth Rate ^ number of years
Population Doubling Time (also works for halving time)
70/Population Growth Rate (as %) (assumes stable growth)
growth rate with real world constraints
Growth Rate: ((Births + Immigrants) - (Deaths + Emigrants))/ Population
pre reproductive
under 15
reproductive
15-45
post reproductive
over 45
Total Fertility Rate (TFR)
Average number of children born per female in childbearing years (15-45)
Worldwide average 2.5
Developing Countries: Up to 6
Developed Countries: Replacement Fertility: ~2 (* replacement fertility rate may be higher than 2 if death rates are high)
why is replacement fertility 2.1 instead of 2?
mortality
GET SPECIFICS, CHECK THIS ANSWER
Female Empowerment and TFR
Strong association between education and TFR
TFR < replacement level in most developed economies. Is this a cause for concern? Or a chance for environmental and natural resource relief?
If developed countries want to increase birth rates for economic reasons, they must balance the challenges of having children in an equitable way without harming social and economic mobility
Human Population Dynamics in modern times
Birth and Death Rates alter human population dynamics
Population growth rates have declined worldwide, but especially in developed countries
Death rates have also dropped, as healthcare has improved
Widening the gap between birth and death rates drives populations up
Demographic Transition Model
As societies advance, growth rate declines
Typically birth and death rates decline, stabilizing populations
Demographic Transition Model: Stage 1
Birth AND Death rates high
Population grows logistically and reaches carrying capacity, based on food supply
Population fluctuates as a result of natural events and disasters
NO access to healthcare or Family Planning Resources
No countries currently in stage 1- some rural areas may follow stage 1 paradigm
Malthusian Theory
Think of this as carrying capacity concepts, but applied to human populations-
Populations grow and falla according to natural resources and conditions (eg. density dependent and independent factors), especially food supply
Demographic Transition Model: Stage 2
Increase in population due primarily to fall in death rates while birth rates remain elevated, exponential growth
Improvements in food supply and public health
Does not follow malthusian theory
Most of Sub-Saharan Africa is in this stage
Demographic Transition Model: Stage 3
Death rates remain low, but birth rates also decline; populations may be nearing replacement fertility.
Female access to education and family planning resources
Egypt, Philippines, Mexico
Demographic Transition Model: Stage 4
Population is at replacement fertility (or below- some debate about adding Stage 5 to model)
Women have access to family planning resources and focus on careers
Disease is low and healthcare is excellent
