Unit 3 - Populations Flashcards
specialists
smaller range of tolerance or narrower ecological niche makes them more prone to extinction
- specific food requirements
- less ability to adapt to new conditions
generalists
larger range of tolerance, broader niche makes them less prone to extinction and more likely to be invasive
- broad food requirements
- high adaptibility
K-selected species (quality)
- large
- stable environment
- few offspring per reproduction event, high parental care
-reproduce many times - live in stable environments
- long life spans
- density dependent
- low biotic potential = slow pop. growth rate
- competition for resources is relatively high
r-selected species (quantity)
- small
- unstable environment
- density independent
- have many offspring, little to no parental care
- may reproduce only once
- shorter lifespan, quick to sexual maturity = high biotic potential = high pop. growth rate
- more likely to be invasive
- better suited for rapidly changing env. conditions
- competition for resources is relatively low
biotic potential
low biotic potential (rep. rate) = hard for pop. to recover after a disturbance (env. change)
r-selected species tend to be
high biotic potential
k-selected species tend to be
low biotic potential
survivorship curves: faster drop in line
quicker die off individual
survivorship curves: slower drop in line
longer avg. lifespan
survivorship curves
line that shows survival rate of a cohort (group of same aged individuals) in a pop. from birth to death
type I
- mostly K-selected
type I - early life
- high survivorship early in life due to high parental care
type I - midlife
- high survivorship in midlife due to large size and defensive behavior
type I - late life
- rapid decrease in survivorship in late life as old age sets in
type II
- in between r & K
- steadily decreasing survivorship throughout life
type III
- mostly r-selected
type III - early life
- high mortality (low survivorship) early in life due to little to no parental care
type III - midlife
- few make it to midlife; slow, steady decline in survivorship in midlife
type III - late life
- even fewer make it to adulthood; slow decline in survivorship in old age
carrying capacity (K)
the max number of individuals in a population that an ecosystem can support
what is carrying capacity based on
based on limiting resources
limiting resources
- highest population size of an ecosystem can support based on limiting resources
overshoot
when a population briefly exceeds carrying capacity
consequence of overshoot
resource depletion
- ex: overgrazing in deer
die-off/die-back
sharp decrease in population size when resource depletion (overshoot) leads to many individuals dying
pop. characteristics: size
- total number of individuals in a given area at a given time
- larger = safer from population decline
pop. characteristics: density
- number of individuals in an area
- high density = high competition, possibility for disease outbreak or depleting of food source
pop. characteristics: distribution
- how individuals in population are spaced out compared to each other
- random (trees)
- uniform (territorial animals)
- clumped (herd/group animals)
pop. characteristics: sex ratio
- ratio of males to females closer to 50:50, the more ideal for breeding (usually)
- die off bottleneck effect can lead to skewed sex ratio, limiting pop. growth
density dependent factors
- tend to be biotic, have a strong influence when the number of organisms per unit area reaches a certain level
- factors that influence population growth based on size
density independent factors
- tend to be abiotic, have an effect on all populations, regardless of size or density
- factors that influence population growth independent of their size
biotic potential
- max potential growth rate, with no limiting resources
- may occur initially, but limiting resources (competition, food, disease, predators) slow growth, and eventually limit population to carrying capacity
age cohorts
groups of similarly aged individuals
0-14 years old
pre- reproductive
15-45 years old
reproductive age
46+ years old
post reproductive age
extreme pyramid
- expanding rapidly
- rapid growth
- ex: guatemala, nigeria, saudi arabia
less extreme pyramid
- slow stable growth
- expanding slowly
- ex: US, Australia, Canada
house
- stable
- little to no growth
- ex: spain, portugal, greece
inverted pyramid
- declining population
- ex: germany, bulgaria, italy
total fertility rate (TFR)
- average number of children a women in a population will bear throughout her lifetime
- higher TFR = higher birth rate, higher population growth rate
replacement level fertility
the TFR required to offset deaths in a population and keep population size stable
what is the replacement level fertility in developed countries
- 2.1 (replace mom and dad)
what is the replacement level fertility in underdeveloped countries
- higher than 2.1 due to higher infant mortality
infant mortality rate (IMR)
- number of deaths of children under 1 year per 1000 people in a population
IMR in lower developed countries
- higher due to lack of access to healthcare, clean water, enough food
higher IMR = ___ TFR
higher IMR = higher TFR due to families having replacement children
factors in IMR decline
- access to clean water
- access to healthcare (hospitals, vaccines)
- more reliable food supply
factors that affect the TFR: development
- more developed or wealthy nations have a lower TFR than lower developed countries
why do developed countries have lower TFR
- more educational access for women
- more economic opportunity for women
- high access to family planning and contraceptives
- later age of first pregnancy
- less need for children to provide income through ag. labor
factors that affect the TFR: gov. policy
- can play a huge role in fertility by coercive (forceful) or noncoercive (encouraging) policies
- forced or voluntary sterilization
- chinas 1 (now 2) child policy
- tax incentives to have fewer children
- microcredits or loans to women without children to start business
malthusian’s theory
- earth has a human carrying capacity probably based on food production
- human population growth is happening faster than growth of food production
- humans will reach a carrying capacity limiting by food
growth rate (r)
% increase in a population (usually per year)
crude birth rate (CBR)
births per 1000 people
crude death rate (CDR)
death per 1,000 people
calculating growth rate
= (CBR - CDR) / 10
- growth rate is always expressed as a %
doubling time (rule of 70)
- the time it takes (in years) for a population to double is equal to 70 divided by the growth rate
doubling time calculations
number of years to double = 70/r (where r is a %, not a decimal)
industrialization
the process of economic and social transition from an agrarian economy to an industrial one (manufacturing based)
demographic transition model
- a model showing how a nation’s population, birth, and death rate are historically correlated when transitioning from agrarian to industrialized
stage 1 of DTM - preindustrial
- high birth and death rate
- high IMR and death rate due to lack of access to clean water, stable food supply, and healthcare
- high TFR due to lack of access to education for women, contraceptives
- little to no growth due to CBR & CDR balancing each other out
- virtually, no country is in stage 1
stage 2 of DTM - industrialized/developing
- modernizations bring access to clean water, healthcare, stable food supply
- IMR & CDR decline
- TFR remains high due to lack of ed. for women, contraceptives, etc.
-rapid growth due to high CBR and declining CDR - short life expectancy
stage 3 of DTM - industrialized/developed
- modernized economy and society increase family income
- TFR declines significantly due to more educational opportunities for women, delayed age of marriage and first child
- access to family planning and contraceptives
- slowing growth rate as CBR drops closer to CDR
- long life expectancy
- high literacy rate
stage 4 of DTM - highly developed
- highly modernized countries that are very affluent
- TFR declines even further as families become more wealthy and spend even more time on educational and career pursuits
- family planning and contraceptives
- CBR drops lower than CDR and growth becomes negative
- longest life expectancy
population momentum calculations
r = (b + i) - (d + e)
- r = population growth rate
- b = birth rate
- i = immigration rate
- d = death rate
- e = emigration rate
density dependent examples
space, water, nutrients/food, shelter, competition, predation, disease, parasitism
density independent examples
natural disaster, temperature, sunlight, human activities, physical characteristics, behaviors
