APES Unit 3: Population and Community Ecology

population size inputs

• immigration and births

population size outputs

• emigration and deaths

population size

• n

• number of individuals

population density

• number of individuals of a species per unit area or volume at a given time

• individuals/area= density (#/km²)

population distribution

• how species/ populations are distributed, spacial locations of each individual within a population

random distribution

• ex.~ dandelions or some marine organisms

  • do so when there are no strong attractions or repulsions between individuals

  • when resources are evenly distributed throughout the environment.

uniform distribution

• evenly spaced

• to minimize direct competition for limited resources or to establish and maintain territories

• Examples include territorial animals like the crested penguin and plants like the sage plant, which space themselves evenly due to their competitive needs for resources like water, sunlight, or the release of toxins that inhibit nearby plant growth. 

clumped distribution

• for protection

• unevenly distributed resources (water, nutrients), the need for protection from predators through group defense, or social and reproductive needs, such as mating or raising young

• Examples include schools of fish, herds of elephants, and oak trees growing near parent trees.

population sex ratio

• ratio of males to females

• number of offspring produced is a function of how many females there are

population age structure

• in a pyramid, describe how population is changing

• male vs. female or developed vs. undeveloped

• slope (top to bottom) determines speed

• 3 colors show pre-productive, reproducing, post-producing (reproductive ages)

density dependent limiting factors

• factors that influence the individuals survival and reproduction in a way that depends on the size of the population

• competition increases (for resources like food, water, etc.)

• spread of disease

• predation

• prey-predator

density independent limiting factors

• factors that affect population size, but is not influenced by changes in population density

• external influences

• nothing to do with how densely pact they are

• human distrubances

• natural disasters

exponential growth model

• J-shaped curve

• all species grow exponentially until r-selected species crash/outcompete themselves: dieoff

• biotic potential: max growth rate

• may grow exponentially because of lots of offspring, maybe no predators, living in ideal environment

logistic growth model

• s-shaped curve

• logarithmic

• organisms that live at their carrying capacity

• more select

• k-selected species

overshoot

• when a population grows beyond the environment's carrying capacity leading to resource depletion

• on a graph: find the peak value that the signal temporarily exceeds after a transition and compare it to the steady-state value

dieback

• a sharp decline in a population size that occurs after the population exceeds its carrying capacity

• on a graph:sharp, steep downward slope or a sudden drop

carrying capacity (K)

• max number of organisms an environment can support

• on a graph: look for the horizontal line that represents the maximum population size the environment can sustain, which is typically the point where an S-shaped (logistic) curve flattens out

biotic potential: r

• max growth rate

• on a graph: looking for the J-shaped (exponential) growth curve

• r- select species typically grow at their biotic potential

k-selected species

• ex.~ elephant

• long life span

• long time for reproductive maturity

• few number for reproductive events

• few offspring

• low biotic potential (gradual/ not steep curve)

• large offspring

• present parental care

• slow pop. growth rate

• density dependent pop. regulation

• strategy is carrying capacity

r-selected species

• opportunistic: reproduce and disperse rapidly

• ex.~ cockroach

• short life span

• short time for reproductive maturity

• many number of reproductive events

• many number of offspring

• high biotic potential (steep slope)

• small size of offspring

• absent parental care

• fast pop. growth rate

• density-independent pop. regulation

• strategy is biotic potential

type 1 survivorship curve

• you have high survival rates for organisms until later in life

• ex.~ humans, tortoises, elephants (k-select species)

• parental care, resource availability, and life-history strategies influence shape

type 2 survivorship curve

• linear decline

• survivorship is independent of age 

• have this because of predation

• consistent external pressures like predation, disease, and stable environmental conditions effect shape

• ex.~ songbirds, squirrels

  

type 3 survivorship curve

• high death rate early in life and those who survive live until later in life (few)

• high early mortality due to factors like predation and low parental care, combined with high reproductive output effects shape

• ex.~ frogs, turtles, fish, trees, (r-select species)

  

population size equation: nert (exponential growth)

• N=Noe^RT 

• N= new pop. size

• No=og. pop. size

• t= time in years

• r= intrinsic growth rate as decimal

• e= e^x key on calc or 2.72, natural log

• always round down

growth rate equation

• r= (b-d) +(i-e)

• b=birth

• d=death

• i=immigration

• e=emigration

• “crude” = #  / 1000

doubling time (rule of 70)

• D.T= 70/R

• rate must be in %

projecting time of pop. growth (rarely used)

• t= (1/r)ln(N/No)

• r= growth rate (as a decimal)

• ln= natural log

• N= future pop. size

• No= current pop. size

theory of island biogeography

• a balance between immigration and extinction rates, which are affected by an island's size and distance from the mainland

pre-industrial stage

• ex.~ north sentinal island

• birth rate is high

  • lack of contraceptives

  • one person having 9-10 children may be common

  • need for people to perform jobs

  • cultural (don’t realize we don’t need that many babies)

• death rate is high 

  • lack of medicine

  • exposed to elements

  • lack of nutrition

  • lack of prenatal care

• pop. size is stable or slowly increasing

transitioning stage

• ex.~ African nations, 3rd world countires

• Birth rate is high

  • lack of contraceptives

  • one person having 9-10 children may be common

  • need for people to perform jobs

  • cultural (don’t realize we don’t need that many babies)

• Death rate is falling rapidly

  • developing medicines

  • better nutrition

  • more education

  • family planning

  • contraceptives

  • advanced medicines

  • hygiene 

• pop. size is rapidly increasing

industrial stage

• ex.~ India, China

• Birth rate is falling

  • less need for manual labor

  • intro of manufacturing 

  • technology replaces need for people

• death rate is falling slowly

  • developing medicines

  • better nutrition

  • more education

  • family planning

  • contraceptives

  • advanced medicines

  • hygiene 

• pop. size: increase is slowing down

post-industrial stage

• ex.~ developed countries

• birth rate is low

  • more educational opportunities, careers over families

  • less need for workers

  • cost

• death rate is low

  • highly structured society

  • working conditions are better

  • advanced medicines

  • elderly care

  • better ideas for nutrition

  • money to have access

• pop size is stabilizing

declining stage

• ex.~ Russia, South Korea

• birth rate is yet to be seen, maybe falling further, then rising again

  • more educational opportunities, careers over families

  • less need for workers

  • cost

• death rate is low

  • highly structured society

  • working conditions are better

  • advanced medicines

  • elderly care

  • better ideas for nutrition

  • money to have access

• pop. size shows little change

population momentum

• the continued population growth that occurs even after fertility rates have fallen, because there is a large cohort of young people who will have children in the future

replacement fertility rate

• needing about 2.1 children per woman to maintain a stable population, considering factors like mortality and emigration

• Rosling uses this to explain that population growth is stabilizing, and even though people often have incorrect ideas about fertility rates, the trend is a decline due to factors like improved education, health, and family planning, which he believes will lead to population growth hitting a limit

total fertility rate

• the average number of children a woman would have in her lifetime, which has declined globally to about 2.5 children per woman

• is also linked to a country's development level

• the documentary uses this metric to argue that the world is not facing an uncontrollable population boom, but instead a manageable one