APES Test 3 - Population Ecology

Characteristics of a Population

geographical distribution, population density, reproduction/survivorship, sex ratio, population size/growth rate, age structure

Density Dependent Factors

factors that limit population growth based on density, ex: food/resource competition, predation

Independent Density Factors

factors that have an impact regardless of density, ex: natural disasters/extreme weather

Carrying Capacity

the maximum number of individuals that an environment can support based off of resources (k), once at it growth (r) =0

Logistic Growth

a population whose growth is initially exponential but slows and stabilizes at the carrying capacity (s curve)

Population Oscillation

recurring cycles of overshoots (more offspring than carrying capacity) then die-offs that lead to oscillating peaks above and below the carrying capacity

K Selected Species

organisms adapted to stable environments and high carrying capacity - invest in a few offspring with high chance of survival due to extensive parental care - long life, slow mature, large body (mammals)

R Selected Species

organisms with short lifespans, rapid reproduction of 100s of offspring, quick exploitation of resources, unstable environments - low chance of survival due to lack of parental care, rapid maturation, small body (insects)

Type I Survivorship Curve

long life spans, mammals (humans/elephants) - K selected species, small amount of offspring survive long and die off together - top line of survivorship curve

Type II Survivorship Curve

probability of mortality constant throughout lifespan, no in/decrease at any age, ex: birds, small mammals, reptiles, turtles - negative slope - middle line of survivorship curve

Type III Survivorship Curve

high mortality rate early in life, lower mortality for middle/later in life, ex: fish, insects, plants, marine species (R selected species) - bottom line of survivorship curve

Metapopulation

group of spatially separated interconnected local populations of the same species that can interact through disperal or migration

Competition

struggle of individuals to obtain a limited resource

Resource partitioning

species divide a resource based on temporal (time), morphological (adaptation), spatial (location) differences - natural selection favors less overlap

Symbiosis

mutualism, commensalism, parasitism

Mutualism

types of symbiosis, both species benefit, ex: clownfish get shelter/protection and anemones protected from parasites the clownfish eats

Commensalism

type of symbiosis, 1 species benefits while 1 species in unaffected, ex: barnacles on whales

Parasitism

type of symbiosis, 1 benefits while other is harmed, ex: ticks on dogs 

Keystone Species

a single species that plays a far bigger role in its ecosystem than its comparative abundance, can be predators that keep prey in check, ecosystem engineers, or mutualist - Ex: yellowstone wolves, sea otters, elephants, starfis

Predator Mediated Competition

organisms that reduce the abundance of the superior competitor, allows inferior competitors to exist, stops domination by one competitor

Succession

a series of predictable changes that occurs after a disturbance in a community - results in a long lasting climax community

Primary Succession

succession that begins when an environment is uninhabited and has NO SOIL, ex: lava covered land, land exposed by melting glaciers, abandoned parking lots - beings with pioneer species that start from nothing

Pioneer Species

1st species to populate a primary succession area - start from nothing, ex: lichen colonizes bare rock w acid which traps water and nutrients which can turn into moss then soil that can growth plants eventually

Secondary Succession

succession after a disturbance which destroys MOST of the community but still HAS SOIL - ex: forest fires/ floods /deforestation/farming - way faster than primary bc has soil and therefore nutrients - nearby unaffected areas can act as sources of nutrients 

Climax Community

what succession ends with, fairly stable predictable collection of organisms 

Intermediate Disturbance Hypothesis

species diversity is highest in ecosystems with intermediate levels of disturbance bc life there is challenged → no dominant species → creates diversity and adaptation

Human Population Growth Over Time

from beginning of humans to 1800 (298000 years) to reach 1 billion people - only 128 years to reach 2 billion people - 32yrs=3bil - 14yrs=4bil - 13yrs=5bil

Current World Population

8.146 Billion

United States Population

342 Million and growing

India Population

1.42 Billion and growing

China Population

1.4 Billion and declining

Population Growth Rate

Decimal Rate = Births - Deaths + Net Migration / 1000 - then multiply by 100 for percentage

Doubling Time / Rule of 70

number of years for a country to double with constant growth

Demographics

Life expectancy, child mortality rate, birth rate, death rate, GDP, school life expectancy, fertility rate, TFR, HIV/AIDS

Age Structure Graphs

show proportion of organisms at each age in a population - helpful for predicting pop growth, can be grouped as pre/post/reproductive years 

Growing Age Structure Graph

more pre-reproductive than reproductive - triangle shape - large incoming generation

Stable Age Structure Graph

pre-reproductive = reproductive - shaped like a house - replacement generation

Shrinking Age Structure Graph

pre-reproductive less than reproductive - diamond shaped, upside down triangle at the bottom - doesn’t replace current generation

Total Fertility Rate

average number of children born to each women in her lifetime - worldwide current =3 - higher in developing countries and lower in developed

Replacement Level Fertility

TFR needed for a population to stay stable - couple replaces themselves with 2 children - actually 2.1 bc some kids die before reproduction

Demographic Transition

the way birth, death and growth rates for a nation change with economic development (subsistence economy → industrialized /affluent economy) once there is a predictable shift in population growth

Phase 1 of Demographic Transition

Pre-industrial / subsistence period characterized by high birth AND death rates, slow population growth, low life expectancy (usually job / healthcare related), high infant mortality and fertility - most people farmers - today even the poorest countries are past this level

Phase 2 of Demographic Transition

Transitional period characterized by stable high birth rates but dramatically decrease in death rates - rapid population growth (improvements in medicine/edu/jobs) - means more people (large families) to provide for than resources - overpopulation causing a Poverty Trap in many developing countries (Somalia + the Congo)

Phase 3 of Demographic Transition

Industrial period characterized by falling birth rates, continuation of low death rates, stable population growth, use of birth control - smaller families, economy and education improve which modernizes employment - escape from poverty trap - developed countries (Mexico + Turkey)

Phase 4 of Demographic Transition

Post Industrial period characterized by very low birth rates and higher death rates - high affluence and economic development - TFR continually dropping, life expectancy increasing, causes population to be top heavy with elderly and shrinking (China + Italy)

High Fertility in Developing Countries

• cultural gender preferences

• lack of reproductive info/ family planning

• poverty trap

• lack of equality for women

• lack of access to birth control

• parents want their kids to take care of them when older

• Kids work for family business

• early age of 1st pregnancy

Ways to decrease TFR

THREE Es

Education - Equality - Employment

increase family planning / reproductive education / access to birth control, increase women’s equality, increase education for women (and job opportunities)

Low Fertility in Developed Countries

• Higher education

• better employment

• increased life expectancy

• later marriage

• increased equality for women

• access to birth control

• cultural focus

Aging Population Problems

caused by high → low birth rate and high life expectancy - high percentage of elderly people that are chronically ill/disabled → require more resources (healthcare) - don’t contribute to the economy (retired) → increased tax burden & SS / Pension strain

IPAT

Impact = Population x Affluence x Technology

Estimate of the impact human lifestyles have on the world - Higher affluence and GDP per capita are generally correlated with higher consumption and environmental impact - urban pops rep ½ of pop but consume ¾ of earths resources