10-15% of The AP Test

Topics

3.1 Generalist and Specialist Species

3.2 K-Selected r-Selected Species

3.3 Survivorship Curves

3.4 Carrying Capacity

3.5 Population Growth and Resource Availability

3.6 Age Structure Diagrams 5 EIN 3.7 Total Fertility Rate

3.8 Human Population Dynamics

3.9 Demographic

These notes are based on Mr Jordan Dischinger-Smedes’s YouTube videos and the fill in template notes for these videos created by Carolyn Kelleher Mendonca. Some changes were made. Videos available here.

Good luck on the AP Test! 🩷

3.1 - Specialist vs Generalist species

Specialists: Smaller range of tolerance, or narrower ecological niche makes them more prone to extinction

• Specific food requirements (bamboo)

• Less ability to adapt to new conditions

Generalists: Larger range of tolerance, broader niche makes them less prone to extinction & more likely to be invasive

• broad food requirements

• High adaptability

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3.2 - K-selected & r-selected

K-selected- “quality”

• few offspring, heavy parental care to protect them

• Usually reproduce many times over lifespan

  • Ex: most mammals, birds

• Long lifespan, long time until to sexual maturity = low biotic potential = slow pop. growth rate

  • More likely to be disrupted by env. change or invasives

r-selected - “quantity”

• Many offspring, little-to-no care

• May reproduce only once

  • Ex: insects, fish, plants

• 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

K-selected

• low biotic potential (rep. rate) = hard for pop. to recover after a disturbance (env. change)

• High parental care means death of parent = death of offspring

• Invasives (usually r) outcompete for resources with high biotic potential & rapid pop. growth

• less likely to adapt & more likely to go extinct

r-selected

• High biotic potential (rep. rate) = more rapid pop. recovery after disturbance

• low parental care means death of parent doesn’t mean death offspring

• Not as impacted by invasive species since their pop. grow quickly

  • More likely to be the invasive

• Larger pop. & faster generation time = higher chance of adaptation & lower chance of extinction

3.3 - Survivorship Curve

Survivorship Curves: line that shows survival rate of a cohort (group of same-aged individuals) in a pop. from birth to death

Faster drop in line = quicker death/life span of individuals

Slower drop in line = longer life span

Type I (mostly K-selected)

• High survivorship early in life due to high parental care

• High survivorship in mid life due to large size and learned defensive behavior

• Rapid decrease in survivorship in late life as old age sets in

  • Ex: most mammals

Type II (mostly r-selected)

• Steadily decreasing survivorship throughout life

Type III (mostly r-selected)

• High morality (low survivorship) early in life due to little to no parental care

• Few make it to midlife; slow, steady decline in survivorship in midlife

• Even fewer make it to adulthood; slow decline in survivorship in old age

  • Ex: insects, fish, plants

3.4 - Population and Carrying Capacity

Carrying Capacity (k): the max. Number of individuals in a pop. that an ecosystem can support(based on limiting resources)

• Fig. 1 is theoretical

• Fig. 2 is more realistic

• Pop. briefly “overshoots” (k) and then die-off happens

• Highest Population an ecosystem can support based on limiting resources:

  • Food

  • Water

  • Habitat (nesting sites, space)

• Overshoot: when a population briefly exceeds carrying capacity

  • Ex: deer breed in fall, give birth all at once in spring; sudden spike in pop. = overshoot

• Consequence of overshoot: Resource depletion ex: overgrazing in deer

• Die-off: when resource depletion (overshoot) leads to many individuals dying

  • Ex: many deer starve with too many new fawns feeding in spring

Example of die-off:

• Reindeer of St. Paul Island

  • 25 introduced in 1910

  • Growth was gradual (10’-30’), then exponential (30’-37’)

  • Carrying Capacity was overshot

  • Die-off lead to pop. crash as food resource (lichen) were severely depleted

• Real pops. don’t always fluctuate around carrying capacity. If resource depletion is severe enough, total population crashes can occur

1. Hare pop. Increase due to low predator pop. (lynx)

2. Lynx pop. Increase due to increase in food/prey (hare)

3. Increasing lynx pop. Decreases hare pop; leads to die-off

4. Hare die-off decrease lynx food source, leading to die-off

5. Hare pop. Increase due to low predator pop. (lynx)

3.5 - Population Change Factors

• Size: total number of individuals in a given area at a given time

  • Larger = safer from population decline

• Density: individuals/area

  • Ex: (12 panthers/km2)

  • High density = higher competition, possibility for disease outbreak, possibility of depleting food source

• Distribution: how individuals in pop. are spaced out compared to each other

  • Random (trees)

  • Uniform (territorial animals)

  • Clumped (herd/group animals)

Growth factors

• Sex ratio: ratio of males to females. Closer to 50:50, the more ideal for breeding (usually)

  • Die-off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting population growth

• Density-Dependent Factors: factors that influence pop. growth based on size:

  • Ex: food, competition for habitat, water, light, growth based on size

  • All of these things limit pop. growth based on their size; aka - small pop. don’t experience these, large do

• Density-independent: factors that influence pop. growth independent of their size

  • Ex: natural disasters
    (flood, fire, tornado, hurricane)

  • It doesn’t matter how big or small a pop. is, natural disasters limit them both

• Food is a density dependent factor. (also a limiting resource)

  • When twice as much food was added to the dish, both species increased carrying capacity by about 2x

• Biotic Potential = max. potential growth rate, with no limiting resources

  • May occur initially, but limiting factors (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

• Biotic potential = exponential growth

Logistical growth = initial rapid growth, then limiting factors to limit population to carrying capacity, or sigmoid curve

3.5 - Population Pyramids

Age cohorts & growth = groups of similarly aged individuals

• 0-14 = prereproductive; 15 - 44 = reproductive age; 45 + = post reproductive

• Size difference between 0-14 & 15-44 indicates growth rate

  • Larger 0-14 cohort = current & future growth

  • Roughly equal 0-14 & 15-44 = slight growth/stable

  • Larger 15-44 = pop. decline

• Extreme Pyramid shape = rapid growth

• Less extreme pyramid = slow, stable growth

• “House” shape = stable, little to no growth

• Narrowest at base = declining pop.

• Highest to Lowest Growth Rate

India > US > China > Germany

Number of 0-14 Individuals

• India = 360 million

• US = 62 million

• Germany = 11.5 million

• China = 270 million

3.7 - Calculating Future Population

• Total Fertility Rate (TFR): average number of child a women will have

  • Higher TFR = higher birth rate, higher pop. growth rate (generally)

• Replacement Level Fertility: The TFR required to offset deaths in a population and keep the population stable

  • About 2.1 in developed countries (replace mom & dad)

  • Higher in less developed countries due to higher infant mortality

• Infant Mortality Rate (IMR): number of deaths of children under 1 per 1,000 people.

  • Higher in less developed countries due to lack of access to: healthcare, clean water, and food

• Higher IMR = higher TFR, due to families having having replacement children

Factors of IMR decline:

• Access to clean water

• Access to healthcare

Factors that affect TFR

• Development (Affluence): the more developed the nation, the lower the TFR

  • More education for women

  • More economic opportunity for women

  • Higher access to family planning and education

  • Later age of first pregnancy

  • Less need for children to provide income through agricultural labor

• Gov. Policy: can play a huge role in fertility by coercive (forceful) or noncoercive (encouraging) policies

  • Forced or voluntary sterilization

  • China’s 1 child policy

  • Tax incentives to have fewer children

• Microcredits or loans to women without children to start businesses.

3.8 Malthusian Theory

(what Malthus theorized):

• 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 limited by food

Technological Advancement

• Humans can alter earth’s carrying capacity with technological innovation

  • Ex: synthetic fixation of Nitrogen in 1918 leads to synthetic fertilizers, dramatically increasing food supply.

• Growth Rate (r) = % increase in a population

  • Ex: a growth rate of 5% for a population of 100 means they grow to 105

• Crude Birth Rate (CBR) & Crude Death Rate (CDR)

  • Births & deaths per 1,000 people in a pop.

    • Ex: Global CBR = 20 & CDR = 8

  • Calculating Growth Rate (r)

  Multiple by 100 for percentage!

• Factors that increase pop. growth

  • Higher TFR → higher birth rate

  • High mortality can drive up TFR (replacement children)

  • High immigration level

  • Increased access to clean water & healthcare (decreases death rate)

• factors that decrease population growth rate

  • High death rate

  • High infant mortality rate

  • Increased development (education & affluence)

  • Increased education for women

  • Delayed age of first child

  • Postponement of marriage age

• Standard of Living

  • What the quality of life is like for people of a country is based on GDP and Life Expectancy.

• Gross Domestic Product (GDP) = key economic indicator of standard of living

  • Total value of the goods & services produced

  • Per capita GDP is total GDP/total population

    • So per capita means per person

• Life expectancy = key health indicator of standard of living

  • Average age a person will live to in a given country

  • Increases with access to food, water, and healthcare.

High GDP & life expectancy are both indicators of development and low population growth.

3.9 Demographic Transition Model

• Industrialization: the process of economic and social transition from an agrarian (farming) economy to an industrial one (manufacturing based)

• Pre-industrialized/Less developed

  • A country that has not yet made the agrarian to industrial transition

  • Typically very poor (low GDP)

  • Typically high DR & high IMR

  • High TFR replacement children & agricultural labor

• Industrializing/developing

  • Part way through this transition

  • Decreasing death rate & IMR

  • Rising GDP

• Industrialized/developed: completed the transition

  • Very low DR and IMR

  • Livery high GDP

  • Low TFR

Stage 1

• High IMR & high death rate due to lack of access to water and healthcare

• High TFR due to lack of access to:

  • Family planning

• Need for child labor

• Little to no growth due to high CBR & CDR balancing each other out

Ex: Virtually no country is in phase 1, but there are pockets or regions in phase 1 within countries who have transitioned to phase 2

Stage 2

• Modernizations bring access to clean water, healthcare, stable food supply

  • IMR and CDR decline

• TFR remains high due to

  • Lack of family planning

  • Need for labor

  • Generational lag

• Rapid growth, due to high CBR and declining CDR

• Econ./societal Indicators

  • Low per Capita GDP

  • High TFR

  • high IMR

  • low literacy rate

Stage 3

• Modernized economy and society increase family income, so TFR declines significantly due to

  • More education for women

  • Delayed age of marriage & first child to focus on ed./career

  • Access to family planning

• Slowing growth rate as CBR drops closer to CDR

• Econ./societal Indicators

  • High per capita GDP

  • long life expectancy

  • TFR near 2.1

  • High literacy rate

Stage 4

• Highly modernized countries that are very affluent

  • TFR declines even further as families become more wealthy and spend even more time on education and career pursuits

  • Increased wealth & education brings even more prevalent use of family planning

• CBR drops lower than CDR & growth becomes negative (pop. decline)

• Econ./Societal Indicators

  • High per capita GDP

  • ~2.1 TFR

  • Long life expectancy

Growth factors

• Sex ratio: ratio of males to females. Closer to 50:50, the more ideal for breeding (usually)

  • Die-off or bottleneck effect can lead to skewed sex ratio (not enough females) limiting population growth

• Density-Dependent Factors: factors that influence pop. growth based on size:

  • Ex: food, competition for habitat, water, light, growth based on size

  • All of these things limit pop. growth based on their size; aka - small pop. don’t experience these, large do

• Density-independent: factors that influence pop. growth independent of their size

  • Ex: natural disasters
    (flood, fire, tornado, hurricane)

  • It doesn’t matter how big or small a pop. is, natural disasters limit them both

• Food is a density dependent factor. (also a limiting resource)

  • When twice as much food was added to the dish, both species increased carrying capacity by about 2x

• Biotic Potential = max. potential growth rate, with no limiting resources

  • May occur initially, but limiting factors (competition, food, disease, predators) slow growth, & eventually limit pop. to carrying capacity (k)

• Biotic potential = exponential growth

Logistical growth = initial rapid growth, then limiting factors to limit population to carrying capacity, or sigmoid curve