Selection & Survivorship
Carrying Cap, Pop Growth, & Resource Availability
Human Population & Total Fertility
Total Fertility & Age Structure Diagrams
The Demographic Transition
100
What is the difference between generalist and specialist species? Be able to list examples.
Which is more susceptible to environmental change? Why?
Generalists: Species that can live under a wide range of biotic/abiotic conditions (raccoons, coyotes, deer, cockroaches, etc.)
Specialists: Species that can live under a narrow range of biotic/abiotic conditions (panda, koala, Canada lynx, etc.) --> More susceptible to environmental change because it requires specific conditions (a certain temp, pH, plant, etc.) to live
100
What are population growth models?
Mathematical equations that can be used to predict population size at any moment in time
100
Until recently in human history, the human population was relatively stable. What happened approximately 400 years ago and why did this happen?
Human pop increased due to better sanitation practices & agricultural output
100
Compare infant and child mortality. What factors can influence infant and child mortality?
Infant - # of deaths of children under 1 year of age per 1,000 live births
Child - # of deaths of children under age 5 per 1,000 live births
Can be indicative of adequate food supply, clean drinking water, good sanitation, level of pollution, access to prenatal care, etc.
Can differ within a country due to socioeconomic status, prenatal care, & exposure to pollution
100
What is the demographic transition? What happens in Stage 1 and 2 of the demographic transition and why?
Theory that a country moves from high to lower birth/death rates as development occurs & moves from a preindustrial to an industrialized economic system
Stage 1:
- Steady-state pop (CBR = CDR; no growth)
- Low life expectancy (dangerous living/working conditions)
- High infant mortality (disease, lack of health care, & poor sanitation)
- Developing agrarian economy (lots of farming)
- Many children = asset
Stage 2:
- Death rates decline while birth rates remain high due to better sanitation, clean drinking water, increased access to food/goods, access to health care
- CBR does not immediately decline because it typically takes a generation. During this time, educational systems can be implemented & birth control becomes more widespread.
200
Understand the difference between K- & r-selected species. Know the difference between their life span, number of offspring & reproductive events, size of offspring, etc. Be able to give examples.
K-selected species:
- Typically large
- Reach reproductive maturity relatively late
- Produce few, large offspring
- Expend significant energy on parental care
- Have low pop growth rate
- Reach carrying capacity (K) and stabilize
- Long life spans
- Competition for resources is high
- Sensitive to environmental due to response time
- Ex: Elephants, humans, whales, other large mammals, most birds, etc.
r-selected species
- Small with high PGR
- Typically overshoot carrying capacity & experience cycles of dieback
- Reach reproductive maturity early
- Reproduce frequently
- Produce many small offspring
- Provide little/no parental care
- Short lifespans
- Wide availability of resources with low competition
- Less vulnerable (often generalists)
- Ex: mice, rabbits, cockroaches, most fish, frogs, bacteria, dandelions, insects, etc.
200
What is an exponential growth model? What does exponential growth look like on a graph?
A model that estimates a pop’s future size over time based on biotic potential and # of reproducing individuals currently in pop
Creates a J-shaped curve
Describes a fixed rate of change applied to a continuously growing pop
Density dependent (dependent on pop size)
Not possible indefinitely --> carrying capacity
200
Understand inputs and outputs to population growth. When is population growth positive? When is it negative? How is a nation's population growth rate (as a %) calculated? Be able to use this formula to calculate a nation's population growth rate.
Inputs: births & immigration
Outputs: deaths & emigration
200
What is an age structure diagram? What do we use them for?
A visual representation of the # of individuals within specific age groups (5 yrs) for a country, typically for males & females. Delineated as pre-reproductive (0 to 14), reproductive (15 to 44), and post-reproductive (45+).
Used to understand how a population might change in the future.
200
What happens during stage 3 of the demographic transition and why?
- Economy & educational system improve
- Eventually, CBR begins to fall due to increased GDP (lowers TFR), excess children becoming a financial burden, more access to education & birth control
- Growth rate slows as CBR & CDR equalize
300
What is biotic potential? What would a graph of this population growth look like?
Under ideal conditions with unlimited resources, every pop has a max potential for growth --> exponential
300
What is a logistic growth model? What does logistic growth look like on a graph?
A Model that describes a pop whose growth is initially exponential, but slows as the pop approaches the carrying capacity of the environment.
S-shaped curve
Occurs as resources limit pop growth
Predicts density-dependent pops
300
Compare crude birth and death rates. How is global population growth calculated (as a %)? Be able to use this formula to calculate global population growth.
Crude Birth Rate (CBR) - # of births per 1,000 individuals per year
Crude Death Rate (CDR) - # of deaths per 1,000 individuals per year
300
Understand how to interpret an age structure diagram based on its shape. What do the shapes indicate about future population growth?
1. Population pyramids - age structure diagram that is widest at bottom/smallest at top, typically of developing countries
- Indicates future potential growth (high #’s of future reproductive females)
- Typical of developing countries (countries with relatively low levels of industrialization & income [less than $3/day/capital])
2. Diagrams with little difference between # of older and younger age groups
- Typical of developed countries (countries with relatively high levels of industrialization & income)
- Natural due to senescence
- Indicative of slow pop growth or no growth at all
3. Inverted pyramid - diagram with greater # of older people than younger people
- Indicates a decreasing growth rate over time
300
What happens during stage 4 of the demographic transition and why?
- Declining pop size with increased relative affluence/economic development
- Fewer young & more older people which can stress social security systems
- TFR sometimes increases after reaching 1.2-1.5 because it becomes somewhat easier to raise children → begin to do so in slightly greater numbers
400
What is a survivorship curve? Be able to identify the three types of survivorship curves and examples of organisms who fall into that type of survivorship.
A graph that represents the distinct patterns of species survival as a function of age.
Type 1 (Late Loss): Pattern of survival in which there is high survival throughout most of the lifespan, but then individuals start to die in large numbers as they approach old age. Includes K-Selected species like elephants, whales, & humans in developed countries.
Type 2 (Constant Loss): Pattern of survival in which there is relatively constant decline in survivorship throughout most of the lifespan. Includes chipmunks, squirrels, & some K-selected species like raptors.
Type 3 (Early Loss): Pattern of survival in which there is low survivorship early in life with few individuals reaching adulthood. Includes r-selected species like mosquitos, many fish, dandelions, & frogs.
400
What is the difference between density-dependent and density-independent factors? Be able to give several examples of each.
Density-Dependent Factors: A factor that influences an individual’s probability of survival/reproduction in a manner that depends on the size/density of the pop. Includes limiting resources, depletion of resources, & biotic influences on a population (i.e. - predation, disease, etc.)
Density-Independent Factors: A factor that has the same effect on an individual’s probability of survival/reproduction at any pop size/density. Includes tornadoes, hurricanes, floods, fires, volcanic eruptions, & climatic events.
400
Compare immigration and emigration. What is the net migration of a country? When is net migration positive? When is it negative?
Immigration - movement of people into a country or region
Emigration - movement of people out of a country or region
Net Migration: The difference between immigration & emigration in a given year per 1,000 people in a country
Positive net migration (immigration > emigration) vs. negative net migration (immigration < emigration)
400
What is total fertility rate (TFR)? What factors influence TFR of a country and how?
An estimate of the average # of children each woman in a pop will bear throughout her childbearing years (15 to 49).
Factors that affect TFR - Age at which someone has a their first child, access to education, access to health care, employment opportunities, access & info about contraceptives, total household income, a nation's gross domestic product (GDP), ability to practice family planning, child labor, average age at marriage, religious/cultural beliefs, social security programs, etc.
400
What is the rule of 70? What is it used for? Be able to use this equation for the exam.
Calculates the doubling time (the number of years it takes a pop to double if we assume a constant growth rate)
500
What is the carrying capacity of an ecosystem? What letter describes the carrying capacity on a graph?
Carrying capacity (K): limit of # of individuals that can be supported by an existing habitat/ecosystem
500
Understand how density-dependent factors like disease and predation can affect the carrying capacity of different organisms.
500
What is life expectancy? What might you infer about a country with a higher average life expectancy vs a lower average life expectancy?
The average # of years that an infant born in a particular year in a particular country can be expected to live, given the current average life span/death rate in that country
Farther along in the demographic transition (higher quality of life, more access to health care, sanitation) vs. less far along in the demographic transition (lower quality of life, less access to health care, little or no sanitation)
500
What is replacement-level fertility? What can replacement-level fertility tell you about future population growth?
The fertility rate required to offset average # of deaths in a pop in order to maintain current pop size
1. TFR = replacement-level fertility & where immigration = emigration → pop is stable
2. TFR is less than 2.1 with no net increase from immigration → pop decrease
3. TFR is greater than 2.1 with no net decrease from emigration → pop growth
500
What is the IPAT equation? Understand how each variable affects environment impact.
A conceptual representation of the 3 major factors that influence environmental impact: population, affluence, & technology
- Population: more people = more impact
- Affluence: More affluence = higher impact
- Technology: Complicated because it can degrade the environment OR minimize impact on environment
