Flashcards in BIO220 Lecture 19 Deck (64):
Humans are a very unique species that need an ___ perspective, and have ___, ___, ___ issues.
The carrying capacity of the Earth is limited by...
- food supply
- land (space)
What impact do humans have on natural systems?
- population size
- affluence (have a lot of money)
Growth trajectory: shape & assumptions
shape: density-dependent, exponential
assumptions: rates are constant, [births + immigration] > [death + emigration]
immigration vs. emigration
immigration: move into population
emigration: move out of population
problem with growth trajectory model
too simple, populations cannot continue to grow unchecked
model/formula for exponential growth trajectory
dN/dt = rN
N_t = (N_0)(e^rt)
with is the simplest model of density-dependent regulation of growth?
logistic growth model
- dN/dt = rN[(K-N)/K)
- sigmoidal curve
- carrying capacity K
what was the first really successful ecology textbook?
The Great APPES
by Allee et. al
in the mid-20th century, ___ was viewed as an ecological law
logistic growth model
What was was predicted by Allee et. al in 1940's regarding human growth?
Human population should level off at 2.6 billion (predicted until 2010)
Current population: 2.4 billion
What is the current population (2011)?
7 billion +
Human population growth curve looks...
exponential rather than logistic
Why did extrapolating from logistic growth model give poor prediction for human growth?
- extrapolating is dangerous
- logistic curve is too simple
- logistic allows no overshoots
- logistic assumes r and K are constant
If we allow populations to overshoot K, what will the population model look like?
- dramatic overshoot (exponential growth)
- dramatic crash (exponential decrease)
= sinusoidal wave (mean of wave is K)
Why is current human population growing so fast?
- birth rate has always been high, but now, death rate is very low (technology, medicine, sanitation, nutritious foods)
- slightly increase in fertility
- increased K due to changes in agriculture (genetics, machine, fertilizers, biocides)
Growth (r) depends on...
fertility rates (bx) & mortality (inverse Lx)
What is the UN's guess about human growth trajectory?
level off at about 9 billion (maybe)
current observations on human growth trajectory
still growing exponentially, but much slower
- 2% growth/year (x^2) -> 1.2% (x^1.2)
- 74 million increase/year
leveling off the growth trajectory requires...
- less birth
- more deaths
___ structure affects trajectory
Shape of age pyramid: fast-growing populations
broad base, small tip: even if r = 0, populations keep growing as children reach reproductive age
shape of age pyramid: slow-growing populations
Who made the first estimate of human capacity of earth? What was his estimate?
Antoni van Leewenhoek;
- estimated land area of globe & applied density of Holland
What was seen in Cohen's history of K estimate?
the carrying capacity prediction varies more as times are more modern
The real answer to human K depends on...
how people are living
Who said that human K depends on how people are living?
Current food production can support ___ people if we consume like India
Current food production can support ___ people if we consume like Canada/US
Demographic Transition Model
1. Pre-industrial: birth & death rate high (r = 0)
2. Death rates fall -> population boom
3. Birth rates fall -> growth rate slows
4. Birth & death rates equilibrate (r = 0)
death rates might fall because of...
birth rates might fall because of...
- changing cultural values
- later marriage
Changes in age distribution have profound consequences for...
- social structure
- government programs (based on more people paying into system than those collecting out of it)
ratio of youth + elderly : working adults
What causes spikes in death rates?
baby boom "echo"
- children born during the baby boom had children themselves
after WWII, people wanted to "replenish the population" to replace those who died in the war
when do we usually see baby booms?
what causes fertility to decline?
- government policy
- decision by parents (greater survival of children, children too expensive, society can take care of them in old age, overpopulation)
- marry later
which countries have government policies to control population growth?
Where are human populations growing the fastest?
Middle East & Africa
Where are human populations not growing?
nowhere, just some places faster than others
where has the highest GDP?
US has most GDP/capita
30 years ago, what were the fastest growing populations?
- Latin America
Which counties has the highest 2011 population?
Problem: GDP/capita vs. population growth
If we want to equalize population growth with resource distribution: populations that are growing the fastest has the least GDP/capita
Will demographic transition model be seen in developing countries?
- unsure why fertility rates fall
- death rates still high (infections, HIV)
- some places oppose contraception
Maybe if women can be educated & given contraception methods, as well as economic opportunites
Different views on population issues: what were the 2 sides?
Neo-Malthusians vs. Cornucopians
Neo-Malthusians was founded by ___. Their view?
Malthus (current leader: Enrlich)
- growth is controlled by natural selection
- continued human population growth is unsustainable
- current level is probably unsustainable
- over-consumption will exhaust K
Cornucopian was founded by ___. Their view?
- technological improvements will increase K
- population can grow without limits
- when resources become limited -> demand increase -> new technologist allow more harvest
Paul Ehrlich is famous for ___. He helped found ____, and urge governments to ___.
The Population Bomb;
Zero Population Growth;
Julian Simon believes that ___ forces can solve problems
what was the first Ehrlich-Simon bet? Outcome?
Metal (Ni, Sn, Cr, W, Cu) prices raise/drop from 1980 -> 1990?
Ehrlich lost: all metals became cheaper due to substitution
What was the Simon-David South bet? Outcome?
Will resource prices raise due to scarcity? Will market price of lumber rise/fall over the next 5 years (1996)?
Simon lost: lumber prices went down
What was the second Ehrlich-Simon bet (1994)? Outcome?
Will selected conditions affected humans get worse/better?
- temperature: warmer
- atmospheric CO2, N2O, ozone, SO2: more
- crop-land per person: less
- firewood/person: less
- area of tropical forest: less
- fishery harvest/person: less
- species of wildlife: less
- death from AIDS: more
- sperm count, reproductive disorders: less, more
- gap in wealth: increase
Simon refused bet (would have lost)
Why is managing populations not popular with left or right-winged political views?
left: rich countries shouldn't boss poor countries around and dictate how much they want to have babies
right: birth control is wrong
How do we address population growth in a good way?
Give women education, legal rights, access to contraception
- fertility rates fall
- standard of living goes up
- no compulsion (force)
There have been no countries in the pre-industrial phase of demographic transition since...
Rwanda in 1990s (war)
countries in phase 2 of demographic transition
countries in phase 3 of demographic transition
countries in phase 4 of demographic transition
Economic development in ___ and ___ accounts for much of recent rise
India & China