BIO220 Lecture 19 Flashcards
Human population ecology
Humans are a very unique species that need an ___ perspective, and have ___, ___, ___ issues.
ecosystem;
political;
sociological;
ethical
The carrying capacity of the Earth is limited by…
- food supply
- land (space)
What impact do humans have on natural systems?
- population size
- consumption
- technology
- 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?
Statistical error: - extrapolating is dangerous - logistic curve is too simple Biological: - 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
age
Shape of age pyramid: fast-growing populations
high momentum;
broad base, small tip: even if r = 0, populations keep growing as children reach reproductive age
shape of age pyramid: slow-growing populations
low momentum;
broad middle
Who made the first estimate of human capacity of earth? What was his estimate?
Antoni van Leewenhoek;
- 4 billion
- estimated land area of globe & applied density of Holland
