Population Ecology
BE SURE TO CLICK
ON THE LINKS IN LECTURE 18 TO KNOW MORE ABOUT POPULATION GROWTH!!
ALSO, NOTE THAT SOME RATES AND POPULATION
SIZES MAY DIFFER FROM THOSE IN LECTURE.
THIS IS BECAUSE POPULATIONS HAVE EITHER
GROWN OR SHRUNK SINCE I WROTE THE LECTURES,
AND ESTIMATES TEND TO VARY DEPENDING
ON WHO IS DOING THE ESTIMATES.
1. Know what affects population size: Births, Deaths, Immigration,
Emigration
2. When do populations change size? Whenever (Births+Immigration)
not equal to (Deaths+Emigration)
3. Ignoring Immigration and Emigration, then populations depend solely
on Births and Deaths
4. Know how to define r, the intrinsic rate of increase.
5. BE ABLE TO USE THE EQUATIONS I HAVE PROVIDED YOU. Here are
some work problems to help you.
The answers are at the end of this study guide.
If you can't work these, you need to study these more or
come to see me. Math phobia is not an excuse
anymore.
a. Suppose you had a population of 100,000 and during
one year there were 350 births, and 250 deaths.
What is r?
b. Suppose you had a population of 1,550,000 and
an intrinsic rate of increase of 2.5%.
By how much would this population
have grown after one year?
c. A population goes from 2,000,000 to 1,940,000 in one year. What is r?
d. How long would it take the population in step a to double? The population in step b?
e. Given a United States population of 280 million
right now, and a rate of increase of 0.8%,
how large do you estimate
it will be in the year 2043?
f. The world population is growing at a rate of 1.4%
globally. As of today, it is 6.28 billion.
What will it be in the year
2050?
6. Go to this URL for some great information on population growth: http://www.prb.org/Content/NavigationMenu/PRB/Educators/Human_Population/Population_Growth/Population_Growth.htm
7. Know the definition of "carrying capacity". What is the growth
rate at the carrying capacity? Are humans above or below K?
8. Know what Thomas Malthus said about population growth and food supply.
9. Be able to distinguish growth rates for developed vs undeveloped
countries.
10. What are the main factors that have allowed such rapid population
growth recently?
11. What are some ways to counteract population growth?
12. How does the demography of a developing country differ from that
of a developed country?
13. Be able to interpret survival curves (Type I, II, and III). Which
type exemplifies humans? Insects? Mollusks?
14. What are the three ways populations can be distributed in the landscape?
Random, Regular, Clumped.
Community Ecology
1. You should be able to recognize communities of North America and
around the world.
2. Know what environmental factors are responsible for shaping major
plant communities.
3. What is succession? Distinguish between primary and secondary
succession processes.
4. Know the major species interactions: mutualisms, parasitism, commensalism,
predatory-prey, etc.
5. What is biodiversity? What are the major global patterns?
6. Who coined the term biodiversity?
7. What the patterns of diversity with respect to island size and distance?
Why?
8. How are humans affecting the planet's biodiversity?
Ecosystem Ecology (only if we get this far on Tuesday
- if we don't, it won't be on the test!!)
1. Ecosystems are the interaction of the biotic and abiotic portions
of the environment
2. Properties include elemental cycling (water, carbon, nitrogen, phosphorus,
etc.) and energy use
3. Nutrients can be recycled, by not energy
4. Energy is lost as one moves up the trophic levels (approximately
90% lost for each level)
5. Food webs represent trophic interactions among species
6. Know the difference between autotrophs and heterotrophs
There is more in the lecture, but we won't get to it by Tuesday, so
stop at this point.
Answers to population ecology questions above:
a. Suppose you had a population of 100,000 and during one year there
were 350 births, and 250 deaths.
What is r?
N = 100,000. Births
- Deaths = r = 350 - 250 = 100. Divide r by 100,000 to get r per
person: 100/100,000 = 0.001
This is a 0.1% growth rate.
b. Suppose you had a population of 1,550,000 and an intrinsic rate of
increase of 2.5%.
By how much would this population
have grown after one year?
dN/dt
is our equation. It is dN/dt = rN
r = 0.025
N = 1,550,000
dN/dt = 0.025*1,550,000 = 38,750
The population would have
grown by 38,750 people in one year.
c. A population goes from 2,000,000 to 1,940,000 in one year.
What is r?
This
is a change of 60,000 people (in this case, 20,000 more people die than
are born!)
r is simply the percent change, so it is:
-60,000/2,000,000 = -0.03
In other words, this population is shrinking at a rate of 3% per year.
d. How long would it take the population in step a to double?
The population in step b?
The
equation for doubling is 0.7/r. Therefore the doubling time is:
0.7/0.01 = 70 years.
e. Given a United States population of 280 million right now, and a
rate of increase of 0.8%,
how large do you estimate
it will be in the year 2043?
Use
our other equation: Nt = No*ert
where
Nt is the population at time t, or 40 years from now,
No is the population now, in 2003, r is the intrinsic rate of increase (0.008) and t is the time (40 years).
Nt = 280,000,000*e(0.008*40) = 280,000,000*1,37713 = 385,595,774 people!!
NOTE:
I don't expect you to be able to figure out how to calculate values raised
to the power of e. I
will give those to you if they appear on the test!!
f. The world population is growing at a rate of 1.4% globally.
As of today, it is 6.28 billion.
What will it be in the year
2050?
Use the same equation as in problem e. Nt = No*ert where t = 47 years and No equals 6.28 B
The answer comes out to be 6.28B * e(0.014*47) = 6.28B * 1.9309 = 12.13 Billion!!
To practice more problems,
consult the websites referred to above, or change the numbers in these
problems
and continue to practice.