Unit 4 Lecture 20

Question 1

Explain the steps of demographic transition

Answer 1

1. Initial, stable population (start with low population size with a high birth rate and death rate)
2. Death rates decline, causing population to grow (have an event which causes death rates to decline, causing population to grow
3. Birth rate lags and starts to decline
4. Population stabilizes again

Question 2

What stages are:
a. US/France/Japan
b. Niger/Chad
c. India/Bangladesh

in

Answer 2

a. Stage 4
b. Stage 2
c. Stage 3

Question 3

What are some hypotheses that explains why birth rate decreases after death rate?

Answer 3

1. Life history trade-off (maybe when they get more wealthy, parents look more at the quantity v quality)
2. Cost of offspring increases with cost of living
3. People copy behavior of prestigious individuals
4. Sexual revolution: release from patriarchy (back in the day men made women have many babies and now we don’t have to)
5. Maximizing wealth and wealth transfer to offspring

Question 4

Explain how energy and energy use affects population density

Answer 4

• As individual energy use goes up, population density goes down
• What we see in the pre-industrial and modern cities is higher individual energy use AND population density
• What we are doing with all of the energy we extract from fossil fuels is pumping it into modern cities

Question 5

Talk about the study with cane toads

Answer 5

• In northern part of Australia these men released cane toads to protect their sugar cane from the caterpillars that was destroying the crop
• They assumed the cane toads would eat this pest species, but they did not and now there is an invasion path of cane toads across australia

Question 6

Whats the difference between K-selection and R-selection?

Answer 6

K-Selection: When population is at carrying capacity, “slow life history” is favored (fewer maturation, larger offspring)

R-Selection: When population is growing exponentially “east life history” favored (earlier maturation, more offspring)

Question 7

What crosses did they do in the cane toad study?

Answer 7

They cross bred toads from different populations to determine if there is heritable difference in life history

Question 8

What was the conclusion of the cane toad study

Answer 8

• if parents came closer to the invasion front, the tadpoles grew faster so they would mature earlier
• Growth rate decreased as you got father from the invasion front
• Life history traits are under strong selection
• Selection on life history may change across time during population growth and range expansion
• Invasive species are important test cases for evolution