1. Chapter 16: Populations

2. 16.1
Population: all the individuals of a species that live together in an area (Ex: ____)
Demography: the statistical study of populations, make predictions about how a population will change

3. Three Key Features of Populations
1. Size
Small populations are most likely to become extinct. WHY?
Natural disturbances –fire, disease, flood
Inbreeding-homozygous for harmful recessive traits (Ex: dog inbreeding may produce deafness, underbite)
reduces diversity
2. Density- # of individuals that live in a given area
3. Dispersion-how individuals are arranged in space
clumped, even, or random –FIGURE 16-3 DRAW

4. Which dispersion pattern are these?
A. B. C.

5. Growth Rate = Birth Rate - Death Rate
1. In Cedar Grove, 15 babies were born in 2000, 4 residents died. What is the growth rate for Cedar Grove?
2. In Springfied, 1500 babies were born in 2000, 1550 residents died. What is the growth rate?

6. Growth Curves J - Shaped (exponential growth)
Population is steadily increasing FIGURE 16-4 DRAW
S - Shaped (logistic model)
Population size that the environment can sustain FIGURE 16-5 DRAW
Populations are limited by space, food, predators, disease, resources.
That limit is called the CARRYING CAPACITY-

7. The graph shows a (J or S) curve at the beginning, then over time it is (J or S)
Place a circle on the line where limiting resources stopped population growth.
Place an X on the graph where the deer reach CARRYING CAPACITY.

8. What Limits Population Size
Density-dependent factors: limited resources- space, food, water, air, shelter, nesting sites
Density-independent factors: random occurrences that can limit population - earthquake, bad weather, fire, etc.
Is disease density dependent, or density independent?

9. Growth Strategies K Strategists R Strategists long life span
reproduce slowly
have few young
parental care
Ex: elephants, humans; Some endangered Sp. (tigers, whales, rhinos, gorillas)
R Strategists
short life span
reproduce quickly
have many young
little parental care
Ex: cockroaches, weeds, sea turtles

10. r or K strategist?
a b. c.

11. Population Pyramids

12. Population of a Stable Country

13. Ways To Estimate Populations
1. Random Sample-sunflowers in a field
2. Mark & Recapture

14. 16.2 How Populations Evolve
Populations change over time as a result of environmental pressure (evolution)
Allele frequences in population change if evolutionary forces act upon them (Hardy Weinberg Principle)
Mutation is the source of variation

15. Evolution of Populations continued
Gene Flow: the movement of individuals to and from a population, migration
Immigration (IN) adds alleles
emigration (OUT) takes them away
Non random mating: individuals mate with others living nearby OR are of their own phenotype OR have certain traits
The probability that two individuals will mate in a population is not the same for all individuals

16. Genetic Drift: occurs in isolated populations, they become more alike (cheetahs)

17. Natural Selection Causes Changes in Populations
Natural selection acts only on:
phenotypes
Traits that are expressed
Peppered Moth
What about recessive alleles?
-NOT eliminated by natural selection
Heterozygous individuals carry allele but do not express it R r
SEE Punnett Square R r

18. Directional Selection: evolution favors an extreme trait, more and more individuals have the trait.
Ex: Rats get longer and longer tails
Stabilizing selection: extremes are selected against, favors the average

19. WHICH type of selection? A. B.
Peccaries naturally choose to consume those cactus plants with the fewest spines. Even with their tough mouths, they prefer to eat the cacti with 70 spines first, before going on to tackle the plants with 80 spines.
A parasitic insect lays its eggs at the base of the cacti's spines. When the grubs hatch, they bore into the cacti to eat the soft inner pulp, to grow, to pupate, and to emerge as new adults later in the year.