1. Evolution by Natural Selection explains the process of change
SCIENCE - an organized way of using evidence to learn about the natural world
EVOLUTION
“descent with modification” - all life on earth shares a common ancestor
change in gene frequencies of a population from generation to generation
Observations of the natural world from many fields of science provide evidence of the pattern of change
Evolution by Natural Selection explains the process of change
This is the genius of Charles Darwin – a mechanism - natural selection – which explains the observation that living things have and continue to change

2. SCIENTIFIC EVIDENCE*? DIRECT OBSERVATION FOSSIL RECORD HOMOLOGY
BIOGEOGRAPHY
*OBSERVATION OF THE NATURAL WORLD MADE WITH THE SENSES, FACTS, REPEATABLE

3. DIRECT OBSERVATION – guppies
Can we observe evolutionary change occurring in a changing environment?
GUPPIES – John Endler, University of California

4. DIRECT OBSERVATION – guppies
Can predation result in natural selection for color pattern in guppies?
Observations – guppies, Poecilia reticulate, Aripo River, Trinidad
No 2 male guppies have the same color pattern (genetic)
Females mate more frequently with brightly colored males
Being a brightly colored male increases the chance genes will pass to the next generation but does it also increase the likelihood that the male will be eaten? Could the presence of predators influence the number of brightly colored males?

6. 15 generations later – guppies transplanted from pike-cichlid pool to killifish pool

7. What if the guppies are returned to the source pool?
Can you discuss this in terms of natural selection?
Genetic variation
Overproduction of offspring
Struggle for existence
Differential survival and reproduction
What is sexual selection?

8. DIRECT OBSERVATION – drug resistant HIV
Can we observe evolutionary change occurring in a changing environment?
3TC LOOKS LIKE A BUILDING BLOCK OF DNA – ENZYME WILL ADD 3TC TO DNA IT IS BUILDING – STOPS DNA REPLICATION

9. DIRECT OBSERVATION – drug resistant HIV
3TC SHUTS THIS PROCESS DOWN

10. DIRECT OBSERVATION – drug resistant HIV
Is there genetic variation in virus?
3TC resistant viruses already existed in the population of viruses
Being resistant is not an advantage until exposure to 3TC
Resistant viruses have a slightly different version of reverse transcriptase
Without 3TC they replicate more slowly than viruses with the typical version of the enzyme
Is there overproduction of offspring?
Is there a struggle for existence?
Is there differential survival and reproduction?

11. Why does resistance develop so rapidly?
Viruses reproduce large numbers of individuals very rapidly – even faster than bacteria
Viruses with a survival advantage will increase in number very rapidly.
Each year’s flu vaccine is slightly different because of this!

12. WHAT IS THE LESSON?
NATURAL SELECTION DOES NOT CREATE GENETIC VARIATION
IT DOES SELECT FOR INDIVIDUALS THAT HAVE A SURVIVAL ADVANTAGE – genetic variation is inherent in populations.
NATURAL SELECTION DEPENDS ON TIME AND PLACE
WHETHER OF NOT A GENETIC VARIATION PROVIDES AN ADVANTAGE DEPENDS ON CURRENT, LOCAL ENVIRONMENT

13. FOSSIL RECORD
Fossils are physical evidence of organisms that lived in the past.
BE SURE TO READ ABOUT FOSSILS PAGE , FIGURE 22.3,
Phil Gingrich made a whale of a discovery in 1978! Watch it here. ~ 5 minutes
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