1. Introduction to Evolution
PHA Biology 9
Moretti/ Dickson

2. EVOLUTION
Genetic changes in a species or population over time

3. Connecting Genetics and Evolution: Cystic Fibrosis Case Study
Figure 1. Chest Radiograph of CF Diffuse Interstitial Disease
Image: Reprinted with permission from LearningRadiology.com. Case of the Week Archives—2003. Cystic Fibrosis. Available at: ocarchives2003.htm. Accessed January 28,

4. Agenda & Goals for Today:
Share ideas from the Do Now
How does cystic fibrosis illustrate evolution?
What causes evolution?
Notes
Vocabulary – Define population, gene pool, and fitness
Levels of Evolution – Explain the difference between micro and macro-evolution
Natural Selection – Identify key principles of natural selection
Videos:
Evolution in Hummingbirds
Evolution in Bacteria
** Announcement: Optional Challenge Questions **

5. Vocabulary Population Gene Pool Evolution (on a population scale)
Group of individuals from the same species that live in the same area and interbreed
Gene Pool
All the genes and all of their alleles in a population
Evolution (on a population scale)
Any change in the proportions of alleles over time
(One allele becomes more common, another becomes less common)
Change in a population NOT change in an individual
Fitness
How well a particular organism can survive and reproduce to pass on its genes to the next generation
Objectives for Class:
Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

6. Macro-Evolution Large-scale, often over a very long time
Branching of one species into two species
All species share a common ancestor
Example: Evolution of whales from four-legged land mammals
Objectives for Class:
Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

7. Micro-Evolution Micro-evolution leads to Macro-evolution Small-scale
Changes in a population’s gene pool over time
Caused by natural selection and/or genetic drift
Example:
CF allele becomes more common in European populations because it protects against tuberculosis
Micro-evolution leads to Macro-evolution
Objectives for Class:
Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

8. How Does Natural Selection Happen? Video: Hummingbirds in Ecuador
What are some adaptations that these hummingbirds have?
As we watch the video: make a list of Principles of Natural Selection
Objectives for Class:
Use actual evidence to explain how the four principles of natural selection shape the evolution of organisms

9. Principles of Natural Selection
Genetic variation between individuals
Due to mutation and gene shuffling (sexual reproduction)
More offspring are born than can survive
Competition/struggle for limited resources
Some individuals are more genetically “fit” than others – they are better at surviving, reproducing, and passing on their genes
Result: Over many generations, the “fit” alleles become more common in the whole population because they are more helpful for surviving and reproducing.
SUMMARY: SURVIVAL & REPRODUCTION OF THE FITTEST

10. Examples of Natural Selection:
Ex. 1: Long beaks become more common in a hummingbird population because long beaks help get food Ex. 2: Sickle cell anemia becomes more common in African populations because SCA protects against malaria Ex. 3: CF becomes more common in Europeans because it protects against tuberculosis Ex. 4: Some TB bacteria have evolved to resist antibiotics

11. Video: Evolution in bacteria
(6 minute video)

12. Notes: SPECIES and SPECIATION
A group of similar organisms
Can breed with each other and produce fertile offspring
Examples:
Human species (Homo sapiens)
Horses and donkeys = two separate species because their offspring (mules) aren’t fertile
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

13. Speciation - The formation of new species from a common ancestor
The gene pools of two populations must become separated
Ex: The Galapagos Finches
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

14. Two Main Steps of Speciation
Reproductive Isolation
Changes in the Gene Pool
Gene Pools Diverge (become different)
Genetic Barriers to Reproduction Arise
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

15. Reproductive Isolation
One population becomes separated and stops breeding with the rest of the species
Behavior:
Changes in courtship or other reproductive strategies
Geographic
Geographic barrier splits population (i.e.: river, mountain, body of water, etc.)
Populations are separated and cannot interbreed
Temporal
Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding)
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

16. Changes in the Gene Pool
Gene Pools Diverge (become different):
The isolated populations become genetically different.
The new environments or behaviors favor different genetic traits (natural selection)
Genetic Barriers to Reproduction Arise
The two populations can no longer interbreed
Due to genetic differences in habitat preference, mating behavior, or physical compatibility
They are now two separate species!
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

17. Hybrid - The offspring of a mating between two different species
If a hybrid can’t have offspring, there are still two separate species!

18. Reproductive Barriers That Maintain Separate Species
Before mating occurs
Geographic barriers
Ecological/habitat differences
Temporal differences
Behavioral/courtship differences
Mechanical differences
Chemical differences
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

19. Reproductive Barriers That Maintain Separate Species
After mating occurs:
Hybrid dies before birth
Hybrid is weak and sickly
Hybrid is sterile (can’t reproduce)
Objectives for Class:
Explain the defining characteristics of a species
Describe the 2 steps of speciation

20. Famous Hybrids that are strong but STERILE!