1. DO NOW: What comes to mind when you hear the word “EVOLUTION”
HOMEWORK: Complete the “In your Own Words” Section of the Hummingbird Activity.

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

3. Micro-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

4. Macro-Evolution Micro-evolution leads to Macro-evolution
Large-scale, often over a very long time
Branching of one species into two species
Leads to the idea that all species share a common ancestor
Example: Evolution of whales from four-legged land mammals
Micro-evolution leads to Macro-evolution

5. Some New Evolution Terms
Population
Group of individuals from the same species that interbreed
Gene Pool
All the genes and all of their alleles in population
Relative Frequency
The proportion of one allele in the whole gene pool
Evolution (on a population scale)
Any change in the relative frequency of alleles over time
One allele becomes more common, another becomes less common
Change in a population NOT change in an individual
Fitness
The ability of a particular genotype to reproduce and pass on its genes to the next generation

6. Hummingbirds and Evolution
How does evolution really work?
Let’s look at the scientists studying natural selection in Hummingbird Populations in Ecuador:

7. Selection – differential survival and reproduction of individuals with different genotypes
Natural selection involves…
More offspring are born than can survive
Competition/struggle for survival for limited resources
Variation between individuals that makes some better able to survive and reproduce
This variation is heritable/genetic (can be passed on)
Result: Over many generations, the genotypes that are better able to survive and reproduce become more common in the population.

8. Sources of Genetic Variation
Mutations
Any change to a DNA sequence
Rare
Sometimes harmful, sometimes helpful
Mutations to egg or sperm = inheritable
Mutations to body cells = not inheritable (CANCER)
Gene Shuffling
Meiosis divides the genetic info and fertilization recombines it
23 pairs of chromosomes = 8.4 million different combinations of genes
Crossing Over during meiosis increases the number of different combinations of alleles

9. Galapagos Finch Activity…

10. Let’s think back: What are the connections to Sickle Cell Anemia and Natural Selection?
Recessive Disorder
Result of a single gene mutation in hemoglobin, the substance that helps blood cells carry oxygen.
Amino acid valine replaces glutamic acid in the hemoglobin protein, making blood cells sickle-shaped.
People who are heterozygous are partially resistant to malaria (carried by mosquitoes)

11. Balanced Polymorphism (a. k. a
Balanced Polymorphism (a.k.a.: Heterozygote Advantage) Ex: sickle cell anemia

12. DO NOW: What is the difference between polygenic vs. single gene traits?
HOMEWORK: no homework… unless you feel like revising the Galapagos Finch Activity (note: 5% reduction)

13. Human Inheritance Single Gene Traits: Polygenic Traits:
Traits controlled by a single gene (A or a)
i.e.: widows peak
Polygenic Traits:
Traits controlled by two or more genes
Often with more than two alleles for gene.
i.e.: skin color, eye color, body shape, height, etc.

14. Frequencies of Polygenic Traits

15. 3 Modes of Selection for Polygenic Traits:
Directional Selection
Stabilizing Selection
Disruptive Selection
Remember:
Natural Selection only really acts on the organism NOT the genes.
It only selects for traits based on whether the organism dies or lives to reproduce.

16. Directional Selection
Individuals with Phenotypes at one extreme die off or fail to reproduce
Individuals with Phenotypes at the other end have greater fitness and leave a higher number of offspring.
This shifts the relative frequency in the direction of the successful extreme.
When it Happens:
If there is a change in the environment that favors the phenotype at one extreme and not the other.

17. Stabilizing Selection
Individuals with phenotypes at both extremes die off or fail to reproduce.
Individuals with intermediate phenotypes have better survival.
Results in populations of individuals with intermediate phenotypes. Less variation at the extremes.

18. Disruptive Selection
Individuals with phenotypes at both extremes have better survival
Individuals with intermediate phenotypes die off or fail to reproduce
Can result in two distinct phenotypes, which can lead to subpopulations

19. What kind of selection is this?

21. Galapagos Finches

22. DO NOW: Log Into Your Computers!
Tuesday:
DO NOW: Log Into Your Computers!
HOMEWORK:
Read Section 16-3 (pgs. 404 – 410)
Finish Analyzing Data Questions (pg. 408 #1-4)
On page 410, answer questions #1-3.

23. Key Questions: 1. What is the evidence that one species can branch into two? 2. What is the evidence that multiple species are evolutionarily related?

24. Evolution Dry Lab Part A:
Computer Lab: All in the Family:
Which Animals are the Closest Relatives?
Link:

25. DO NOW: What do you think a “species” is?
Wednesday:
Title: Species and Speciation
DO NOW: What do you think a “species” is?
HOMEWORK:
No HOMEWORK TONIGHT (unless you need to work on Part A or revise last night’s HW) 

26. SPECIES
A group of similar organisms
Breed with each other
Produce Viable Offspring

27. Speciation – The formation of new species.
The gene pools of two populations must become separated
Ex: The Galapogos Finches

28. Steps of Speciation: Reproductive Isolation Changes in the Gene Pool
Gene Pools Diverge
Genetic Barriers to Reproduction

29. I. Reproductive Isolation
One population becomes isolated from 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
Conditions of their local environment select certain traits
Temporal
Species reproduce at different times or have other behavior that becomes time sensitive (i.e.: feeding)

30. II. Changes in the Gene Pool
Gene Pools Diverge:
The isolated populations become genetically different.
Due to selection and/or genetic drift
Two separate gene pools emerge
Genetic Barriers to Reproduction
The two populations are no longer able to interbreed
Due to genetic differences in habitat preference, mating behavior, or physical compatibility
Competition may arise between these two new species
They are now two separate species!

31. Reproductive Barriers That Maintain Separate Species
Before mating occurs
Geographic barriers
Ecological/habitat differences
Temporal differences
Behavioral/courtship differences
Mechanical differences
Chemical differences
After mating occurs
Hybrid inviability
Hybrid breakdown
Hybrid sterility

32. Famous Hybrids

33. (Less so)… Famous Hybrids
Real-World Research…

34. Move to “Evidence for Evolution Presentation”