1. Question of the Day Mar 14 Which is not true about a species?
A. Members live in populations
B. They cannot breed with one another
C. They can breed between different populations.
D. All members contribute to the species gene pool.

2. AGENDA Mar 14
Objective: Investigate how genetic variation is responsible for natural selection.
1. Question of the DAY
2. Chapter 16-1 Genes and Variation 3. Homework Check 16-1 Guided Reading
4. Review and Homework
16-2 Guided Reading

3. Evolution of Populations
Chapter 16
Evolution of
Populations

4. 16-1: Genes and Variation natural selection relies on variation
genes are the source of inheritable variation
when variation occurs, nature selects the successful ones
individuals do not change, a population does

5. Genes and Variation
At least two different alleles account for inherited traits.
Body size, coat color, seed shape
“Invisible” variation also present
Small differences in biochemical processes

6. Genes and Variation
Individual organisms are heterozygous for many genes
15% of genes in insects
4 – 8% in fish, reptiles, and mammals

7. Evolution as Genetic Change
evolutionary biologists study populations
collection of individuals of the same species in a given area
share a gene pool
relative frequency: number of times an allele occurs in a gene pool compared with the number of times other alleles for the same gene occur
What is the relative frequency of the purple allele?

8. Genetic Variation within a Species
species: group of similar organisms that breed with each other and produce viable offspring because they share the same gene pool
How do mutations occur?
Mistakes in replication, radiation, and chemicals
Gene Shuffling - Meiosis

9. Genetic Variation within a Species
How many different combinations of genes can be produced from homologous x-somes in a human?
8.4 million
Number of phenotypes produced for a trait depends on how many genes control the trait
Single-gene trait
Polygenic trait

10. Single-gene and Polygenic

11. QUESTION of the DAY Mar 17
The success of an organism in surviving and reproducing is a measure of
A. an adaptation to an environmental factor
B. its fitness
C. its polygenic traits
D. single gene traits

12. AGENDA Mar 17
Objective: Explain the five conditions needed to maintain genetic equilibrium.
1. Question of the DAY
2. Chapter 15 Test Grades in GENESIS
3. Chapter 16-2 Evolution as Genetic Change 4. Homework Check 16-2 Guided Reading
5. Review and Homework

13. 16-2 Evolution as Genetic Change
Why does natural selection never act on specific genes?
An entire organism either survives and reproduces or dies out.
Organisms that die do not contribute to gene pool.
Relative frequencies within a population change over time.

14. Natural Selection on Single Gene Traits
Leads to changes in allele frequencies
Consider a population of lizards…
Normal skin = Brown
Mutations produce Red and Black skin
Predict the number of red lizards after 30 generations if the environment the lizards live in is a desert.
Black lizards? WHY?

15. Natural Selection on Polygenic Traits
What type of curve is produced when measuring a range of phenotypes?
Bell curve
Interpret the phenotypes found within the individuals of this population.

16. Three types of Selection
Directional Selection – individuals at one end of the curve have higher fitness than those in middle or at the end.
Dotted line = Original
distribution of
individuals

17. Types of Selection
Stabilizing Selection – Individuals near the center of the curve have higher fitness than any other individuals.
Dotted line = Original
distribution of human
babies

18. Types of Selection
Disruptive Selection – Individuals at upper and lower ends of curve have higher fitness than those in the middle.
Dotted line = Original
distribution of
individuals

19. Types of Adaptations
Morphological Adaptation: Structural feature that aids a species in fitting into its environment.
Physiological Adaptation: An adjustment of the body involving metabolic processes that allows an organism to best adapt to its environment.
Behavioral Adaptation: Traits that develop to better allow an organism to survive or reproduce.
Bears hibernating in winter
Sheep running away from types of noises

20. Examples

21. QUESTION of the DAY Mar 18
When average sized seeds become more scarce but smaller and larger seeds are still available as food sources, the type of selection that represents this change is
A. Directional
B. Disruptive
C. Stabilizing
D. Drifting

22. AGENDA Mar 18
Objective: Apply Hardy-Weinberg equations to determine allele frequencies.
1. Question of the DAY
2. Chapter 16-2 Hardy-Weinberg Equilibrium
Problem Solving
3. Review and Homework

23. GENETIC DRIFT
What controls genetics and the passing down of genes?
PROBABILITY
Genetic drift: random change in the frequency of a gene that happens by chance
Greater # of changes as population sizes decrease
Founder effect – change in allele frequencies due to the migration of a small subgroup of individuals.

24. Hardy-Weinberg Principle
states that allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change
only applies during genetic equilibrium: when allele frequencies remain constant
Conditions to maintain equilibrium
random mating
very large population
no movement into or out of the population
no mutations
no natural selection

25. Calculating Gene Frequencies
when a population is in Hardy-Weinberg equilibrium, genotypes can be calculated from allele frequencies
p + q = p2 + 2pq + q2 = 1
p = dominant allele
q = recessive allele
p2 = homozygous dominant
2pq = heterozygous
q2 = homozygous recessive

26. Hardy-Weinberg Problems
In a population of 3000 fruit flies, 270 flies have white eyes. White eye color is the recessive trait. Determine the frequencies of the red and white eye color alleles. How many flies are heterozygous for red eye color?
APPLY the 2 H-W Equations.

27. SOLUTION STEP 1 – Determine q2 STEP 2 – Find q and p
STEP 3 – Determine p2
STEP 4 – Find 2pq
STEP 5 – Find # of heterozygous flies

28. Hardy-Weinberg Problem
Coloration in the scarlet tiger moth is listed below for 1612 individuals.
White-spotted (AA) = 1469
Intermediate (Aa) = 138
Little spotting (aa) =5
Calculate the following frequencies.
A, a, AA, Aa, and aa

29. 16-3: The Development of New Species
speciation: process in which new species evolve from old ones
niche: combination of an organism’s profession and the place it lives
no two species can occupy the same niche in the same location for a long period of time
any species that occupies an unoccupied niche will better survive and potentially form a new species

30. Process of Speciation new species form when populations are separated
reproductive isolation: when populations are separated so they do not interbreed
when populations better adapt to different environments, their gene pools become dissimilar
Darwin’s finches

31. Mechanisms of Reproductive Isolation
Behavioral isolation – two populations
Capable of interbreeding
Differences in courtship rituals or reproductive strategies
Eastern and western meadowlarks
Different mating songs

32. Mechanisms
Geographic isolation – two population separated by geographic barriers
Mountains, rivers, bodies of water
Does not guarantee isolation.
May not isolate every organism from one another

33. Mechanisms
Temporal isolation – two or more species reproduce at different times.
Similar orchids living in a rain forest.
Each releases pollen at a different time

34. Peter and Rosemary Grant
Tested natural selection
Documented effects in finches on Galapagos
Individual birds with different beak sizes had different chances of survival during a drought
Big-beaked birds
obtain food when scarce
mate with other big-beaked birds

35. Speciation in Darwin’s Finches
1. Founders species – first finches arrive on Galapagos
2. Geographic isolation - Some finches arrived on another island and adapted to survive
3. Different Gene Pools on each island
4. Reproduction isolation – Two species on same island
finches mate with those having same beak size
5. Competition – both species compete on same island
6. Continued evolution – produced 13 different species

36. Speciation and Adaptive Radiation
adaptive radiation: process in which one species gives rise to many species
also known as divergent evolution
convergent evolution: process in which different species evolve to have similar appearances and behaviors
analogous structures: structures that are similar in appearance and function but have different origins

37. Pace of Evolution
punctuated equilibrium: involves long periods of stability that are interrupted by episodes of rapid change
gradualism: evolution occurs slow and steady over a long period of time