1. Diversity and Evolution
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2. Survival of the Sneakiest
Roles:
Boy/narrator (B)
Girl (G)
Sound effect person (SE)
Male cricket 1 STRONG, ATTRACTIVE, SINGING (MC1)
Female cricket (FC)
Male Cricket 2 SNEAKY (MC2)
Bat (BAT)
Male cricket 3 (MC3)
Minor cricket 4 (MC4)
Minor cricket 5 (MC5)

3. 4 Main Principles of Natural Selection
Variation exists within a population
Organisms compete for limited resources
Organisms produce more offspring than can actually survive
Individuals with variations suitable for their habitat are the ones that SURVIVE and REPRODUCE

4. Sources of Variation -Natural selection requires variation…this is where it comes from:
Mutations
Alleles can be randomly created
Only source of variation not involving rearranging alleles
Sexual reproduction (genetic recombination)
Crossing over (prophase 1)
Independent assortment of homologues (metaphase 1)
Random joining of gametes during fertilization
Diploidy
Having two copies of each chromosome therefore having two alleles for every phenotype
Heterozygous genotypes allow recessive allele to be stored secretly in gene pool
Outbreeding
Mating with unrelated partners  increases probability of making different combos of alleles
Balanced polymorphism
Maintaining different phenotypes in the population
This does NOT involve recombining alleles
All these involve recombination of alleles

5. Genetic variation comes from several sources. Can you think of some?
Mutation is a random change in the DNA of a gene.
can form new allele
How can mutations be passed on to offspring?
Recombination forms new combinations of alleles.
usually occurs during meiosis, What is the process called?
CROSSING OVER
parents’ alleles arranged in new ways in gametes

7. Sexual Reproduction Two parent cells join to form new individual
Parent cells are called GAMETES
Gamete cells different than other body cells b/c they only have HALF the total number of chromosomes
Male gamete sperm cell (human gamete= 23 chromosomes)
Female gamete egg cell (human gamete= 23 chromosomes)
During sexual reproduction, new cell recieves 23 chrm. From mom and 23 chrm. From dad for a total of 46 chrm. (a complete human set)
Offspring= 46 chromosomes
The genes are not inherited in the same exact pattern, therefore the offspring is slightly different from parents
Offspring from sexual reproduction are GENETICALLY DIFFERENT from parents

8. Recombination during Gamete Formation
Gametes form during a process called meiosis (more on this later)
During meiosis, chromosomes that are similar in size, shape and genetic material pair up with each other (homologous chromosomes)
These paired up chromosomes swap parts in process called “crossing-over”
Process in which chromosome segments are broken off and exchanged
Crossing Over INCREASES the # of possible genetic combinations in the offspring

9. Germ Mutation Mutation in a gamete
CAN BE passed off to offspring and AFFECT survival of those offspring and their descendants
Helpful mutations persist (stay around) in population
Helpful mutations contribute to evolution and speciation

10. 5 Types of Natural Selection
Directional selection
Disruptive selection
Stabilizing selection
Sexual Selection
Artificial selection
(form of directional selection; not natural)

11. 1. Directional selection
Favors traits at one EXTREME of the range of possible traits
Result:
traits at the opposite end disappear
If this continues for many generations, favored traits become more and more extreme
Result: distinct changes in allele frequencies of the population
Examples:
Insecticide resistance
Peppered moth

13. 2. Disruptive Selection
Environment favors more EXTREME or UNUSUAL traits over common traits
Extreme or unusual traits at both ends of the spectrum are favored…common traits disappear over time
Leads to BALANCED POLYMORPHISM
Population divided into two phenotypes

14. 3. Stabilizing Selection
Favors the more common traits in a population as opposed to the more EXTREME or unusual traits
Eliminates individuals that have EXTREME or unusual traits
Maintains the existing population frequencies of common traits while selecting against all other trait variations
Example: Infant birth weight

17. 4. Sexual Selection Females Males
Differential mating of males (sometimes females) in a population
Mating behavior in a population that produces more NUMEROUS and/or more FIT offspring
Females
greater energy investment in producing offspring than males
increase fitness by increasing QUALITY of offspring by selecting SUPERIOR males to mate with
Males
contribute little energy to the production of offspring
Males increase fitness by maximizing the QUNATITY of offspring produced

19. 4. Sexual Selection (continued)
Two types of Sexual Selection
Male competition
Males compete with other males for mating opportunities
Males compete with other males to produce greater quantities of offspring
Leads to contests of strength that award mating opportunities to the strongest male
Female choice
Leads to traits or behaviors in males that attractive to females
Females tend to strengthen the gene pool by choosing superior males to mate with
Females respond to behaviors or traits (dances, songs, colors) that attract them to certain males

20. 5. Artificial Selection Type of DIRECTIONAL selection
Carried out by humans
Sowing seeds
Cauliflower, Brussels sprouts, broccoli, kale bred from one species of wild mustard
Breeding animals
Dogs
Race horses
Not NATURAL selection

24. Mechanisms for Evolution VARIATION is important
OTHER than
1. Natural Selection:
VARIATION is important
in all of these!
Modern genetics has shown us that there are other ways to change the allele frequencies in a population besides natural selection….
Genetic Drift
Gene Flow
Non-Random Mating
Mutation

25. Overview Natural Selection Genetic Drift Gene Flow Non-random mating
Increase or decrease in allele frequencies due to impact of ENVIRONMENT
Genetic Drift
RANDOM increase or decrease in allele frequencies in a population
Gene Flow
Introduction or removal of alleles from population when individuals leave (emigrate) or enter (immigrate)
Non-random mating
When individuals choose mates based on particular traits
When individuals only choose nearby individuals to mate with
Mutations
Introduce NEW alleles that may provide a selective advantage
MOST mutations are deleterious (HARMFUL)

26. 2. Genetic Drift
changes in the allele frequency within a population that occur by chance
genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals
No guarantee that the new population will be better suited to its environment than the original population
Effect of Genetic drift is very strong and dramatically influences evolution of small populations (fewer than 100)
Before
After
The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals. That, in a nutshell, is genetic drift.

27. 2. Genetic Drift Two types of Genetic Drift Founder Effect
When allele frequency of group of migrating individuals, by CHANCE, are different from their original population
Bottleneck Effect
Occurs when a population undergoes a dramatic decease in size
Regardless of cause of bottleneck (natural disaster, predation, disease), small population is now very vulnerable to genetic drift
Certain alleles have greater effect on population than other alleles
The genes of the next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better adapted” individuals. That, in a nutshell, is genetic drift.

29. migration of alleles INTO or OUT of a population
3. Gene Flow
migration of alleles INTO or OUT of a population
Usually INCREASE population’s genetic diversity
Biggest Factor that Effects Gene Flow: MOBILITY
For example:
The immigration and emigration of organisms.
The dispersal of seeds or spores.

30. 2 Major Forms of Non-Random Mating
Choice of mate based on preference
Example:
Similarity to one’s own traits
Differences from one’s own traits
Geographical proximity to mate
2 Major Forms of Non-Random Mating
Inbreeding
When individuals mate with relatives
Sexual Selection
Females choose male mate based upon:
Attractiveness
Behavior
Ability to defeat other males in contests

31. 5. Mutations
CAUSES:
Spontaneous
Natural factors
Ultraviolet radiation from the sun
Exposure to chemicals
Exposure to radiation
Introduces new alleles into a gene pool that NEVER existed before
VITAL b/c provides source for new variation
What is a mutation:
Change to an organisms genetic material (DNA)
Change the NUCLEIC ACIDS that make up one or more genes
Changes can produce new traits that can either HELP or HURT the survival of an organism
BENEFICIAL Mutations help organism
NEUTRAL Mutations have no effect on organism
NEGATIVE Mutations hurt organisms chances for survival

32. Allele frequencies measure genetic variation.
how common allele is in population
can be calculated for each allele in gene pool
Calculate the allele frequency for G(Green frogs) in the population
Calculate the allele frequency for g (brown frogs) in the population

33. How to calculate the ALLELE Frequency in a Gene Pool
Allele X or Allele x for certain TRAIT
Allele frequency X = # of allele X in population (gene pool)
total # of alleles (X + x) in population (gene pool)