Chapter 16

For Wednesday, January 31

• Read over chapter 22

• Make sure you Bring text

January 28 Outline

• 1.5 Scientific Method• 16.3 Darwin Principles • 16.5 Individuals do not evolve, populations do• 16.6 Mutations• 16.7 Directional Selection• 16.8 Selection against or in favor of extreme

phenotypes• 16.9 Maintaining variations in a population• 16.10 Genetic Drift• 16.11 Gene flow

1.5 Biological Inquiry

You are normally successful in your studies but for some reason in one class your average has slipped.

Q: What series of steps do you carry out to find the root of the problem?

No simply blaming the professor

is not an option!

1.5 Biological Inquiry

1. Research Problem2. Hypothesis 3. Prediction4. Experimental Tests5. Conclusion

– (confirm or refute the hypothesis)6. Repeat or revise

• Increased number to trials by peers further VALIDATES

7. Report test results

1.5 Biological Inquiry1. Research Problem2. Hypothesis 3. Prediction

4. Experimental Tests• Materials• Procedure

o Control group a placebo (1.6) to avoid ???o Experimental group (1.6)

Independent Variable (is the tested Dependent Variable

• Observations and data collection (graphs, charts, table)o Qualitative and Quantitative

• Analysis of Data 5. Conclusion

– (confirm or refute the hypothesis)6. Repeat or revise

• Increased number to trials by peers further VALIDATES 7. Report test results

16.3 Darwin's Inquiry1. Research Problem:

• Why the echinoderms do not over populate?

2. Hypothesis: • Nature has checks and balances

3. Prediction:4. Experimental Tests

• Observations• Populations have inherent reproductive capacities• No population can survive w/o competition of resources

• Analysis of Data • Darwin's Concept of Competition

5. Conclusion 6. Repeat or revise

• Consistent patterns within his data

7. Report test results (On the Origin of Species)

1.6 Experimental Tests

• Controlled Experiment

• Open ended Experiments

• Field Experimental– Mimicry

All must avoid inner Biasness

16.3 Darwin Principles

• George Cuvier revolutions– Missing?

• Jean Lamark – Inheritance of Acquired Characteristics

• hereditary mechanism by which changes in physiology acquired over the life of an organism (such as muscle enlarged through use) are purportedly transmitted to offspring

– What is incorrect with this???

• Weisman – Mouse Hater or Scientist??? Disproved Lamark

Lamark’s GiraffesLamark’s Giraffes

Darwin• Cambridge Degree in Theology / Naturalists• 1859 The Origin of Species by Means of Natural Selection,1859 The Origin of Species by Means of Natural Selection,• Or Or The Preservation of Favored Races in the Struggle for The Preservation of Favored Races in the Struggle for

LifeLife

• Charles Darwin devised a theory of evolution based on Charles Darwin devised a theory of evolution based on variation and natural selection variation and natural selection

• Included in hid theory were five main ideas:Included in hid theory were five main ideas:1.1. Overpopulation Overpopulation 2.2. CompetitionCompetition3.3. Survival of the Fittest Survival of the Fittest 4.4. Reproduction Reproduction 5.5. SpeciationSpeciation

This would be Darwin’s View of Lamark’s giraffes .

16.5 Population Terms • Morphological: Form

• Physiological: helps the body function in an environment– Genotype: Genetic expression on a gene– Phenotypes: Physical representation of a gene

16.5 Population Terms • Chromosomes: consist of a single

molecule of DNA, a unit of heredity• The Gene Pool: all of the genes in a

population– Genes: genetic traits,

• Eye color–Alleles: variation of genes,

» Blue, Brown, green, hazel

• Leads to variations in phenotypes

16.5 Five reasons for VariationsWhy you are not like your Folks

1. Gene Mutations • produces new alleles

2. Crossing over • New combination of alleles w/i Sperm and egg• Chromosomes break and exchange information

3. Independent Assortment: • Never can predict which chromosomes will pair up• Sperm and egg

4. Fertilization • Combines alleles from two parents

5. Change in Chromosome Number or Structure• Loss, duplication, repositioning of genes.

16.6 Mutations Revisited

• Mutation Rate probability between replication

Mutations are random and the phenotypic outcome may be neutral, beneficial, harmful, or even lethal to the individual depending on other interactions.

• Neutral, Beneficial, lethal mutations• Growth rate vs. Collagen • Rethink Giraffe Neck????

16.6 Mutations Revisiteda. Lethal mutation is an expression of a gene that

results in death.

b. Neutral mutations, whether or not they are expressed in phenotype, have no effect on survival and reproduction.

c. Beneficial mutations are those that bestow survival advantages.

Mutations are the only source of new alleles—the genetic foundation for biological diversity.

16.6 Mutations Revisited

16.7 Directional Selection• Alleles frequencies that give rise to a range of

variations in a phenotype tend to shift in a consistent direction. – Forms at one end of a Phenotypic range become

more common then midrange forms• Pesticide Resistance• Antibiotic Resistence

• Two forms– Stabilizing Selection– Disruptive Selection

Response to change in the environment

THE KEY IS THE ENVIRONMENT

16.7 Directional Selection• How could any dark morphed pocket mice

survive in the Arizona’s Sonoran Desert ?

Stabilizing Selection Link

Disruptive Selection Link

16.9 Maintaining Variations 16.9 Maintaining Variations

in a Population,Sexual dimorphism in a Population,Sexual dimorphism

• Two different morphologies. male and female– phenotypes or secondary sexual characteristics.

• Sexual selection is based on any trait that gives the individual a competitive edge in mating and producing offspring.

• Many times the males compete for the privilege of mating with certain females but at other times the females are the agents of selection when they pick their mates.

• Through nonrandom mating, alleles for preferred traits increase.

• This leads to increased sexual dimorphism

16.9 Balanced Polymorphism

• Balanced polymorphism (having many forms) is the maintenance of two or more forms of a trait in fairly steady proportions over time.

• This occurs when nonidentical alleles are maintained at frequencies greater than one percent. • Malaria• Sickle-cell anemia • Heterozygotes HbS/HbA, comprise about one third of the pop

• It is now known that heterozygous individuals are more resistant to the protozoan that causes malaria.

• They survive in greater numbers than the homozygotes.

16.10 Genetic Drift- The Chance Changes

• The random change in allele frequencies over time, due to chance occurrences alone.

• More significant in small populations. – “Easier to spread”

• Sampling error Rule of Probability– 50 coin flips, 500 flips

– explains why the chance of any given allele becoming more or less prevalent is more pronounced in a small population.

• Fixation means that one kind of allele remains at a specified locus in a population.

16.10 Genetic Drift- The Chance Changes

• Genetically modified fruit makes the News

http://www.gmoinfo.ie/papaya.php

16.10 Bottlenecking Examples of Genetic Drift: elephant seals, cheetahs, humans (amish)

16.10 Bottlenecking

GM papayas Yummy goodness or DestroyerOf the Human Genome?

Using the key terms from 16.9-16.11

Iiwi pronounced “EEVEE

16.10 Bottlenecking

Iiwi(Vestiaria coccinea)

'I'iwis are some of the most spectacular birds found in the Hawaiian Islands, with their long, decurved bills and striking red and black feathers. This species is still relatively common in high-elevation forests on the island of Hawaii, and has smaller populations on four other main islands; but its high susceptibility to avian malaria could make it extremely vulnerable to the future introduction of mosquitoes capable of surviving at high elevations.

http://www.audubon2.org/webapp/watchlist/viewSpecies.jsp?id=108

16.11 The flow of Genes

• Q: What is the difference between Immigration and Emigration?

• A: The Gene Flow: physical flow of alleles between tow or more populations.– Immigration: population gains alleles– Emigration: population loses alleles

16.10 Genetic Drift- The Chance Changes

• Bottleneck Effect• This is a severe reduction in population size that

causes pronounced drift. – Contagious disease, habitat loss, hunting

• For example, the elephant seal population was hunted down to just 20 individuals.

• Then the population rebounded to 130,000.

• In bottlenecks, some stressful situation greatly reduces the size of a population leaving a few (typical or atypical) individuals to reestablish the population.

The Founder Effect• Genetic outcomes also can be unpredictable

after a few individuals establish a new population– Seedling on birds– Acorns and Blue Jays

• In the founder effect, – a few of these original founders had a mutation, the

gene defect would then be passed on to their descendants for generations to come.

• Amish, cultural isolation • Selective Inbreeding• Geographic Isolation????

The Founder Effect• Genetic outcomes also can be

unpredictable after a few individuals establish a new population– Seedling on birds

• It is the effect of drift when a small number of individuals start a new population.

• By chance, allele frequencies of founders may not be the same as those in the original population.

finito