Unit 9 – Evolution
The Process of Natural Selection
- What is evolution?
- How has life evolved?
How does variation lead to changes in populations?
- What is variation?
- How does it occur?
- What is the effect of variation within a population?
Theories for changes in species over time.
- Inheritance of acquired characteristics:
- Use vs. disuse
- Evidence against…
- Charles Darwin traveled on the HMS Beagle and felt species were “unstable.”
- Role of environment
- Role of inheritance
- Artificial selection was a model for natural selection.
- Selective breeding/agriculture
The process of natural selection:
- Variation exists
- Competition
- Differential reproduction
- Selection FORCE produces survival of the “best fit”
- Reproduce more, trait is inherited
- Population has changed
- What is fitness?
- Reproductive success depends on many elements of survival.
- What natural selection patterns can be observed?
- Other natural selection patterns are based on relationships.
- Co-evolution
- Predator/prey
- Competition
- Symbiosis (mutualism, commensalism, parasitism)
- Pollinators
- Read about a coevolution study on toxin “Biological warfare and the coevolutionary arms race”
- Or watch Evolutionary Arms Race “Evolution Arms Race Toxin”
- How is natural selection researched?
- “Endler and the Flashy Fish” – PBS resource
- What are the environmental conditions?
- How was natural selection seen?
- What are practical applications of evolution in society?
- Antibiotic resistance tuberculosis/consumption
- “Why does evolution matter now?” – PBS resource
Review Questions
- How would each of the following explain why a turtle has a shell?
- Jean-Baptiste Lamarck
- August Weissman
- Charles Darwin
- Describe why each of the “steps” of natural selection is essential
- Describe the three main patterns natural selection produces.
- Identify situations in which coevolution would occur.
Extra resources
- A variety of natural selection and evolution resources
- Natural selection steps and examples
Measuring Evolutionary Change
- How do we know if a population is changing over time?
- Phenotype is caused by genotype.
- Gene Pool
- Allelic frequency
- p + q = 1
- p and q are the phenotypes
- p2 + 2pq + q2 = 1
- what is p2
- what is 2pq
- what is q2
A population has a percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following:
The frequency of the "aa" genotype.
The frequency of the "a" allele.
The frequency of the "A" allele.
The frequencies of the genotypes "AA" and "Aa."
- Hardy-Weinberg Applications
- Allows us to predict the occurrence of alleles in a population
- Determines the % of genotypical heterozygotes from phenotypical
dominants
- Heterozygote advantage:
Sickle cell anemia and malaria protection
- Hardy-Weinberg Equilibrium assumes evolution is NOT occurring if allele frequencies stay the same from generation to generation under these conditions:
- Population size is large
- Random mating is occurring
- No mutations are occurring
- No genes are input from other source (immigration)
- No selection is occurring
- Under the following conditions, the Hardy-Weinberg Equation will predict evolutionary change:
- Mutation
- Gene Flow
- Non-random mating
- Genetic drift
- Selection
Review Questions
- Describe the function of the Hardy-Weinberg Equilibrium.
- Differentiate between the three components of the equation.
- Given the above population of beetles, explain how each of the agents of evolutionary change could result in evolution.
Extra resources
- Review of Hardy-Weinberg and examples
- Hardy-Weinberg practice problems
When evolutionary change leads to new species
- How does variation lead to new species?
- What is a species?
- A common ancestor can give rise to a variety of species.
- Patterns:
- Allopatric populations
- Sympatric populations
- Mechanisms
- Pre-zygotic
- Ecological
- Behavioral
- Temporal
- Mechanical
- Gamete Fusion
- Post-zygotic
- Zygote mortality
- Hybrid sterility
- Polyploidy
Review Questions
- Define speciation.
- Describe how each different mechanism can lead to speciation.
- Differentiate between allopatric and sympatric populations.
- Predict the outcome of multiple speciation events.
Extra resources-- Speciation tutorial