AP Bio Review Day 3

Agenda: 1.Phylogenetics and Evolution

2. Osmosis and Transport3. Phylogenetic Worksheets

4. Exit Ticket

Warm Up

• Summarize the osmosis lab we complete as a class with the mystery solutions and potatoes. – What were we trying to find?– What calculations did we do with our data?– What was our conclusion?

Adaptations and Fitness• An adaptation is a genetically controlled

trait that is favored by natural selection and gives the organism a reproductive advantage ensuring the trait is passed on to its descendants.

• This trait may also allow the individual to survive longer thus increasing the reproductive rate of that individual.

• Compare and contrast these hares and identify the differences in their traits

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Adaptations and Fitness• The antelope hare lives in the desert,

and the snowshoe hare lives in the mountains.

• Explain how the differences in their traits enhance their ability to survive in their respective environments.

• Evolutionary success or fitness refers to the contribution of genes to the gene pool and NOT how long an organism lives.

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The Effect of Environmental Change

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• Earth’s environment is NOT STATIC, but rather ever changing.

• As a consequence, traits or adaptations that were favorable may become unfavorable.

• The peppered moth, Biston betularia is native to England and exists in two forms, one is dark and the other light with a “peppered” appearance. Birds are its main predator.

• Prior to the industrial revolution, only 2% of the moths were dark.

• The industrial revolution produced vast amounts of sulfur dioxide and soot from the burning of coal which altered the environment.

• Fifty years later 95% of the moths were dark. • Propose an explanation!

Industrial Melanism

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England has since regulated the burning of coal and as a result, the trees are returning to their original state (A).

Consequently, the coloring among the population of moths in Britain has shifted back so that the peppered moths are once again favored.

Evolution Defined• Evolution is defined as a change in the

inherited characteristics of biological populations over successive generations. – More simply: Genetic change over time

• Evolutionary processes give rise to diversity at every level of biological organization, from the molecular to the macroscopic.

• As a result diversity is prevalent among molecules such as DNA as well as individual organisms and species of organisms.

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MicroevolutionMicroevolution is simply a change in gene frequency within a population.

•Evolution at this scale can be observed over short periods of time such as from one generation to the next.

•Example: The frequency of a gene for pesticide resistance in a population of crop pests increases.

•Predict some reasons why these changes would come about

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MicroevolutionMicroevolution is simply a change in gene frequency within a population.

•Evolution at this scale can be observed over short periods of time such as from one generation to the next.

•Example: The frequency of a gene for pesticide resistance in a population of crop pests increases.

•Such a change might come about because

– natural selection favored the gene

– the population received new immigrants carrying the gene (gene flow)

– nonresistant genes mutated into a resistant version of the gene

– of random genetic drift from one generation to the next

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Microevolution• A gene is a sequence of DNA nucleotides

that specify a particular polypeptide chain.

• Genes code for proteins.

• An allele is a particular form of a gene. For example: B represents the allele for black coat color and b for white coat color.

• Selection acts on phenotype because differential reproduction and survivorship depend on phenotype not genotype.

• Natural selection acts on individuals, but only populations evolve.

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More Evolution Terms

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• Species-a group of interbreeding organisms that produce viable and fertile offspring in nature

• Gene pool-sum total of all the genes in a given species

• Allelic frequency-is the percent occurrence for a given allele

Phylogenetic Trees

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• Phylogeny is the study of the evolutionary relationships among a group of organisms.

• A phylogenetic tree is a construct that represents a branching “tree-like” structure which illustrates the evolutionary relationships of a group of organisms.

Phylogenies are based on

•Morphology and the fossil record

•Embryology

•DNA, RNA, and protein similarities

Phylogenetic Trees Basics

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Phylogenies can be illustrated with phylogenetic trees or cladograms. Many biologist use these constructs interchangeably.

•A cladogram is used to represent a hypothesis about the evolutionary history of a group of organisms.

•A phylogenetic tree represents the “true” evolutionary history of the organism. Quite often the length of the phylogenetic lineage and nodes correspond to the time of divergent events.

Phylogenetic Trees of Sirenia and Proboscidea

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This phylogenetic tree represents the “true” evolutionary history of elephants. The nodes and length of a phylogenetic lineage indicate the time of divergent events. Also any organism not shown across the top of the page is an extinct species.

Traditional Classification and Phylogenies

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This phylogenetic tree is a reflection of the Linnaean classification of carnivores, however with the advancements in DNA and protein analysis, changes have been made in the traditional classification of organisms and their phylogeny.

For example, birds are now classified as true reptiles.

Taxa

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A taxon is any group of species designated by name. Example taxa include: kingdoms, classes, etc.

Every node should give rise to two lineages. If more than two linages are shown, it indicates an unresolved pattern of divergence or polytomy.

Sister Taxa

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Sister taxa are groups or organisms that share an immediate common ancestor. Also note the branches can rotate and still represent the same phylogeny.

Definition of a clade

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• A clade is any taxon that consists of all the evolutionary descendants of a common ancestor

• Each different colored rectangle is a true clade.

Molecular Clocks

• The molecular clock hypothesis states: Among closely related species, a given gene usually evolves at reasonably constant rate.

• These mutation events can be used to predict times of evolutionary divergence.

• Therefore, the protein encoded by the gene accumulates amino acid replacements at a relatively constant rate.

Molecular Clocks• The amino acid replacement

for hemoglobin has occurred at a relatively constant rate over 500 million years.

• The slope of the line represents the average rate of change in the amino acid sequence of the molecular clock.

• Different genes evolve at different rates and there are many other factors that can affect the rate.

Molecular Clocks

Molecular Clocks

• Molecular clocks can be used to study genomes that change rather quickly such as the HIV-1 virus (a retrovirus).

• Using a molecular clock, it as been estimated that the HIV-1 virus entered the human population in 1960’s and the origin of the virus dates back to the 1930’s.

Making a Cladogram Based on Traits

• Examine the data given.

• Propose a cladogram depicting the evolutionary history of the vertebrates.

• The lancet is an outgroup which is a group that is closely related to the taxa being examined but is less closely related as evidenced by all those zeros!

• The taxa being examined is called the ingroup.

Making a Cladogram Based on Traits

Pick 6 animals and create a table of their traits and then create a cladogram that represents their evolutionary relationship

Transport Review

Exit Ticket

• A plant cell has a solute potential of –2.0 and a pressure potential of 0.0. It is placed in a solution with a water potential of –1.0. What will happen to this plant cell? Explain your reasoning.