Notes for the Week of February 22nd
Notes for the Week of February 22nd BIO 113
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This 2 page Class Notes was uploaded by Amanda Howard on Thursday February 25, 2016. The Class Notes belongs to BIO 113 at Wake Forest University taught by Anderson, Todd Michael and Clifford W. Zeyl in Spring 2016. Since its upload, it has received 20 views. For similar materials see Evolutionary and Ecological Biology in Biology at Wake Forest University.
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Date Created: 02/25/16
February 23, 2016 Convergence in cichlids radiation in different lakes All the fish in a lake have a common ancestor separate from that of the fish in another lake However, fish in the two lakes who are specialized to eat the same food closely resemble each other This is an example of convergence in that In addition disruptive selection is at work similar to that found in forest birds in that mutants become more specialized for specialized food types One of the possible reasons for cichlid radiation is that they have two sets of jaws which can have many uses in the different types of fish o In clam eaters for example the oral jaws may grab the clam and the second set may grind the shell o In predators may use their oral jaws to catch fish while the pharyngeal jaws may grind the prey o These two sets of jaws may allow speciation to occur more quickly by allowing rapid specialization o This trait is passed on even if one group of fish dies out: For example: if the algae eaters die due to chemical runoff, the pharyngeal jaw is still present in other cichlids meaning that the algae eating adaptations have the potential to reevolve later Genes Replication DNA RNA Protein “gene regulation” = how it is determined when and in what cells a gene actually produces the Protein (and thus the trait) it encodes o for many genes, regulation = whether or not transcription is initiated o genes in different parts of the body contain the DNA for all parts of the body, however regulation prevents an eye from developing in the stomach o however it is possible for there to be mutations or mistakes in transcription Here’s how transcription is initiated for a typical gene o Once a gene is replicated it takes transcription factors to turn it to RNA o “transcription factor”= a protein that affects the initiation of transcription, by binding to either a promoter, other TFs, or both o The RNA polymerase will only bind to a transcription factor after transcription factors are present, but the RNA can be blocked if too many transcription factors are present o Basically it is a question of whether or not transcription factors are present to allow for RNA transcription o In the case of cichlids and the second set of jaws: The fish had already evolved to be able to create bone, teeth, and jaws The process of creating a second set of jaws was not another long slow evolution The only requirement was that the gene for jaws was turned on or transcribed somewhere it wasn’t necessarily supposed to be Examples: o If you look at mice, flies, sharks, and squids, all three have similar genes to code for the placement of eyes meaning they are homologous o However the genes for the eyes themselves are completely different o This means that though the animals all share a common ancestor from who they got the gene that regulates were eyes develop for eye placement even before the evolution of eyes o However the eyes themselves evolved completely independently Another example: o Fly
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