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ECOL 182 (Spring) Intoductory Biology - Lecture 1 - comment and summary

I cannot emphasize more the importance of understanding how the there is a parallel between the issues we dicussed in this lecture and the "two theories of evolution" that Dr. Schaffer has discussed at length.

In our phylogenetics lecture, I said that you have to think about the most straightforward catagorization of taxa in a phylogeny as a description of decent with modification, based on the assumption that 'life-comes-from-life". When more sophisticated treatments are considered (such as when molecular data are used), then the second part of the "two theories of evolution" must be used to understand or interpret the data (produce the tree). This is important for the following reason:

(1) when a model is used to interpret data, the results of the analysis cannot be used to test the validity of important model assumptions (think about some of the assumptions, or mechanisms, associated with the second of the 'two theories of evolution). For example, such a molecular derived tree should not be used as evidence for the role of natural selection in driving adaptive evolution - it is implicit in the model.

(2) the addition of a model to such an analysis limit inference (e.g., what can be understood from an analysis)

DON'T FORGET - YOU'LL HAVE TO MAKE A TREE AT SOME POINT - USE THE EXAMPLE (FIG. 25.5) IN THE BOX TO HELP YOU UNDERSTAND

Some other key concepts we addressed (in the form of questions):

(1) Why is it important to understand evolutionary relationships?

(2) What is a phylogenetic tree?

(3) There is an expectation from phylogenetics - what does it mean about the relatedness of species?

(4) What is a derived trait? What is an ancient trait?

(5) Why are monophyletic groups necessary for understanding evolutionary relationships?

(6) What is a homology?

(7) How do you make a simple phylogenetic tree (see example in book)?

(8) What are the two forces that make phylogenetics difficult?

(9) What is the difference between trees constructed from catagorical traits, versus molecular sequences?