Daily News Letter January 13, 2012

Daily Newsletter                                        January 13, 2012

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Today's Topic: Evolution Friday

Welcome to evolution Friday.  Every Friday we will discuss evolution in context of the week's topic.  This week is an introduction to the topic of evolution.

First, you must remember that as scientists we build models to help us understand how the world works, and to provide the ability to predict and control natural phenomena.  Evolutionary theory is no different.  The model we create regarding evolution allows us to look at the diversity and interrelation of living organisms, understand strong connections between organisms, and even understand what happens when population sizes get low (endangered species).  Our modern model of evolution can stated at a simple level as the changes in phenotypic frequencies within a population through time.  Let's analyze that statement:

1. Phenotype:  This is the physical, expressed form of an organism.
2. Population:  A group of individuals of the same species inhabiting the same time and space (habitat).
3. Unless there is an identical twin, each organism in a population is phenotypically unique (diversity).
4. Even with this diversity, there is a range of expressed phenotypes; or a phenotypic ratio.
5. Evolution looks at this phenotypic ratio over time to see if there are changes.
6. Another way to look at this right now is to say that we are looking at the PREVALENCE of a given phenotype (characteristic) over time.

A good example of this comes from the historic changes in the phenotype of the pepper moth.  A fun online tutorial about the pepper moth can be found at http://www.techapps.net/interactives/mothproject.htm.  In reading the article and going through the tutorial, keep in mind that what you are looking at are population level shifts in the frequency in which you see a given form.

The idea that natural selection can affect phenotypic frequencies is a central model used in biology.  It informs our hypotheses and conclusion.

Read the following article:

Tilman D, Downing JA. Biodiversity and stability in grasslands. Nature. 1994;367(6461):363-365.

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Daily Challenge: Evolution


This challenge has two components. First I would like you to discuss the modern concept of evolution in your own words by answering the question: What is Evolution? Second, I would like you to read the above article and discuss the following question: How does evolutionary theory inform the conclusion to this article? Another way to put this, how does evolutionary theory inform the author's conclusion about the stability of grasslands.