Chapters 1-4

As much as I hate to read (I always have), I actually enjoyed reading chapters 1 through 4. I find evolution a fun and interesting topic, and learning about it is very exciting.
Chapter 1 mostly discussed the HIV and its continuing evolving pattern. What interested me the most about HIV was how its populations can resist to certain drugs or treatments. This occurs due to mutation, inheritance, and differences in survival to AZT for example, which results in a change in the composition of the population over time. HIV is one of the fastest evolving entities known. It reproduces sloppily, accumulating lots of mutations when it copies its genetic material. It also reproduces at a lightning-fast rate, a single virus can spawn billions of copies in just one day. To fight HIV, we must understand its evolution within the human body and then ultimately find a way to control its evolution. When all is said and done, there are 3.1 million AIDS related deaths per year ( as acquired from Yale AIDS watch), and I am hoping someone finds a cure ASAP.
Chapter 2 went more into detail of "decent from a common ancestor." There is numerous examples and evidence of this. The example that caught my attention was the observation by Louis Agassiz who observed the similarities of embryos. Figure 2.20 on page 55 shows that embryos from different vertebrates (from snakes to possums to humans) all have very similar traits, such as a tail and pharyngeal pouches in early stages.
Natural selection is broadly defined in chapter 3. A huge portion of this chapter discussed Darwin's 4 postulates, or components. These are:

1. Variation. Organisms within populations exhibit individual variation in appearance and behavior. These variations may involve body size, hair color, facial markings, voice properties, or number of offspring. On the other hand, some traits show little to no variation among individuals—for example, number of eyes in vertebrates. 
2. Inheritance. Some traits are consistently passed on from parent to offspring. Such traits are heritable, whereas other traits are strongly influenced by environmental conditions and show weak heritability.
3. High rate of population growth. Most populations have more offspring each year than local resources can support leading to a struggle for resources. Each generation experiences substantial mortality.
4. Differential survival and reproduction. In other words, survival and reproduction are NOT random. Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation. 

The panda's thumb was pretty interesting. Figure 3.9 explains the modified wrist bone helps the panda grasp a bamboo stalk. This of course is an example of preadaptation.
I found learning about phylogenetic trees in chapter 4 fascinating. I had a little bit of this topic in general biology, but learning it more extensive was entertaining. A phylogenetic tree is defined (from our textbook) as a diagram or estimate of the relationship of ancestry and descent among a group of species or populations; in paleontological studies the ancestors may be known from fossils, whereas in studies of extant species the ancestor may be hypothetical constructs. That definition is quite extensive, and a bit confusing. This YouTube video helped me better understand a phylogenetic tree:

















For more information on these topics, check out these websites:

http://www.eou.edu/~jjohnson/Chapter%20Five%200909.pdf

http://onthehuman.org/2010/06/common-ancestry-and-natural-selection-in-darwin%E2%80%99s-origin/

http://www.nature.com/scitable/topicpage/reading-a-phylogenetic-tree-the-meaning-of-41956