This video is about cladograms. According to the video, a cladogram is a phylogenetic tree with characteristics that are shared by organisms, and it puts together a hypothesis based on how the organisms are related. The video uses the example of some imaginary pond organisms: A, B, C, D, E, F, and G.
Based on their physical characteristics, they are sorted into a cladogram (from left to right they are C, B, G, D, A, F, E). The physical characteristics should be sorted as such: cell membrane, circle, eye, 4 arrows, mouth, red eye, and 12 arrows. The video states that a cladogram is based on time: the most left organism has evolved from a common ancestor the earliest and the organism to the most right has most recently evolved from a common ancestor. Also, the theory of parsimony is discussed in relationship to cladograms. It states that if all things are equal, the simplest explanation for how something occurred is usually the most right. In addition, the video talks about how at first, people used physical traits to determine evolutionary history in a cladogram. However, that can be inaccurate (analogous structures). Therefore, now, modern scientists use DNA evidence to make cladograms.
Relevance to Class:
We learned about cladograms in class, and even had to make a cladogram based on evidence from skulls in our lab practical. This video goes over how to make and interpret a cladogram in a helpful manner.
Video Information:
Link/URL: http://www.youtube.com/watch?v=ouZ9zEkxGWg
Author: Paul Anderson
Date: May 11, 2012
Why can using physical traits be an inaccurate way of determining evolutionary history?
ReplyDeleteBecause organisms that look alike aren't necessarily closely related to each other. For example, organisms may have analogous structures because they are adapted to the same or similar niche, instead of evolving from a common ancestor.
ReplyDeletewho was the person to make the first cladogram?
ReplyDelete