Blog #6

Now that we have transitioned into our evolution unit, we are learning about tools that help scientists study evolution. Cladograms play a significant role in determining relationships among organisms. What distinguishes a cladogram from an evolutionary tree is that it does not directly show how descendants are related to their ancestors. If you look at the visuals below, you can see that the cladogram links shared characteristics between organisms as opposed to the heritage of the organisms as in the phylogenetic tree.

Evolutionary (phylogenetic) tree (source: Phylogenetic-classification. Digital image. Open Curriculum. N.p., n.d. Web. 9 Nov. 2014. <http://media.opencurriculum.org/articles_manual/ck12_biology/phylogenetic-classification/2.png>.)

Cladogram (source: Cladogram. Digital image. Biology Evolution. N.p., n.d. Web. 9 Nov. 2014. )

Scientists can look at trees to study organisms as a means of researching certain anatomical traits, ancestry, and how organisms evolve. As an example, if you look at the Primates and Rodents & Rabbits categories of the cladogram you can see that the common trait between the two groups is hair because they're both mammals. The lines that extend leftward off of the main line indicate a group of organisms that has acquired that characteristic over time. For example, since Crocodiles are far along in the cladogram, it means that species possesses vertebrae, a bony skeleton, four limbs, amniotic egg, and eggs with shells.

Source:

Enzor, Laura. "Cladograms and Phylogenetic Trees- Evolution Classifications." Education Portal. N.p., n.d. Web. 09 Nov. 2014.