Ichthyostega is a 370-million-year-old fossil from Greenland. Ichthyostega had digits, eyes on the top of its head, and strong, armlike bones. It also had no gills and a reduced tail. Acanthostega, Eusthenopteron, and Tiktaalik all had gills and full tails. Which organism would you place Ichthyostega closest to on this phylogenetic tree?

Closer to Acanthostega

Explanation: Phylogenetic tree is a diagram that represents evolution patterns of species. The ramification of the tree indicates how the species evoluted from a series of commom ancestor. Two species are closely related if the ancestor is closer to them. By it, it means that two species are closer if their characteristics are similar to each other. As the question stated, Ichthyostega had digits and reduced tail. Among the three others, Acanthostega has arms with digits, gills, tails and no fin.

So, in the phylogenetic tree, the branch that has acanthostega would be closer to the one with Ichthyostega, as this one is likely the descendent of the previous one.

1. the energy lost to disorder metabolism     -entropy

2. related to or possessing motion potential     -kinetic

3. all of the chemical reactions in an organism required for maintenance of the processes of life entropy     -metabolism

4. possible; ability to go into action or perform work kinetic     -potential

5. the study of energy and its transformations thermodynamics     -thermodynamics