2. Look at Fig15. A. Could this phylogeny be rotated or redrawn so that humans a

Question

2.
Look at Fig15.
A. Could this phylogeny be rotated or redrawn so that humans are NOT the outgroup? Explain your reasoning.
B. The branch leading to humans is very long in this phylogeny. Why?

Fig. 15 A straight line does not mean that no change has occurred. This tree provides a simple illustration of the fact that the outgroup lineage cannot be assumed to be "basal," "primitive," or "ancestral" to the other species included on the tree. In this case, humans are accurately used as the outgroup to the echinoderms, which includes sea lillies, brittle stars, sea stars, sea cucumbers, and sea urchins. Of course, humans do not resemble the common ancestor of echino- derms, and there has been an enormous amount of branching among vertebrates since the very distant split of these two lineages from their common ancestor. It is most commonly argued that the sister group of the echinoderms is the hemichordates, both of which are more closely related to vertebrates than to any other group of the category "invertebrate" phylogenetically invalid 93 animals, thus making

Explanation / Answer

Please find the answers bleow:

Answer 1: According to the figure shown, it can be clearly seen that the human group has been represented as an outgroup. However, it must be carefully noted that all other phylogenetic groups in this image are not directly related to humans. Hence, the phylogenetic tree cannot be drawn in a manner which prevents the observance of humans as an outgroup.

Answer 2: The length of hte phylogenetic tree line representing the humans is largest in nature in the image. This represents the long evolutionary trend followed by the humans and does not relate to the fact that no evolution has been taken place since then. Since humans body represents a very complex organization comprising of large number of cells, organs and organ systems, they have undergone very high extent of evolution with time. However, this evolutionary dependency was not related to other invertebrate plant/animal/fungal/bacterial sources, hence the tree shows unrelatedness with these organisms.

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