Accessibility Mode Prin ancestors at internal nodes. (10 pts) 3) A page or two w
ID: 217244 • Letter: A
Question
Accessibility Mode Prin ancestors at internal nodes. (10 pts) 3) A page or two with answers to these six questions: (3.1) Are some cladograms that look different really the same? Explain (3 pts) (3.2)Is it possible, using the same table of character states, to have different cladograms with number of total evolutionary events? Explain. (3 pts) (3.3) Is the most parsimonious cladogram necessarily the true evolutionary tree? (3 pts) (3 4) ls it possible, using the same table of character states, to have different cladograms with tf minimum number of events? Why or why not? (3 pts) 3.5) If so, how would you choose the best one? (3 pts) G.6) What new testable predictions are generated by a cladogram? (3 pts) Exam COCX hpExplanation / Answer
3.6
There are three basic assumptions in cladistics:
Testing Predictions
All predictions should be testable, meaning it should be possible to design an experiment that would verify or invalidate the prediction. With the solvent, for example, you could test your prediction by dissolving different compounds in water at different temperatures and measuring the solubility. You would soon find that some substances actually become less soluble with increasing temperature. Since the prediction made by your hypothesis is false, you would realize your hypothesis is flawed and try to find a new one that could account for the facts.
Assumptions
There are three basic assumptions in cladistics:
1. Change in characteristics occurs in lineages over time.
The assumption that characteristics of organisms change over time is the most important one in cladistics. It is only when characteristics change that we are able to recognize different lineages or groups. We call the "original" state of the characteristic plesiomorphic and the "changed" state apomorphic.
2. Any group of organisms is related by descent from a common ancestor.
This assumption is supported by many lines of evidence and essentially means that all life on Earth today is related and shares a common ancestor. Because of this, we can take any collection of organisms and hypothesize a meaningful pattern of relationships, provided we have the right kind of information.
3. There is a bifurcating, or branching, pattern of lineage-splitting.
This assumption suggests that when a lineage splits, it divides into exactly two groups. There are some situations that violate this assumption. For example, many biologists accept the idea that multiple new lineages have arisen from a single originating population at the same time, or near enough in time to be indistinguishable from such an event (as in the case of the cichlid fish described previously). The other objection raised against this assumption is the possibility of interbreeding between distinct groups, which occurs at least occasionally in some groups (like plants). While such exceptions may exist, for many groups they are relatively rare and so this assumption often holds true.