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An introduction to cladograms, which are diagrams used to depict ancestor-descendant relationships among organisms based on homology. It covers the basics of cladograms, their components, and how to read them. It also addresses common misconceptions about cladograms and provides examples to clarify concepts.
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INTERPRETING CLADOGRAMS
BIG IDEA: PHYLOGENIES DEPICT ANCESTOR AND DESCENDENT RELATIONSHIPS AMONG ORGANISMS BASED ON HOMOLOGY
THESE EVOLUTIONARY RELATIONSHIPS ARE REPRESENTED BY DIAGRAMS CALLED CLADOGRAMS (BRANCHING DIAGRAMS THAT ORGANIZE RELATIONSHIPS)
● A diagram which shows ___________ among organisms.
● Lines branching off other lines. The lines can be traced back to where they branch off. These branching off points represent a hypothetical ancestor.
● Is not an evolutionary tree, ___________show how ancestors are related to descendants or how much they have changed
Each lineage has unique ____to itself alone and traits that are shared with other lineages.
each lineage has _______that are unique to that lineage and ancestors that are shared with other lineages — common ancestors.
● Read like a family tree: show ________of shared ancestry between lineages.
●What is
a_________?
● A group that includes a common ancestor and all the descendants (living and extinct) of that ancestor.
● Looking at the image to the right:
● Is the green box a clade?
● The blue?
● The pink?
● The orange?
● Clades are nested within one another ● they form a nested hierarchy.
● A clade may include many thousands of species or just a few.
Outgroup All members of the group of interest are more closely related to each other than they are to the outgroup. Outgroups give you a sense of where on the bigger tree of life the main group of organisms falls.
●What is
a_________?
● Species, family, or class
● Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.
● Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."
● The points described above cause the most problems when it comes to human evolution.
● It is important to remember that: ● Humans did not evolve from chimpanzees. Humans and chimpanzees are evolutionary cousins and share a recent common ancestor that was neither chimpanzee nor human. ● Humans are not "higher" or "more evolved" than other living lineages. Since our lineages split, humans and chimpanzees have each evolved traits unique to their own lineages.
● What is this called?
● What do you think the red lines represent?
BUT HOW DO WE
CONSTRUCT A CLADOGRAM?
3 Alternative, mutually exclusive Cladograms
How Do We Choose Between Them?
