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Interpreting Cladograms: Understanding Evolutionary Relationships among Organisms, Study notes of Biology of microorganisms

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.

What you will learn

  • What is a cladogram?
  • How do we construct a cladogram?
  • What is an outgroup in the context of cladograms?
  • What is a clade?
  • What are ancestral and derived character states in cladograms?

Typology: Study notes

2021/2022

Uploaded on 09/12/2022

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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)
Interpreting Cladograms Notes
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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)

Interpreting Cladograms Notes

What is a Cladogram

● 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

Reading Cladograms

  • When an ancestral lineage______: speciation is indicated due to the “arrival” of some new trait.

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.

Quick Question

●What is

a_________?

● A group that includes a common ancestor and all the descendants (living and extinct) of that ancestor.

Quick Question

● Looking at the image to the right:

● Is the green box a clade?

● The blue?

● The pink?

● The orange?

Reading Cladograms: Clades

● 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.

Quick Question

●What is

a_________?

● Species, family, or class

(mis)Interpreting Cladograms: One

● Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.

(mis)Interpreting Cladograms: Two

● Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

Interpreting Phylogenies: Human Example

● 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.

Quick Question

● 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?