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imageClades (1 of 2) Definition
A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny — all of the organisms on that pruned branch make up a clade.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageClades (2 of 2) Nested clades
Clades are nested within one another — they form a nested hierarchy. A clade may include many thousands of species or just a few. Some examples of clades at different levels are marked on these phylogenies. Notice how clades are nested within larger clades.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageGalapagos finch phylogeny
Genetic sequences show that finches with similar feeding approaches tend to be closely related to one another.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageHumans on the tree of life
This tree is based on morphological and genetic data. Chimpanzees and humans form a clade with genes sequences that differ by only 1%. This genetic similarity made it hard to figure out exactly how these two primates are related, but recent genetic studies have strongly suggested that chimpanzees and humans are each other's closest living relative.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (1 of 5) Vertebrate character matrix
Character data for some major vertebrate lineages. Characters were limited to characters that are likely homologous (note that many vertebrate lineages and many characters were excluded from this example for the sake of simplicity).

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (2 of 5) Vertebrate ancestor characters
From studying fossils and lineages closely related to the vertebrate clade, we hypothesize that the ancestor of vertebrates had none of these features.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (3 of 5) Amniotic egg clade and phylogeny
We focus in on the group of lineages that share the derived form of the egg character, an amniotic egg (A), and hypothesize that they form a clade (B.)

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (4 of 5) All clades and phylogeny
If we go through the whole table like this, grouping clades according to shared derived characters (C) we get the following hypothesis (D).

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (5 of 5) Comparison of two hypotheses
The parsimony principle tells us to choose the simplest scientific explanation that fits the evidence. Hypothesis 1 requires six evolutionary changes and Hypothesis 2 requires seven evolutionary changes, with a bony skeleton evolving independently, twice. Although both fit the available data, the parsimony principle says that Hypothesis 1 is better — since it does not hypothesize unnecessarily complicated changes.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (1 of 3) Tree-like not ladder-like
Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (2 of 3) Left to right
Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (3 of 3) Order doesn't matter
For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary. These phylogenies are equivalent.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (1 of 3)
Often, one sees phylogenies that include polytomies, nodes with more than two descendent lineages, creating a "pitchfork."

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (2 of 3) Lack of knowledge
A polytomy may mean that we don't have enough data to figure out how the lineages are related. There are six possible solutions to this polytomy. Often, gathering more data can resolve a polytomy.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (3 of 3) Rapid speciation
A polytomy may mean that multiple speciation events happened at the same time.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageThree domains
The three domains: Archaea, Bacteria, and Eukaryota.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (1 of 4)
Understanding a phylogeny is a lot like reading a family tree. The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (2 of 4)
When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (3 of 4)
Phylogenies trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (4 of 4)
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages — common ancestors.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny - Amphibia, synapsida, sauropsida
Vertebrate phylogeny

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny with characters
Evolutionary relationships of major vertebrate groups.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny with time
This phylogeny represents vertebrate evolution. The lengths of the branches have been adjusted to show when lineages split and went extinct.

Audience: 13-16

Source: UC Museum of Paleontology

Resource type: Image

imageClades (1 of 2) Definition
A clade is a grouping that includes a common ancestor and all the descendants (living and extinct) of that ancestor. Using a phylogeny, it is easy to tell if a group of lineages forms a clade. Imagine clipping a single branch off the phylogeny — all of the organisms on that pruned branch make up a clade.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageClades (2 of 2) Nested clades
Clades are nested within one another — they form a nested hierarchy. A clade may include many thousands of species or just a few. Some examples of clades at different levels are marked on these phylogenies. Notice how clades are nested within larger clades.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageGalapagos finch phylogeny
Genetic sequences show that finches with similar feeding approaches tend to be closely related to one another.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageHumans on the tree of life
This tree is based on morphological and genetic data. Chimpanzees and humans form a clade with genes sequences that differ by only 1%. This genetic similarity made it hard to figure out exactly how these two primates are related, but recent genetic studies have strongly suggested that chimpanzees and humans are each other's closest living relative.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (1 of 5) Vertebrate character matrix
Character data for some major vertebrate lineages. Characters were limited to characters that are likely homologous (note that many vertebrate lineages and many characters were excluded from this example for the sake of simplicity).

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (2 of 5) Vertebrate ancestor characters
From studying fossils and lineages closely related to the vertebrate clade, we hypothesize that the ancestor of vertebrates had none of these features.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (3 of 5) Amniotic egg clade and phylogeny
We focus in on the group of lineages that share the derived form of the egg character, an amniotic egg (A), and hypothesize that they form a clade (B.)

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (4 of 5) All clades and phylogeny
If we go through the whole table like this, grouping clades according to shared derived characters (C) we get the following hypothesis (D).

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageParsimony (5 of 5) Comparison of two hypotheses
The parsimony principle tells us to choose the simplest scientific explanation that fits the evidence. Hypothesis 1 requires six evolutionary changes and Hypothesis 2 requires seven evolutionary changes, with a bony skeleton evolving independently, twice. Although both fit the available data, the parsimony principle says that Hypothesis 1 is better — since it does not hypothesize unnecessarily complicated changes.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (1 of 3) Tree-like not ladder-like
Evolution produces a pattern of relationships A B C D among lineages that is tree-like, not ladder-like.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (2 of 3) Left to right
Just because we tend to read phylogenies from left to right, there is no correlation with level of "advancement."

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePhylogenies (3 of 3) Order doesn't matter
For any speciation event on a phylogeny, the choice of which lineage goes to the right and which goes to the left is arbitrary. These phylogenies are equivalent.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (1 of 3)
Often, one sees phylogenies that include polytomies, nodes with more than two descendent lineages, creating a "pitchfork."

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (2 of 3) Lack of knowledge
A polytomy may mean that we don't have enough data to figure out how the lineages are related. There are six possible solutions to this polytomy. Often, gathering more data can resolve a polytomy.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imagePolytomy (3 of 3) Rapid speciation
A polytomy may mean that multiple speciation events happened at the same time.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageThree domains
The three domains: Archaea, Bacteria, and Eukaryota.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (1 of 4)
Understanding a phylogeny is a lot like reading a family tree. The root of the tree represents the ancestral lineage, and the tips of the branches represent the descendents of that ancestor. As you move from the root to the tips, you are moving forward in time.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (2 of 4)
When a lineage splits (speciation), it is represented as branching on a phylogeny. When a speciation event occurs, a single ancestral lineage gives rise to two or more daughter lineages.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (3 of 4)
Phylogenies trace patterns of shared ancestry between lineages. Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageUnderstanding phylogenies (4 of 4)
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages — common ancestors.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny - Amphibia, synapsida, sauropsida
Vertebrate phylogeny

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny with characters
Evolutionary relationships of major vertebrate groups.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image

imageVertebrate phylogeny with time
This phylogeny represents vertebrate evolution. The lengths of the branches have been adjusted to show when lineages split and went extinct.

Audience: 9-12

Source: UC Museum of Paleontology

Resource type: Image


 

Teachers' lounges 9-12 Undergrad 6-8 3-5 K-2

All-level resources
Guide to Evo 101

Conceptual framework

Teaching resource database

Image library

Dealing with objections to evolution

Correcting misconceptions

Alignment with science standards

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