Cladogram - Wikipedia
The output from a phylogenetic analysis is a hypothesis of relationship of different taxa. This hypothesis can be represented as a cladogram, a branching diagram. Cladograms bear a lot in A cladogram shows us hypothesized clades. A phylogenetic tree was a bit like a family tree, showing who the nearest Organisms were related to one another, and these relationships could form the basis. Yes, because it is believed that all organisms derived from a common ancestor and a cladogram shows the characteristics that the organisms.
But, a phylogenetic tree describes an evolutionary history by showing how ancestors are related to their descendants and how much those descendants have changed over time.
There are further distinctions, and to further complicate matters, different analyses and new information can yield different possible evolutionary relationships. Luckily, for the scope of this lesson, you can think of a phylogenetic tree as a cladogram with a few added bells and whistles.
The phylogenetic tree shown here might help illustrate this concept a little better. A phylogenetic tree can be used to chart evolutionary relationships Types of Clades A clade is a group of species used in cladograms and phylogenetic treeswhich consists of one ancestor and all its descendants.
The term clade comes from the Greek word klados, which means branch. Relating this back to our family tree - one clade would consist of the great-great grandparents, all the way down to the siblings. Just like there are different types of families, there are different types of clades.
The three major types are: Monophyletic refers to just one clade; meaning these terms are interchangeable. As stated before, a monophyletic clade includes one ancestor and all of its descendants.
An example of this would be the genus Homo. This genus includes all the species from ancestral humans up to modern-day humans, or Homo sapiens. In biology, the ancestors are often gone sometimes without a trace.
All we have left are the children. Reading cladograms is much like reading a family tree. Both are rich in information.
Cladograms, like family trees, tell the pattern of ancestry and descent. Unlike family trees, ancestors in cladistics ideally give rise to only two descendent species.
Also unlike family trees, new species form from splitting of old species. In speciation, it does not take two to tango. The formation of the two descendent species is called a splitting event. The ancestor is usually assumed to "die" after the splitting event. In the first tree, labelled Cladogram A, notice the small circles. These mark the nodes of the tree.
The stems of the tree end with the taxa under consideration. At each node a splitting event occurs.
The node therefore represents the end of the ancestral taxon, and the stems, the species that split from the ancestor. The two taxa that split from the node are called sister taxa.
Diagraming Evolution, or How to read a Cladogram | Paleocave Blog
They are called sister taxa because they are like the siblings from the parent or ancestor. This was acceptable because a no one could think of anything better, and b most people at the time believed in the 'fixed species' concept in which organism had been created in their current form and could never change.
After Darwin it was realized that organisms could indeed change, and that all current forms of living things had arrived at that form by change and natural selection, the mechanism of evolution. Scientists began to construct phylogenies, lists or diagrams that showed the evolutionary paths taken by populations of organisms through many generations and over long periods of time.
These phylogenetic diagrams quickly started to look like trees, as it was realized that ancestral stocks occasionally broke up, branched and became two or more different species, which could later branch again and again. A phylogenetic tree was a bit like a family tree, showing who the nearest relatives were and who shared a common ancestor, and when.
Organisms were related to one another, and these relationships could form the basis of a new type of taxonomy; on based on evolutionary origin and evolutionary relatedness. Two main types of taxonomy have arisen from this principle. They look alike, but there are serious differences.