How do derived characteristics affect cladograms?

The Impact of Evolution

Darwin changed everything. The publication of his work on The Origin of Species in 1859, threw the whole of biological science into a new paradigm, including the study of classification theory and the principles of taxonomy.

While using logic as the basis of their work, both Aristotle and Linnaeus had developed their classification schemes on taxonomic principles that were fundamentally arbitrary. Their groups, while logical, were not based on any obvious relationships of a biological nature. They were convenient groups that humans could quickly see, identify and use.

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.

Explanation:

The Impact of Evolution

Darwin changed everything. The publication of his work on The Origin of Species in 1859, threw the whole of biological science into a new paradigm, including the study of classification theory and the principles of taxonomy.

While using logic as the basis of their work, both Aristotle and Linnaeus had developed their classification schemes on taxonomic principles that were fundamentally arbitrary. Their groups, while logical, were not based on any obvious relationships of a biological nature. They were convenient groups that humans could quickly see, identify and use.

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.