Unit 5.4: Cladistics Flashcards
List the benefits of classifying organisms.
- Organization of data helps to identify organisms
- Suggests evolutionary links between organisms with similar characteristics, which suggest the closeness of a relationship
- Allows the prediction of characteristics shared by members of a group
Define a clade.
A clade is a group of organisms that evolved from a common ancestor.
How are the organisms in a clade determined?
The organisms of a clade can be determined by matching base sequences of a gene to the corresponding amino acid sequence of a protein.
Define cladistics.
Cladistics is a method of classifying groups of organisms together according to the characteristics that have evolved most recently.
What is a cladogram?
A cladogram is a diagram that divides groups of organisms into separate branches, called clades.
What do cladograms show/have shown?
They show that traditional methods based on morphological similarities rather than differences resulted in inaccurate groupings. Cladograms allowed for the reclassification of branches of organisms based on base and amino acid sequences. This has only been possible since the late half of the 20th century.
Note:
Be able to analyze the relationships among organisms in a cladogram.
At what kind of a rate do mutations occur?
Mutations occur at a constant rate. Mutations accumulate gradually over a long period of time, resulting in a number of differences between two organisms (often determined by mitochondrial DNA).
How is the number of differences between organisms used?
The number of differences between two organisms can be used to deduce how long ago the two separated from a common ancestor.
Explain the evolutionary concept of molecular clocks.
Molecular clocks is an evolutionary concept in which a stretch of DNA accumulates mutations at a rate that is regular enough to measure how long ago two species diverged from a common ancestor.
