Cladograms, Dichotomous Keys, and Phylogenetic Trees
What is a cladogram or phylogenetic tree?
A diagram that shows the relationships between different species based upon the similarities or differences in traits.
What are the ways to compare organisms?
Anatomical Comparison Embryological Development Molecular Comparison AEM (These letters are in alphabetical order)
What is a cladogram or phylogenetic tree made with?
Characteristics or traits that have either been derived (gained) or lost over time.
In comparative embryology, what can you do?
Compare embryos of different species to find their relationship.
What has the advantage of being more accurate than protein or amino acid comparison?
DNA comparison.
Has embryological development been helpful or very accurate at determining how closely organisms are related?
No. The embryos are too similar to create a relationship or organizational chart.
What are analogous structures?
Structures that are different structures, but have the same function. E.g. The wings of a bird, butterfly, fish-wing, etc.
What is the root?
The ancestral organism that all other organisms in a cladogram are being compared to.
Give an example of a derived structure.
The heart is derived over time from fish → amphibian → reptile → birds and mammals.
What are lost structures, traits or organs?
Vestigial structures, traits or organs that are no longer necessary for the survival of the organism. E.g. The human appendix perhaps came from the rumen in the past. Whale leg bones.
What is a dichotomous key used for?
an aid that is used to identify organisms and that consists of the answers to a series of questions
What does dichotomous thinking mean?
viewing problems and solutions in rigid either/or terms