Chapter 5- Cladistics Flashcards
How can evidence of a species which are part of a clade be obtained?
From the base sequences of a gene or the corresponding amino acid sequence of a protein
Species that have recent common ancestors can be expected to have what?
Few differences in a base or amino acid sequence
What does the fact that sequence difference accumulate gradually affect?
So there is a positive correlation between the number of differences between two species and the time since they diverged from a common ancestor
What can be used as a molecular clock?
There is evidence that mutations occur at roughly constant rate so they can be used as a molecular clock
What are two things traits can be?
Analogous or homologous
What are homologous structures
are similar because of similar ancestry; for example chicken wing, human arm and other forelimbs
What are analogous structures
Similar because of convergent evolution- the human eye and octopus eye show similarities in structure and function but they are analogous because they evolved independently
What are cladograms
Tree diagrams that show the most probable sequence of divergence in clades
Cladograms are based on what?
Based on base or amino acid sequences
What are the branching points on cladograms called?
Nodes
What does evidence from cladistics show
That classification of some groups based on structures did not correspond with the evolutionary origins of a group of species
What were the 5 clades that had been incorrectly combined into one family in the figwort family
1) two small families were merged with the figwort family
2) nearly 15 genera have been moved to plantain family
3) about 12 genera of parasitic plants have been moved to the boomrape family
4) 13 genera have been transferred to a newly- created family , the lindernia family
5) two genera were moved to the newly created family, the calceolaria family
What is a clade?
A group of organisms that have evolved from a common ancestor
