3 - Phylogeny 1 Flashcards
What is phylogenetics?
The study of how species are related to each other.
What are cladistics and phenetics?
Two approaches to studying relationships between species.
What does cladistics focus on?
Shared derived characters and evolutionary relationships.
What is phenetics based on?
Overall similarity regardless of evolutionary history.
What is parsimony in phylogeny?
Seeking the simplest explanation with the fewest changes.
What are synapomorphies?
Traits shared by a group’s common ancestor and descendants.
How are phylogenetic trees estimated?
By minimizing the number of character changes (parsimony).
What is homoplasy?
Character similarity not due to common descent.
What can cause homoplasy?
Convergent evolution or evolutionary reversals.
How can homoplasy affect reconstructions?
It can mislead phylogenetic reconstructions.
What are monophyletic groups?
Ancestor and all of its descendants in a tree.
What are outgroups used for?
To determine ancestral and derived character states.
step 1 in tree estimation?
Choosing synapomorphies for clades.
What does step 2 involve?
Using outgroups to determine ancestral and derived states.
Step 3 tree estimation
Finding characters shared by two taxa.
step 4 of tree estimation?
Expanding clades by adding characters with state “1”.
What does a polytomy indicate?
Uncertainty in relationships in a phylogenetic tree.
Why can’t all traits be relied upon?
Some traits may appear similar due to homoplasy.
What is a monophyly criterion for?
Higher taxa in phylogenetics.
What do modern cladistic classifications aim for?
Reflecting evolutionary history accurately.
What is the significance of transitional fossils like Tiktaalik?
Providing insights into evolutionary transitions.
What evidence helped predict Tiktaalik’s location?
Upper-Devonian rocks in Northern Canada.
What does Tiktaalik represent?
A transitional form between fish and tetrapods.
What are some homologous traits of Tiktaalik with tetrapods?
Wrist and neck structures.
