Phylogenetics (7) Flashcards
Phylogeny?
= a diagram that shows lines of evolutionary descent from a common ancestor.
Cladogram?
= a branching diagram tracing evolutionary history.
Branch?
= unbroken lines of descent.
Terminal taxa?
= extant organisms.
Apomorphies?
= derived features.
What do branches do?/What do they show? (4)
• Show evolutionary histories.
• Show lineages.
• Summarize evolution across lineages.
• Show divergence from a common ancestor (speciation).
Natural groups?
= groups that share common ancestor, ie. monophyletic.
Monophyly?
= common ancestor + all its descendants.
Paraphyly?
= common ancestor + some of its descendants.
Polyphyly?
= no recent common ancestor/group that doesn’t contain a single common ancestor of the group.
Steps for Tree Reading? (3)
• Tree tip order = not important.
• No terminal node is ancestral to any other terminal node.
• No terminal node is more evolved than any other terminal node.
Tree styles? (2)
• Mammal phylogeny.
• Rectangular cladogram.
Transition?
= interchanges of purine for purine (A-T or G-C).
Transversion?
= interchanges of purine for pyramidine (A-G or T-C).
Which is slower between transversion & transition?
Transversion.
Molecular clock?
= probabilities of where you can estimate/calculate time.
How do we obtain a cladogram? (2)
• From Morphological data.
• From Fossils.
Why are polyploids important?
Important for biodiversity.
Eg of polyploidy & biodiversity?
Grey tree frogs.
How are polyploids formed?
Via autopolyploidy.
Autopolyploidy?
= polyploid within same species.
Phylogram?
= diagram that includes evolutionary change information.
Branch length in Phylogram?
= amount of change/ diversification rates.
Eg of Phylogram?
Dwarf chameleons.
Branch length of Phylogram occurs under what?
Mutation selections.
How do we obtain a cladogram from eg. Morphological data?
Use the categorical/binary (0,1,1,2…) scores.
Steps to draw a Phylogenetic tree? (5)
• Choose the taxa.
• Select the characters.
• Determine polarity (using fossil evidence).
• Group the features by synapomorphies.
• Work through all synapomorphies & group accordingly.
How do you choose the best tree?
Via the Principle of Maximum Parsimony.
Parsimony?
= the most likely phylogeny is the simplest one/the one with the least evolutionary events.
Principle of Maximum Parsimony?
= principle where we use simplest explanation with the least assumptions & the shortest tree is the preferred hypothesis of relationships.
Why use the Principle of Maximum Parsimony? (2)
• To avoid guessing & complication.
• Has the least number of steps.
Principle of Maximum Parsimony conclusion? / What does it conclude? (2)
• That it’s much easier to lose a trait than it is to gain it a second time.
• The simplest tree with the least no. of events is the best tree.
Bayesian?
= Stats & priors.
Homologous characters?
= features that are similar in structure/position due to common ancestry.
Analogous characters?
= features similar not due to common ancestry but due to function.
Homology?
= basis of analysis (that basis being the common ancestor).
Result of analogy?
Homoplasy.
Homoplasy type?
• Convergence.
Result of homology?
Congruence.
Eg of homology?
Protea &
Egs of analogy? (2)
• Vertebrate eye & Octopus eye.
• Pitcher plants.
How do we identify homology?
• Common ancestor via same structure/position.