Theme 5AB Flashcards
What is phylogeny
History of descent with branching, a way of organizing our knowledge of biodiversity
What are phylogenetic trees
Branching diagram that shows relationships between species, often according to the time since a common ancestor
For each species, it shows which other species they share a common ancestor with. Provides hypothesis of evolutionary relationship
What is a phylogram
A phylogenetic tree where branch lengths represent amount of evolutionary change/time
What is a cladogram
Phylogenetic tree where all branches are equal length (just branching, no time)
Both type of trees can show lineages, not just species
What is a node?
The point where the branch splits. This shows the common ancestor the species split from
What are sister groups
Two species (or groups of species) that share a common ancestor that isn’t shared by any other species or group
When are trees equivalent?
When the nodes can be rotated without changing evolutionary relationship
How do we infer phylogenies based on characters shared between species
Look at their
morphological (wing patterns)
chromosomal (number of chromosomes)
Molecular (DNA sequence)
What are characters and character states
Character: character state
Flower colour: blue, yellow
wings: present, absent
What are homologous characters (homologies)
Characters that are shared because of common ancestry
They share ancestral and derived characters that came from ancestor
What are analogous characters (homoplasies)
Similar characters in appearance but not in origin. They’re similar due to convergent evolution
Look same, same function, but not from common ancestor
How do we recognize homologies
Structural similarity (how wing is made)
Relations between parts
Embryonic development (do they develop by same pathways)
What is a synapomorphy
Homologous characters in descendants shared from the ancestral species
Why is the tree with the fewest number of changes needed the best
Because it minimizes the total number of independent origins of character states
It’s the best estimate of the true phylogeny and is parsimonious (energetically favourable)
How do we use distance method to infer relations of species
Descendants of more recent common ancestor have had little time to evolve differences, but ancient common ancestor they have more time to evolve
So the DNA sequences differences reflect the time since a common ancestor
