Lecture 9 - Phylogenetics Flashcards
Classification
Coming up with convenient ways of grouping together similar things
Scala Naturae
Humans at the pinnacle of life
Does not represent evolution
What is the taxonomic order?
Life, domain, Kingdom, Subphylum, Class, Order, Family, Genus, Species
Systematics
Study of patterns of evolutionary relationships
Cladistics
Hypothesizing relationships among organisms based upon uniquely shared charecters or traits
Phylogenetics
The study of the tree of life (slightly less broad than systematics)
What are the rules for cladistics?
Characters change or are acquired over time,
Any group of organisms are related by common descent,
Character similarities and differences reflect evolutionary history
Phylogeny
Inferred evolutionary history of clades/hypothesis of evolutionary relationships
What things to consider when building a phylogeny?
Molecular characters, morphological characters
How many trees of life are there?
There is only one true tree of life with each phylogenetic tree an estimation to try and get closer to the true tree of life
What are the uses of phylogenies?
Fundamental for understanding evolution: processes and history,
Can inform effective conservation: biodiversity, priorities and risks
Important for understanding and treatment of infectious disease
What molecular characters are measured when considering evolution?
DNA sequences, RNA sequences, Amino acid sequences
What is the best molecular character to measure?
Amino acid sequences however it is difficult and expensive so DNA is often used
How are homologous molecular sites established?
Sequence alignment using algorithms
How are morphological charecters compared?
Presence or absence
Condition (e.g. pubis direction)
Multistate (i.e. how many there are)
Homology
Similarity due to shared ancestry between different taxa
Homoplasy
A similarity that does not arise from shared ancestry
Convergence
Distantly related organisms independently evolve similar traits to adapt to similar necessitites
Examples of Convergence
Camara eyes in humans and cephalopods,
Body shape in marine vertebrates,
Echolocation in bats and whales
Morphological vs molecular studies: data size
Morphology- hundreds of characters but maybe over saturated
Molecules - Very abundant but also could be over saturated
Morphological vs molecular studies: Character identification
Morphology - subjective, up to human interpretation
Molecules - objective, computer algorithms
Morphological vs molecular studies: Accesibility
Morphology - labour intensive, but museum specimens available
Molecules - Expensive, but becoming cheaper and cheaper
Morphological vs molecular studies: Time scales
Morphological - Fossil record
Molecules - Molecular clocks
What is total evidence in evolution?
Combined molecular and morphological analyses of molecular data act as a scaffold for fossils that can break up gaps and provide timescales. The inclusion of morphology can increase congruence
