Phylogeny Video & Notes (W1 Lecture)

Phylogeny is the evolutionary history of a species of group of related species.

Systematics is a sub-discipline of phylogeny, focused on classifying organisms and determining their evolutionary relationships.

Carl Linnaeus created the Binomial Nomenclature system as it is today in the late 1700s and is referred to as the “Father of modern taxonomy”.

Scientific name structure: Genus-species (Genus is always capitalized)

  • underlined when handwriting, Italicized when typed.

  • The specific epithet is unique for each species within the genus.

  • You can abbreviate MOST genus names to shorten the writing.

  • Example E. coli.

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species. A group at any level is called a taxon (the plural is Taxa)

“Dear King Philip came over for good soup!”

  • The classification gets more selective/ less inclusive further down/ up the tree.

L.U.C.A Last Universal Common Ancestor (Unknown)

4 Kingdoms for our class (6 kingdoms in more recent publishings)

  • Protists- a diverse group ranging from single- celled to multicellular forms. Some use photosynthesis and some must acquire their own food. They include algae, protozoans, and water molds.

  • Plantae- Multicellular, photosynthetic.

  • Fungi- are the familiar molds and mushrooms that decompose dead organisms. Parasitic in nature

  • Animalia- Multicellular organisms that ingest and process their food.

Ancestors: are the forks in the tree of life.

Bacteria exist everywhere vs Archaea live in extreme conditions.

  • Phylogenetic tree = Linnaean system = tree of life = taxonomic system = (Dear, King, Philp…)

  • The tree is more for understanding the evolutionary line but can be used with classification.

  • Linnaean systems of classification do not always reflect the evolutionary relationships. For example if a species has lost a key feature shared by its close relatives, it may be misclassified.

“In science nothing is ever to be true, Only to be supported”

We use the DNA sequence to determine if species had a common ancestor and where the lineage split. As more DNA technology advances, we will find new pieces of the puzzle. (Supported by fossil records).

Lumpers 

  • Focus on similarities and commonalities

  • Assign examples broadly

  • Combine similar things into larger categories

  • Reduce the number of categories

  • Assume that separation of populations is rarely complete

  • Assume that mutations don't occur often

Splitters 

  • Focus on differences and fine-grained categories

  • Create new categories for samples that differ in key ways

  • Break up larger groups into smaller ones

  • Assume that speciation occurs relatively quickly

  • Assume that separation of populations is usually complete

Example: Brachiosaurus split to Apatosaurus, then was lumped back.

The tree represent a hypothesis about evolutionary relationships, Each Branch Point represents the divergence of two lineages from a common ancestor.

An Evolutionary Lineage: is a sequesnce of ancestral organisms leading to a particular descendant taxon.

Sister Taxa: Are groups that share a common ancestor that is not shared by any other group. From the same branch of the tree.

The Last Common Ancestor is the largest branch (closer to the “trunk) on a phylogenic tree.

  • Trees can be Horizontal, Vertical, or Diagonal.

Branches of the tree can be rotated around a branch point without changing what they convey about the evolutionary relationships. The order in which Taxa appears at the branch tips is not significant. It is ordered for what is easy to read as far as evolutionary relationships and aesthetics.

A Rooted Tree includes a branch to represent the most recent common ancestor of ALL TAXA in the tree.

Basal Taxon: A lineage that diverges from all other members of the group early in the history of the group.