Evolutionary Biology: Phylogenies, Homology, and Taxonomy

mes (67)in DTube • last month

In this video I go over phylogenies, which represent the evolutionary history of a group of organisms or their genes. Phylogenetic trees are used to compare and group different species. All living organisms are classified into one of three domains: Archaea, Bacteria, or Eukarya (which includes animals). Phylogenetic trees can be reconstructed based on specific interests, leading to various evolutionary trees. The principle of parsimony, or Occam's razor, is applied to choose the most likely phylogenetic tree by selecting the one with the fewest evolutionary assumptions. These trees can also depict organisms with homologous (inheritable) features, such as the bones in the forelimbs of vertebrates—an argument Charles Darwin used to support evolution.

Phylogeny is grounded in Linnaean taxonomy, which ranks organisms within a hierarchical classification system: domain, kingdom, phylum, class, order, family, genus, and species. Each species is given two names: the genus (capitalized) and the species, both italicized. Humans, for example, are classified as Homo sapiens.

Time stamps:

Phylogeny is an evolutionary history of a specific group of organisms or their genes: 0:00
Clade is composed of a common ancestor and all its lineal descendants: 2:05
Paraphyletic group excludes a branch of its lineage (descendants): 4:02
Phylogenetic trees are the basis for comparing and grouping different species: 6:38
Homology of the bones in the forelimbs of vertebrates: 7:53
Phylogenies can be reconstructed as ingroups and outgroups based on primary interests: 9:18
Comparing a cladogram with a phylogenetic tree: 10:45
Occam's razor is used to select most accurate phylogenetic tree: 12:05
- Occam's razor or principle of parsimony states that competing solutions with the fewest assumptions is most likely to be true: 13:42
Phylogeny is based on Linnaean taxonomy: Domain, kingdom, phylum, class, order, family, genus, species: 16:14
- Humans are classed as Homo sapiens where Homo is the genus and sapiens is the species: 18:03