Bell Work

• Dogs of a certain breed can have black fur or white fur. Black fur is dominant, but the breeder only wants puppies with white fur. Cross two heterozygous dogs until that happens.

Biology – Lecture 59

Phylogeny

Taxonomy

• The classification, identification, and naming of organisms

• Connected to phylogenetics

Phylogenetics

• The study of evolutionary relationships among groups of organisms which are discovered through molecular sequencing data and morphological data matrices.

Phylogeny

• The evolutionary history of taxonomic groups• Made from the results of phylogenetic studies

Example of Phylogeny

Phylogeny Branches

• Evolution is a branching process.• Populations are altered over time and may

split into separate branches, hybridize together, or terminate by extinction.

Phylogenetic Tree

• A hypothesis of the order in which evolutionary events are assumed to have occurred.

Tracing Relationships

• Biologists estimate that there are about 5 to 100 million species of organisms living on Earth today.

Tracing Relationships

• Evidence suggests that all organisms on Earth are genetically related, and the genealogical relationships of living things can be represented by a vast evolutionary tree, the Tree of Life.

The Tree of Life

• Phylogenetic analyses have become essential in researching the evolutionary tree of life.

• The tree of life is a large project to trace the evolutionary relationships of large groups of organisms.

Example - Tree of Life

The Tree of Life

• Implies that different species arise from previous species and that all organisms are connected via descent to one another.

How is a Phylogeny Created?

• Matrix-based methods are used to construct trees based on overall similarity, which is often assumed to approximate phylogenetic relationships.

Flaws of Hypothesis

• There is no way to measure whether a particular phylogenetic hypothesis is accurate or not, unless the true relationships among the taxa being examined are already known.

Phylogeny Vocabulary

• Monophyletic clade – all the members in a group with the same characteristics

• Synapomorphy – a particular trait within the phylogeny

• Autapomorphic trait – only one organism has this trait

• Outgroup - The simplest form of a common ancestor• Sister Groups – Two groups that can be traced back

to a single split.

Example - Phylogeny of Beasties

• Reconstruct the evolutionary history of a group of imaginary organisms known as Beasties.

• The Beasties are a morphologically diverse group, and your analysis will take advantage of this diversity.

• You will infer the simplest phylogenetic tree for the group of Beasties.

• The outgroup taxon is indicated, as are six other Beastie taxa (A-F).

The Beasties

Step 1

• Conduct a character analysis by examining the similarities and differences.

Example ChartCharacteristic

ABCDEF

The Beasties

Step 2

• Figure out those that are most similar to one another.

• Start by comparing to the Outgroup (if given).• If no outgroup is given, start with the one with

the most “no” responses.

Step 3

• Draw the initial branch and then make branches off of that branch based on the similarities and differences of the organisms.

Drawing Our Phylogeny

Answer Phylogeny

outgroup E D B F A C

Tongue

Spots

BeardPointed Feet

Brushy Tail

Branched Antenna

Fin

• Based on your tree, find all the groups in the list that are sister to each other.