PHYLOGENETIC TREES

What does LUCA stand for

•  last universal common ancestor

When do we use LUCA

• if there is an unknown common ancestor

What are phylogenetic trees also called

• evolutionary trees

What do branching trees infer

• evolutionary relationships

The phylogenetic tree of life

Is a product of what theory?

What does it illustrate?

• Darwin’s evolutionary theory

• Illustrates the interconnectedness of all life forms through evolution

Phylogenetic trees can be created by using

• Genetic Data Molecular homology sequences

Genetic Data Molecular homology sequences include

• Amino acids 

• RNA 

• DNA

DNA sequences could be

• nuclear or mitochondrial 

• coding or non-coding

What do the tips/terminals of a tree represent

• the descendant groups (taxa)

What do nodes in a phylogenetic tree denote

• An ancestor of two (or more) descendants, referred to as the recent common ancestor

What do branches in a phylogenetic tree indicate

• A speciation event

• The relationship between an ancestor and a descendant of that ancestor

What is the root of a phylogenetic tree

• The common ancestor of all taxa shown in the tree

What are sister taxa

• Two groups, such as two species, with a common ancestor that is not shared with other taxa

What does branch length convey in a phylogenetic tree

• Time scale (longer branches denote longer time periods)

  OR

• Molecular scale (amount of molecular sequence change, i.e., difference in DNA or amino acids)

What lines can be used to draw phylogenetic trees

• Diagonal, horizontal, or vertical lines

What is the first step to construct a phylogenetic tree

• Calculate the number of differences between the different species or groups provided

What is the second step in constructing a phylogenetic tree

• Identify the sequences with the fewest differences

What is the third step in constructing a phylogenetic tree

• Connect these groups with the fewest differences as sister taxa, joined via a node

What is the fourth step in constructing a phylogenetic tree

• Determine the next group with the fewest differences to the sister taxa and add to the tree as a branch

What is the fifth step in constructing a phylogenetic tree

• Continue this until all groups are added to the phylogenetic tree

What is the sixth step in constructing a phylogenetic tree

• Determine the outgroup, if necessary, as the most distantly related group

Sample problem

maybe?

What taxonomic group is included with humans in a phylogenetic tree of vertebrates

• Humans are included with the other placentals

How can phylogenetic trees be examined

• To infer various relationships

• Such as humans being more closely related to marsupials than monotremes among mammals that branched off 350 million years ago

What can phylogenetic analysis identify within natural populations

• Genetic variation within a species and its subspecies

How does phylogenetic analysis assist in understanding species

• By reconstructing the evolutionary history of a species or a genus

How is phylogenetic analysis valuable for understanding human prehistory

• It assists in understanding

• including early migrations of modern humans and clarifying the relationship between modern humans, Homo sapiens, and the extinct Homo species

How does phylogenetic analysis help with zoonotic diseases

• By identifying the origin of human viral diseases that have jumped from other species