BIOL 112 Lecture 11

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Chapter 26: Phylogeny and the Tree of Life

Phylogeny

Evolutionary history between organisms

Compares shared characteristics in a tree

Systematics

analytical approach to determine phylogenetic relationships

traditional approach: morphology, embryology, biochemistry

new approach: molecular systematics (genome sequencing)

Building Trees using Genomic Data

Compare sequence similarities between homologous genes in different species

Comparison results in percent-identity score.

Slowly Evolving Sequences

Also called conserved, some genes are critical for function, and cannot tolerate mutations well.

• rDNA genes
• Krebb's cycle enzyme genes (cellular respiration)

These are used to compare distantly related organisms (e.g. humans and bacteria)

Orthologs of these genes are easily to identify since they will be very similar.

Fast Evolving Sequences

Not functionally important, therefore change frequently

• Regions of mitochondrial genome (not used for metabolism or electron transport)

Used to compare closely related organisms (e.g. races within a species) since slowly evolving sequences would be identical

Pre-Sequence Data

Whittaker's 5 kingdoms:

1. Autotrophic - plants
2. Heterotrophic (ingestive) - animals
3. Heterotrophic (absorptive) - fungi
4. Protists
5. Prokaryotes - Monera

After sequencing, we found that:

• fungi are more closely related to animals than plants
• Prokaryotes actually consist of bacteria and archaea: They're different enough to be in separate domains