Chapter 15- Tracing Evolutionary History

• “evo-devo”• Analogy• Binomial nomenclature• Clades• Cladistic analysis• Class • Continental drift• Convergent evolution• Derived characters• Exaptation• Family• Five-kingdom system• Fossil record• Genus

• Geologic time scale• Kingdom• Macroevolution• Molecular clock• Order• Paedomorphosis• Parsimony• Phylogenetic trees• Phylogeny• Phylum• Plate tectonics• Radiometric dating• Species• Three-domain system

The fossil record• Shows macroevolution

– Major changes in the history of life on Earth

• Gives geologic time scale– Eras, periods, separated by extinctions

• Radiometric dating- calculates fossil age– Using radioactive isotopes (C for fossils younger than

50,000yrs old)

Mass extinctions

• Followed by periods of mass diversification– Due to available resources (niches, space,

lack of predators)– Key adaptations allow some species to grow

after extinction– Exaptation- a structure that evolved in 1

context and is later adapted for another function

• Bird feathers- 1st for temp regulation; later for flight

Continental drift

• Plays a role in macroevolution

• Slow movement of continents due to movement of Earth’s crust

• Explains distribution of ancient species

• Plate tectonics- forces that move crust

Things to consider:

• Evolution is NOT trying to reach a goal– Results from changes in the environment– Causes some to survive and others not to

• Gradual evolutionary changes come from genetic changes– “evo-devo”- field that studies how slight genetic variance can

magnify morphological differences– Paedomorphosis- adults keeping juvenile features

Phylogeny • Evolutionary history of a group of

organisms– Represented by phylogenetic trees

Classification

• Taxonomy- the study of naming and classifying species and groups of species

• Linnaeus system assigned 2 part latinized names– Ex: Homo sapiens

• Kingdom-Phylum-Class-Order-Family-Genus-Species

• Kings – Play – Cards – On – Fat – Green – Stools

• In order to classify an organism scientists must use all available evidence to classify properly

Classification and phylogeny

Homology vs. Analogy

• Homology- structures may look and function differently but they have evolved from the same structure– Indicates common ancestor

• Analogy- similarities due to convergence– Convergent evolution- species from different evolutionary

branches come to resemble one another due to living in similar environments

Now-

• Molecular biology helps classify organisms– Protein comparisons- amino acid sequencing– DNA and RNA comparisons-

• mtDNA – compares closely related species, because it mutates quickly

• rDNA- changes slowly, used to trace early branching – Molecular clock- evolutionary timing method based on genes

that evolve at constant rates

Cladistic Analysis

• Atudies evolutionary history of clades (groups consisting of ancestor and all of its descendents)– New traits that arise – derived characters– Phylogenetic tree based on onset of derived characters =

cladogram– Parsimony- quest for simplest explanation of observed

phenomena

5 Kingdom vs. 3 Domain

• Pictures in textbook show where groups in each fit into the systems pg 312

• Always up for research and debate