Chapter 15- Tracing Evolutionary History
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Transcript of Chapter 15- Tracing Evolutionary History
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