The main idea
Several observations of chemistry, geology, and development explain how larger taxa can arise by the microevolutionary mechanisms we already studied.
Briefly describe the history of life on Earth, noting the major eras and time frames and what major changes happened in each.
Larger taxa have arisen through the process of macroevolution, and can be arranged into four evolutionary “faunas” corresponding with geologic eras.
KNOW THE NAMES OF ERAS, roughly when they begin and end and during which the following events happened: (p.299)
- First prokaryote life
- First eukaryote cells
- Cambrian Explosion
- Colonization of land
- Dinosaur radiation and extinction
- Radiation of mammals and birds
- Radiation of flowering plants
Describe how absolute and relative ages for a fossil can be determined.
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The fossil record shows what life forms existed during which era, period. Relative ages of fossils can be obtained by the sequence of strata. -
Radiometric dating of associated rocks shows more detailed time estimates (e.g. to ca. 50,000 ybp ± 10% for C14 dating) due to known decay rates of radioisotopes
Describe the major geological influences on the history of life
- Tectonic activity drastically affects life though splitting of populations via continental drift, climate change and tectonic disruptions (volcanoes, etc.)
- There have been at least five mass extinctions over the history of multicellular life. Each has been followed by diversification of survivors (adaptive radiation)
- Species may survive and proliferate after mass extinctions due to key adaptations, then modify traits for new purposes
Describe four ways developmental genetic control genes can produce major changes in structure.
- Changes in rate and timing of development (e.g. paedomorphosis)
- Changes in spatial pattern
- New genes and changes in genes, often by gene duplication
- Changes in gene regulation
Describe three reasons that major evolutionary innovations can happen without being "perfect" during in-between stages
Critics of evolution often assert that major structures could not arise by the sort of small, gradual changes typically associated with evolution (e.g. "Half an eye would not be any good, and would be selected against") and that the fossil record seems to show almost goal-directed changes.
However:
- Complex structures arise in increments from simpler versions having the same basic structure that may be fully functional for "simpler" animals. (e.g. eye development in molluscs)
- Exaptation: Structures may arise through one selective regime and then be co-opted for another use (e.g. feathers of birds)
- Chance events can determine the larger direction of life's diversity (e.g. stochastic, not goal-oriented). Selective examination of fossil evidence can give the appearance of goal directed change instead of the diversification/extinction pattern typically seen.
Explain the goal of modern systematics and the basic premises by which classification of life proceeds
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Taxonomy based on the Linnean binomial system since the 1700's -
Modern goal is classification consistent with phylogeny -
Homology indicates common ancestry, but analogy does not -
Molecular biology provides a limited but less ambiguous character set -
Phylogentic trees are usually created using cladistics and are based on the principle of parsimony
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