5.1: The Origin and Diversity of Life
- Page ID
- 83875
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- Identify the major evolutionary leaps at given points in the geologic timeline
- Identify the origins of given taxonomic groupings on the geologic timeline
- Explain possible causes of mass extinction in Earth's history
- Utilize phylogeny and biogeography to identify reasons for the present distribution of various organisms
- Describe the current hypotheses on the origin of life
- Describe the evidence for the evolution of prokaryotes and eukaryotes
- 5.1.1: Deep Time
- Evolutionary changes coincide with geologic changes on the earth. Consider that changes in geology (e.g., mountain formation or lowering of the sea level) cause changes in climate and together these alter the habitats available for life. Two types of geologic change seem to have had especially dramatic effects on life: continental drift and the impact of asteroids.
- 5.1.2: Origins of Life
- To account for the origin of life on our earth requires solving several problems: how the organic molecules that define life (for example, amino acids and nucleotides) were created, how these were assembled into macromolecules (for example, proteins and nucleic acids) in a process requiring catalysts, how these were able to reproduce themselves, and how they were assembled into a system delimited from its surroundings (i.e., a cell). Several hypotheses address each of these problems.
- 5.1.3: Evidence for Early Life
- Prokaryotic organisms were the first living things on earth and still inhabit every environment, no matter how extreme. Prokaryotes are well adapted to living in all types of conditions, including extreme ones, and some prefer to live in colonies called biofilms. Archaea are believed to have evolved from gram-positive bacteria and can occupy more extreme environments.
- 5.1.4: Eukaryotic Origins
- Living things fall into three large Domains: Archaea, Bacteria, and Eukarya. The first two are prokaryotic and the third contains all eukaryotes. A relatively sparse fossil record is available to help discern what the first members of each of these lineages looked like, so it is possible that all the events that led to the last common ancestor of extant eukaryotes will remain unknown. However, comparative biology of currently living organisms and the fossil record provides insight.