3.3: History of Life on Earth
- Page ID
- 94621
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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
- Discuss the major transitions for Plantae (particularly land plants) and Animalia
- Utilize phylogeny and biogeography to identify reasons for the present distribution of various organisms
- 3.2.1: Systematics and Classification
- Scientists continually obtain new information that helps to understand the evolutionary history of life on Earth. Part of this information includes relationships between organisms. While phylogeny represents the full understanding of evolutionary relationships, scientists also classify organisms into groups in order to use a common framework of language for all species known as binomial nomenclature.
- 3.2.2: Phylogeney and Cladistics
- Scientists collect information that allows them to make evolutionary connections between organisms. Similar to detective work, scientists must use evidence to uncover the facts. In the case of phylogeny, evolutionary investigations focus on two types of evidence: morphologic (form and function) and genetic.
- 3.3.1: Deep Time
- Evolutionary changes coincide with geologic changes on the earth. But 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
- 3.3.2: Origins of Life
- To account for the origin of life on our earth requires solving several problems: how the organic molecules that define life, e.g. amino acids, nucleotides, were created, How these were assembled into macromolecules, e.g. proteins and nucleic acids, - a process requiring catalysts, how these were able to reproduce themselves, and how these were assembled into a system delimited from its surroundings (i.e., a cell). A number of theories address each of these problems.
- 3.3.3: 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 prefer to live in colonies called biofilms. Archaea are believed to have evolved from gram-positive bacteria and can occupy more extreme environments.
- 3.3.4: Eukaryotic Origins
- Living things fall into three large groups: Archaea, Bacteria, and Eukarya. The first two have prokaryotic cells, 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 extant organisms and the limited fossil record provides insight.