Origins of cells: evidence and limits
| English | 中文 | Pinyin |
|---|---|---|
| endosymbiosis/ˌendəʊˌsɪmbaɪˈəʊsɪs/ | 内共生 | nèi gòng shēng |
| inference/ˈɪnfərəns/ | 推论 | tuī lùn |
What would explain this observation?
- Mitochondria have their own DNA and divide within cells. These features invite an evolutionary explanation that can be tested against other evidence.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- The endosymbiotic model explains mitochondria and chloroplasts as descendants of bacteria living within another cell lineage. Double membranes, ribosomes, DNA and division provide several lines of evidence. This model is distinct from a complete explanation for the origin of the first life.
- endosymbiosis 内共生: One organism living within another in an evolutionary association; inference 推论: An explanation drawn from observations and reasoning.
Which observation is relevant evidence for mitochondrial endosymbiosis?
Independent observations strengthen a model when they make a consistent prediction. Similarity is evidence to evaluate alongside ancestry, sequence comparisons and alternative explanations, rather than proof from one feature.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Independent observations strengthen a model when they make a consistent prediction. Similarity is evidence to evaluate alongside ancestry, sequence comparisons and alternative explanations, rather than proof from one feature.
- Use attributed micrographs and sequence data. Separate observations from inferences in a table. Check whether each comparison concerns a mitochondrion, chloroplast, bacterial cell or eukaryotic nucleus.
Which two habits make the investigation or model in this case more defensible?
Use attributed micrographs and sequence data. Separate observations from inferences in a table. Check whether each comparison concerns a mitochondrion, chloroplast, bacterial cell or eukaryotic nucleus.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: 18 of 24 compared sequence sites are identical. Identity = 18/24 × 100 = 75%. Identity across this short alignment cannot alone date an evolutionary split or establish that one organism is the direct ancestor of another.
21 of 28 compared sites match. Calculate percentage identity. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
21 of 28 compared sites match. Calculate percentage identity.
The result is 75 %. Known: 18 of 24 compared sequence sites are identical. Identity = 18/24 × 100 = 75%. Identity across this short alignment cannot alone date an evolutionary split or establish that one organism is the direct ancestor of another.
Check the conclusion and its limits
- The endosymbiotic model does not say that every organelle arose from an engulfed bacterium. A laboratory model of early chemistry is not a recreation of the whole historical event.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
One matching sequence proves the complete origin of life. This claim is false: The endosymbiotic model does not say that every organelle arose from an engulfed bacterium. A laboratory model of early chemistry is not a recreation of the whole historical event.
Origins of cells: evidence and limits: Independent observations strengthen a model when they make a consistent prediction. Similarity is evidence to evaluate alongside ancestry, sequence comparisons and alternative explanations, rather than proof from one feature.
One matching sequence proves the complete origin of life.
The endosymbiotic model does not say that every organelle arose from an engulfed bacterium. A laboratory model of early chemistry is not a recreation of the whole historical event.
One organism living within another in an evolutionary association: write the technical term.
endosymbiosis means One organism living within another in an evolutionary association.