Overview
This lecture covers scientific explanations and theories in biology, focusing on how theories develop, are tested, refined, and applied, with examples from evolution, genetics, and the scientific method.
Scientific Theories and Explanations
- Scientific inquiry involves gathering data, analyzing results, and forming explanations over time.
- A scientific theory is a well-tested explanation for how aspects of the natural world work.
- Theories, like natural selection, develop from repeated testing and refinement based on evidence.
- Theories are modified or replaced when new evidence emerges that cannot be explained by current models.
- Feedback loops ensure theories continuously align with observed data.
Examples in Biology
- Natural selection explains how species, like Galapagos finches, adapt over time.
- Antibiotic resistance in bacteria is an example of natural selection in action.
- Feedback loops regulate processes like blood glucose; mutations in receptors can affect these explanations.
- Environmental factors can influence gene expression without changes in DNA sequence (via histone modification and methylation).
- The sequence of amino acids in proteins determines their structure and function.
Working with Scientific Theories
- Justify claims with evidence, e.g., identifying metabolic strategies in different organisms.
- Construct explanations based on experimental data, such as interpreting bacterial growth on antibiotic plates.
- Refine theories when evidence, like gene linkage or polygenic traits, expands beyond Mendel’s original laws.
- Make predictions about natural phenomena and discuss impacts on genetic makeup, e.g., genetic drift, migration, or artificial selection.
- Work through genetic data to determine parental genotypes and recognize sex-linked traits.
Key Terms & Definitions
- Theory — A well-substantiated explanation of natural phenomena, repeatedly tested and refined.
- Natural Selection — Mechanism by which evolution occurs; organisms with favorable traits survive and reproduce.
- Genetic Drift — Random change in allele frequencies due to chance events, especially in small populations.
- Artificial Selection — Human-directed breeding to select for desired traits.
- Sex-linked Trait — A trait associated with genes on sex chromosomes, affecting inheritance patterns.
- Feedback Loop — A system where outputs are fed back as inputs, regulating biological processes.
Action Items / Next Steps
- Practice justifying claims and constructing explanations using provided experimental data.
- Review Mendelian and non-Mendelian inheritance patterns.
- Apply theories to new data scenarios, as done in practice questions.