What is Continuing Evolution?
Continuing evolution refers to the ongoing process of genetic changes within populations over time due to natural selection, genetic drift, mutations, and gene flow. While evolution has shaped life for billions of years, it is still occurring today. In AP Biology, understanding this concept is crucial for explaining biodiversity, species adaptation, and evolutionary trends.
In this guide, we’ll break down the key aspects of continuing evolution, including evidence, mechanisms, and real-world examples to help you ace the AP Biology test!
1. Mechanisms of Continuing Evolution
A. Natural Selection
- Organisms with beneficial traits survive and reproduce, passing those traits to offspring.
- Example: Antibiotic resistance in bacteria shows how species evolve in response to environmental pressures.
B. Genetic Drift
- Random changes in allele frequencies, especially in small populations.
- Example: Founder effect and bottleneck effect impact genetic diversity.
C. Gene Flow (Migration)
- Movement of alleles between populations, increasing genetic variation.
- Example: Interbreeding between two populations of birds can introduce new traits.
D. Mutations
- Changes in DNA that introduce new genetic variations.
- Example: A mutation in a butterfly’s wing color could make it more camouflaged, improving survival.
2. Hardy-Weinberg Equilibrium & Evolutionary Change
The Hardy-Weinberg principle states that if no evolution occurs, allele frequencies remain constant. However, real populations do evolve due to natural selection, genetic drift, gene flow, and mutations.
Hardy-Weinberg Conditions (No Evolution)
- No natural selection
- No mutations
- No migration
- Large population size
- Random mating
Since these conditions are rarely met in nature, evolution is always occurring to some extent.
3. Evidence for Continuing Evolution
A. Fossil Record & Transitional Species
- Shows gradual changes in species over time.
- Example: Tiktaalik, a transitional fossil, links fish and amphibians.
B. Observable Evolutionary Change
- Bacterial resistance to antibiotics is a real-time example of evolution.
- Peppered moths changed color due to industrial pollution, demonstrating directional selection.
C. Molecular & Genetic Evidence
- DNA comparisons reveal genetic similarities among species, supporting common ancestry.
4. Speciation & Adaptive Radiation
New species arise when populations become reproductively isolated.
Types of Speciation:
- Allopatric Speciation – Physical barrier separates populations.
- Sympatric Speciation – New species arise in the same geographic area due to factors like polyploidy (common in plants).
Adaptive Radiation:
- A single species evolves into multiple different species, adapting to different environments.
- Example: Darwin’s finches evolved different beak shapes for different food sources.
5. Practice Questions for AP Biology
- Explain how genetic drift can lead to evolutionary changes.
- How does antibiotic resistance in bacteria demonstrate natural selection?
- What factors disrupt Hardy-Weinberg equilibrium and promote evolution?
Conclusion: Evolution is Ongoing!
Understanding continuing evolution is crucial for explaining biodiversity and adaptation. Evolution never stops—it shapes species over time in response to environmental changes. By mastering these concepts, you’ll be prepared for the AP Biology test and beyond.
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