Evolution
Explain population change without intention: variation exists, environments filter it, and inherited traits change in frequency across generations.
Evolution
Not yet verified on this browser.
Individuals are selected; populations evolve
Evolution is a change in inherited population characteristics across generations. Natural selection occurs when individuals vary, some differences are heritable, and those differences affect reproductive success.
The environment does not give organisms the traits they need. Variation already exists or arises through mutation. Selection changes how common inherited variants become. Other mechanisms—including genetic drift, gene flow, and mutation—also change populations.
Fitness is contextual
Fitness means reproductive success in a particular environment. A useful trait in one habitat may be harmful in another.
Evidence works together
Fossils, anatomy, biogeography, embryology, and molecular similarities provide independent evidence of common ancestry.
Variation → inheritance → unequal reproduction → frequency change
Problem: After pesticide use, resistant insects become common.
Do not say: The insects changed because they needed resistance.
Recognize: Heritable resistance was already present or arose by mutation. Susceptible insects died more often. Resistant insects left more offspring.
Conclusion: The resistance allele increased in frequency through natural selection.
Why it works
This four-step chain prevents goal-directed explanations and separates natural selection from changes caused by chance or migration.
Five forms you should recognize
Deeper-beaked birds leave more offspring during a drought with hard seeds. If beak depth is inherited, the population average may shift.
A storm randomly leaves a small sample of an island population. Allele frequencies change by chance, not because the survivors were better adapted.
Migrants reproduce in a new population and introduce alleles from their original population.
The same forelimb bone pattern modified for swimming, flying, and walking supports descent from a shared ancestor.
Dark coloration may improve camouflage on lava but reduce camouflage on pale sand. Fitness is not universal.
Check before you commit
- Saying individuals genetically evolve during their lifetime
- Explaining adaptation as wanting or trying
- Using fitness to mean strength only
- Assuming every evolutionary change is natural selection
- Confusing analogous structures with common structural ancestry
- Treating a cladogram tip as the direct ancestor of another tip
Do you need the lesson-or just practice?
One original question in each form recommends your next step. It does not yet verify mastery.
Work at the level you need.
Foundations
Build the core procedure with immediate explanations.
Core Practice
Use mixed forms with less scaffolding.
UPCAT-Style Transfer
Apply the competency in unfamiliar representations.
Ready to verify this competency?
A score of 5/5 verifies mastery. An unsuccessful attempt loads a different five-form bank.
Evolution FAQ
Does natural selection create needed mutations?
No. Mutation is not directed toward need; selection changes the frequencies of variants under particular conditions.
Is evolution always progress toward perfection?
No. Evolution is population change, and adaptations involve trade-offs and environmental context.
Can evolution occur without natural selection?
Yes. Mutation, gene flow, and genetic drift can change allele frequencies.
Continue your science review.
Your progress stays on this browser.
Mastery results save to your Teacher Abi study profile.
Return to Student Hub View UPCAT Coverage
No comments:
Post a Comment