Which of these is an example of evolution?

Question

BlackTom AI · Accepted Answer

Natural selection, a mechanism of evolution, requires heritable variation in a trait that causes differential reproductive success so that alleles for the beneficial trait increase in frequency over generations.

Relevant concepts:
- Evolution = change in allele frequencies in a population over time.
- Natural selection = non-random process where individuals with heritable traits that confer higher fitness leave more offspring.
- Genetic drift/bottleneck = random changes in allele frequencies due to chance events.
- Mere presence/absence of organisms or ecological replacement is not necessarily evolution unless allele frequencies change.

Step-by-step reasoning:
1. Identify the key elements in each choice: Is there heritable variation? Does it lead to differential reproductive success? Will allele frequencies change?
2. Option c: “A bird with a bigger beak able to get more energy from seeds passing more of its genes on than its counterparts.”
   - Variation: beak size differs among individuals (heritable trait).
   - Advantage: bigger beak allows more energy intake, increasing survival/reproduction.
   - Outcome: individuals with bigger beaks pass more genes to the next generation so the alleles for larger beaks increase in frequency.
   - Therefore this is a clear example of natural selection driving evolution.
3. Option a: A species unable to eat food in one area and competitors populate it.
   - This describes local extinction or competitive exclusion and community change, not necessarily a change in allele frequencies within the original species due to selection. It’s ecological replacement rather than documented evolution of the species.
4. Option b: One species cannot tolerate warmer water while others can.
   - This is a statement of difference in tolerance, not the process that changed allele frequencies; it could be an outcome of past evolution but as stated it’s an observation, not an example of evolution occurring.
5. Option d: A tidal wave wipes out half a turtle population and the other half repopulate.
   - While bottlenecks can cause genetic drift (a mechanism of evolution), the choice merely describes a population reduction and repopulation without specifying a change in allele frequencies or selection. The stem’s best, explicit example of evolution by selection is c.

Why c is correct: it explicitly links a heritable trait to increased reproductive success and the passing on of genes, matching the definition of evolution by natural selection.

Conclusion: The correct answer is c, matching the provided answer.

Which of these is an example of evolution?Single choice

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