Spontaneous mutation and changes in the DNA make each individual in a species unique. How does this relate to evolution?

Question

BlackTom AI · Accepted Answer

Mutation generates genetic variation: spontaneous mutations and other DNA changes create new alleles that make individuals genetically distinct. This is the essential raw material for evolution.

1. Relevant knowledge points and concepts
- Mutation: random changes in DNA sequence that can create new alleles.  
- Genetic variation: differences among individuals in allele frequencies and genotypes.  
- Heritability: some mutations are passed to offspring, so variation can persist across generations.  
- Natural selection: environmental pressures cause individuals with advantageous traits to survive and reproduce more, changing allele frequencies.  
- Evolution: change in allele frequencies in a population over time; requires variation, heritability, and differential reproductive success.

2. Step-by-step reasoning
- Step 1: Spontaneous mutations occur during DNA replication or from environmental mutagens, producing new genetic variants.  
- Step 2: These variants make individuals unique in genotype and often phenotype.  
- Step 3: If a variant affects fitness (survival or reproduction), it can influence the individual's reproductive success.  
- Step 4: Natural selection favors alleles that increase fitness; those alleles become more common in subsequent generations.  
- Step 5: Over many generations, the population’s allele frequencies shift—this is evolution.

3. Intermediate steps / calculations
- No numerical calculations are required. The logical intermediate steps are: mutation → heritable variation → differential reproductive success → change in allele frequencies.

4. Why the correct answer is correct
- The provided answer states that mutation causes variation and that natural selection by the environment favors the fittest genomes/species. This correctly links mutation (source of variation) with selection (mechanism that sorts variation), which together produce evolutionary change.

5. Why other possible answers would be incorrect
- Incorrect alternatives might claim mutations are always beneficial, purposeful, or sufficient alone to cause adaptation; these are wrong because most mutations are neutral or harmful, mutations are random (not goal-directed), and without selection or drift, allele frequencies need mechanisms to change over time.

6. Conclusion
- The correct answer is: "This is what causes the variation within a species. Natural selection by the environment then favors the fittest genomes/species." This explanation confirms and supports that answer.

Spontaneous mutation and changes in the DNA make each individual in a species unique. How does this relate to evolution?单项选择题

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