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In pea plants, purple flower color, $C$, is dominant to white flower color, $c$. The table shows the frequencies of the dominant and recessive alleles in three generations of peas in a garden.



\begin{table}

\captionsetup{labelformat=empty}

\caption{Allele Frequency for Flower Color in Peas}


Generation		$p$$q$

1		0.60.4

2		0.70.3

3		0.80.2




\end{table}



Which statement is a conclusion that may be drawn from the data in the table?


AThe population of pea plants in the garden is in Hardy-Weinberg equilibrium.
BThe population of pea plants in the garden is growing larger in each generation.
CThe decreasing frequency of white-flowered alleles shows that the population is drifting.
DThe increasing frequency of purple-flowered alleles shows that the population is evolving.

Verified Answer :

  • The provided data indicates that the allele frequencies \(p\) and \(q\) are changing across three generations.
  • Because allele frequencies are not constant, the population is not in Hardy-Weinberg equilibrium.
  • The table contains no data on population size, making conclusions about growth impossible.
  • By definition, a change in allele frequencies over time constitutes evolution, supporting the statement that the increasing frequency of purple-flowered alleles shows the population is evolving.
  • Final Answer: \(\boxed{\text{The increasing frequency of purple-flowered alleles shows that the population is evolving.}}\)

Explanation

  1. Analyze the allele frequency data

To analyze the population of pea plants, we first observe the allele frequencies for the dominant allele (\(p\)) and the recessive allele (\(q\)) over three successive generations:

  • Generation 1: \(p = 0.6, q = 0.4\)
  • Generation 2: \(p = 0.7, q = 0.3\)
  • Generation 3: \(p = 0.8, q = 0.2\)

The allele frequency for the dominant (purple) allele is increasing from \(0.6\) to \(0.7\) to \(0.8\), while the frequency for the recessive (white) allele is decreasing from \(0.4\) to \(0.3\) to \(0.2\).

  1. Evaluate the Hardy-Weinberg and population growth claims

The Hardy-Weinberg equilibrium principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences. Since our data shows that the allele frequencies are changing, we can conclude that the population is not in Hardy-Weinberg equilibrium. Furthermore, the table provides no information regarding the total number of individuals in the population, so we cannot make any conclusions about population growth.

  1. Identify the correct conclusion regarding evolution

In biological terms, evolution is defined as any change in the allele frequencies within a population over time. Because the frequency of the dominant purple-flower allele is increasing across the generations, this provides direct evidence that the population is changing, or in other words, it is evolving. While genetic drift is a mechanism that can cause such changes, the most direct and accurate conclusion supported by the definition of evolution is that the increasing frequency of the purple-flowered alleles demonstrates that the population is evolving.

Examples

Understanding how allele frequencies change over time is crucial for studies in population genetics. For example, if a researcher tracks the frequency of a gene responsible for drought resistance in a crop species over several years, they can determine if the population is evolving to better survive changing climate conditions. This foundational knowledge helps in breeding better crops and managing biodiversity in ecosystems. Mathematically, if we see that the frequency of an allele changes from \(p_1\) to \(p_2\), where \(p_1 eq p_2\), the change in frequency \(\Delta p = p_2 - p_1\) is a direct indicator of evolutionary dynamics within that population.

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