Natural Selection：练习题

In a population of beetles, the allele frequency of a recessive trait (b) is 0.4. If the population is in Hardy-Weinberg equilibrium, what is the frequency of the homozygous dominant genotype (BB)?

In a phylogenetic tree, a group of organisms that includes an ancestral species and some, but not all, of its descendants is referred to as:

A population of a specific bird species shows a wide range of beak sizes. After several generations of intense drought, researchers observe that birds with very small beaks and birds with very large beaks have higher survival rates than those with average-sized beaks. This is an example of which type of selection?

A researcher is studying a population of wildflowers in a meadow. Due to a sudden flood, a small group of 10 plants is isolated on a new sandbar. This small group happens to have a much higher frequency of red flowers than the original population. This change in allele frequency is primarily due to:

A population of bacteria is exposed to a low dose of an antibiotic. Over time, the population becomes resistant to the drug. Which of the following statements best describes the mechanism of this change?

In a population of flowering plants in Hardy-Weinberg equilibrium, the frequency of a recessive allele for white petals is \( q = 0.4 \). If a sudden change in pollinator preference selects against the dominant purple phenotype, reducing its survival rate by \( 50\% \) in one generation, calculate the new frequency of the recessive allele and explain why the population is no longer in equilibrium.

In a specific population of bacteria, the introduction of a bacteriostatic antibiotic leads to a shift in allele frequencies over several generations. If the environmental pressure remains constant, explain why the genetic diversity of the population might decrease while the biological fitness of the surviving individuals increases.