Variation within populations Knowledge-Based Practice

Questions

1. 1.

   Which of the following best explains why phenotypic variation caused exclusively by environmental factors cannot directly lead to evolutionary change by natural selection?

   • A) Environmental influences invariably reduce reproductive success across all members of a population.
   • B) The observed differences are not encoded in the genetic material and therefore cannot be inherited by offspring.
   • C) Natural selection can only act upon traits that display discrete and non-overlapping phenotypic categories.
   • D) Traits shaped by environmental conditions are restricted to asexual organisms and cannot undergo selection.
2. 2.

   Which of the following best explains why genetic variation within a population is essential for evolutionary adaptation by natural selection?

   • A) It guarantees that all individuals within the population have equal chances of reproductive success under any environmental conditions.
   • B) It prevents environmental fluctuations from exerting selective pressures on members of the population.
   • C) It allows individual organisms to deliberately develop advantageous physical traits during their lifetimes in response to stress.
   • D) It provides a diverse range of phenotypes, ensuring that some individuals possess traits that favor survival and reproduction when conditions change.
3. 3.

   Which of the following statements correctly characterizes discontinuous variation within a biological population?

   • A) It produces a broad, unbroken gradient of measurable phenotypes influenced primarily by environmental factors.
   • B) It results from the cumulative contribution of many additive polygenic loci with no distinct phenotypic boundaries.
   • C) It results in distinct, non-overlapping phenotypic categories governed primarily by one or a few genes.
   • D) It fluctuates continuously throughout an individual's lifetime in response to changing local habitat conditions.
4. 4.

   Which of the following statements correctly describes continuous variation within a population?

   • A) It is typically influenced by multiple genes and environmental factors, producing an unbroken spectrum of phenotypes.
   • B) It is determined by a single gene locus with two alleles, producing distinct and non-overlapping phenotypic categories.
   • C) It results entirely from somatic mutations that cannot be transmitted to subsequent generations.
   • D) It produces discrete phenotypic classes that exhibit no intermediate measurements among individuals.
5. 5.

   Which of the following biological processes serves as the ultimate source of entirely novel genetic variation within a population?

   • A) Independent assortment of homologous chromosomes
   • B) Crossing over between non-sister chromatids
   • C) Random fertilization of gametes
   • D) Mutation altering nucleotide sequences in DNA

Answers and step-by-step solutions appear after you finish the test.