Question

which of the following statements is true?
complex traits can be lost over time as a result of natural selection
only one evolutionary mechanisms works at a time to shift allele frequencies.
all evolutionary mechanisms lead to well - adapted populations.
natural selection is unpredictable with respect to its effect on fitness.
evolution requires natural selection.

Explanation:

• Complex traits can be lost over time as a result of natural selection: This is true. For example, some cave - dwelling organisms have lost eyesight (a complex trait) over generations. In a dark cave environment, the energy cost of maintaining eyesight (e.g., developing and nourishing eye tissues) may outweigh any benefits (since there is no light to see). Natural selection can favor individuals that invest less energy in non - functional or costly traits.
• Only one evolutionary mechanisms works at a time to shift allele frequencies: False. Multiple evolutionary mechanisms (such as natural selection, genetic drift, gene flow) can act simultaneously. For example, a population may experience both natural selection for a particular trait and gene flow (immigration/emigration) that also affects allele frequencies.
• All evolutionary mechanisms lead to well - adapted populations: False. Genetic drift, for example, is a random change in allele frequencies. It can lead to the fixation of harmful alleles or the loss of beneficial alleles in a population, which does not result in a well - adapted population.
• Natural selection is unpredictable with respect to its effect on fitness: False. Natural selection acts to increase the fitness of individuals in a given environment. It is a non - random process that favors traits that enhance survival and reproduction.
• Evolution requires natural selection: False. Evolution can occur through other mechanisms such as genetic drift (random changes in allele frequencies in a population) and gene flow (movement of genes between populations) even in the absence of natural selection.

Answer:

Complex traits can be lost over time as a result of natural selection.