Evolution (C736)

Explanation:

Macroevolution refers to evolutionary changes that occur over long time scales, affecting entire lineages or groups of species. It encompasses phenomena such as speciation, adaptive radiation, and large-scale morphological changes. Unlike microevolution, which involves small genetic changes within populations, macroevolution addresses broad patterns of evolutionary change and diversification in life forms.

Correct Answer:

macroevolution

Why Other Options Are Wrong:

microevolution

Microevolution refers to small-scale changes in allele frequencies within a population over relatively short time periods. It does not account for large-scale evolutionary trends across multiple species.

fossilization

Fossilization is the process by which organisms are preserved in the geological record. While fossils provide evidence of evolution, fossilization itself is not a term for evolutionary change.

homologous change

Homologous structures indicate common ancestry, but the term “homologous change” is not used to describe large-scale evolutionary trends. It does not encompass broad evolutionary patterns like macroevolution does.

Explanation:

Artificial selection is the process by which humans intentionally breed organisms to enhance or favor specific traits. In the case of broccoli, cauliflower, and kale, selective breeding over generations produced different varieties with desirable characteristics. Unlike natural selection, which is driven by environmental pressures, artificial selection is directed by human choice, allowing certain traits to become more common in the population due to deliberate reproductive selection.

Correct Answer:

Artificial selection

Why Other Options Are Wrong:

Negative-frequency dependent selection

Negative-frequency dependent selection occurs when the fitness of a trait decreases as it becomes more common in a population. This concept involves natural population dynamics and does not describe deliberate human-driven breeding, making it incorrect.

Natural selection

Natural selection is driven by environmental pressures that favor certain traits over others for survival and reproduction. While similar in effect, it differs from artificial selection, which is guided intentionally by humans, so this option is incorrect.

Founder effect

The founder effect occurs when a small population becomes isolated and certain alleles are overrepresented by chance. This mechanism does not involve selective breeding for specific traits, so it is not the correct answer.

Stabilizing selection

Stabilizing selection favors intermediate phenotypes and reduces variation around a mean trait. It occurs naturally and is not a result of intentional breeding, so it does not describe the process in the question.

Explanation:

A control group provides a baseline for comparison to determine whether an experimental treatment produces a measurable effect. If the control group shows no significant behavioral changes, any differences observed in the treated group can reasonably be attributed to the experimental manipulation. Therefore, the treatment likely influenced the behavior of the experimental group, validating the hypothesis that the manipulated variable affects mating or other behaviors.

Correct Answer:

The experimental treatment likely had a significant effect on the behavior of the treated birds compared to the control group.

Why Other Options Are Wrong:

The control group was not affected by any external factors.

While true, this statement alone does not provide a conclusion about the experimental treatment’s effect on the treated group. It merely describes the control condition without addressing the outcome.

The experimental treatment was ineffective and should be discarded.

This is incorrect because the absence of changes in the control group highlights the contrast with the experimental group. Observed differences in the treated birds suggest the treatment was effective, not ineffective.

The control group was too small to draw any conclusions.

The question does not provide information about sample size limitations. Assuming the control group is valid, the lack of changes allows for meaningful comparisons. Therefore, this option is incorrect.

Explanation:

Sexual selection is a form of natural selection where traits that increase an individual’s mating success are favored. In sticklebacks, females prefer males with brighter red coloration, leading to increased reproductive success for those males. This selective mating drives the evolution of traits that enhance attractiveness rather than directly affecting survival, which is the hallmark of sexual selection.

Correct Answer:

Sexual selection

Why Other Options Are Wrong:

Artificial selection

Artificial selection occurs when humans intentionally breed individuals with desirable traits. Female mate choice in sticklebacks is a natural process, not human-directed, making this option incorrect.

Natural selection

While sexual selection is a type of natural selection, general natural selection refers to traits that improve survival and overall fitness. Bright coloration primarily affects mating success rather than survival, so “sexual selection” is the more precise term.

Directional selection

Directional selection favors one extreme of a trait distribution due to environmental pressures on survival. While sexual selection can cause directional change in traits, the key factor here is mating preference rather than survival, so directional selection is not the best choice.

Explanation:

This statement describes Darwinian fitness, which refers to an organism’s ability to survive and reproduce in a specific environment relative to other individuals. Traits that increase reproductive success are naturally selected, leading to the proliferation of those advantageous traits in subsequent generations. Fitness in Darwinian terms measures reproductive success, not just survival, emphasizing the non-random nature of evolution through natural selection.

Correct Answer:

Darwinian fitness

Why Other Options Are Wrong:

Gradualism

Gradualism is the concept that evolutionary changes occur slowly and steadily over long periods of time. While it relates to the pace of evolution, it does not specifically describe the relationship between inherited traits and reproductive success.

Inheritance of acquired characteristics

This concept, associated with Lamarck, suggests that traits acquired during an organism’s lifetime can be passed to offspring. It is different from Darwinian fitness, which depends on naturally selected heritable traits.

Developmental homology

Developmental homology refers to similarities in embryonic development among different species that indicate common ancestry. It does not describe survival or reproductive success in a population.

Random genetic drift

Random genetic drift refers to changes in allele frequencies due to chance rather than selection. It is a random process and does not account for the non-random survival advantage described in the statement.

Explanation:

A scientific theory is a well-substantiated explanation of some aspect of the natural world that is based on a body of evidence and has withstood repeated testing and scrutiny. Unlike a mere hypothesis, a scientific theory integrates multiple lines of evidence, explains observed phenomena, and can make reliable predictions. While it is widely accepted, it remains open to refinement or falsification if new evidence emerges.

Correct Answer:

scientific theory

Why Other Options Are Wrong:

proven theory

No scientific concept is considered absolutely “proven” because science remains open to revision with new evidence. This makes the term misleading in a scientific context.

testable hypothesis

A testable hypothesis is a starting point for investigation, not a broadly accepted explanation supported by extensive evidence. It has not yet been confirmed through repeated testing.

scientific law

A scientific law describes a consistent natural phenomenon, usually mathematically, but does not explain why it occurs. A theory provides explanatory power, so a law is not the same as a theory.

speculative idea

A speculative idea is a guess or conjecture without substantial evidence, which does not meet the criteria for a scientific theory.

law of nature

A law of nature describes patterns or regularities in nature but does not explain underlying mechanisms. A scientific theory explains phenomena, so this option is incorrect.

Explanation:

In this experiment, the independent variable that is manipulated is the length of the male's tail. Researchers alter tail length to observe how it affects female mate choice. This manipulation allows scientists to determine whether tail length influences mating success, demonstrating sexual selection in action.

Correct Answer:

The length of the male's tail

Why Other Options Are Wrong:

The number of females present

This is not manipulated to test mate selection; the focus of the experiment is on male tail length and its influence on female choice, not on female density.

The color of the males' feathers

While feather color could potentially influence mating, this was not the variable manipulated in this specific experiment, making it incorrect.

The age of the males

Male age is not altered or controlled in this experiment; the study specifically investigates tail length as the factor affecting female selection.

Explanation:

Jean-Baptiste Lamarck proposed the theory of inheritance of acquired traits, suggesting that characteristics an organism develops during its lifetime can be passed on to its offspring. For example, he hypothesized that if an organism developed stronger muscles through use, this trait could be inherited by its descendants. Although modern genetics has shown that most acquired traits are not inherited in this way, Lamarck’s idea was an early attempt to explain evolutionary change.

Correct Answer:

Lamarck

Why Other Options Are Wrong:

Darwin

Charles Darwin proposed natural selection as the mechanism of evolution, where heritable traits that increase survival and reproduction become more common over generations. He did not suggest that acquired traits could be inherited, making this option incorrect.

Linnaeus

Carl Linnaeus focused on the classification and naming of organisms (taxonomy) and did not propose mechanisms of trait inheritance or evolutionary change. Therefore, this option is incorrect.

Explanation:

Mechanical isolation is a prezygotic reproductive barrier in which structural differences in reproductive organs or flower morphology prevent successful mating or pollination. In plants, differences in flower shape or size can prevent pollen transfer between species with incompatible structures, ensuring that mating occurs only between compatible individuals and maintaining species boundaries.

Correct Answer:

Mechanical isolation occurs when differences in physical structures prevent successful mating between species.

Why Other Options Are Wrong:

Mechanical isolation is a type of temporal barrier that affects mating seasons.

Mechanical isolation is not related to timing of reproduction; it is based on physical compatibility. This option confuses mechanical and temporal isolation, making it incorrect.

Mechanical isolation refers to the geographical separation of species.

Geographical separation is a form of allopatric isolation, not mechanical isolation, so this option is wrong.

Mechanical isolation allows for hybridization between species with different traits.

Mechanical isolation prevents, rather than facilitates, hybridization by blocking mating between incompatible structures, making this option incorrect.