Evolution by Natural Selection Concepts

What is the main concept behind natural selection as proposed by Charles Darwin?

• Inheritance of acquired characteristics

• Survival of the fittest

• Use and disuse of organs

• Spontaneous generation

Answer explanation

The main concept of natural selection, as proposed by Charles Darwin, is 'survival of the fittest.' This means that individuals best adapted to their environment are more likely to survive and reproduce, passing on their traits.

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Which type of selection favors individuals with extreme phenotypes over those with intermediate phenotypes?

• Directional selection

• Stabilizing selection

• Disruptive selection

• Gradual selection

Answer explanation

Disruptive selection favors extreme phenotypes, leading to a split in the population. In contrast, stabilizing selection favors intermediate phenotypes, while directional selection favors one extreme. Thus, the correct answer is disruptive selection.

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Explain how directional selection can affect the traits of a population over time.

• It maintains the status quo by favoring average traits.

• It shifts the population's traits towards one extreme.

• It increases genetic diversity by favoring multiple extremes.

• It causes random changes in traits without a specific direction.

Answer explanation

Directional selection favors individuals with traits at one extreme, leading to a shift in the population's traits over time. This results in a more pronounced expression of those advantageous traits, enhancing adaptation.

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Compare and contrast Darwin's theory of natural selection with Lamarck's theory of inheritance of acquired characteristics.

• Both theories suggest that traits are passed down unchanged.

• Darwin's theory involves natural selection, while Lamarck's involves use and disuse.

• Lamarck's theory is based on genetic mutations, while Darwin's is not.

• Both theories emphasize the role of environmental changes in evolution.

Answer explanation

Darwin's theory of natural selection explains evolution through survival of the fittest, while Lamarck's theory suggests that traits are acquired through use and disuse, which are then passed on. This highlights their fundamental differences.

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Which type of selection is most likely to result in a population with reduced genetic diversity?

• Disruptive selection

• Stabilising selection

• Directional selection

• Punctuated selection

Answer explanation

Stabilizing selection favors average traits, reducing variation and leading to decreased genetic diversity. In contrast, disruptive and directional selection can maintain or increase diversity by favoring extremes or specific traits.

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Describe a scenario where punctuated equilibrium might occur in a population.

• A population gradually adapts to a slowly changing environment.

• A population remains stable for long periods, interrupted by rapid changes due to environmental shifts.

• A population experiences continuous, slow changes over time.

• A population undergoes random genetic drift without environmental influence.

Answer explanation

Punctuated equilibrium describes a pattern where a population is stable for long periods, then experiences rapid changes due to environmental shifts, making the second choice the correct answer.

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Analyze how stabilizing selection can impact the evolution of a species.

• It can lead to the development of new species by favoring extreme traits.

• It can maintain the status quo by favoring average traits and reducing variation.

• It can increase genetic diversity by favoring multiple phenotypes.

• It can cause a population to adapt to new environments rapidly.

Answer explanation

Stabilizing selection favors average traits, which helps maintain the status quo in a population by reducing variation. This process ensures that extreme traits are less common, promoting stability in the species' characteristics.

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What is the primary difference between gradual selection and punctuated selection in evolutionary theory?

• Gradual selection involves sudden changes, while punctuated selection is slow and steady.

• Gradual selection is a slow, continuous process, while punctuated selection involves rapid changes.

• Both involve rapid changes, but punctuated selection is more frequent.

• Gradual selection occurs only in small populations, while punctuated selection occurs in large populations.

Answer explanation

The correct choice highlights that gradual selection is a slow, continuous process, while punctuated selection involves rapid changes, reflecting the contrasting mechanisms of evolution in these theories.

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Evaluate the impact of disruptive selection on a population's genetic diversity.

• It decreases genetic diversity by favoring average traits.

• It increases genetic diversity by favoring extreme traits at both ends.

• It has no impact on genetic diversity.

• It leads to a uniform population with similar traits.

Answer explanation

Disruptive selection increases genetic diversity by favoring individuals with extreme traits at both ends of the spectrum, rather than those with average traits. This leads to a wider range of traits within the population.

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How did Darwin's observations during his voyage on the HMS Beagle contribute to his theory of natural selection?

• He observed that all species were perfectly adapted to their environments.

• He noted variations among species that were suited to different environments.

• He found that species did not change over time.

• He discovered that acquired traits were inherited by offspring.

Answer explanation

Darwin's observations of variations among species in different environments showed that these differences could lead to better adaptation, forming the basis of his theory of natural selection.

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