Problem 10 - Astronomy: At Play in the Cosmos

Question

Which of the following statements about natural selection is not true? a. Different traits are more favorable in different environments. b. Natural selection can lead to better adaptation of an organism to the environment. c. Traits that enhance the probability of reproduction tend to prolif- erate d. Less adaptive traits die out in one generation. e. Natural selection may begin with a random genetic change.

Step-by-Step Solution

Answer

Statement D is not true.

Step 1: Understanding the Question

Read the question carefully and understand that we need to identify the statement among the given options that is not true about natural selection.

Step 2: Review Each Statement

Go through each statement one-by-one to check its validity based on the principles of natural selection.

Step 3: Evaluate Statement A

Statement A says that different traits are more favorable in different environments. This is true because different environments exert different selective pressures resulting in various traits being favored.

Step 4: Evaluate Statement B

Statement B states that natural selection can lead to better adaptation of an organism to the environment. This is true, as natural selection enhances traits that help in survival and reproduction.

Step 5: Evaluate Statement C

Statement C claims that traits enhancing the probability of reproduction tend to proliferate. This is true because natural selection favors traits that increase reproductive success.

Step 6: Evaluate Statement D

Statement D suggests that less adaptive traits die out in one generation. This is not necessarily true, as less adaptive traits may not die out in a single generation; it can take several generations for such traits to diminish significantly.

Step 7: Evaluate Statement E

Statement E mentions that natural selection may begin with a random genetic change. This is true since natural selection acts on existing genetic variation, which often arises from random mutations.

Step 8: Identifying the False Statement

Determine that Statement D is incorrect, as it incorrectly suggests that natural selection results in the immediate disappearance of less adaptive traits within only one generation.

Key Concepts

Genetic Variation

Genetic variation refers to the differences in DNA sequences among individuals within a population. These differences are crucial for the process of natural selection. Without genetic variation, all individuals would be genetically identical, leaving no room for selection to act upon. Genetic variation arises through different mechanisms:

• Mutations: Random changes in DNA that can introduce new traits.
• Sexual reproduction: Shuffles genes in offspring, leading to a mixture of parental traits.
• Gene flow: When individuals from different populations interbreed, introducing new genes.

Genetic variation is what gives a population the potential to adapt to changing environments. In the face of environmental changes, some individuals might possess genetic traits that provide a survival advantage. This potential for adaptation is critical for the long-term survival and evolution of species.

Adaptive Traits

Adaptive traits are characteristics that improve an organism's ability to survive and reproduce in its environment. These traits can arise from natural selection acting on genetic variation within a population. For example, a thick fur coat might be an adaptive trait for animals living in cold climates, as it provides insulation and warmth.

• Adaptive traits often result from generations of evolutionary pressure.
• They provide a better chance of survival and reproductive success.
• Adaptive traits may differ based on environmental context.

An adaptive trait in one environment may not be beneficial in another. For instance, a trait that helps an organism conserve water in a desert might be disadvantageous in a rainforest where water scarcity is not an issue. This highlights the importance of understanding the environmental context when assessing whether a trait is adaptive.

Evolutionary Fitness

Evolutionary fitness is a central concept in biology that measures an organism's ability to survive and reproduce. Contrary to common misunderstandings, evolutionary fitness is not about being the strongest or the fastest. Rather, it relates to an organism's genetic contribution to the next generation.

• Fitness involves both survival and reproductive success.
• Organisms with higher fitness are more likely to pass their genes to future generations.
• Fitness can vary depending on environmental conditions and available resources.

Natural selection tends to favor individuals with traits that enhance their evolutionary fitness. Over time, these traits become more common in the population. Fitness is a relative measure and is entirely dependent on the specific environment an organism inhabits, emphasizing the dynamic nature of evolution. This underlines why natural selection leads to a diverse range of life forms well-suited to their respective niches.