Question

A trait is adaptive if it __________ . a. arises by mutation b. increases fitness c. is passed to offspring d. occurs in fossils

Short answer

An adaptive trait increases fitness.

Step-by-step solution

Understand Adaptive Traits

Adaptive traits are characteristics that enable an organism to survive and reproduce in its environment. These traits enhance the fitness of the organism by increasing its ability to survive longer and produce more offspring.

Examine Option A

Option A suggests that a trait is adaptive if it arises by mutation. While mutations can lead to adaptive traits, not all mutations are beneficial or adaptive. Thus, simply arising by mutation does not make a trait adaptive.

Examine Option B

Option B states that a trait increases fitness. An adaptive trait increases an organism’s fitness by helping it survive and reproduce better than others without the trait, making option B a strong candidate for being correct.

Examine Option C

Option C claims a trait is adaptive if it is passed to offspring. While inheritance is important for the spread of adaptive traits, just being inheritable does not necessarily make a trait adaptive unless it also increases fitness.

Examine Option D

Option D suggests the trait is adaptive if it occurs in fossils. While adaptive traits can be found in fossils, their presence alone in fossils does not determine if a trait was adaptive, as not all traits found in fossils were advantageous.

Determine the Correct Answer

Considering all the options, the defining characteristic of an adaptive trait is its ability to increase an organism's fitness, therefore the correct answer is option B.

Key concepts

Mutation

A mutation refers to any change in the sequence of DNA in an organism. These changes can occur naturally as part of biological processes or due to environmental factors.

• Mutations are crucial for introducing genetic variation in populations, which is essential for evolution.
• They can result in new phenotypes that may or may not be better suited to an organism's environment.

It is important to note that not all mutations lead to positive outcomes. Some might have no noticeable effect, while others can be detrimental to the organism. Rarely, a mutation might confer a new ability or trait that improves the species' fitness. These beneficial mutations can be a driving force for evolutionary change over time.
Therefore, while mutations can lead to adaptive traits, the mere occurrence of a mutation does not guarantee that a trait will be adaptive. Adaptiveness depends on the trait's context and its impact on the organism's survival.

Fitness

In the context of biology, fitness refers to an organism's ability to survive and successfully reproduce in its environment. An organism with higher fitness is more likely to pass on its genes to the next generation.

• Fitness is directly related to the concept of natural selection, where organisms with advantageous traits tend to leave more offspring.
• These advantageous traits, known as adaptive traits, ultimately become more common in the population over generations.

An increase in fitness indicates that the individual is better adapted to its environment than those with lower fitness. Thus, identifying traits that enhance fitness is a central aspect of studying evolution.
A trait is considered adaptive if it improves fitness, enabling the organism to outcompete others, reproduce more efficiently, and ensure the survival of its offspring.

Inheritance

Inheritance is the process through which traits are transmitted from parents to offspring via genetic material. This genetic material is typically carried within an organism’s DNA.

• Inheritance allows for the transfer of adaptive traits across generations.
• It plays a critical role in the persistence and spread of these traits in a population.

While inheritance is a fundamental principle of genetics and evolution, it alone does not define a trait as adaptive. For a trait to be adaptive, it must also contribute to an organism’s fitness.
Traits that are inherited but neutral or detrimental to fitness do not necessarily contribute to evolutionary success. Therefore, the context and effect of the trait are crucial for determining its adaptive value.

Fossils

Fossils are the preserved remains or traces of organisms from the past, typically found in sedimentary rock. They provide a historical record of life on Earth and help scientists understand evolutionary processes.

• Fossils can show how species have changed over time and reveal how adaptive traits developed and were passed down.
• They offer insight into environments of the past and how organisms adapted to them.

However, the presence of a trait in fossils does not inherently label it as adaptive. Some traits preserved in fossils may have been neutral or even disadvantageous under certain conditions.
Analyzing fossil records helps scientists reconstruct the evolutionary history and adaptative changes in lineages, although current environmental factors too can influence the adaptiveness of traits.