Question

Which of the following best characterizes an adaptive radiation? a. Speciation occurs extremely rapidly, and descendant populations occupy a large geographic area. b. A single lineage diversifies rapidly, and descendant populations occupy many habitats and ecological roles. e. Natural selection is particularly intense, because disruptive selection occurs. d. Species recover after a mass extinction.

Short answer

The correct answer to the question is option B, which states: "A single lineage diversifies rapidly, and descendant populations occupy many habitats and ecological roles." This fully characterizes the concept of adaptive radiation, focusing on rapid diversification from a single lineage and the occupation of various ecological roles by descendant species.

Step-by-step solution

Evaluate Answer Option A

Speciation occurs extremely rapidly, and descendant populations occupy a large geographic area. This aspect is somewhat related to adaptive radiation, but it doesn't capture the whole concept. Adaptive radiation also involves a single ancestral lineage diversifying into various forms that occupy different ecological roles.

Evaluate Answer Option B

A single lineage diversifies rapidly, and descendant populations occupy many habitats and ecological roles. This option accurately describes the concept of adaptive radiation, as it includes the rapid diversification of species from a single ancestral lineage, as well as the occupation of various habitats and ecological roles by these descendant species.

Evaluate Answer Option C

Natural selection is particularly intense, because disruptive selection occurs. While natural selection certainly plays a role in driving adaptive radiation, this option does not explicitly state that species are diversifying from a single ancestral lineage or that they occupy different ecological roles.

Evaluate Answer Option D

Species recover after a mass extinction. Although a mass extinction event could potentially initiate adaptive radiation, this option does not convey the whole concept, as it does not capture the diversification of species from a single ancestral lineage or their occupation of various ecological roles.

Identify the correct choice

The correct answer is option B because it fully characterizes the concept of adaptive radiation, focusing on rapid diversification from a single lineage and the occupation of various ecological roles by descendant species.

Key concepts

Speciation

Speciation is a fundamental process in evolution where new species arise from a single common ancestor. It is a key component in understanding adaptive radiation. Speciation usually occurs when populations of a single species become isolated over time. This isolation can happen due to geographical, ecological, behavioral, or genetic factors.

Once isolated, these populations start to diverge genetically as natural selection and other evolutionary forces, such as genetic drift and mutation, act on them. During adaptive radiation, speciation happens at an accelerated pace. For instance, in a new environment, different populations might evolve distinctive traits that allow them to exploit different resources. This leads to the rapid development of new species equipped to handle various ecological niches. The end result is a diverse group of species originating from a single ancestral lineage, each adapted to a specific environment or role within an ecosystem.

In essence, speciation is the divergent evolution of populations, and in the context of adaptive radiation, it results in species that are specially adapted to thrive in diverse habitats.

Ecological Roles

Ecological roles refer to the various functions and positions that organisms occupy within an environment. Each ecological role is unique, based on how a species interacts with its environment, including factors like diet, habitat use, and relationships with other species. During adaptive radiation, descendant species from a single ancestor evolve to fill different ecological roles, often in a relatively short amount of time. These roles can include being a predator, herbivore, scavenger, or even a pollinator, depending on how the species adapts to the available resources.

As species adapt to occupy diverse roles, they reduce direct competition for resources in their environment. This specialization allows a broader spectrum of life forms to coexist, enhancing biodiversity. In adaptive radiation, the variety of ecological roles is a reflection of the intricate dance of evolution and adaptation in response to new challenges and opportunities within ecosystems.

Understanding these roles is crucial for appreciating how complex ecosystems function and how adaptive radiation can lead to flourishing and resilient biodiversity.

Natural Selection

Natural selection is a driving force behind evolutionary change, including adaptive radiation. It operates on the principle that individuals with advantageous traits are more likely to survive and reproduce, passing those traits on to the next generation. In the context of adaptive radiation, natural selection can lead to the emergence of new species with unique adaptations. When a population enters a new environment, different selective pressures, such as changes in food sources or predators, may favor different traits. Over time, these pressures can result in substantial evolutionary changes.

These changes enable species to exploit new or underutilized ecological niches, leading to the rapid expansion of diversity that characterizes adaptive radiation. Disruptive selection, a form of natural selection, might play a role here by favoring individuals at the extreme ends of the trait spectrum. This can enhance the differences between populations, eventually contributing to speciation.

Natural selection not only shapes the physical and behavioral attributes of species but also strengthens their ecological roles, allowing them to thrive in specific environments. It underscores the dynamic nature of evolution and the role of environmental challenges in sculpting the vast tapestry of life.