Problem 4 - Campbell Biology

Question

Adaptive radiations can be a direct consequence of three of the following four factors. Select the exception. (A) vacant ecological niches (B) genetic drift (C) colonization of an isolated region that contains suitable habitat and few competitor species (D) evolutionary innovation

Step-by-Step Solution

Answer

B

Step 1: Understand Adaptive Radiation

Adaptive radiation is the evolution of many diverse species from a common ancestor in a relatively short period of time. This usually happens when new ecological opportunities arise.

Step 2: Identify Factors That Drive Adaptive Radiation

Examine each provided factor to determine if it can drive adaptive radiation. Factors that typically cause adaptive radiation include the availability of vacant ecological niches (A), colonization of isolated regions with suitable habitats and few competitors (C), and evolutionary innovations (D).

Step 3: Examine Genetic Drift

Genetic drift (B) refers to random changes in allele frequencies in a population. It is more related to random evolutionary changes rather than adaptive radiation which is driven by natural selection and adaptation.

Step 4: Select the Exception

Since adaptive radiations are typically not driven by genetic drift, identify (B) as the exception among the four factors.

Key Concepts

Ecological Niches

Ecological niches are specific roles or positions that a species occupies in its environment. Think of it as the job a species performs in the ecosystem. This includes how it gets its food, its habitat, and its interactions with other organisms. Different species can adapt to different niches in the same environment.

During adaptive radiation, species evolve to fill various ecological niches. For example, Darwin's finches adapted to different niches by developing unique beak shapes to exploit different food sources. Each niche provides a set of resources and conditions that can drive the evolution of species to take advantage of them. When many niches are vacant, such as on newly formed islands, adaptive radiation can occur quickly as there is less competition.

Key points:

• Roles or positions in an ecosystem
• Involves food, habitat, and interactions
• Drives species evolution to utilize resources

Evolutionary Innovation

Evolutionary innovation refers to the development of new physical or behavioral traits that allow organisms to exploit their environments in new ways. These innovations can occur through mutations, genetic recombination, or changes in developmental processes.

Some famous examples include the evolution of wings in insects and birds, which allowed them to fly and access new niches, and the development of photosynthesis in plants, which enabled them to harness solar energy. These innovations provide species with new advantages, enhancing their survival and reproductive success.

Evolutionary innovations often lead to rapid diversification of species, as seen in adaptive radiation. When a new trait allows species to exploit different resources or environments, they can quickly radiate into new species, each adapted to a specific niche.

Key points:

• New physical or behavioral traits
• Arise from mutations or genetic recombination
• Allow exploitation of new environments
• Drive rapid species diversification

Genetic Drift

Genetic drift is a mechanism of evolution that involves random changes in allele frequencies within a population. Unlike natural selection, which is driven by the advantages of certain traits, genetic drift occurs by chance. It is more pronounced in smaller populations where random events can have a larger impact.

Examples of genetic drift include the bottleneck effect, where a large population is drastically reduced in size by an event like a natural disaster, and the founder effect, where a new population is started by a small number of individuals from a larger population. Both cases result in a random loss of genetic variation.

While genetic drift can lead to changes in a population's genetic makeup, it does not usually drive adaptive radiation. Adaptive radiation is typically driven by natural selection and adaptation to ecological niches, whereas genetic drift is random and does not necessarily result in better-adapted species.

Key points:

• Random changes in allele frequencies
• Significant in small populations
• Examples: bottleneck effect and founder effect
• Not a driver of adaptive radiation