Problem 8 - Biology

Question

Which of the following is least likely to have occurred after a small population of finches reached the Galápagos Islands from the South American mainland? (a) after many generations, the finches became increasingly different from the original population (b) over time, the finches adapted to their new environment (c) after many generations, the finches were unchanged and unmodified in any way (d) the finches were unable to survive in their new home and died out (e) the finches survived by breeding with one another

Step-by-Step Solution

Answer

Option (c) is least likely, as evolutionary change is expected over generations.

Step 1: Identify the Situation

We are asked to determine which scenario is least likely after a small population of finches reaches the Galápagos Islands from the South American mainland. The question involves evolutionary principles regarding adaptation and survival.

Step 2: Evaluate Each Option

Examine each answer choice for likelihood based on evolutionary biology: (a) Suggests divergence from the original population over generations, which aligns with adaptive radiation and evolution. (b) Describes adaptation over time, which is a key concept in evolutionary theory. (c) Implies no change after many generations, which contradicts natural selection theory, making it least likely. (d) Suggests they could die out, which is plausible if the environment was not suitable. (e) Implies surviving by interbreeding, which is a normal part of population survival.

Step 3: Apply Biological Concepts

Apply principles of evolution: - Natural selection and adaptation typically lead to changes in a population over generations, making options (a) and (b) quite likely. - Genetic drift and selection pressures often mean a lack of change (c) is extremely improbable over many generations in a new environment. Hence, (c) is least likely based on these principles.

Step 4: Determine the Least Likely Outcome

Given the understanding from evolutionary biology, option (c) is the least likely because it suggests stagnation without evolutionary change, which contradicts known mechanisms of natural selection and adaptation in new environments.

Key Concepts

Natural Selection

Natural selection is a fundamental concept in evolutionary biology. It explains how populations evolve over time through the differential survival and reproduction of individuals with favorable traits. This process was first described by Charles Darwin and has become a cornerstone of modern biological science.

In an environment, there are limited resources, and organisms with traits that are better suited to their surroundings tend to survive and reproduce. Over successive generations, these advantageous traits become more common in the population.

• For example, if a population of finches arrives on an island with limited food sources, those with beak sizes that can access available food more efficiently will likely thrive.
• These finches will reproduce and pass their beneficial traits to their offspring.
• Over time, the population evolves, reflecting the traits best suited for survival in that specific environment.

Therefore, natural selection is not just about survival of the fittest, but about reproduction of the most advantageous. It is through natural selection that populations adapt to changes in their environment, leading to increased differentiation and specialization.

Adaptive Radiation

Adaptive radiation occurs when a single species rapidly evolves into a multitude of new forms to occupy various niches. This phenomenon often follows events where a population is introduced to a new environment with diverse opportunities and minimal competition.

The classic example of adaptive radiation is Darwin's finches in the Galápagos Islands. These birds diversified into various species with different beak shapes and sizes to exploit the different food sources available on the islands.

• When the original finch population arrived in the Galápagos, they encountered a variety of unoccupied ecological niches.
• Over time, natural selection favored finches that adapted to these specific conditions, leading them to evolve into multiple distinct species.

This process allows for a greater understanding of how new species arise and how organisms adapt to ecological opportunities. Adaptive radiation highlights the role of environmental pressures and opportunities in shaping the diversity of life on Earth.

Genetic Drift

Genetic drift is another important mechanism of evolution, distinct from natural selection. It refers to the random changes in allele frequencies within a population, which can lead to significant genetic variation over time, especially in small populations.

Unlike natural selection, which is driven by environmental pressures, genetic drift occurs by chance. This randomness can lead to the loss of some alleles and the fixation of others purely by luck.

• For instance, if a small group of finches colonizes an island, the genetic makeup of their offspring can be quite different from the original population.
• Even without significant environmental changes, these random fluctuations can lead to noticeable evolutionary changes over generations.

It is important to understand that genetic drift can have a more profound effect in small populations where random events play a larger role in shaping genetic diversity. This concept emphasizes the stochastic nature of evolution where chance events can lead to significant evolutionary changes over time.