Problem 2 - Biology: Science for Life with Physiology

Question

What observations did Charles Darwin make on the Galápagos Islands that helped convince him that evolution occurs? A. the existence of animals that did not fit into Linnaeus's classification system; B. the similarities and differences among mockingbirds and tortoises on the different islands; C. the presence of species he had seen on other tropical islands far from the Galápagos; D. the radioactive age of the rocks of the islands; E. fossils of human ancestors

Step-by-Step Solution

Answer

Darwin's observation of variations among mockingbirds and tortoises (Option B) convinced him of evolution.

Step 1: Read the Question Carefully

The question asks what observations Darwin made on the Galápagos Islands that contributed to his ideas on evolution. It is important to focus on his biological observations, as these were key to his formation of the theory of evolution.

Step 2: Analyze Each Option

Each option represents a different type of observation or evidence. We will analyze them to determine if they fit with how Darwin developed his theories on evolution.

Step 3: Evaluate Option A

Option A states: "the existence of animals that did not fit into Linnaeus's classification system." Darwin's observations were focused on variability and adaptation within existing classifications rather than completely new organisms outside the system. This option is not directly relevant.

Step 4: Evaluate Option B

Option B states: "the similarities and differences among mockingbirds and tortoises on the different islands." This is a relevant observation because Darwin noted how species varied between islands and adapted to their environments, supporting his concept of natural selection.

Step 5: Evaluate Option C

Option C states: "the presence of species he had seen on other tropical islands far from the Galápagos." While Darwin did notice similarities between species on different islands, his focus was more on the variations within the Galápagos, making this indirect evidence.

Step 6: Evaluate Option D

Option D states: "the radioactive age of the rocks of the islands." Darwin focused on biological evidence rather than geological dating, which was not used in his time. This option is not relevant to his observations.

Step 7: Evaluate Option E

Option E states: "fossils of human ancestors." Darwin did not find fossils of human ancestors on the Galápagos Islands, nor would such fossils relate directly to his observations on evolution there.

Step 8: Conclusion

Based on the evaluation, Option B is the most accurate observation that supported Darwin's theory of evolution, due to its focus on the variation and adaptation of species on the Galápagos Islands.

Key Concepts

Theory of Evolution

The theory of evolution is a scientific explanation of how life on Earth has developed over millions of years. It suggests that species change over time and that all living organisms share a common ancestor. Charles Darwin's journey to the Galápagos Islands played a crucial role in shaping this theory. His observations there led him to understand how species could evolve through gradual changes. Darwin proposed that these changes accumulate over successive generations, leading to the diversity of life forms we see today.

At the core of Darwin's theory is the idea that species are not fixed and unchangeable. Instead, they are capable of undergoing evolutionary transformations. This insight came from noticing differences and similarities between different island species, most notably among mockingbirds and tortoises. These observations demonstrated how species could adapt to distinct environments over time, leading to new species formation. Darwin's theory was revolutionary because it provided a mechanism—natural selection—that explained how such changes could occur.

Natural Selection

Natural selection is the process whereby organisms better adapted to their environment tend to survive and produce more offspring. This concept is central to Darwin's theory of evolution and was largely inspired by his observations on the Galápagos Islands. Here, he noted that variations in species, such as the size and shape of tortoise shells, were related to their habitats.

Darwin inferred that these variations affected the animals' abilities to survive and reproduce in their specific environments. For instance:

• Mockingbirds with different beak shapes were more suited to different food sources.
• Tortoises with particular shell shapes could better navigate their island's terrain and vegetation.

Over time, natural selection would favor traits that enhanced survival, leading to gradual changes in the species. This principle explains how tiny variations, which may seem insignificant at first, can lead to significant evolutionary changes over long periods. By linking the adaptability of organisms to their environment, Darwin provided a scientific basis for the survival of the fittest.

Species Variation

Species variation is a fundamental aspect of the natural world, highlighted by Darwin's observations on the Galápagos Islands. Each island hosted different species that, while similar, had unique adaptations to their distinct environments. This variety among species laid the groundwork for Darwin’s concept of evolution and natural selection.

Darwin observed that species' differences were not random but related to environmental conditions and the resources available. Key examples included:

• Mockingbirds with varying plumage and beak sizes depending on the ecological niches they occupied on different islands.
• Giant tortoises with differing shell shapes that allowed them to access varied diets.

Such variations within species suggest that they possess the inherent ability to adapt over time, which is critical for their survival. This adaptability ensures that species can remain suited to their environments, even as those environments change. Darwin's observations of species variation on the Galápagos Islands provided compelling evidence of the dynamic nature of living organisms and the evolutionary processes shaping them.