Question

Darwin observed a variety of beaks in small black birds inhabiting Galapagos Islands. Explain what conclusions did he draw and how ?

Hint:

Adaptive Radiation is a form of {Divergent Evolution}.
It happens when "Nature" selects the best tool (beak) for the job (eating).

Answer 1

Step 1: Understanding the Concept:
The Galapagos Islands are a chain of volcanic islands that were never connected to the mainland.
When a small group of ancestral finches arrived there, they found diverse habitats with little competition.
Step 2: Detailed Explanation:
Darwin's thought process followed these steps:
1. Diversity Observation: He saw finches with heavy beaks for crushing seeds, thin beaks for catching insects, and long beaks for drinking nectar or pecking wood.
2. Common Origin: He hypothesized that these birds did not arrive as separate species from South America. Instead, a single ancestral "seed-eating" species reached the islands.
3. Geographical Isolation: As the birds moved to different islands, they became isolated.
4. Natural Selection: On an island with many insects, birds with slightly more pointed beaks survived better and passed on those traits. On an island with hard seeds, birds with stronger beaks flourished.
5. Adaptive Radiation: He concluded that this was a classic example of "Adaptive Radiation"—the process where one species evolves into many different forms to fill different ecological niches in a new environment.
Step 3: Final Answer:
Darwin concluded that the varied beaks were adaptations driven by natural selection in response to different feeding habits, proving that evolution is a branching process from a common ancestor.