Q.91 The finches on the Galapagos Islands have widely differing beaks adapted according to
their diets. This is an example of
(A) Adaptive radiation (B) Parallel evolution
(C) Adaptive convergence (D) Co-adaptation
Answer: (A) Adaptive radiation
Galapagos finches evolved diverse beak shapes from a common ancestor to exploit varied food sources on isolated islands, exemplifying adaptive radiation. This process highlights rapid speciation driven by natural selection in new ecological niches.
Option Analysis
Adaptive Radiation
Single ancestral species diversifies into multiple forms adapted to different niches, often in isolated environments like islands. Darwin’s finches on Galapagos show this through beak variations for seeds, insects, or nectar.
Parallel Evolution
Unrelated species evolve similar traits independently in comparable environments. Finches share a recent common ancestor, ruling this out.
Adaptive Convergence
Unrelated organisms develop analogous structures due to similar selective pressures (e.g., shark and dolphin fins). Galapagos finches are closely related, not convergent.
Co-adaptation
Mutual evolutionary changes between interacting species, like predator-prey or pollinator-plant. Beak diversity here reflects individual adaptation to diet, not interspecies co-evolution.
Galapagos finches adaptive radiation showcases evolution in action, where one ancestral bird species radiated into 13+ descendants with specialized beaks matching island diets—from cracking seeds to probing cactus flowers.
Darwin’s Finches Beak Adaptations
Charles Darwin observed finches during his 1835 voyage; genetic studies confirm a single South American ancestor arrived ~2-3 million years ago. Isolation on islands spurred divergence: ground finches gained crushing beaks for tough seeds, while warbler finches developed probing bills for insects.
Adaptive Radiation Mechanism
Key triggers include ecological opportunity (empty niches post-isolation), genetic variation, and natural selection. Rapid speciation bursts create phenotype-environment matches, as in finch beaks correlating with food types.
Comparison with Other Options
| Concept | Key Feature | Applies to Finches? | Example |
|---|---|---|---|
| Adaptive Radiation | Divergence from common ancestor | Yes | Galapagos finches |
| Parallel Evolution | Similar traits in unrelated lineages | No | Marsupial vs. placental moles |
| Adaptive Convergence | Analogous structures in unrelated species | No | Wings in bats vs. insects |
| Co-adaptation | Mutual trait evolution between species | No | Fig wasps and figs |
