- A Two closely related species gradually diverging in form and function from one shared recent common ancestor over time in many documented cases according to conventional understanding
- B Unrelated species independently evolving similar traits due to similar environmental pressures (e.g., dolphin and ichthyosaur streamlined body shape)
- C Two genetically identical twins developing together from a single fertilized zygote during early embryogenesis in routine practice overall in most cases
- D The gradual reduction in size and eventual loss of an ancestral trait observed within a single evolutionary lineage under typical conditions according to standard textbooks
Correct answer: B. Unrelated species independently evolving similar traits due to similar environmental pressures (e.g., dolphin and ichthyosaur streamlined body shape)
Explanation: Convergent evolution: unrelated species independently evolve similar features (analogous structures) because they face similar environmental challenges. Examples: streamlined body in dolphins (mammal) and sharks (fish); wings in bats and birds; eyes in vertebrates and cephalopods; echolocation in bats and dolphins.
Concept context
Origin of life, Darwin's theory, natural selection, speciation, and evidence for evolution.