- A The slow, gradual evolution of a single ancestral species without any branching into separate descendant species, occurring uniformly across an unchanging environment with no new ecological niches ever becoming available
- B Rapid diversification of a single ancestral species into many species filling different ecological niches; example: Darwin finches on Galapagos, Australian marsupials, Hawaiian honeycreepers, East African cichlids
- C The widespread extinction of many previously diverse species following a sudden environmental catastrophe, an event typically followed by a long period of reduced diversity rather than rapid new species formation
- D The seasonal long-distance migration of animal populations between separate, geographically distant habitats, a pattern that produces no lasting change whatsoever in either body form or ecological niche occupied
Correct answer: B. Rapid diversification of a single ancestral species into many species filling different ecological niches; example: Darwin finches on Galapagos, Australian marsupials, Hawaiian honeycreepers, East African cichlids
Explanation: Adaptive radiation: one ancestral species rapidly diversifies into many species exploiting different niches (ecological opportunity). Classic examples: (1) Darwin finches (13 species from one finch ancestor, beak shapes for different foods); (2) Australian marsupials (isolated continent, diversified into niches filled by placental mammals elsewhere); (3) East African cichlids (600+ species, different feeding strategies); (4) Hawaiian silverswords.
Concept context
Origin of life, Darwin's theory, natural selection, speciation, and evidence for evolution.