Which of the following phenomena might have influenced the evolution of organisms?
- 1.Continental drift
- 2.Glacial cycles
Select the correct answer using the code given below.
Answer & explanation
Answer: (c) Both 1 and 2
Both phenomena can shape evolution because they change where organisms live and which populations are isolated. Continental drift splits or joins landmasses, and glacial cycles push species into isolated refuges. Both can drive divergence and diversification, so both statements hold.
- ✓ 1. As continents drift apart, populations are separated and evolve along their own paths (vicariance). Research on the break-up of Pangaea finds that isolation between continents might have increased net diversification rates. Fossils such as Mesosaurus, a shallow brackish-water reptile found only in South Africa and Brazil, show that these now widely separated landmasses were once joined.
- ✓ 2. During glacial periods, species retreat into isolated refuges and later expand again. This isolation drives genetic divergence, and studies credit glacial cycles with driving divergence between species.
- ✗ (a) It leaves out glacial cycles, which are documented as a cause of divergence between species.
- ✗ (b) It leaves out continental drift, which isolates populations on separate landmasses.
Remember · Anything that isolates populations or alters climate and habitat, such as continental drift or glacial cycles, can steer evolution and speciation.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 4 (practise this chapter)
Sources
- Jordan et al., Quantifying the effects of the break up of Pangaea on global terrestrial diversification (Phil. Trans. R. Soc. B, 2016; US National Library of Medicine, PMC) ↗ “the break up of Pangaea and isolation between continents might have increased net diversification rates.”
- Fletcher et al., Glacial cycles drive rapid divergence of cryptic field vole species (Ecology and Evolution, 2019; US National Library of Medicine, PMC) ↗ “underscoring the role that glacial cycles play in driving divergence between these species.”
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 4 “Mesosaurus was a small reptile adapted to shallow brackish water. The skeletons of these are found only in two localities: the Southern Cape province of South Africa and Iraver formations of Brazil.”
Question: UPSC Civil Services (Preliminary) 2014, General Studies Paper I. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·
