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Q13 (IAS/2014) Environment & Ecology › Ecology & Ecosystem Basics › Evolutionary processes Official Key

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.

Result
Your answer: —  ·  Correct: C
Explanation

Both continental drift and glacial cycles have influenced the evolution of organisms.

Continental drift began around 200 million years ago when Pangaea split into Laurasia and Gondwanaland, which subsequently broke into smaller continents that exist today.[1] This breakup separated populations of organisms across different landmasses, leading to geographic isolation. When species are isolated on different continents, they evolve independently in response to different environmental conditions, resulting in divergent evolution and speciation.

During the last one million years there had been alternating glacial and inter-glacial episodes.[2] These glacial cycles created dramatic environmental changes—ice ages brought harsh, cold conditions while inter-glacial periods were warmer. Such climatic variations acted as selective pressures, forcing organisms to adapt or face extinction. Species that could adapt to changing temperatures, food availability, and habitats survived and evolved, while others perished.

Both phenomena—continental drift causing geographic isolation and glacial cycles causing climatic variations—served as major evolutionary drivers by creating diverse environmental pressures that shaped the characteristics of organisms over geological time.

Sources
  1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > CONTINENTAL DRIFT > p. 27
  2. [2] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > IntroductIon. > p. 8
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Which of the following phenomena might have influenced the evolution of organisms? 1. Continental drift 2. Glacial cycles Select the c…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10

This is a classic 'Interdisciplinary Bridge' question. It tests if you can connect Physical Geography (NCERT Class XI) with Basic Biology. It validates that you shouldn't study Geography in a silo; you must understand the *consequences* of geological events (Drift, Ice Ages) on the biosphere.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Did continental drift influence the evolution of organisms?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > Post-drift Studies > p. 28
Presence: 5/5
“It is interesting to note that for continental drift, most of the evidence was collected from the continental areas in the form of distribution of flora and fauna or deposits, like tillite. A number of discoveries during the post–World War II period added new information to geological literature. Particularly, the information collected from the ocean floor mapping provided new dimensions for the study of distribution of oceans and continents.”
Why this source?
  • Explicitly states that much evidence for continental drift came from distribution of flora and fauna — linking continental movement to organismal distribution.
  • Implies that changes in continental positions affected where species lived, a key mechanism for evolutionary change (vicariance, isolation).
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > CONTINENTAL DRIFT > p. 27
Presence: 4/5
“This was regarding the distribution of the oceans and the continents. According to Wegener, all the continents formed a single continental mass and mega ocean surrounded the same. The super continent was named PANGAEA, which meant all earth. The mega-ocean was called PANTHALASSA, meaning all water. He argued that, around 200 million years ago, the super continent, Pangaea, began to split. Pangaea first broke into two large continental masses as Laurasia and Gondwanaland forming the northern and southern components respectively. Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today. A variety of evidence was offered in support of the continental drift.”
Why this source?
  • Describes the breakup of Pangaea into Laurasia and Gondwanaland, a major geographic reorganization that would separate populations.
  • Provides the historical-geological context (continental fragmentation) that can drive speciation and divergent evolution.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 7: Tectonics > 7.2. Continental Drift Theory > p. 95
Presence: 3/5
“• A German geophysicist named Alfred Wegener suggested Continental Drift Theory (CDT) in 1912. According to CDT, there existed one big landmass called Pangaea which was covered by one big ocean called Panthalassa. A sea called Tethys divided the Pangaea into two huge landmasses: Laurentia (Laurasia) to the north and Gondwanaland to the south of Tethys. Drift started around 200 million years ago (Mesozoic Era Triassic Period Late Triassic Epoch), and the continents began to break up and drift away from one another.”
Why this source?
  • Gives timing and the existence of a single supercontinent (Pangaea) and its later breakup (~200 Ma), allowing correlation with major evolutionary events.
  • Establishes the large-scale continental movements necessary for long-term biogeographic and evolutionary effects.
Statement 2
Did glacial cycles influence the evolution of organisms?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 3: Geological Time Scale The Evolution of The Earths Surface > 3.3. Proterozoic Eon (2,500 mya to 550 mya) > p. 44
Presence: 4/5
“• It is the last eon of the Precambrian supereon. Bacteria begin producing oxygen. Eukaryotes (have a nucleus), emerge, including some forms of soft-bodied multicellular organisms such as corals.• It was a very tectonically active period in the Earth's history. It featured the first definitive supercontinent cycles and modern orogeny (mountain building). Most of the of modern continental crust was formed in the Proterozoic. The dominant supercontinent was Rodinia (~1000–750 Ma).• The early and late phases of this eon may have undergone Snowball Earth periods (the planet suffered below-zero temperatures, extensive glaciation and as a result drop in sea levels).• Snowball Earth: The Snowball Earth hypothesis proposes that Earth's surface became entirely or nearly entirely frozen at least once, sometime earlier than 650 Mya (million years ago).”
Why this source?
  • Describes extensive Proterozoic glaciations (Snowball Earth) and associated sea-level change — an environmental upheaval likely to alter habitats and selective pressures.
  • Places major glaciation events within the geological timeline when key biological innovations (e.g., emergence of eukaryotes) occurred, implying temporal overlap of climate forcing and evolutionary change.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > IntroductIon. > p. 8
Presence: 3/5
“Global climatic changes, a continuous process, has been great and diverse during the Earth's history of 4.6 billion years. In general, Global climate has undergone more or less cyclic variations. Some periods have seen a warm climate, some cold, and, in many instances, there was an abrupt change from one period to another. Te early climatic history of the world is, however, not well understood but it is known that during the last one million years there had been alternating of glacial and inter-glacial episodes.”
Why this source?
  • States that global climate underwent cyclic variations with alternating glacial and interglacial episodes over the last million years — establishing the regular occurrence of glacial cycles.
  • Provides the climatic context (repeated cold/warm shifts) that can drive habitat change, isolation, and extinction/speciation processes relevant to evolution.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 2: PLANT AND ANIMAL KINGDOMS > convergent Evolution and convolution > p. 2
Presence: 3/5
“Cumulative development in the characteristics of species over time is known as evolution. Classically, evolution is regarded as the progressive change in the features of populations, occurring through the course of sequential generations brought about by the process of natural selection. In fact, evolution also explains the diversifcation of organisms of the presumed common ancestry through geological time and must, therefore, account for speciation and extinction, as well as progressive change as a result of natural selection. Convergent evolution is the process by which unrelated or distinctly related groups evolve similar morphologies or adaptation traits, e.g. the reduced limbs of whales and penguins.”
Why this source?
  • Explains that evolution across geological time must account for speciation and extinction — the biological processes through which environmental changes (like glaciations) exert evolutionary impact.
  • Links the conceptual mechanism (natural selection, diversification) which makes climatic drivers relevant to evolutionary outcomes.
Pattern takeaway: UPSC loves 'Macro-Drivers'. They rarely ask for definitions of drift or cycles anymore; they ask for the *implications*. If a geological phenomenon changes the map (Drift) or the thermometer (Glacial), it automatically influences Evolution. Prepare the *impacts* of physical geography.
How you should have studied
  1. [THE VERDICT]: Sitter. Directly inferable from NCERT Class XI Fundamentals of Physical Geography (Ch 3: Continental Drift evidence includes fossils; Ch 11: Climate Change mentions glacial cycles).
  2. [THE CONCEPTUAL TRIGGER]: Biogeography & Palaeoclimatology — specifically the external drivers of Speciation (Vicariance) and Extinction.
  3. [THE HORIZONTAL EXPANSION]: 1. Wallace Line (Tectonics separating Asian/Australian fauna). 2. Great American Biotic Interchange (Isthmus of Panama formation). 3. Milankovitch Cycles (Eccentricity, Obliquity, Precession driving ice ages). 4. Beringia (Glacial land bridge for human migration). 5. Cambrian Explosion (linked to oxygen/geology).
  4. [THE STRATEGIC METACOGNITION]: Adopt a 'Cause-Effect' mindset. When reading about Plate Tectonics, ask 'What happened to the animals on the moving plates?' When reading about Glaciation, ask 'How did species adapt or die?' The syllabus intersection is where the questions hide.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Continental drift & biogeography (flora and fauna distribution)
💡 The insight

References state that distribution of flora and fauna was primary evidence for continental drift and link geographic change to organismal distribution.

High-yield for UPSC: questions often ask how geological processes shape biodiversity and endemism. Connects physical geography to ecology and evolution; enables answers on vicariance, species distribution and fossil correlations. Master by learning NCERT cases and mapping examples of disjunct taxa and fossil matches.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > Post-drift Studies > p. 28
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > CONTINENTAL DRIFT > p. 27
🔗 Anchor: "Did continental drift influence the evolution of organisms?"
📌 Adjacent topic to master
S1
👉 Pangaea breakup and timing (Mesozoic ~200 Ma)
💡 The insight

Sources describe Pangaea and its breakup around 200 million years ago — crucial for relating plate movements to evolutionary timescales.

Useful for linking geological timelines with evolutionary events in answers. Frequently tested in questions that require synthesis across geology and biological evolution. Prepare by memorizing major breakup stages and their broad biological consequences (isolation, speciation).

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 7: Tectonics > 7.2. Continental Drift Theory > p. 95
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > CONTINENTAL DRIFT > p. 27
🔗 Anchor: "Did continental drift influence the evolution of organisms?"
📌 Adjacent topic to master
S1
👉 Types of evidence used to link plates and life
💡 The insight

References list distribution of flora/fauna, fossils, tillite and palaeomagnetism as evidence connecting continents and biotic patterns.

Evidence-based reasoning is repeatedly tested; knowing concrete evidence types lets aspirants evaluate claims and construct balanced answers. Learn by categorizing geological vs biological evidence (fossils, tillites, paleomagnetism, biogeographic patterns) and practicing short evidence-driven explanations.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > Post-drift Studies > p. 28
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 7: Tectonics > Palaeomagnetism > p. 99
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 7: Tectonics > 7.5. Comparison: Continental Drift – Seafloor Spreading – Plate Tectonics > p. 109
🔗 Anchor: "Did continental drift influence the evolution of organisms?"
📌 Adjacent topic to master
S2
👉 Glacial–interglacial cycles
💡 The insight

Glacial and interglacial alternations are the specific climatic fluctuations asserted to influence organisms by changing habitats and selective pressures.

High-yield for UPSC: asked in physical geography and environment sections. Connects climate change to biodiversity and human prehistory; enables answering questions on drivers of speciation/extinction and palaeoclimate evidence. Prepare by linking cycle mechanisms, timescales, and ecological consequences using NCERTs and standard texts.

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 7: Climate Change > IntroductIon. > p. 8
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 11: World Climate and Climate Change > CLIMATE CHANGE > p. 95
🔗 Anchor: "Did glacial cycles influence the evolution of organisms?"
📌 Adjacent topic to master
S2
👉 Snowball Earth / deep‑time glaciations
💡 The insight

Extreme Proterozoic glaciations (Snowball Earth) illustrate how severe climate episodes coincide with major shifts in the biosphere.

Useful for questions on geological time scale, major evolutionary events, and mass‑change drivers. Helps answer 'why' and 'when' evolutionary turnovers occurred; study via timelines of Earth history and case studies (e.g., Snowball Earth).

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 3: Geological Time Scale The Evolution of The Earths Surface > 3.3. Proterozoic Eon (2,500 mya to 550 mya) > p. 44
🔗 Anchor: "Did glacial cycles influence the evolution of organisms?"
📌 Adjacent topic to master
S2
👉 Evolutionary outcomes across geological time (speciation & extinction)
💡 The insight

Evolutionary theory requires accounting for speciation and extinction through geological periods, linking environmental change (like glaciations) to biological change.

Core concept for environment and ecology questions in UPSC: underpins explanations of biodiversity patterns and fossil record interpretation. Master mechanisms (natural selection, isolation, extinction) and relate them to climatic drivers; use examples from fossil and palaeoclimate records.

📚 Reading List :
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 2: PLANT AND ANIMAL KINGDOMS > convergent Evolution and convolution > p. 2
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 2: The Origin and Evolution of the Earth > Origin of Life > p. 16
🔗 Anchor: "Did glacial cycles influence the evolution of organisms?"
🌑 The Hidden Trap

Milankovitch Cycles. Since UPSC asked about the *effect* (Glacial Cycles), the logical sibling is the *cause*. Memorize the three orbital parameters: Eccentricity (100k yr), Obliquity (41k yr), and Precession (26k yr).

⚡ Elimination Cheat Code

The 'Broad Possibility' Rule. The question asks what 'might' influence evolution. Evolution is driven by environmental pressure. Both Continental Drift (habitat separation) and Glacial Cycles (temperature/sea-level change) are massive planetary events. In Science/Env questions, massive environmental changes *always* influence biology. 'Might' + 'Major Event' = True.

🔗 Mains Connection

Anthropology & History (GS-1): Glacial cycles lowered sea levels, creating the 'Beringia' land bridge. This allowed the migration of Homo sapiens from Eurasia to the Americas. Physical Geography dictates Human History.

✓ Thank you! We'll review this.

SIMILAR QUESTIONS

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Which of the following are the evidences of the phenomenon of continental drift? I. The belt of ancient rocks from Brazil coast matches with those from Western Africa. II. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side. III. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere. Select the correct answer using the code given below.

IAS · 2008 · Q46 Relevance score: -1.64

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Which of the following factors influence the ocean currents ? 1. Coriolis force 2. Gravity 3. Heating by solar energy 4. Wind Select the answer using the code given below :

NDA-I · 2022 · Q68 Relevance score: -5.26

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