UPSC Prelims 2014 Question:

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:

Explanation:

• Continental drift was proposed by Alfred Wegener in 1912. The theory explains that continents shift position on Earth's surface and that Earth must have once been a single supercontinent before breaking up to form several different continents. This explained how similar rock formations and plant and animal fossils could exist on separated continents. Modern science recognizes this ancient supercontinent called Pangaea did exist before breaking up about 200 million years ago, as Wegener theorized. So, point 1 is correct.
  
  
• Large, continental ice sheets in the Northern Hemisphere have grown and retreated many times in the past. We call times with large ice sheets “glacial periods” (or ice ages) and times without large ice sheets “interglacial periods.” These glacial–interglacial cycles occur, as variations in Earth’s orbit through time have changed the amount of solar radiation Earth receives in each season. Interglacial periods tend to happen during times of more intense summer solar radiation in the Northern Hemisphere. Another interesting fact is that temperature variations in Antarctica are in phase with solar radiation changes in the high northern latitudes. As these glacial cycles have a profound impact on climate worldwide, it also influences the evolution of organisms. So, point 2 is correct.
  
  

Therefore, option (3) is the correct answer.

Subject: Geography | Geomorphology