UPSC PRELIMS 2020 : Nematodes


Topic : Nematodes

Topic in Syllabus: Indian Geography




Grab a pinch of soil and you can find over a hundred soil worms or nematodes, says the first global analysis of nematodes.



Nematodes are roundworms and their size can vary from a tiny 0.2 millimetre to a few metres.


Global Analysis:

  • A team of over 50 researchers collected over 6,500 soil samples from all seven continents of the world and found that there are about 57 billion nematodes for every human being on Earth.
  • The study was done only on the top 15 cm of soil. Their total biomass comes to around 300 million tonnes which is about 80% of the combined weight of Earth’s humans.
  • The study adds that these nematodes are responsible for “around 2.2% of the total carbon emission from soils”.
  • Soils from Western and Eastern Ghats of India and the Himalayas were used for the study.
  • At 38% of the total, sub-Arctic regions have the highest abundance of nematodes. The temperate region has the next highest abundance followed by the tropical regions.



  • Soil organic matter content was the key driver for nematode abundance.
  • The low temperature and high moisture in the sub-Arctic regions reduce the decomposition rate of organic matter.
  • This leads to accumulation of organic matter and the nematodes happily thrive on them



  • Predicting climate change requires that we understand global carbon and nutrient cycles. We currently have a great understanding of the physics and chemistry of our planet, but we know far less about the biological organisms that drive these cycles. Improving our understanding of these organisms at a global level is critical if we are going to understand and address climate change.”
  • “Various kinds of bacteria, fungi, arthropods and a wide variety of nematodes inhabit the soil. We can study the environmental changes by looking at a small amount of soil as they can represent the entire food web


Sample Question:

Nematoda means

a. pointed ends

b. pointed bodies

c. pointed cells

d. peaked heads


Answer: a