How many eyes are found in an earthworm?

Earthworms are invertebrates belonging to the phylum Annelida. A notable feature of earthworms is that they do not have eyes. Instead of relying on vision, earthworms are highly sensitive to light, vibrations, and chemical stimuli in their environment. This adaptation allows them to survive in soil, which is typically dark, where eyesight would be less useful.

Even though earthworms lack true eyes, they possess light-sensitive cells on their body surface, especially on the skin of their dorsal side. These cells can detect changes in light intensity, which helps earthworms avoid exposure to bright light that could dry out their bodies or expose them to predators. Additionally, earthworms use mechanoreceptors to sense touch and vibrations, and chemoreceptors to detect chemicals in the soil, helping them navigate underground and find food.

Other options in the MCQ are incorrect:

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  One is incorrect because earthworms do not have a single eye.

  
  


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  Many is incorrect as they do not possess multiple eyes.

  
  


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  Two is also incorrect since they lack paired eyes entirely.

  
  

Earthworms play a crucial role in soil ecosystems, helping in aeration, decomposition, and nutrient recycling. Their adaptation to a visionless life is an example of how organisms evolve traits suitable for their habitat and survival. By detecting light and moisture through their skin rather than eyes, earthworms maintain a life underground, safely avoiding predators and harsh environmental conditions.

Understanding why earthworms have no eyes helps students connect animal anatomy, sensory adaptations, and ecology. It highlights the diversity of sensory mechanisms in the animal kingdom and shows that not all animals rely on vision for survival, especially those living in environments where sight is less practical.