Biology · Photosynthesis in Higher Plants · NEET
NCERT gives exactly two reasons. (1) It is the primary source of all food on Earth. (2) It is responsible for the release of oxygen into the atmosphere by green plants. NEET loves this two-point answer, so memorise both together: food and oxygen.
An autotroph makes (synthesises) its own food using light energy. Green plants do this by photosynthesis, so plants are autotrophs. A heterotroph cannot make its own food and depends on plants (directly or indirectly) for food. All animals, including humans, are heterotrophs. Autotrophic nutrition is found only in plants (and some other photosynthetic organisms).
'Auto' means self and 'troph' means feeding. Green plants use light energy to synthesise the organic food (sugars) they need, so they feed themselves. Because they make food rather than take it, they are called autotrophs. This self-made food also feeds every heterotroph that eats them.
Yes. NCERT states that ultimately all living forms on Earth depend on sunlight for energy. Plants trap this sunlight in photosynthesis and store it as chemical energy in food. Heterotrophs then get this energy by eating plants. So the use of sunlight by plants doing photosynthesis is the basis of life on Earth.
No. Green plants, algae (like Chara), and cyanobacteria (like Nostoc) split water and release oxygen. But green and purple sulphur bacteria use H2S instead of water as the hydrogen donor, so they release sulphur or sulphate, not oxygen. This is a common NEET trap: oxygen release is not universal to all photosynthesis.
Oxygen is not produced during photosynthesis by
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Photosynthesis is important for two reasons: it is the primary source of all food on Earth, and it releases oxygen into the atmosphere. Without it there would be no food and no oxygen for most life.
Humans are heterotrophs. We cannot make our own food and must eat plants or animals that ate plants. Only green plants and some other photosynthetic organisms are autotrophs.
Photosynthesis is the primary source of all food on Earth. Green plants (autotrophs) trap light energy and make organic food, and every heterotroph depends on this food directly or indirectly.
No. Besides making food, photosynthesis also releases oxygen into the atmosphere. Both of these are the two reasons NCERT gives for why photosynthesis is important.
