CBSE Class 7 Science Exemplar Chapter 1: Nutrition in Plants NCERT Solutions

Organisms that can produce their own food using basic, naturally occurring substances like carbon dioxide and water, often with the help of sunlight, are known as autotrophs. Plants are a prime example of autotrophs.

In contrast, heterotrophs are organisms that cannot prepare their own food and rely on other organisms for nutrition. Parasites obtain nutrients by living on or inside a host organism, harming it in the process. Saprophytes, like yeast and fungi, feed on dead and decaying organic matter.

Photosynthesis is the process by which green plants use sunlight, water, and carbon dioxide to create their own food (glucose) and release oxygen. This process primarily occurs in the leaves. Chlorophyll, the green pigment found in chloroplasts within plant cells, plays a vital role by absorbing light energy from the sun. Without chlorophyll to capture this energy, photosynthesis cannot take place, even if other necessary components like guard cells, vacuoles, or intercellular spaces are present.

Let's analyze each statement:

• Statement (i) is correct: All green plants contain chlorophyll and are capable of preparing their own food through photosynthesis.
• Statement (ii) is incorrect: Most animals are heterotrophs, meaning they cannot produce their own food and must consume other organisms.
• Statement (iii) is incorrect: Carbon dioxide is a crucial raw material required for photosynthesis.
• Statement (iv) is correct: Oxygen is released as a byproduct during the process of photosynthesis.

Therefore, statements (i) and (iv) are correct.

The pitcher plant is a unique carnivorous plant. While it performs photosynthesis to produce carbohydrates, it grows in soils that are deficient in essential nutrients, particularly nitrogen. To supplement its nitrogen requirements, the pitcher plant has evolved a specialized structure, the pitcher, which traps and digests insects. The nutrients absorbed from the digested insects help the plant meet its nitrogen needs for growth and development.

Yeast, mushrooms, and bread-mould are all examples of fungi. These organisms obtain their nutrition from dead and decaying organic matter. This mode of nutrition, where an organism feeds on non-living organic material, is called saprophytic nutrition. They secrete digestive juices onto the dead or decaying matter, breaking it down into simpler substances, which they then absorb.