NCERT Class 7 Science Chapter 1 Notes

NCERT Class 7 Science - Chapter 1: Nutrition in Plants

Introduction

All living organisms require food for their survival. Plants are capable of making their own food, while animals depend on plants and other organisms for nutrition. This chapter explores the different modes of nutrition in plants and how they obtain essential nutrients.

Modes of Nutrition in Plants

1. Autotrophic Nutrition

   • Plants prepare their own food through photosynthesis using sunlight, carbon dioxide, and water.
   • Green plants that make their food are called autotrophs.

2. Heterotrophic Nutrition

   • Some plants depend on other organisms for food.
   • Such plants are called heterotrophs.

Photosynthesis: The Process of Food Making in Plants

Photosynthesis is the process by which green plants make their own food using sunlight, water, and carbon dioxide.

Raw Materials Required for Photosynthesis:

• Sunlight: Provides energy for the process.
• Chlorophyll: A green pigment in leaves that absorbs sunlight.
• Water: Absorbed from the soil by roots.
• Carbon dioxide: Taken from the air through stomata (tiny openings in leaves).

Equation of Photosynthesis:

6CO_2 + 6H_2O \xrightarrow{Sunlight, Chlorophyll} C_6H_{12}O_6 + 6O_2

Importance of Photosynthesis:

• It provides food for plants and other living organisms.
• It releases oxygen into the atmosphere, which is essential for respiration.

Types of Heterotrophic Plants

1. Parasitic Plants:

   • These plants obtain nutrients from other living plants (hosts).
   • Example: Cuscuta (Amarbel), which grows on other plants and absorbs nutrients from them.

2. Insectivorous Plants:

   • These plants trap and digest insects to obtain nutrients.
   • Example: Pitcher plant, Venus flytrap.

3. Saprophytic Plants:

   • These plants obtain nutrients from dead and decaying matter.
   • Example: Mushrooms, Fungi.

4. Symbiotic Plants:

   • Some plants live in a mutual relationship with other organisms for survival.
   • Example: Lichens, where fungi and algae live together in symbiosis.

Nutrient Replenishment in Soil

• Continuous cultivation depletes nutrients in the soil.
• Farmers use fertilizers and manure to replenish nutrients.
• Nitrogen fixation is done by bacteria like Rhizobium present in root nodules of leguminous plants.

Conclusion

Plants have different modes of nutrition to obtain food and essential nutrients. Photosynthesis is the fundamental process through which autotrophic plants produce food, while heterotrophic plants rely on other sources. Understanding plant nutrition is essential for maintaining soil fertility and agricultural productivity.