Quick Revision Notes: Class 7 Science

Chapter: Nutrition in Plants

---

### Introduction to Nutrition

• Nutrition: The mode of taking food by an organism and its utilization by the body.
• Nutrients: Components of food that are necessary for our body (such as carbohydrates, proteins, fats, vitamins, and minerals).

---

### Modes of Nutrition in Plants

Plants are classified based on how they get their food into two main categories:

1. Autotrophic Nutrition (स्वपोषी पोषण):

   • Definition: The mode of nutrition in which organisms make food themselves from simple substances.
   • Example: Green plants (Autotrophs / स्वपोषी).

2. Heterotrophic Nutrition (विषमपोषी पोषण):

   • Definition: The mode of nutrition in which organisms take in ready-made food prepared by plants.
   • Example: Animals and non-green plants like fungi (Heterotrophs / विषमपोषी).

---

### Photosynthesis: Food Making Process in Plants

• Photosynthesis (प्रकाश संश्लेषण): The process by which green plants prepare their own food using carbon dioxide and water in the presence of sunlight and chlorophyll.

Key Equation for Photosynthesis:

Carbon dioxide + Water --(Sunlight & Chlorophyll)--> Carbohydrate + Oxygen

Raw Materials Required:

1. Water and Minerals: Absorbed from the soil by the roots and transported to leaves.
2. Carbon Dioxide ($CO_2$): Taken from the air through tiny pores called Stomata (रंध्र) present on the surface of leaves.
3. Sunlight: Trapped by the green pigment called Chlorophyll (क्लोरोफिल).
4. Oxygen: Released as a byproduct during the process.

---

### Other Modes of Nutrition in Plants

Some plants do not have chlorophyll and cannot synthesize their own food. They use alternative modes:

1. Parasitic Mode (परजीवी):

   • Parasite (परजीवी): An organism that lives on or inside another living organism (host) and derives its food from it.
   • Example: Cuscuta (Amarbel / अमरबेल).

2. Insectivorous Plants (कीटभक्षी पौधे):

   • Green plants that trap and digest insects to fulfill their nitrogen requirements.
   • Example: Pitcher plant (घटपर्णी), Venus flytrap.

3. Saprotrophic Nutrition (मृतजीवी पोषण):

   • Saprotrophs (मृतजीवी): Organisms that take in nutrients from dead and decaying matter.
   • Example: Fungi (Mushroom, bread mold / कवक या फफूंद).

4. Symbiotic Relationship (सहजीवी संबंध):

   • A relationship in which two organisms live together and share both shelter and nutrients.
   • Example: Lichens (लाइकन) – An alga and a fungus live together. The fungus provides shelter, water, and minerals, while the alga prepares and provides food.

---

### Replenishment of Nutrients in the Soil

• Plants absorb minerals and nutrients from the soil, causing their amount in the soil to decline.
• Fertilizers and Manures: Contain plant nutrients like nitrogen, potassium, and phosphorus. Adding them replenishes the soil.
• Rhizobium bacteria: Live in the roots of leguminous plants (like gram, peas, beans) and convert atmospheric nitrogen into a soluble form that plants can use.