Notes on Nutrition in Animals

Introduction

• Overview of Chapter 1 of NCERT Class 7: Nutrition in Animals
• Recap of nutrients from Class 6:
  • Carbohydrates, fats, proteins, vitamins - essential for normal body functioning

Modes of Nutrition

1. Autotrophs

   • Produce their own food (e.g., plants)
   • Classified into:
     • Photoautotrophs: Perform photosynthesis (use sunlight)
     • Chemoautotrophs: Perform chemosynthesis (chemical reactions, found in deep waters)

2. Heterotrophs

   • Cannot produce their own food; rely on others (e.g., humans)
   • Depend on autotrophs for survival

Photosynthesis in Plants

• Process:
  • Plants manufacture food through photosynthesis
  • Requires: Water, minerals (from roots), carbon dioxide (from air), and sunlight
• Key Components:
  • Chlorophyll: Green pigment in leaves essential for photosynthesis
  • Stomata: Openings in leaves for gas exchange, surrounded by guard cells

Photosynthesis Equation

• Water + Carbon Dioxide + Sunlight + Chlorophyll = Food (Starch) + Oxygen

Testing for Starch

• Iodine Test:
  • Leaf in iodine solution turns blue-black, indicating starch presence
• Potassium Hydroxide Test:
  • Absorbs CO2; leaf does not turn blue-black, indicating CO2 is essential for photosynthesis

Transportation in Plants

• Xylem: Transports water and minerals from roots to leaves
• Phloem: Transports prepared food from leaves to other parts of the plant

Modifications in Plants

• In desert areas, leaves may be modified into spines (e.g., cactus) to reduce water loss

Types of Plants

1. Autotrophic Plants: Produce their own food
2. Heterotrophic Plants: Cannot produce their own food
   • Parasitic Plants: E.g., Cuscuta, takes nutrients from host plants
   • Insectivorous Plants: E.g., Pitcher plant, traps insects for nutrients
   • Saprophytic Plants: E.g., Mushrooms, feed on decaying material

Symbiotic Relationships

• Mutualism: Both organisms benefit (e.g., Rhizobium and plants)
• Commensalism: One benefits, the other is unaffected (e.g., orchids on trees)
• Parasitism: One benefits at the expense of the other (e.g., malaria parasite in humans)

Soil Fertility

• Manure: Dead and decaying material, affects the top layer of soil (humus)
• Fertilizers: Can be organic or inorganic; enhance soil fertility and productivity
  • NPK: Nitrogen, Phosphorus, Potassium are essential nutrients

Importance of Soil Replenishment

• Soil Erosion: Loss of top fertile layer due to runoff
• Need for replenishment of soil using manure and fertilizers

Conclusion

• Understanding nutrition is fundamental for further studies in biology
• Next chapter will focus on nutrition in animals

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Key Terms

• Autotrophs
• Heterotrophs
• Photosynthesis
• Stomata
• Xylem & Phloem
• Symbiotic Relationships
• Manure & Fertilizers
• Soil Erosion

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