Nutrients: Components of food like carbohydrates, proteins, fats, vitamins, and minerals necessary for the body.
Nutrition: The mode of taking food by an organism and its utilisation by the body.
Autotrophs vs Heterotrophs
Autotrophic Nutrition: Mode where organisms make food themselves from simple substances (e.g., plants). Organisms are called autotrophs.
Heterotrophs: Organisms (animals and humans) that depend on food prepared by plants.
1.2 Photosynthesis — Food Making Process in Plants
The Mechanism of Photosynthesis
Leaves: The food factories of plants where food synthesis occurs.
Stomata: Tiny pores on the leaf surface surrounded by guard cells used for gas exchange ($CO_2$ intake).
Chlorophyll: Green pigment in leaves that captures solar energy.
Photosynthesis Equation: Carbon dioxide + Water in the presence of Sunlight and Chlorophyll yields Carbohydrate + Oxygen.
Starch: A carbohydrate whose presence in leaves indicates that photosynthesis has occurred.
Cell Structure
Cells: Tiny units that make up the bodies of living organisms.
Cell Membrane: Thin outer boundary enclosing the cell.
Nucleus: Centrally located, spherical structure in a cell.
Cytoplasm: Jelly-like substance surrounding the nucleus.
Synthesis of Other Nutrients
Carbohydrates contain Carbon, Hydrogen, and Oxygen, used to synthesise proteins and fats.
Proteins require nitrogen. Plants obtain nitrogen from the soil where Rhizobium bacteria convert gaseous nitrogen into a usable soluble form.
1.3 Other Modes of Nutrition in Plants
Parasitic Plants
Cuscuta (Amarbel): A non-green plant that climbs on a host plant to derive readymade food, acting as a parasite.
Insectivorous Plants
Insectivorous Plants: Insect-eating plants (e.g., Pitcher plant) that trap and digest insects using specialized leaf structures to fulfill nutrient requirements.
1.4 Saprotrophs and Symbiosis
Saprotrophic Nutrition
Saprotrophic Nutrition: Mode of nutrition where organisms take in nutrients from dead and decaying matter.
Saprotrophs: Organisms like fungi that use saprotrophic nutrition.
Symbiosis
Symbiosis: A relationship where two organisms live together and share shelter and nutrients.
Lichens: A symbiotic partnership between a chlorophyll-containing alga and a fungus.
1.5 How Nutrients are Replenished in the Soil
Soil Enrichment
Nutrients like nitrogen, potassium, and phosphorus are replenished using manures and fertilizers.
Rhizobium bacteria live in the root nodules of leguminous plants (peas, gram, moong) to fix atmospheric nitrogen, sharing a symbiotic relationship.
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