Class 7 - Chapter 1: Nutrients CBSE /ICSE Notes

Nutrients

➥ Nutrients: Groups of food that include proteins, fats, vitamins, and minerals.

➥ Nutrition: The process of taking in and using nutrients like carbohydrates, fats, proteins, minerals, vitamins, and water by an organism.

Modes of Nutrition

⟹There are mainly two types of nutrition:-

1. Autotrophic Nutrition

   • ➥ The word "auto" means self and "trophic" means nutrition. Thus, autotrophic means self-nutrition.

   ➥ Organisms prepare their own food. They are known as autotrophs.

   • eg:- Green plants.
   • Photosynthesis:

     ➥ Photosynthesis is how green plants make their own food using sunlight. They use a green substance called chlorophyll to turn carbon dioxide and water into glucose (sugar) and oxygen.

     
   • ⟹ Process of Autotrophic Nutrition:

     ➥ Absorption of light energy by chlorophyll.

     ➥ Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

     ➥ Reduction of carbon dioxide to carbohydrates.

     

Stomata

➥ Stomata are small openings on the leaf surface that allow gas exchange (CO2 and O2) with the atmosphere.

➥ They enable the evaporation of water from the leaf surface, which helps in transpiration.

➥ Stomata also allow the intake of carbon dioxide and the release of oxygen during photosynthesis.



2. Heterotrophic Nutrition

   ➥ Organisms depend on other organisms for food.

   ➥ eg:- animals, fungi, and some bacteria.

   • ⟹ Types of Heterotrophic Nutrition:
     • 1. Saprotrophic Nutrition:
       • ➥ The word "sapro" means rotten.
       • ➥ Obtaining food from dead and decaying matter.
       • eg:- Mushroom, yeast, bacteria.....etc.
     • 2. Parasitic Nutrition:
       • ➥ Obtaining food from a host organism without killing it.
       • eg:- Cuscuta (Amarbel), tapeworms, lice.
     • 3. Holozoic Nutrition:
       • ➥ Taking in solid food and digesting it.
       • eg:- Humans and most animals.
       • Types of Holozoic Nutrition:
         1. (i)Herbivores: Animals that eat only plants. eg:- Cow, deer.
         2. (ii) Carnivores: Animals that eat other animals. eg:- Lion, tiger.
         3. (iii) Omnivores: Animals that eat both plants and animals. eg:- Humans, bears.

     Note:-Detritivores: Animals that feed on dead organic matter. Example: Earthworm.

     • Symbiosis:
       • ➥ Symbiosis is a close and often long-term interaction between two different biological species.
       • eg:- Lichen (an association between algae and fungi).