CBSE Class 7 Science Notes Chapter 1 Nutrition in Plants

Learn from School Connect Online in this chapter we will learn about All living organisms require food. The food gives energy to the organisms for growth and maintenance of their body functions. Carbohydrates, proteins, fats, vitamins and minerals are the components of food. These components of food are necessary for our body and are called nutrients.Nutrition in Plants Class 7 Notes Science Chapter 1

Here we have given Nutrition in Plants Class 7 Notes Science Chapter 1

The different topics covered in CBSE Class 7 Science Chapter 1 are tabulated below:

Ex. 1.1 – Mode of Nutrition in Plants

Nutrition is the mode of taking food by an organism and its utilisation by the body.

• Nutrition is very important as the nutrients from the food consumed enables living organisms to build their bodies and grow.
• Nutrition helps to repair damaged parts and organs.
• Nutrition also provides energy for carrying out various functions.

Modes of Nutrition

On the basis of a different mode of nutrition, organisms are categorised into two major types, i.e.

(i) Autotrophs (auto-self, troppos-nourishment) Autotrophic nutrition is the mode of nutrition in which organisms make their own food from the simple substance (e.g. CO2 and H2O) by the process of photosynthesis. Therefore, plants are called autotrophs.

(ii) Heterotrophs (heteros-other) Humans and animals do not contain chlorophyll and are dependent on plants for their food in readymade form. Those organisms which cannot prepare their own food and take food from green plants or animals are called heterotrophs and the mode of nutrition is called heterotrophic nutrition.

Living and Nonliving Organisms

• Living organisms like human beings, plants and animals need food to survive and exist.
• Living organisms reproduce, respond to the environment and also adapt.
• Living organisms respire and excrete as well.

Cells

Cells are tiny units that help make up a living organism. Hence, they are also called building blocks of an organism.

• A cell is constituted of three major parts :
• A thin outer layer called the cell membrane.
• A spherical structure located at the centre of the cell called a nucleus.
• A jelly-like substance that surrounds a nucleus called the cytoplasm.

Single and Multicellular Organisms

• Organisms that are made up of just one cell are called single-celled or Unicellular organisms. E.g.  Amoeba
• Organisms with more than one cell in their body are called multicellular organisms.
• All human beings, plants and animals are multicellular organisms

Ex. 1.2 – Photosynthesis: Food Making Process in Plants

The process by which autotrophic green plants make their own food from simple inorganic substances (carbon dioxide and water) in the presence of sunlight and green pigment or chlorophyll is known as photosynthesis.

Site of Photosynthesis

The process of photosynthesis takes place in green leaves, therefore leaves are referred to as the food factories of plants. The photosynthetic process can occur in other green parts of the plant-like stem but is not enough for meeting all the needs of the plant.

Ex. 1.3 – Other Modes of Nutrition in Plants

There are some plants which do not contain chlorophyll in them and thus, cannot prepare their own food. These plants obtain their food from other plants or animals, i.e. they are heterotrophic in nature.

Symbiotic Relationship

Organisms that live together and share their shelter and nutrients are said to be in a symbiotic relationship.

• Certain fungi live in the roots of trees.
• The tree provides nutrients to the fungus and, in return, receives help from it to take up water and nutrients from the soil.
• This association works well for both the fungi and the tree.
• Another most common example is of Rhizobium bacteria.
• They reside in the root nodules of leguminous plants.
• The bacteria provide a plant with nitrogen that they fix and in turn, they get shelter and food from the plant.

Rhizobium

• Rhizobium is a type of bacteria that convert atmospheric nitrogen into a soluble form that can be utilised by plants (nitrogen fixation).
• It usually resides in the roots of leguminous plants like peas, gram, moong etc and is instrumental in providing these plants with a rich source of nitrogen.

Nitrogen Fixation

• Nitrogen is an important nutrient required for soil and for plants.
• However, nitrogen in the atmosphere is not easily accessible.

The process by which nitrogen is converted into a form that can be used by plants and other living organisms is called nitrogen fixation.

Parasites

A  parasite is a heterotroph that completely depends on another organism for its food.

• The organism to which the parasite latches onto is called the host.
• The host, in the process, is deprived of all nutrients for its own growth as they are consumed by the parasite.
• For example, Cuscuta (Amarbel) is a non green plant that takes readymade food from the plant on which it is growing.

Ex. 1.4 – Saprotrophs

Organisms which rely on dead and decaying matter for their food are called Saprotrophs.

• This mode of nutrition is called saprotrophic nutrition.
• For example, Fungi.
• Fungi secrete digestive juices on the dead and decaying matter and convert it into a solution.
• Then they absorb the nutrients from it.

Insectivorous Plants :

Plants that feed on insects are called Insectivorous plants.

• These plants are green and carry out photosynthesis.
• But, they grow in nitrogen-deficient soils.
• So, in order to get nitrogen, they feed on insects.
• These insectivorous plants have their parts modified for attracting and catching insects.
• For example, The pitcher plant, Venous flytrap

Ex. 1.5 – How Nutrients are Replenished in the Soil?

• Plants absorb mineral nutrients from the soil in order to make their own food and for other important processes.
• Soils need to be enriched with nutrients such as nitrogen, phosphorus, potassium etc regularly.
• Only then can we grow plants and keep them healthy.
• There are 17 most important nutrients for plants.
• 6 are called macronutrients and rest are called micronutrients.
• Macronutrients are required in large quantities while micronutrients are required in very small quantities.

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