These DAV Class 7 Science Notes and DAV Class 7 Science Chapter 1 Notes – Nutrition in Living Organisms: Plants act as excellent revision resources, particularly in preparation for board exams.
Nutrition in Living Organisms: Plants Class 7 DAV Notes
→ Nutrition: The process of obtaining and utilizing food is called nutrition.
→ Essential Nutrients: Carbohydrates, proteins, fats, vitamins and minerals.
→ Autotrophic Nutrition: The mode of nutrition in which a living being makes its own food is called autotrophic nutrition. All green plants and some bacteria are autotrophs.
→ Heterotrophic Nutrition: The mode of nutrition in which a living being depends on others for food is called heterotrophic nutrition. All animals and non-green plants are heterotrophs.
→ Saprotrophic Nutrition: The mode of nutrition in which a living being feeds on dead remains of plants and animals is called saprotrophic nutrition. In this case, the digestion of food takes place before ingestion. Examples: mushroom, bread mould and some bacteria.
→ Parasitic Nutrition: The mode of nutrition in which a living being feeds on a living being; either by living on or inside the body of the host; is called parasitic nutrition. Examples: Dodder, Cuscuta, etc.
→ Holozoic Nutrition: The mode of nutrition in which an animal ingests its food and digestion happens inside the body of the organism is called holozoic nutrition. Examples: Amoeba, man, etc.
→ Photosynthesis: This is the process by which green plants prepare their own food. The process of photosynthesis can be written as following equation:
→ Raw Materials for Photosynthesis:
→ Water and minerals are absorbed by roots from soil. The transportation of materials in plants happens through very fine vessels which run from roots to different plant parts.
→ Carbon dioxide is taken by leaves from air through tiny pores; called stomata; present on leaves’ surface. Stoma is surrounded by guard cells.
→ Sunlight: Sunlight provides solar energy. The solar energy is used by plants to prepare food and due to this, the process is called photosynthesis.
→ Chlorophyll: Chlorophyll is a green coloured pigment which is present in green parts of the plant. Chlorophyll captures solar energy.
→ Products of Photosynthesis: Carbohydrate (glucose) is the main product of photosynthesis. It is converted into starch in leaves and is then stored in different parts of a plant. Carbohydrate is a compound of carbon, oxygen and hydrogen. Some carbohydrates are also converted to proteins which also contains nitrogen.
→ Nitrogen is important for the formation of protein. Although nitrogen is present in the highest percentage in the atmosphere but plants cannot use gaseous form of nitrogen. Some bacteria which are present in the soil change the gaseous nitrogen into a form which can be used by plants. This process is called nitrogen fixation. Additionally, farmers add fertilisers to provide nitrogen to the plants.
→ Parasitic Plants: Some plants do not contain chlorophyll. These plants live on another plant to obtain food. Cuscuta is an example of parasitic plant.
→ Insectivorous Plants: Some plants which grow in marshy swamps do not get nitrogen because the soil is nitrogen deficient in such areas. Such plants trap insects and suck their juices to fulfill their need for nitrogen. Pitcher plant and Venus Fly Trap are examples of insectivorous plants.
→ Saprophytic Plants: Fungi are often referred to as saprophytic plants. They grow on dead and decaying matter. These organisms secrete digestive juices on dead and decaying matters and take food only after digestion. Such type of digestion is called extracellular digestion. Examples: Mushroom, rhizopus (bread mould), Mucor (pin mould), yeast, etc.
→ Symbiotic Relationship: Lichens present a very good example of symbiotic relationship. Lichen is a combination of two types of organisms, i.e. algae and fungi. The fungal part absorbs water and mineral from the substratum, while the algal part carries out photosynthesis to prepare food.
→ Symbiosis for nitrogen fixation: Rhizobium bacteria live in roots of leguminous plants (pulses). Pulses provide shelter to Rhizobium. In lieu of that, Rhizobium helps in nitrogen fixation in soil.
→ Nutrient Replenishment in Soil: When farming is done for many seasons, soil loses nutrients. These nutrients need to be replenished or restored. This is done in the following ways:
- Farmers add manure to soil.
- Farmers add fertilizers to soil.
→ Dead remains of plants and animals decompose. Decomposition results in formation of humus in soil. Humus is beneficial for soil.
→ Nitrogen fixation helps in replenishment of nutrients in soil.
→ Nutrition: The process of obtaining and utilizing food is called nutrition.
→ Heterotrophic Nutrition: The mode of nutrition in which a living depends on other organisms for food.
→ Autotrophic Nutrition: The mode of nutrition in which a living being makes its own food.
→ Saprophytic Nutrition: The mode of nutrition in which a living being feeds on dead and decaying matters; by extracellular digestion.
→ Parasitic Nutrition: The mode of nutrition in which a living being feeds on live organism; by living either on or inside the body of its host.
→ Holozoic Nutrition: The mode of nutrition in which a living being ingests the food and digestion is intracellular.
→ Insectivorous Plants: Plants which trap and ‘eat’ insects.
→ Chlorophyll: A green coloured pigment; present in green parts of plants.
→ Lichen: A symbiotic association of algae and fungi.
→ Symbiosis: Relation between two organisms in which both benefit each other.
→ Nitrogen Fixation: Process of changing nitrogen gas to a suitable form in soil so that plants can uptake nitrogen.
→ Stomata: Tiny pores on surface of leaves.
→ Vessels: Channels to transport water and minerals in plants.