Human beings are complex animals; which have a complex digestive system. The human digestive system is composed of an alimentary canal and some accessory glands. The alimentary canal is divided into several parts, viz. oesophagus, stomach, small intestine, large intestine, rectum and anus. Salivary gland, liver and pancreas are the accessory glands which lie outside the alimentary canal.
Nutrition in Amoeba
Amoeba is a unicellular animal which follows holozoic mode of nutrition. The cell membrane of amoeba keeps on protruding into pseudopodia. Amoeba surrounds a food particle with pseudopodia and makes a food vacuole. The food vacuole contains the food particle and water. Digestive enzymes are secreted in the food vacuole and digestion takes place. After that, digested food is absorbed from the food vacuole. Finally, the food vacuole moves near the cell membrane and undigested food is expelled out.
Steps of Holozoic Nutrition Steps of Holozoic Nutrition
Ingestion: The process of taking in the food is called ingestion.
Digestion: The process of breaking complex food substances into simple molecules is called digestion. Simple molecules; thus obtained; can be absorbed by the body.
Absorption: The process of absorption of digested food is called absorption.
Assimilation: The process of utilization of digested food; for energy and for growth and repair is called assimilation.
Egestion: The process of removing undigested food from the body is called egestion.
Animal Nutrition
1. Heterotrophic Nutrition: When an organism takes food from another organism, it is called heterotrophic nutrition. Different heterotrophic organisms follow different methods to take and utilize food. Based on this, heterotrophic nutrition can be divided into two types:
2. Saprophytic Nutrition: In saprophytic nutrition, the digestion of food takes place before ingestion of food. This type of nutrition is usually seen in fungi and some other microorganisms. The organism secretes digestive enzymes on the food and then ingests the simple substances. Saprophytes feed on dead materials and thus help in decomposition dead remains of plants and animals.
3. Holozoic Nutrition: In holozoic nutrition, the digestion of food follows after the ingestion of food. Thus, digestion takes place inside the body of the organism. Holozoic nutrition happens in five steps, viz. ingestion, digestion, absorption, assimilation and egestion.
Significance of Photosynthesis
● Photosynthesis is the main way through which the solar energy is made available for different living beings.
● Green plants are the main producers of food in the ecosystem. ● All other organisms directly or indirectly depend on green plants for food.
● The process of photosynthesis also helps in maintaining the balance of carbon dioxide and oxygen in the air.
Steps of Photosynthesis
1. Sunlight activates chlorophyll; which leads to splitting of water molecule.
2. The hydrogen; released by splitting of water molecule is utilized for reduction of carbon dioxide to produce carbohydrates.
3. Oxygen is the byproduct of photosynthesis.
4. Carbohydrate is subsequently converted into starch and is stored in leaves and other storage parts.
5. The splitting of water molecules is part of the light reaction.
6. Other steps are part of the dark reaction during photosynthesis.
How do raw materials for photosynthesis become available to the plant?
Water comes from soil; through the xylem tissue in roots and stems.
Carbon dioxide comes in the leaves through stomata.
Plant Nutrition
Green plants prepare their own food. They make food in the presence of sunlight. Sunlight provides energy. carbon dioxide and water are the raw materials. Chloroplast is the site where food is made.
Photosynthesis: The process by which green plants prepare food is called photosynthesis. During this process; the solar energy is converted into chemical energy and carbohydrates are formed. Green leaves are the main sites of photosynthesis. The green portion of the plant contains a pigment chloroplast; which contains chlorophyll. The whole process of photosynthesis can be shown by following equation:
6CO2 + 6H2O ⇨ C6H12O6 + 6O2
Types of Nutrition
1. Autotrophic Nutrition: The mode of nutrition in which an organism prepares its own food is called autotrophic nutrition. Green plants and blue-green algae follow the autotrophic mode of nutrition.
2. Heterotrophic Nutrition: The mode of nutrition in which an organism takes food from another organism is called heterotrophic nutrition. Organisms; other than green plants and blue-green algae follow heterotrophic mode of nutrition. Heterotrophic nutrition can be further divided into two types, viz. saprophytic nutrition and holozoic nutrition.
Saprophytic Nutrition: In saprophytic nutrition; the organism secretes the digestive juices on the food. The food is digested while it is still to be ingested. The digested food is then ingested by the organism. All the decomposers follow saprophytic nutrition. Some insects; like houseflies; also follow this mode of nutrition.
Holozoic Nutrition: In holozoic nutrition; the digestion happens inside the body of the organism, i.e. after the food is ingested. Most of the animals follow this mode of nutrition.
Nutrition
The process by which an organism takes food and utilizes it is called nutrition.
Need of nutrition: Organisms need energy to perform various activities. The energy is supplied by the nutrients. Organisms need various raw materials for growth and repair. These raw materials are provided by nutrients.
Nutrients: Materials which provide nutrition to organisms are called nutrients. Carbohydrates, proteins and fats are the main nutrients and are called macronutrients. Minerals and vitamins are required in small amounts and hence are called micronutrients.
Life Process
Various functions carried out by living beings; which are necessary to maintain and continue life are called life process. Following are the life processes in living beings:
1. Nutrition
2. Respiration
3. Transportation of substances
4. Excretion
5. Movement
6. Reproduction
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