NCERT Notes for Class 10 Science Chapter 6 Life Processes
CBSE Class 10 Science notes will assist students in studying the topic thoroughly and clearly.
These CBSE Class 10 Science notes were written by subject experts who made the study material very basic, both in terms of language and format.
Nutrition is the process through which organisms receive nutrients from food and use them for energy production, tissue construction, and repair.
Nutrients are described as substances needed for the normal development and proper functioning of a living body, i.e. they are compounds that offer energy to an organism.
The Modes of Nutrition
This refers to an organism’s mechanism of food acquisition. Food is not obtained in the same way by all living species.
For instance, plants and certain microorganisms contain chlorophyll (also known as the green pigment) which aids in the process of photosynthesis.
Similarly, mammals, fungus, and other microorganisms eat other species and plants. There are two major forms of feeding based on this, namely heterotrophic and autotrophic.
What is Autotrophic Nutrition
Certain organisms feed on basic inorganic elements such as water and carbon dioxide. Autotrophs are these organisms.
For instance, some microbes and green plants. This style of nourishment is called autotrophic nutrition.
Plant Nutrition: Photosynthesis
It’s a sophisticated process by which green plant components synthesise organic nourishment.
This meal is made by converting water and carbon dioxide into green plants in the presence of sunshine and chlorophyll. This response entails the following:
The equation makes it abundantly evident that the input ingredients for photosynthesis are water and carbon dioxide, and that the end products are oxygen and glucose (carbohydrate).
Carbohydrates are required by the plants to generate energy.
Carbohydrates that are not consumed promptly are preserved as starch.
It works as the plant’s internal energy store and is drawn upon as needed. In animals, glycogen acts as an internal energy store that is drawn upon as necessary.
Events in Photosynthesis
The following major events occur during photosynthesis:
- Light energy is absorbed by chlorophyll.
- Light energy is converted to chemical energy, and water molecules are divided into hydrogen and oxygen.
- Carbon dioxide is reduced to carbohydrates.
The preceding processes may or may not occur sequentially, for example, desert plants take in Co2 at night and produce an intermediate molecule.
This intermediate chemical is used up by the energy received from the chlorophyll throughout the day.
Site of Photosynthesis: Chloroplasts
Leaves are a plant’s primary photosynthetic organ. They possess a huge surface area in the shape of leaves, vascular tissue for food and water delivery, and gas exchange mechanism.
Chloroplasts are green-colored organelles found in leaves.Because chloroplasts contain chlorophyll pigments, they are the size of photosynthesis.
The Cross-Section of Leaf
A leaf comprises the following major components:
(i). Epidermis – It’s the leaf’s outermost one-cell thick layer and is divided into two different layers. The upper epidermis lacks chloroplasts. It protects the interior leaf by limiting excessive evaporation of water. The lower epidermis includes stomata, which aid in gas exchange inside the plant.
(ii). Stomata – These are microscopic pores found mostly in the lower epidermis. They facilitate gas exchange between the plant and the atmosphere by allowing gases to enter and leave the leaf more swiftly.
(iii). Guard Cells – These cells, shaped like beans, surround the stomatal openings. They are chloroplast-containing and have a cell wall.
What Are The Conditions Necessary for Photosynthesis
Numerous investigations have highlighted that photosynthesis requires the presence of chlorophyll and sunlight. They are described in further detail below:
(i) Solar energy Photosynthesis is influenced by the quality, intensity, and duration of sunshine.
(ii) Chlorophyll – A pigment with a green hue that is there in the chloroplast of a plant. It is in charge of absorbing solar energy.
Raw Materials Required for Photosynthesis
The following basic ingredients are required for photosynthesis to work in plants:
(i) Carbon dioxide – This gas is emitted in the atmosphere by organisms during cellular respiration and enters the leaf through stomata. Later are microscopic holes found on the surface of leaves that allow for huge amounts of gaseous exchanges. Additionally, the surface of stems, leaves, and roots participates in gaseous exchange.
(ii) Water by the roots is taken from the soil and carried upward via the xylem to the leaves and then to the photosynthetic cell through the xylem. In the presence of sunshine, these water molecules split to generate hydrogen and oxygen. This process is known as photolysis of water. Hydrogen ions are utilised to decrease CO2, and O2 is produced as a byproduct.
(iii) Additional materials – Nitrogen, phosphorus, iron, and magnesium are also absorbed from the soil. Nitrogen is a critical component of proteins and other organic molecules. It is taken up in the form of organic compounds or as inorganic nitrates (or nitrites) generated from ambient nitrogen by symbiatic bacteria such as Rhizobium.
Organisms are unable to prepare food on their own under the heterotrophic method of feeding. Heterotrophs acquire energy from organic molecules that autotrophs have previously created.
These organisms do this via the usage of biocatalysts known as enzymes. The modes in heterotrophic nutrition vary across species, depending on the kind, availability, and manner by which an organism gets the food resources.
Heterotrophs include carnivores, herbivores, omnivores, saprotrophs and parasites. Heterotrophs may be classified into three distinct nutritional modes:
(i) Holozoic Nutrition – Carnivores (meat eaters), Herbivores (plant eaters), and omnivores (plant and meat eaters) all consume in a holozoic manner. In this form of feeding, complex food molecules are ingested and subsequently broken down into smaller, more soluble ones. For instance, an amoeba, a cow, a goat, a dog, a cat, or a human person.
(ii) Saprotrophic Nutrition (saprophytic nutrition) – Saprotrophs are organisms that feed on decomposing organic matter, breaking down and absorbing complex components from the environment, such as fungi such as mushrooms, yeast, bread moulds, and bacteria.
(iii) Parasitic Nutrition – Parasites are organisms that feed on other species. These creatures feed on or within the body of another organism (host) for gaining sustenance without harming it, for example, lice, tapeworm, ticks, leech, plasmodium, flatworm, and plants such as Cuscuta (amarel), yellow rattle, and others.
Nutrition in Amoeba
It is a single-celled omnivore. Amoeba has a holozoic method of feeding. It is accomplished by the use of pseudopodia (finger-like extensions). When food comes into touch with its cell surface through ingestion, it engulfs it.
Pseudopodia forms a vacuole around the food particle. Within the food vacuole, complex food is broken down into tiny soluble molecules that are easily absorbed by the cytoplasm, a process known as absorption.
The undigested food material is eliminated by the cell membrane, which spontaneously ruptures at any location and removes the undigested food, a process known as egestion.
Nutrition in Human Beings
The process of ingesting necessary nutrients in the form of food occurs in humans through an extensive system which is known as the digestive system.
Digestion is a catabolic process in which complicated and massive food components are broken down into their smaller and simpler components using a variety of hydrolytic enzymes.
These simpler versions are then absorbed by various sections of the body.
The digestive system in humans is made up of a lengthy tube structure called the alimentary canal and a variety of digestive glands. These glands produce a variety of digesting enzymes.
It is a lengthy 7-8 metre tube that contains the complete digestive process. The alimentary canal performs the whole process of ingestion, absorption, digestion, assimilation, and egestion of food material.
The alimentary canal’s principal segments are mentioned below:
Mouth – It’s the initial section of the digestive system since it is where food enters the alimentary canal. The mouth is mostly composed of two key components:
- Tongue – The tongue is a muscular and also sensory organ located in the buccal cavity’s floor. It has a variety of caste buds and aids in salivating and in the mixing of food. Along with this, it aids in speech production.
- Teeth – Teeth are hard structures found on both the upper and lower jaw bones. Teeth are mostly used for cutting, grinding, and chewing food.
(ii) Pharynx – A small chamber in a funnel form positioned behind the mouth cavity. It is in communication with both the trachea (windpipe) and the oesophagus.
(iii) Oesophagus – It’s a long, slender muscular tube that connects to the stomach.
(iv) Stomach – It is a portion of the alimentary canal that is the most dilated. It is located under the diaphragm, between the small intestine and the oesophagus. It acts as a food storage area, where food is partially digested by the release of gastric glands. The stomach’s muscular walls aid in appropriately mixing the food.
(v) Small Intestine – It’s the alimentary canal’s longest segment. It is crammed into a little area near our belly because of its substantially coiled form.
The small intestine’s length varies amongst species based on their feeding choices; for example, herbivores have a lengthy small intestine to aid in the digestion of cellulose. Carnivores have a shorter small intestine due to the ease with which meat is digested.
The small intestine is where food is completely digested into its component parts. The liver and pancreatic secretions reach the gut to aid in digestion.
The small intestine’s inner lining is covered with many finger-like extensions called villi, which enhance the surface area available for absorption.
(vi) Large Intestine – Although it is shorter, it is referred to as the big intestine due to its diameter being more than the small intestine.
(vii) Rectum – Rectum is the narrow and wide chamber-like structure that helps to temporarily store faecal waste.
(viii) Anus – Anus is the terminus of the alimentary canal, which aids in the departure of waste material. The regulation of the process takes place in the anal sphincter.
Numerous glands are connected with the alimentary canal and are involved in the process of food digestion. These are as follows:
(i) Salivary glands – These three kinds of glands produce saliva with an enzyme called salivary amylase (ptyalin).
At an optimal pH of around 7, it transforms starch to sugar. The mouth starts watering as a result of these salivary glands when we smell or eat something we like.
(ii) Gastric Glands – These are present in the stomach’s wall.
Gastric glands produce digestive fluid comprising hydrochloric acid, pepsin, and mucus. Hydrochloric acid (HCI) destroys microorganisms that are consumed with food.
It produces an acidic medium with a pH of around 2, which facilitates the activity of the pepsin enzyme.
It binds to proteins found in meals. As the acidic nature of HCL is very high, it inhibits the starch’s digestion in the stomach. Additionally, it prepares the food that is eaten for further processing in the small intestine.
Mucus protects the stomach lining from the effect of hydrochloric acid generated under normal circumstances.
(iii) Liver – It is the body’s biggest gland, secreting bile juice. These fluids reduce the size of big fat molecules, enhancing the effectiveness of enzyme activity. Bile fluids are stored in the gallbladder for future use.
(iv) Intestinal Glands – Small intestines’ walls are lined by numerous glands which are responsible for the secretion of intestinal juice containing proteolytic, amylolytic, and lipolytic enzymes.
(v) Pancreas – Pancreatic juice is secreted by the pancreas and includes enzymes such as trypsin, amylase, and lipase. The pancreas is attached to the small intestine by a duct called the pancreatic duct.
Mechanism of Digestion of Food
Our diet comprises a variety of nutrients such as carbs, fats, proteins, vitamins, and minerals.
The following are the several processes involved in the digestion of the nutrients:
It is the oral consumption of food. Before swallowing, saliva moistens the food and teeth masticate it into smaller bits.
Digestion is a process by which big organic molecules (such as carbohydrates) are broken down into smaller organic molecules (such as simple sugars).
It is accomplished by the use of enzymes.
It consists of the following major steps:
- The digestion of carbohydrates begins in the mouth. Salivary amylase converts starch to simple sugar.
- Pepsin and renin are used to convert proteins to peptones.
- Emulsification of fats is done using bile juices.
- Lipase catalyses the breakdown of emulsified fat.
- Amino acid, glucose, and fatty acid synthesis with the assistance of pancreatic and intestinal fluids.
It is the process by which partially digested food from the alimentary canal gets absorbed into the circulation.
The intestines absorb all digested food via their walls, which are coated with lacteals (small lymph capillary found in the villi of the small intestine) and many villi. Villi increases the surface area available for absorption.
Assimilation is a process by which digested food components are distributed to the body’s numerous cells. The small intestine’s villi are densely packed with blood vessels.
It transports ingested nutrients to each and every cell in the body. It is then used to generate energy, produce new tissues, and repair damaged ones.
The process of egestion is the removal of undigested food from the colon of the large intestine through the anus. Peristalsis is the gradual movement of undigested food from the small intestine to the large intestine.
Following reabsorption of water and ions, the remaining material is held in the rectum for a while before being expelled from the body via anus.