Class 10 Chapter Science Life Processes NOTES
“Nutrition in Plants and Animals – Life Processes Class 10 Notes”
Nutrition: Nutrition refers to the process by which an organism acquires and utilizes food. Need for Nutrition: Organisms require energy to carry out various activities, which is provided by nutrients. Nutrients also supply the raw materials needed for growth and repair. Nutrients: Nutrients are substances that provide nourishment to organisms. The main nutrients, which are required in large amounts, are carbohydrates, proteins, and fats (also known as macronutrients). Micronutrients, such as minerals and vitamins, are needed in smaller amounts. Modes of Nutrition:
There are two main modes of nutrition: autotrophic nutrition and heterotrophic nutrition.
Autotrophic nutrition :
Autotrophic nutrition refers to the mode of nutrition in which an organism prepares its own food. Green plants and blue-green algae are examples of organisms that follow the autotrophic mode of nutrition.
Organisms that carry out autotrophic nutrition are called autotrophs, with green plants being a prominent example.
Autotrophic nutrition is achieved through the process of photosynthesis, in which autotrophs take in carbon dioxide and water, and convert them into carbohydrates in the presence of chlorophyll and sunlight. The equation for photosynthesis is:
6CO2 + 6H2O + sunlight → C6H12O6 + 6O2
In the case of green plants, they prepare their own food using sunlight as an energy source, with carbon dioxide and water serving as the raw materials. Chloroplasts are the sites where food is synthesized within the plant.
Photosynthesis requires three raw materials: sunlight, carbon dioxide (CO2), and water. Chlorophyll, a green pigment present in chloroplasts, absorbs sunlight and initiates the process of photosynthesis. CO2 enters the leaves through stomata and oxygen (O2) is released as a byproduct through stomata on the leaf. Water is taken up by the roots from the soil along with dissolved minerals like nitrogen and phosphorous. The water travels through the xylem tissue in roots and stems to reach the leaves, where it is used in photosynthesis.
Chapter 5 : Life Processes (NCERT solution)
Site of Photosynthesis:
Photosynthesis mainly occurs in the chloroplasts present in the leaves of green plants. Chloroplasts contain chlorophyll, which absorbs light energy and initiates the process of photosynthesis.
Main Events of Photosynthesis:
Photosynthesis involves several steps,including
i. The absorption of light energy by chlorophyll,
ii. Conversion iof light energy into chemical energy, the splitting of water into hydrogen and oxygen,
iii. The reduction of CO2 to carbohydrates, and the release of oxygen as a byproduct. Sunlight activates chlorophyll, which leads to the splitting of water molecules. The hydrogen released during this process is used to reduce carbon dioxide and produce carbohydrates, while oxygen is released as a byproduct. Carbohydrates are subsequently converted into starch and stored in leaves and other storage parts. The splitting of water molecules is a part of the light reaction, while other steps are part of the dark reaction during photosynthesis.
Stomata – Life Processes Class 10 Notes:
Stomata are tiny pores present in the epidermis of leaves or stems through which gaseous exchange and transpiration occur. They play an important role in the exchange of gases, such as O2 and CO2, and the loss of water (water vapor) during transpiration. The opening and closing of stomatal pores are controlled by the turgidity of guard cells. When guard cells uptake water from surrounding cells, they swell to become a turgid body, which enlarges the pore in between, leading to stomatal opening. While, when water is released, they become flaccid and shrink, leading to stomatal closing.
Chapter 5 : Life Processes (NCERT solution)
Significance of Photosynthesis:
Photosynthesis is a vital process that produces oxygen and food for different living beings. Green plants are the primary producers of food in the ecosystem, and all other organisms directly or indirectly depend on them for food. Photosynthesis also plays a crucial role in maintaining the balance of carbon dioxide and oxygen in the air.
EXPERIMENTS :
1. Title: Investigating the Role of Sunlight in Photosynthesis using a Variegated Plant
Aim: To determine the role of sunlight in photosynthesis by observing the distribution of starch in a variegated plant’s leaves.
Materials:
- Potted plant with variegated leaves (e.g., money plant or crotons)
- Dark room
- Sheet of paper
- Boiling water
- Alcohol
- Beaker
- Water-bath
- Dilute solution of iodine
Procedure:
- Keep the potted plant in a dark room for three days to use up all the starch.
- Place the plant in sunlight for six hours.
- Pluck a leaf from the plant and mark the green areas on it.
- Trace the marked areas of the leaf on a sheet of paper.
- Dip the leaf in boiling water for a few minutes.
- Immerse the leaf in a beaker containing alcohol.
- Place the beaker in a water-bath and heat it until the alcohol boils.
- Observe the color of the leaf and the solution in the beaker.
- Dip the leaf in a dilute solution of iodine for a few minutes.
- Rinse off the iodine solution from the leaf.
- Observe the color of the leaf and compare it with the tracing done earlier.
Results and Conclusion: The green areas of the leaf contain chlorophyll, which absorbs light energy during photosynthesis. After immersing the leaf in alcohol, the color of the leaf turns white, indicating the removal of chlorophyll. The alcohol solution turns green, indicating the presence of chlorophyll. When the leaf is dipped in the dilute solution of iodine, the green areas turn blue-black, indicating the presence of starch, which is a product of photosynthesis. Therefore, we can conclude that sunlight is required for photosynthesis, and the green areas of the leaf, which contain chlorophyll, produce starch during photosynthesis.
EXP- 2
Title: Comparison of Photosynthesis in Plants with and without Carbon Dioxide Absorption
Aim: To investigate the effect of carbon dioxide absorption on photosynthesis in plants.
Materials Required: Two healthy potted plants, glass plates, watch-glasses, potassium hydroxide, bell-jars, vaseline, iodine solution, and droppers.
Procedure:
- Take two healthy potted plants of similar size.
- Keep them in a dark room for three days.
- Place each plant on a separate glass plate.
- Place a watch-glass containing potassium hydroxide by the side of one of the plants to absorb carbon dioxide.
- Cover both plants with separate bell-jars as shown in Fig. 5.4.
- Use vaseline to seal the bottom of the jars to the glass plates so that the set-up is air-tight.
- Keep the plants in sunlight for about two hours.
- Pluck a leaf from each plant and check for the presence of starch using the iodine solution.
- Observe the leaves for the presence of starch and note down the results.
Observations:
- The leaf from the plant without the potassium hydroxide (control plant) shows the presence of starch.
- The leaf from the plant with the potassium hydroxide (experimental plant) shows the absence of starch.
Conclusion:
The leaf from the plant with the potassium hydroxide shows the absence of starch, indicating that there was a lack of carbon dioxide in the experiment. This suggests that carbon dioxide is required for photosynthesis to occur. Therefore, the presence of carbon dioxide is essential for the process of photosynthesis to take place
Chapter 5 : Life Processes (NCERT solution)
Heterotrophic nutrition
is the mode of nutrition where an organism obtains food from another organism. This type of nutrition is followed by organisms other than green plants and blue-green algae and can be classified into three types: saprophytic, holozoic, and parasitic.
In saprophytic nutrition, the organism secretes digestive juices onto the food, which is then digested before being ingested. This type of nutrition is followed by decomposers and some insects like houseflies.
In holozoic nutrition, digestion occurs inside the organism’s body after ingestion. This type of nutrition is followed by most animals and occurs in five steps: ingestion, digestion, absorption, assimilation, and egestion.
Parasitic nutrition occurs when an organism lives inside or outside another organism (host) and derives nutrition from it. Examples of parasites include Cuscuta and ticks.
Steps of Holozoic Nutrition:
- Ingestion: The process of taking in food is known as ingestion.
- Digestion: The process of breaking down complex food substances into simpler molecules is called digestion. These simpler molecules can then be absorbed by the body.
- Absorption: The process by which digested food is taken up by the body is known as absorption.
- Assimilation: The process of utilizing digested food for energy, growth, and repair is called assimilation.
- Egestion: The process of eliminating undigested food from the body is called egestion.
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Nutrition in amoeba
Amoeba, a unicellular animal, follows holozoic nutrition. Its cell membrane protrudes into pseudopodia, which surround a food particle and create a food vacuole. Digestive enzymes are secreted into the food vacuole, and after digestion, the digested food is absorbed. Finally, the undigested food is expelled out of the cell membrane.
Nutrition in Human Beings – Life Processes Class 10 Notes
The human body is a complex organism, possessing an intricate digestive system consisting of both an alimentary canal and accessory glands. The alimentary canal comprises several parts, including the esophagus, stomach, small intestine, large intestine, rectum, and anus. The accessory glands, including the salivary gland, liver, and pancreas, lie outside the alimentary canal.
Structure of the Human Digestive System: The human digestive system consists of the alimentary canal and associated digestive glands.
Alimentary Canal: The alimentary canal consists of the mouth, esophagus, stomach, small intestine, and large intestine. Associated Glands: The main associated glands are the salivary gland, gastric glands, liver, and pancreas.
Fig : Human Digestive system
Mouth or Buccal Cavity:
The mouth has teeth and a tongue. Salivary glands in the mouth secrete saliva, which helps to make the food slippery and easy to swallow. Saliva also contains the enzyme salivary amylase, which digests starch and converts it into sucrose (maltose). The tongue has gustatory receptors that perceive the sense of taste, and it helps to mix the food with saliva. Teeth break down the food into smaller particles, making it easier to swallow. There are four types of teeth in human beings. The incisor teeth are used for cutting the food, the canine teeth are used for tearing and cracking hard substances, the premolars are used for the coarse grinding of food, and the molars are used for fine grinding of food.
Chapter 5 : Life Processes (NCERT solution)
Oesophagus:
The oesophagus is a muscular tube that carries food from the mouth to the stomach by rhythmic contraction of the muscles of the lining of the alimentary canal, called peristaltic movement.
Stomach:
The stomach is a bag-like organ with highly muscular walls that help to churn the food. The walls of the stomach secrete hydrochloric acid, which kills germs that may be present in the food and makes the medium inside the stomach acidic, necessary for gastric enzymes to work. The enzyme pepsin, secreted in the stomach, partially digests protein. The mucus secreted by the walls of the stomach protects the inner lining of the stomach from getting damaged by hydrochloric acid.
Small Intestine:
The small intestine is a highly coiled tube-like structure divided into three parts: the duodenum, jejunum, and ileum. It is longer than the large intestine, but its lumen is smaller. The major part of digestion takes place in the duodenum.
The liver plays an important role in digestion. It produces a greenish-yellow fluid called bile, which is stored in the gallbladder and released into the small intestine when needed. Bile helps in the digestion of fats by breaking them down into smaller droplets in a process called emulsification. This process increases the surface area of the fat particles, making them easier for enzymes to digest. Bile, which breaks down fat into smaller particles, is produced by the liver and stored in the gallbladder.
The pancreas is an important accessory gland of the human digestive system. It is a long, flattened organ located just below the stomach. The pancreatic juice secreted by the pancreas contains three types of enzymes: Trypsin, lipases, and amylases. Trypsin are enzymes that break down proteins into amino acids. Lipases are enzymes that digest fats and convert them into fatty acids and glycerol. Amylases are enzymes that break down carbohydrates into simple sugars like glucose.
The wall of the small intestine secrets numbers of enzymes which converts carbohydrates into glucose, protiens into amino acids and fats into fatty acids and glycerol which can be absorbed by the wall of the intestine.
The jejunum and ileum are responsible for the absorption of the digested food. The inner wall of the ileum is projected into numerous finger-like structures, called villi. These villi increase the surface area of the small intestine so that optimum absorption can take place. Moreover, the villi also reduce the lumen of the ileum so that food can stay for a longer duration in it, for optimum absorption. Nutrients such as glucose, amino acids, and fatty acids are absorbed by the villi and transported to the bloodstream.
Large Intestine:
The large intestine is smaller than the small intestine and absorbs water and salt. Undigested food goes into the large intestine, and excess water is absorbed by the walls of the large intestine. The undigested food goes to the rectum, from where it is expelled out through the anus (egestion).
Chapter 5 : Life Processes (NCERT solution)
NOTE : DENTAL CARRIES
Tooth decay, also known as dental caries, is a condition that causes a gradual softening of the enamel and dentine of the teeth. It occurs when bacteria present in the mouth act on sugars and produce acids that demineralize the enamel.
As these bacteria grow, they form masses together with food particles on the teeth, creating a sticky substance called dental plaque. When plaque covers the teeth, saliva cannot reach the tooth surface to neutralize the acid. Over time, the acid produced by the bacteria in the plaque causes the enamel to soften and erode.
Brushing the teeth after eating helps to remove the plaque before the bacteria produce acids. If left untreated, the microorganisms in the plaque can invade the pulp, which is the soft tissue inside the tooth, causing inflammation and infection.
Therefore, maintaining good oral hygiene practices such as brushing and flossing regularly, using mouthwash, and visiting a dentist regularly can prevent dental caries and promote healthy teeth and gums.
Chapter 5 : Life Processes (NCERT solutions )
Click her for Part2 Notes RESPIRATION
Click her for Part3 Notes CIRCULATION
Click her for Part4 Notes EXCRETION