Saturday, 7 November 2026

Life Processes - 1 Notes

MG SCHOOL SCIENCE

CHAPTER NOTES

CLASS 10 – SCIENCE

LIFE PROCESSES – 1

Complete Chapter Study Material

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📚 TABLE OF CONTENTS

01. Introduction 02. Life Processes 03. Nutrition 04. Autotrophic Nutrition 05. Photosynthesis 06. Experiment – Starch Test in Leaves 07. Heterotrophic Nutrition 08. Nutrition in Humans and Other Organisms 09. Small Intestine and Complete Digestion 10. Digestive Secretions and Absorption 11. Large Intestine and Respiration Overview

01. Introduction ＋

Earth is the only known planet to support life. There are beings who live, die and become part of nature again.

Living organisms can be differentiated from inanimate entities on various parameters of life processes.

Key Point: Life processes help us identify and understand the activities that maintain living organisms.

02. Life Processes ＋

The maintenance of living organisms is essential even if they are moving, resting or sleeping.
The processes that together maintain life are known as life processes.
The various life processes which take place in living organisms are called metabolic activities or metabolism.
Nutrition, respiration, transportation and excretion are some of the life processes essential for the functioning and maintenance of living organisms.

Definition – Life Processes: The processes that together maintain life in living organisms are called life processes.

Nutrition

Obtaining and utilising food.

Respiration

Breaking down food to release energy.

Transportation

Movement of materials within organisms.

Excretion

Removal of waste materials.

03. Nutrition ＋

Definition – Nutrition: Nutrition is a process by which living organisms procure food or synthesise it and convert it into simple absorbable form by a series of biochemical processes.

Definition – Nutrient: A nutrient is a substance that an organism obtains from its surroundings and uses as a source of energy as well as a source of raw materials for growth and repair.

Basic Modes of Nutrition

1. Autotrophic Nutrition

Organisms prepare their own food.

2. Heterotrophic Nutrition

Organisms depend on other organisms or organic materials for food.

04. Autotrophic Nutrition ＋

Autotrophic organisms meet their carbon and energy needs through photosynthesis.
This process involves the conversion of carbon dioxide and water into carbohydrates using light energy.
During photosynthesis, autotrophs absorb carbon dioxide and water, converting them into carbohydrates with the help of sunlight and chlorophyll.
Carbohydrates produced are used as an energy source for the plant's activities.
Excess carbohydrates are stored as starch, acting as an internal energy reserve for the plant's future needs.
In a similar manner, humans store energy from food as glycogen.

Remember: Plants store excess carbohydrates as starch, whereas humans store energy from food as glycogen.

05. Photosynthesis ＋

Definition – Photosynthesis: Photosynthesis is the synthesis of organic compounds (carbohydrates) from CO₂ and H₂O using radiant energy or solar energy by chlorophyll molecules.

Events During Photosynthesis

Absorption of light energy by chlorophyll.
Conversion of light energy to chemical energy as well as splitting of water molecules into hydrogen and oxygen.
Reduction of carbon dioxide to carbohydrates.

These stages do not have to occur directly one after the other. For instance, some desert plants absorb carbon dioxide at night and then use the energy captured by chlorophyll during the day.

Chloroplasts and Stomata

Inside some cells, there are green structures known as chloroplasts that contain chlorophyll.
A large amount of gas exchange occurs in the leaves through tiny openings called stomata during photosynthesis.

Carbon Dioxide + Water
↓ Sunlight and Chlorophyll
Carbohydrates

06. Experiment Activity – Starch Test in Leaves ＋

Objective

To test the presence of starch in different areas of a variegated leaf.

Procedure

Take a potted plant with variegated leaves, such as a money plant or crotons.
Place the plant in a darkroom for three days to deplete starch reserves.
Expose the plant to sunlight for about six hours.
Pluck a leaf, mark the green areas and trace them on a sheet of paper.
Boil the leaf in water and then immerse it in alcohol.
Heat the alcohol in a water bath until it boils.
Observe colour changes in the leaf and solution.
Dip the leaf in a dilute iodine solution and compare colours with the initial tracing.
Draw conclusions about starch presence in different leaf areas.

Observation and Conclusion

Compare the iodine colour changes in different areas of the leaf with the original tracing to identify starch presence.

07. Heterotrophic Nutrition ＋

Heterotrophic organisms cannot prepare their food. They are dependent on plants, animals or dead and decaying organic materials for their food.

Saprophytes derive their nourishment from dead and decaying matter.
Organisms adapt to their environment, and their nutrition methods vary based on food type, availability and how it is acquired.
The nature of the food source, whether stationary like grass or mobile like a deer, influences how it is accessed.
Differences exist in the nutritive apparatus used by animals like cows and lions.
Some organisms externally break down food before absorption, for example fungi such as bread moulds, yeast and mushrooms.
Others ingest whole material and break it down internally.
Some organisms obtain nutrition from plants or animals without killing them, employing parasitic strategies.

Types and Examples

Saprophytic Nutrition

Obtaining nourishment from dead and decaying matter.

Parasitic Nutrition

Obtaining nutrition from a host.

Examples: Cuscuta, ticks, lice, leeches and tapeworms.

Holozoic Nutrition

A mode of nutrition that involves swallowing solid food material.

Holozoic Nutrition: Ingestion, digestion, absorption, assimilation and egestion are the various steps involved in holozoic nutrition.

08. Nutrition in Humans and Other Organisms ＋

In animals, procurement of food is highly variable.
The process of nutrition becomes more complex in multicellular organisms as compared to unicellular organisms.
In single-celled organisms like Amoeba, food is taken in through the general body surface.
In humans, the digestive system consists of a long alimentary canal and digestive glands.

Parts of the Human Alimentary Canal

Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine

Digestion in the Mouth

Food is crushed by teeth and mixed with saliva secreted by salivary glands.
Saliva contains an enzyme called salivary amylase that breaks down starch into simple sugar.

Peristaltic Movements

When we swallow food (bolus), it is pushed forward by rhythmic contraction and relaxation of muscles present in the wall of the alimentary canal. These movements are called peristaltic movements.

Digestion in the Stomach

The stomach is a large J-shaped hollow organ that expands when food enters it.
The muscular walls of the stomach help in mixing food thoroughly with gastric secretions.
The gastric glands present in the wall of the stomach secrete hydrochloric acid, pepsin and mucus.
Hydrochloric acid facilitates the action of pepsin, as this enzyme works in an acidic medium.
Hydrochloric acid prevents fermentation of food and kills harmful microorganisms present in the food.
Mucus protects the inner wall of the stomach from the highly acidic HCl.
Partially digested food (chyme) enters the small intestine from the stomach.
A sphincter muscle regulates the exit of food from the stomach into the small intestine in small amounts.

Important Terms:
Bolus – Swallowed food.
Peristalsis – Rhythmic muscular movements.
Chyme – Partially digested food.

09. Small Intestine and Complete Digestion ＋

The length of the small intestine differs in various animals depending on their feeding habits.
Herbivores have a longer small intestine to allow cellulose to be digested.
Carnivores have a shorter small intestine because meat is easier to digest.
The small intestine is the site of complete digestion of carbohydrates, proteins and fats.

Herbivores

Longer small intestine.

Carnivores

Shorter small intestine.

10. Digestive Secretions and Absorption in Small Intestine ＋

Digestive Juices

The small intestine produces digestive juice, which mixes with pancreatic juice and bile to break down food.

Absorption

The small intestine absorbs nutrients, water and minerals from digested food.

Enzymes

The pancreas secretes digestive enzymes into the duodenum that break down proteins, fats and carbohydrates.
The small intestine receives secretions from the liver and pancreas.

Bile Emulsification

Bile juice from the liver contains bile pigments and bile salts.
Bile salts break fats into small globules by a process called emulsification.
This increases the efficiency of enzyme action (lipase).

Pancreatic Juice

The pancreas secretes slightly alkaline pancreatic juice which contains three major enzymes:

Trypsin

Digests proteins.

Lipase

Digests fats.

Amylase

Digests carbohydrates.

Intestinal Juice

The walls of the small intestine contain glands that secrete intestinal juice.

Proteins are finally converted into amino acids.
Complex carbohydrates are converted into glucose.
Fats are converted into fatty acids and glycerol.

Villi and Surface Area

The inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption of digested food.

The villi are richly supplied with blood vessels.
These blood vessels take absorbed food to every cell of the body.
The absorbed food is utilised for obtaining energy, building new tissues and repairing old ones.

11. Large Intestine and Respiration Overview ＋

Large Intestine

Undigested food is sent into the large intestine where more water is reabsorbed from it.
The rest of the undigested food material is removed from the body via the anus.
The anal sphincter regulates the exit of this waste material.

Respiration Overview

Definition – Respiration: Respiration is the process in which food is broken down to release energy.

The food material taken in during nutrition is used by cells to provide energy for various life processes.

Some organisms use oxygen to bring about the complete breakdown of glucose in cells into carbon dioxide and water. This is called aerobic respiration.

Aerobic Respiration

Uses oxygen for the complete breakdown of glucose into carbon dioxide and water.

Respiration

Can occur with or without oxygen.

⭐ Quick Revision – Important Points ＋

Life processes maintain life in living organisms.
Nutrition is the process of obtaining and utilising food.
Autotrophs prepare food through photosynthesis.
Chlorophyll absorbs light energy.
Stomata are tiny openings in leaves.
Excess carbohydrates are stored as starch in plants.
Humans store energy as glycogen.
Holozoic nutrition involves five steps.
Salivary amylase breaks down starch.
Peristaltic movements push food through the alimentary canal.
Pepsin is a protein-digesting enzyme.
Bile salts help in emulsification of fats.
Villi increase the surface area for absorption.
The large intestine reabsorbs water.
Respiration releases energy from food.

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