Class 10 Science – Life Processes

Class 10 Science Chapter 5: Concepts

Chapter 5: Life Processes

Introduction

All living organisms perform essential activities to sustain life. These activities are called life processes and include nutrition, respiration, transportation, and excretion. These processes require energy, which is obtained through the breakdown of food molecules.

To distinguish living beings from non-living things, scientists consider the presence of these life processes as the defining characteristic of life. Even if an organism appears inactive, life processes continue at the cellular level.

Nutrition

Nutrition is the process by which organisms obtain and utilize food to produce energy for growth, repair, and maintenance. Food provides essential nutrients like carbohydrates, proteins, fats, vitamins, and minerals required by the body.

Based on the mode of obtaining food, nutrition is of two types:

A. Autotrophic Nutrition

Autotrophic nutrition is a mode of nutrition in which organisms make their own food. Green plants and some bacteria use photosynthesis to prepare food using sunlight, water, and carbon dioxide. This process occurs in the presence of chlorophyll and produces glucose and oxygen.

The chemical equation for photosynthesis is:

B. Heterotrophic Nutrition

Heterotrophic nutrition is the mode of nutrition in which organisms depend on other organisms for food. These organisms cannot prepare their own food and obtain nutrients from other sources.

Heterotrophic nutrition can be of three types:

  1. Holozoic Nutrition: Organisms take in complex food and break it down inside the body. Example: Humans, Amoeba.
  2. Saprophytic Nutrition: Organisms feed on dead and decaying organic matter. Example: Fungi, Bacteria.
  3. Parasitic Nutrition: Organisms live on or inside another organism and obtain food from it. Example: Tapeworm, Cuscuta (Amarbel).

Nutrition in Humans

The human digestive system is responsible for breaking down food and absorbing nutrients. It consists of several organs that help in digestion.

Human Digestive System

  1. Mouth: Digestion starts here with the help of salivary amylase, which breaks down starch into simple sugars.
  2. Esophagus: The chewed food passes through the esophagus to the stomach via peristalsis (wave-like muscle contractions).
  3. Stomach: Contains gastric juices composed of hydrochloric acid (HCl), pepsin (enzyme for protein digestion), and mucus.
  4. Small Intestine: The major site of digestion and absorption of nutrients. It receives bile (from the liver) and pancreatic enzymes for the digestion of fats, proteins, and carbohydrates.
  5. Large Intestine: Absorbs water from undigested food, forming feces.
  6. Anus: Removes waste from the body.

Respiration

Respiration is the biological process in which food (mainly glucose) is broken down to release energy in the form of ATP (Adenosine Triphosphate). This energy is used for various life activities.

Types of Respiration

  1. Aerobic Respiration: Occurs in the presence of oxygen, producing carbon dioxide, water, and a large amount of energy.

    C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (ATP)

    Example: Humans, plants.

  2. Anaerobic Respiration: Occurs in the absence of oxygen, producing alcohol or lactic acid with lesser energy.

    C6H12O6 → Alcohol + CO2 + Energy

    Example: Yeast undergoes anaerobic respiration. In humans, muscle cells perform anaerobic respiration during intense exercise, producing lactic acid.

Transportation in Plants and Animals

Every living organism needs a transportation system to carry nutrients, gases, and waste products to and from different parts of the body.

A. Transportation in Plants

Plants use vascular tissues to transport water, minerals, and food.

  1. Xylem: Transports water and minerals from roots to leaves.
  2. Phloem: Transports food from leaves to other parts of the plant.

The process by which water moves through the xylem is called transpiration, which helps in cooling the plant and pulling water upward from the roots.

B. Circulatory System in Humans

The human circulatory system consists of the heart, blood, and blood vessels that transport nutrients, oxygen, and waste.

  1. Heart: A muscular organ that pumps oxygenated and deoxygenated blood.
  2. Arteries: Carry oxygen-rich blood from the heart to different body parts.
  3. Veins: Carry oxygen-poor blood back to the heart.
  4. Capillaries: Allow the exchange of gases, nutrients, and waste between blood and tissues.

The heart follows double circulation, meaning blood passes through the heart twice in one complete cycle of circulation.

Excretion

Excretion is the process of removing metabolic waste products from the body. These waste products include carbon dioxide, urea, and excess salts.

A. Excretion in Humans

The human excretory system is responsible for filtering blood and removing nitrogenous waste in the form of urine. It consists of:

  1. Kidneys: Filter urea, excess salts, and water from the blood.
  2. Ureter: Carries urine from kidneys to the urinary bladder.
  3. Urinary Bladder: Stores urine until it is expelled.
  4. Urethra: Removes urine from the body.

Waste products like carbon dioxide are removed through the lungs and sweat is excreted through the skin.

B. Excretion in Plants

Plants remove waste products in various ways:

  1. Stomata: Release oxygen (by-product of photosynthesis).
  2. Leaf Shedding: Removes accumulated waste.
  3. Resins and Gums: Store waste materials in non-functional cells.
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