Life Processes – Easy Notes
Class 10 Biology | Nutrition • Respiration • Transportation • Excretion
Simple explanations, important terms, diagrams, experiments and exam-ready points
1. What are Life Processes?
Life processes are the basic activities that living organisms perform to stay alive and maintain their bodies.
- Nutrition: taking in food and using it for energy, growth and repair.
- Respiration: breaking down food to release usable energy.
- Transportation: carrying materials such as food, oxygen, water and wastes from one part of the body to another.
- Excretion: removing harmful metabolic wastes from the body.
2. Nutrition
Nutrition is the process by which organisms obtain food and use it. Food provides energy, materials for growth and materials to repair damaged parts.
2.1 Types of nutrition
| Type | Meaning | Examples |
|---|---|---|
| Autotrophic nutrition | Organisms make their own food from simple inorganic substances. | Green plants and some bacteria. |
| Heterotrophic nutrition | Organisms obtain food from other organisms or organic matter. | Humans, cats, fungi and many bacteria. |
2.2 Main types of heterotrophic nutrition
- Holozoic: food is taken into the body, digested, absorbed and used. Examples: humans, cats and Amoeba.
- Saprotrophic (saprophytic): organisms obtain nutrients from dead and decaying organic matter. Examples: many fungi, bread mould and mushrooms.
- Parasitic: an organism lives on or inside another organism, called the host, and obtains food from it, often harming the host. Examples: lice, leeches and tapeworms. Cuscuta is a parasitic plant and lacks normal green leaves/chlorophyll for making enough food.
2.3 Photosynthesis
Photosynthesis is the process by which green plants make food from carbon dioxide and water using sunlight in the presence of chlorophyll. Oxygen is released during the process.
Balanced summary equation: 6CO₂ + 6H₂O —light/chlorophyll→ C₆H₁₂O₆ + 6O₂
Photosynthesis: plants use light, carbon dioxide and water to make food. If this image does not load, open photosynthesis diagrams on Wikimedia Commons.
2.4 Conditions and materials needed for photosynthesis
- Sunlight: supplies energy.
- Chlorophyll: the green pigment that absorbs light energy.
- Carbon dioxide: enters the leaf mainly through tiny pores called stomata.
- Water: absorbed from the soil by roots and carried to leaves.
Site: Photosynthesis mainly occurs in the leaves, inside cell structures called chloroplasts. Chloroplasts contain chlorophyll.
Plants also need minerals. Nitrogen is absorbed mainly as soluble nitrates/nitrites (and other usable nitrogen compounds); phosphorus, magnesium and iron are also important for healthy growth.
2.5 What happens during photosynthesis?
- Chlorophyll absorbs light energy.
- Light energy is converted into chemical energy; water molecules are split, releasing oxygen.
- Carbon dioxide is used to make carbohydrates such as glucose.
- Some glucose is used immediately; some is stored as starch. In animals, stored carbohydrate is mainly in the form of glycogen.
2.6 Experiments that show the requirements for photosynthesis
- Keep a potted plant in the dark for a period so stored starch is used up.
- Take a variegated leaf (one with green and non-green areas) and expose the plant to sunlight.
- Boil the leaf in water, then heat it in alcohol in a water bath to remove its green colour. Alcohol is flammable, so it must never be heated directly over a flame.
- Rinse the leaf and add iodine solution.
Conclusion: starch is formed in the green areas, showing that chlorophyll is needed for photosynthesis.
- Destarch a potted plant by keeping it in darkness.
- Place a leaf in an airtight flask/jar containing potassium hydroxide (KOH), which absorbs carbon dioxide. Keep a comparable leaf exposed to normal air as a control.
- Keep the setup in sunlight, then test both leaves for starch with iodine solution.
Conclusion: carbon dioxide is necessary for photosynthesis. KOH is caustic and should only be handled with suitable supervision and protection.
2.7 Nutrition in Amoeba
Amoeba is a single-celled organism and uses holozoic nutrition.
- Ingestion: temporary finger-like projections called pseudopodia surround and take in the food particle. Pseudopodia also help Amoeba move.
- Digestion: a food vacuole forms around the food. Digestive enzymes break complex food into simpler soluble substances.
- Absorption: digested food passes into the cytoplasm.
- Assimilation: the absorbed food is used for energy, growth and repair.
- Egestion: undigested material moves to the cell surface and is expelled.
Amoeba and its cell structures. More diagrams: Wikimedia Commons – Amoeba.
2.8 Nutrition in Paramecium
- Paramecium is a single-celled organism with a definite, slipper-like shape.
- Hair-like structures called cilia move food towards a specific spot where a food vacuole forms.
- Cilia also help the organism move.
- Food is digested in the vacuole; useful nutrients are absorbed and undigested matter is removed.
2.9 Human digestive system
The alimentary canal is the long tube through which food passes from the mouth to the anus. Digestion breaks large, complex food molecules into small, soluble molecules that can be absorbed.
Human digestive system. Source: Wikimedia Commons.
| Part | What it does |
|---|---|
| Mouth / buccal cavity | Teeth cut and crush food. The tongue mixes food with saliva and helps swallowing. |
| Salivary glands | Secrete saliva. Salivary amylase starts breaking down starch into simpler sugars. |
| Oesophagus (food pipe) | Moves food to the stomach by rhythmic contraction and relaxation of its wall, called peristalsis. |
| Stomach | Gastric glands release hydrochloric acid, pepsin and mucus. Acid creates the acidic medium needed by pepsin and kills many germs. Pepsin digests proteins. Mucus protects the stomach lining. |
| Liver | Produces bile. Bile helps make acidic food from the stomach less acidic and emulsifies fats into tiny droplets. |
| Gall bladder | Stores and releases bile. |
| Pancreas | Releases pancreatic juice. Trypsin digests proteins; lipase breaks down fats. Pancreatic juice also contains enzymes that digest carbohydrates. |
| Small intestine | Completes most chemical digestion and absorbs digested nutrients. It receives bile and pancreatic juice. |
| Villi | Finger-like projections on the inner wall of the small intestine. They increase surface area and contain blood vessels to carry absorbed nutrients away. |
| Large intestine (colon) | Absorbs more water and some salts from undigested material. |
| Rectum and anus | Faeces are stored temporarily in the rectum and removed through the anus. Sphincter muscles help control release. |
Final products of digestion
| Food type | Final products |
|---|---|
| Carbohydrates | Simple sugars, mainly glucose |
| Proteins | Amino acids |
| Fats | Fatty acids and glycerol |
2.10 Experiment – Saliva acts on starch
- Take two samples containing starch. Add saliva to one and water to the other (control).
- Leave them for some time at a suitable warm temperature.
- Add iodine solution to each sample.
Observation: the control sample with starch turns blue-black. The sample treated with saliva shows little or no blue-black colour if the starch has been broken down.
Conclusion: salivary amylase breaks down starch.
3. Respiration
Respiration is the breakdown of food (especially glucose) inside cells to release energy. Cells use some of this energy in a usable form called ATP.
3.1 Aerobic and anaerobic respiration
| Feature | Aerobic respiration | Anaerobic respiration |
|---|---|---|
| Oxygen | Requires oxygen. | Occurs without oxygen. |
| Breakdown of glucose | Usually complete. | Incomplete. |
| Energy released | More energy. | Less energy. |
| Site | Starts in cytoplasm; most energy-releasing steps occur in mitochondria. | Occurs in cytoplasm. |
| End products | Carbon dioxide and water. | In yeast: ethanol and carbon dioxide. In some muscle cells: lactic acid. |
Aerobic: Glucose + oxygen → carbon dioxide + water + energy
Anaerobic in yeast: Glucose → ethanol + carbon dioxide + energy
Anaerobic in muscles: Glucose → lactic acid + energy
During intense exercise, muscle cells may not receive oxygen fast enough for their energy demand. Anaerobic respiration can then produce lactic acid, which is associated with muscle fatigue and cramps.
Fermentation: anaerobic breakdown of sugars by microorganisms such as yeast. Yeast can convert sugar into ethanol and carbon dioxide.
3.2 Human respiratory system
Human respiratory system. Source: Wikimedia Commons.
| Part | Function |
|---|---|
| Nostrils and nasal passage | Air enters through the nostrils. Hairs and mucus trap dust and help filter, warm and moisten air. |
| Pharynx | Common passage for food and air. |
| Larynx | Voice box; contains vocal cords and allows air to pass into the trachea. |
| Trachea | Windpipe carrying air towards the lungs. Rings of cartilage help prevent it from collapsing. |
| Bronchi | Two main branches that carry air into the two lungs. |
| Bronchioles | Smaller branches of the bronchi that lead to alveoli. |
| Alveoli | Tiny, thin-walled, moist air sacs surrounded by blood capillaries. They provide a large surface area for gas exchange. |
| Diaphragm | A dome-shaped muscle separating the chest cavity from the abdomen; its movement changes chest volume during breathing. |
3.3 Gas exchange in alveoli
- Oxygen concentration is higher in the air in the alveoli than in the deoxygenated blood arriving at their capillaries, so oxygen diffuses into the blood.
- Carbon dioxide concentration is higher in the arriving blood than in alveolar air, so carbon dioxide diffuses into the alveoli and is breathed out.
- Alveoli have thin walls, a moist surface, many capillaries and a large total surface area, making gas exchange efficient.
Alveoli and gas exchange. If this image is unavailable, browse alveoli diagrams on Wikimedia Commons.
3.4 Inhalation and exhalation
| Inhalation (inspiration) | Exhalation (expiration) |
|---|---|
| Diaphragm contracts, flattens and moves down. | Diaphragm relaxes and becomes dome-shaped, moving up. |
| Rib cage moves up and out as chest volume increases. | Rib cage moves down and in as chest volume decreases. |
| Pressure in the chest decreases, so air enters the lungs. | Pressure in the chest increases, so air leaves the lungs. |
Residual volume is the air that remains in the lungs even after forceful exhalation. It helps keep the lungs from completely emptying and allows gas exchange to continue between breaths.
3.5 Gas exchange in plants
- Plants exchange gases mainly through stomata in leaves; woody stems may also exchange gases through lenticels.
- Photosynthesis uses carbon dioxide and releases oxygen, and it requires light.
- Respiration occurs both day and night and uses oxygen while releasing carbon dioxide.
- In daylight: photosynthesis is usually faster than respiration, so the net gas exchange is commonly carbon dioxide entering and oxygen leaving.
- At night: photosynthesis stops without light, but respiration continues, so the net gas exchange is oxygen entering and carbon dioxide leaving.
3.6 Breathing in fish and other organisms
Fish take water in through the mouth and pass it over the gills. Dissolved oxygen diffuses from the water into the blood; carbon dioxide diffuses from the blood into the water.
| Terrestrial organisms | Aquatic organisms |
|---|---|
| Obtain oxygen from air, which contains more oxygen per volume than water. | Use oxygen dissolved in water, which is less available. |
| Often need a lower breathing rate than aquatic animals of comparable activity, though rates vary with species and conditions. | Often breathe faster to obtain enough dissolved oxygen. |
4. Transportation
Transportation is the movement of substances such as food, oxygen, carbon dioxide, water, minerals and wastes from one part of an organism to another.
4.1 Transportation in human beings
The human circulatory system consists of the heart, blood and blood vessels. It carries oxygen and nutrients to cells and transports carbon dioxide and other wastes away.
Blood and its components
| Component | Function |
|---|---|
| Plasma | Pale-yellow liquid part of blood. Transports nutrients, hormones, carbon dioxide and dissolved wastes. |
| Red blood cells (RBCs) | Contain haemoglobin, which binds oxygen and gives blood its red colour. They carry most oxygen to tissues. |
| White blood cells (WBCs) | Help defend the body against pathogens; different types perform different immune functions, including antibody production. |
| Platelets | Help blood clot and stop bleeding. |
4.2 Blood vessels
| Feature | Arteries | Veins | Capillaries |
|---|---|---|---|
| Direction | Carry blood away from the heart. | Carry blood towards the heart. | Connect small arteries and veins. |
| Pressure | Generally high. | Generally low. | Low enough for exchange across thin walls. |
| Walls | Thick, muscular and elastic. | Thinner and less elastic than arteries. | Extremely thin, about one cell thick. |
| Valves | Generally absent along most arteries. | Present in many veins, especially in limbs, to prevent backflow. | Absent. |
| Oxygen content | Usually oxygen-rich. | Usually oxygen-poor. | Depends on the exchange taking place. |
4.3 Human heart
The heart is a muscular organ, roughly the size of a fist, that pumps blood. It has four chambers: right atrium, right ventricle, left atrium and left ventricle. Valves help keep blood flowing in the correct direction.
Heart structure. More diagrams: Wikimedia Commons – human heart.
Path of blood through the heart
- Oxygen-poor blood from the body enters the right atrium through the venae cavae.
- It moves to the right ventricle, which pumps it through the pulmonary artery to the lungs.
- In the lungs, blood releases carbon dioxide and receives oxygen.
- Oxygen-rich blood returns to the left atrium through the pulmonary veins.
- It moves to the left ventricle, which pumps it through the aorta to the body.
The walls of the ventricles are thicker than those of the atria because ventricles pump blood out of the heart. The left ventricle has the thickest wall because it pumps blood to the whole body at high pressure.
4.4 Double and single circulation
- Double circulation: blood passes through the heart twice during one complete circuit of the body—once through the heart–lungs route and once through the heart–body route. This keeps oxygen-rich and oxygen-poor blood separate in humans.
- Single circulation: blood passes through the heart once in one complete circuit, as in fish.
- Complete double circulation: oxygen-rich and oxygen-poor blood remain fully separated, as in birds and mammals.
- Partial/incomplete double circulation: some mixing can occur because the heart does not completely separate the two streams, as in amphibians and many reptiles.
Human circulation. Source: Wikimedia Commons.
4.5 Lymphatic system
Lymph is a pale, colourless or light-yellow fluid formed when some fluid from blood capillaries passes into the spaces around cells and enters lymph vessels. It usually contains fewer proteins than blood plasma and does not normally contain red blood cells.
- Lymph carries absorbed fats from the small intestine.
- It returns excess tissue fluid to the bloodstream.
- It contains lymphocytes and helps protect the body against infection.
- Lymph travels through lymph capillaries and larger lymph vessels, which eventually drain into veins.
4.6 Transportation in plants
Plants do not move from place to place and many plant tissues have low energy needs, so they use comparatively slow transport systems. The two main conducting tissues are xylem and phloem.
| Feature | Xylem | Phloem |
|---|---|---|
| Transports | Water and dissolved minerals. | Food, mainly sugars, made by photosynthesis; also other organic substances such as amino acids. |
| Direction | Mainly upward, from roots to stems and leaves. | From sources (where food is made or released) to sinks (where it is used or stored); can be upward or downward. |
| Structure | Vessels and tracheids are important conducting elements; most are dead at maturity. | Sieve tubes and companion cells are important conducting structures; sieve-tube elements are living. |
| Energy | Movement is driven mainly by physical forces such as transpiration pull, with root pressure contributing in some conditions. | Loading and unloading sugars requires energy; transport is pressure-driven. |
4.7 How water moves through a plant
- Root uptake: root cells take up mineral ions from the soil. Water enters root cells by osmosis, following water-potential differences.
- Root pressure: mineral uptake can cause water to enter the xylem, creating pressure that can push water upward over short distances.
- Transpiration: loss of water vapour from aerial parts of the plant, mainly through stomata.
- Transpiration pull: evaporation of water from leaves creates a pulling force that draws a continuous column of water upward through xylem.
- Cooling: evaporation during transpiration helps cool the plant.
Transpiration and water movement. Browse plant transpiration diagrams if needed.
4.8 Translocation in phloem
Translocation is the movement of food made in leaves to other parts of the plant through phloem. Food is sent to growing regions and storage organs such as roots, fruits and seeds. Phloem transport can occur in both upward and downward directions depending on where food is needed. Loading and unloading food requires energy (ATP).
5. Excretion
Excretion is the removal of harmful metabolic waste products from the body. It is different from egestion, which is the removal of undigested food from the digestive tract.
5.1 Human excretory system
Human excretion removes nitrogen-containing wastes, especially urea, along with extra water and salts. The main urinary organs are the kidneys, ureters, urinary bladder and urethra.
Human urinary system. More pictures: Wikimedia Commons – urinary system.
| Part | Function |
|---|---|
| Kidneys | Filter blood and help remove urea, extra salts and water by making urine. |
| Ureters | Carry urine from each kidney to the urinary bladder. |
| Urinary bladder | Stores urine temporarily. Its muscular wall contracts when urine is released. |
| Urethra | Carries urine from the bladder out of the body. |
| Renal artery | Brings blood containing wastes to the kidney for filtration. |
| Renal vein | Carries filtered blood away from the kidney. |
5.2 Nephron – the working unit of a kidney
A nephron is the structural and functional unit of a kidney. Each kidney contains many nephrons.
Nephron structure. Source: Wikimedia Commons.
- Glomerulus: a cluster of tiny blood vessels where blood is filtered under pressure.
- Bowman’s capsule: a cup-shaped structure around the glomerulus that collects the filtrate.
- Tubule: the long tube where useful substances and much of the water are selectively reabsorbed; some additional wastes and ions are secreted into it.
- Collecting duct: receives fluid from nephrons and carries it towards the urine-collecting passages.
5.3 How urine is formed
Blood is filtered in the glomerulus. Water and small dissolved substances such as salts, glucose, amino acids and urea enter Bowman’s capsule. Blood cells and most proteins remain in the blood.
Useful substances, including all or nearly all glucose under normal conditions, amino acids, needed salts and a large amount of water, return from the filtrate to surrounding blood capillaries. The amount of water reabsorbed varies with the body’s needs.
Additional wastes and excess ions may be moved from blood into the tubule. The remaining fluid becomes urine and passes through collecting ducts, ureters and into the bladder.
5.4 Dialysis and artificial kidney
- If kidneys fail to remove wastes adequately, dialysis can remove nitrogenous wastes and excess salts and water from the blood.
- In haemodialysis, blood flows along one side of a selectively permeable membrane and dialysis fluid flows on the other side.
- The dialysis fluid has a suitable concentration of useful substances but lacks nitrogenous wastes, allowing wastes to diffuse out of the blood.
- Dialysis does not perform all the regulatory and hormonal functions of healthy kidneys and does not reproduce selective reabsorption in the same way a nephron does.
5.5 Excretion in plants
Plants do not have a separate excretory system like humans. They remove or store wastes in several ways:
- Oxygen produced during photosynthesis and carbon dioxide produced during respiration can diffuse out through stomata and other openings.
- Excess water is lost mainly through transpiration.
- Some wastes are stored in leaves, bark and fruits that are later shed.
- Some waste substances are stored as gums and resins in plant tissues.
- Some wastes may be released into the soil around the roots.
6. Quick Revision and Exam-Ready Answers
Photosynthesis is the process in which green plants use sunlight and chlorophyll to make food from carbon dioxide and water. It mainly occurs in chloroplasts in leaves. The released oxygen comes from the splitting of water molecules.
Potassium hydroxide absorbs carbon dioxide from the air inside the flask. If the leaf cannot obtain carbon dioxide, starch is not formed there under the experimental conditions.
Amoeba surrounds food with pseudopodia and forms a food vacuole. Enzymes digest the food; soluble nutrients are absorbed into the cytoplasm and used by the cell. Undigested material is expelled through the cell surface.
Hydrochloric acid creates the acidic medium needed by pepsin and kills many germs. Pepsin digests proteins. Mucus protects the stomach lining from acid and digestive enzymes.
Villi are finger-like projections in the small intestine. They greatly increase the surface area for absorption and contain blood capillaries that carry absorbed nutrients around the body.
Aerobic respiration uses oxygen and usually completely breaks down glucose, releasing more energy. Anaerobic respiration occurs without oxygen, incompletely breaks down glucose and releases less energy.
They have thin, moist walls, a large surface area and a rich supply of blood capillaries, so oxygen and carbon dioxide can diffuse quickly.
Atria push blood only into the ventricles, while ventricles pump blood out of the heart. The left ventricle is especially thick because it pumps blood throughout the body.
Lymph is tissue fluid that enters lymph vessels. It returns excess tissue fluid to the blood, carries absorbed fats from the intestine and helps defend the body through immune cells.
Xylem carries water and minerals mainly upward from roots. Phloem carries food from sources to places where it is used or stored, and transport can occur in either direction.
Transpiration is the loss of water vapour from aerial parts of a plant. It helps cool the plant and creates transpiration pull, which helps draw water and minerals upward through xylem.
Glomerular filtration, selective reabsorption and tubular secretion.
- Ureter: carries urine from kidney to bladder.
- Urethra: carries urine out of the body.
- Glomerulus: filters blood.
- Nephron tubule: reabsorbs useful substances and water and helps secretion of wastes/ions.
They release gases through stomata and other openings, lose excess water by transpiration, store wastes in leaves or bark that may be shed, store substances such as gums and resins, and may release some wastes into the soil.
7. Important Terms at a Glance
| Term | Easy meaning |
|---|---|
| ATP | A molecule cells use to transfer usable energy. |
| Stomata | Tiny pores on leaves for gas exchange and water-vapour loss. |
| Chlorophyll | Green pigment that absorbs light energy. |
| Pseudopodia | Temporary finger-like projections of Amoeba for movement and feeding. |
| Cilia | Short hair-like structures that move Paramecium and direct food. |
| Peristalsis | Wave-like contraction and relaxation that pushes food through the alimentary canal. |
| Alveoli | Tiny air sacs in lungs where gases are exchanged. |
| Haemoglobin | Protein in red blood cells that carries oxygen. |
| Transpiration | Loss of water vapour from plant aerial parts. |
| Translocation | Movement of food through phloem. |
| Nephron | Structural and functional unit of the kidney. |
| Dialysis | Artificial removal of wastes and excess substances from blood when kidneys cannot do so adequately. |
Picture links in these notes point to Wikimedia Commons. Images load from the internet, so they require an internet connection. If a particular image does not display, use the linked Commons category beside it to select another suitable diagram.