CBSE Class 10 Science Life Processes Notes Set 06

TOPICS

•  What are Life Processes?
•  Nutrition
•  Respiration
•  Transportation
•  Excretion

Weightage Xtract

• Maximum total weightage is of Topic 5.2 Nutrition.
• Maximum MCQ, VSA and SAI type questions were asked from Topic 5.2 Nutrition.
• Maximum SA II type questions were asked from Topic 5.2 Nutrition and Topic 5.4 Transportation.
• Maximum LA type questions were asked from Topic 5.3 Respiration, Topic 5.4 Transportation and Topic 5.5 Excretion.

QUICK RECAP

Living organisms : All the plants and animals (including human beings) are alive or living organisms. All living organisms have some common characteristics which make them different from non-living things.

Characteristics of living organisms:

• They can move by themselves.
• They need food, air and water.
• They can grow.
• They can reproduce and can have young ones.
• They respire (release energy from food).
• They excrete (get rid of waste materials from their body).
• They can respond to changes around them and they are sensitive.

Nutrition

It is defined as the process of intake of nutrients such as carbohydrates, fats, proteins, etc., and their utilisation by an organism for various biological activities.

Modes of nutrition

Autotrophic: A kind of nutrition in which the organisms prepare (or synthesise) their own organic food by utilising the inorganic raw materials present in their surroundings. It is found in green plants.

Heterotrophic: A kind of nutrition in which the organisms derive energy from the intake and digestion of the organic substances prepared by autotrophs and other organic sources.

• Saprotrophic: A kind of nutrition in which the organisms derive their nutrients from dead and decaying organic matter (such as rotten leaves, rotten bread, dead animals, household wastes, non-living organic matter present in the soil, etc.).
• Parasitic: A type of nutrition in which the organisms (or parasites) derive their nutrients or food from other living organisms without killing them. Parasitic mode of nutrition is observed in several fungi, bacteria, a few plants like Cuscuta and some animals like Plasmodium and roundworms.
• Holozoic: In this type of nutrition, an organism takes the complex organic food materials into its body by the process of ingestion. The ingested food is digested and then absorbed into the body cells of the organisms. Human beings and most of the animals have holozoic mode of nutrition.

Nutrition in plants

The process by which green plants make their own food (like glucose) from carbon dioxide and water by using sunlight in the presence of chlorophyll, is called photosynthesis. The process of photosynthesis can be represented as:

\[ 6CO_2 + 6H_2O \xrightarrow[\text{Chlorophyll}]{\text{Light energy}} C_6H_{12}O_6 + 6O_2 \]

• The process of photosynthesis takes place in the green leaves of a plant because they contain green pigment called chlorophyll in special cell organelles called chloroplasts. They have green coloured grana embedded in liquid hyaline stroma.
• The food prepared is in the form of simple sugar called glucose. Extra glucose is changed to a complex carbohydrate called starch for storage.
• Plants take carbon dioxide through tiny pores called stomata present on the surface of leaves.
• Water is absorbed from the soil by the roots of plants.

Mechanism of photosynthesis:

• Light reaction: Initiates when light falls on green leaves. Chlorophyll absorbs visible light and breaks water into hydrogen protons \( (H^+) \), electrons \( (e^-) \) and evolves molecular oxygen \( (O_2) \). This is called photolysis. Electrons and protons are used in the production of assimilatory power in the form of NADPH and ATP. This step occurs in the granum.
• Dark reaction: The assimilatory power is used to utilise carbon dioxide \( (CO_2) \) for the production of carbohydrate. This is an enzymatic process occurring in the stroma.

Nutrition in animals

Depending upon food habits, holozoic animals are classified into 3 categories:

• Herbivores: Eat only algae or plant materials (cow, rabbit, goat, etc.).
• Carnivores: Eat only flesh of other animals (lion, tiger, frog, etc.).
• Omnivores: Eat both plants and other animals (man, sparrow, crow, etc.).

Five steps in animal nutrition:

• Ingestion: Taking food into the body.
• Digestion: Breaking down large, insoluble molecules into small, water-soluble molecules.
• Absorption: Digested food passes through the intestinal wall into the blood stream.
• Assimilation: Absorbed food is used by body cells for energy, growth and repair.
• Egestion: Removal of undigested food from the body.

Nutrition in Amoeba: Amoeba obtains food through phagocytosis by forming pseudopodia to form a food vacuole.

Nutrition in human beings

The human digestive system consists of an alimentary canal and many digestive glands.

• Mouth: Passage for ingestion; guarded by soft movable lips.
• Buccal (Oral) cavity: Contains teeth and tongue. Three pairs of salivary glands secrete saliva containing enzyme ptyalin (salivary amylase), which splits starch into maltose.
• Pharynx: funnel-shaped vertical canal serving as a passage way for food.
• Oesophagus: tubular structure that carries food to the stomach via peristaltic movement.
• Stomach: C-shaped muscular sac. Secretes gastric juice (HCl, pepsin and mucus). HCl makes the medium acidic for pepsin to break down proteins into peptones.
• Small intestine: Longest part (6 metres). Receives secretions from liver (bile) and pancreas (pancreatic juice). Bile emulsifies fats. Villi increase the absorptive surface area.
• Large intestine: Consists of colon and rectum. Absorbs water and collects undigested food as faeces to be expelled via the anus (egestion).

Respiration

The process of releasing energy from food is called respiration.

• Breathing: Physical process of taking in air rich in oxygen and expelling air rich in carbon dioxide.
• Cellular respiration: Oxidation of respiratory substrate (mainly glucose) inside cells to release energy (ATP).
  • Aerobic respiration: Breakdown in presence of oxygen. Occurs in cytoplasm (glycolysis) and mitochondria (Krebs' cycle).
    \( \text{Glucose} \xrightarrow{\text{Glycolysis}} \text{Pyruvic acid} \xrightarrow{\text{Krebs' cycle}} CO_2 + H_2O + \text{Energy} \)
  • Anaerobic respiration: Breakdown in absence of oxygen. In yeast, it produces ethanol, \( CO_2 \) and energy.
    \( \text{Glucose} \xrightarrow{\text{Glycolysis}} \text{Pyruvic acid} \xrightarrow{\text{In yeast}} C_2H_5OH + CO_2 + \text{Energy} \)

Respiratory system in human beings: Includes nostrils, nasal cavities, pharynx, larynx, trachea, and a pair of lungs containing alveoli for gas exchange.

Pathway of air: External nares \( \to \) Nasal cavities \( \to \) Internal nares \( \to \) Pharynx \( \to \) Glottis \( \to \) Larynx \( \to \) Trachea \( \to \) Bronchi \( \to \) Bronchioles \( \to \) Alveolar ducts \( \to \) Alveoli.

Mechanism of Breathing

• Breathing in (Inhalation): Rib muscles contract (rib cage moves up and out), diaphragm contracts (moves downward). Chest cavity space increases, air is sucked into lungs.
• Breathing out (Exhalation): Rib muscles relax (rib cage moves down and in), diaphragm relaxes (moves upward). Chest cavity space decreases, air is pushed out.

Respiration in other organisms

• Fish: Use gills to extract oxygen dissolved in water.
• Earthworm: Absorbs oxygen through its moist skin.
• Amoeba/Paramecium: Breathe through cell membranes.
• Insects: Use spiracles and tracheae.
• Plants: Use stomata (stems and leaves) and roots (diffusion from soil) for respiration.

Transportation

Life process in which a substance synthesised or absorbed in one part is carried to other parts of the body.

Transportation in human beings

Consists of blood vascular system and lymphatic system.

• Blood: Red connective tissue containing haemoglobin.
  • Plasma: Liquid part (90% water) containing proteins, food, and wastes.
  • Red blood cells (RBCs): Carry oxygen; lack nuclei.
  • White blood cells (WBCs): "Soldiers of the body"; fight infection.
  • Platelets: Tiny fragments involved in blood clotting.
• Blood Vessels:
  • Arteries: Thick-walled, carry blood away from the heart at high pressure.
  • Veins: Thin-walled, bring blood back to the heart at low pressure.
  • Capillaries: Narrow vessels where exchange of materials occurs.
• Human Heart: 4-chambered muscular pump. Upper chambers (atria), lower chambers (ventricles). Performs double circulation.
• Blood Pressure: Normal value is 120/80 (Systolic/Diastolic) mm Hg.

Lymphatic system: Transports lymph (extracellular fluid) from tissues back to the blood circulatory system. Lymph contains lymphocytes for immunity.

Transportation in plants

• Transportation of water and minerals: Conducted by xylem (vessels and tracheids). Driven by ascent of sap (root pressure) and transpiration pull.
• Transportation of food (Translocation): Conducted by phloem (sieve tubes and companion cells). Organic solutes move from leaves to other parts using energy.

Excretion

Biological process of removal of toxic wastes from the body. Osmoregulation maintains water and ionic balance.

Excretion in human beings

Consists of a pair of kidneys, ureters, urinary bladder and urethra.

• Nephron: Functional unit of the kidney.
  • Glomerulus: Filters blood (water, glucose, salts, urea pass through).
  • Tubule: Selective reabsorption of useful substances (glucose, amino acids) back into blood.
• Kidney Failure: Treated by dialysis (artificial kidney machine) or kidney transplant.

Excretion in plants

• Gaseous wastes (\( CO_2, O_2 \)) released through stomata and lenticels.
• Excess water removed by transpiration.
• Waste stored in cellular vacuoles, leaves that fall off, or as resins and gums in old xylem.