simplified and sorted

• Life processes


  Maintenance functions of living organisms that must go on even when they are not doing anything particular
• Living organisms must keep repairing and maintaining their structures made up of molecules
• Maintenance processes in living organisms

  • Nutrition
  • Respiration
  • Excretion
  • Transportation
• Autotrophs


  Organisms that use simple food material obtained from inorganic sources in the form of carbon dioxide and water
• Heterotrophs


  Organisms that utilise complex substances and have to break them down into simpler ones before they can be used for the upkeep and growth of the body
• Photosynthesis


  1. Absorption of light energy by chlorophyll

  2. Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen

  3. Reduction of carbon dioxide to carbohydrates
• Chloroplasts contain chlorophyll which is essential for photosynthesis
• Stomata are tiny pores on the surface of leaves that allow for gaseous exchange for photosynthesis
• Guard cells control the opening and closing of stomatal pores
• Plants take up water, nitrogen, phosphorus, iron and magnesium from the soil for growth
• Heterotrophic nutrition


  Organisms break down food material outside the body and then absorb it, or take in whole material and break it down inside their bodies, or derive nutrition from plants or animals without killing them
• Single-celled organisms can take in food using the entire surface, but in complex organisms different parts become specialised to perform different functions in obtaining nutrition
• Organisms that break-down food material outside the body and then absorb it

  • Fungi like bread moulds, yeast and mushrooms
• Organisms that derive nutrition from plants or animals without killing them (parasitic nutritive strategy)

  • Cuscuta (amar-bel), ticks, lice, leeches and tape-worms
• How organisms obtain their nutrition

  1. Food is taken in by the entire surface (single-celled organisms)

  2. Different parts become specialised to perform different functions (complex organisms)
• Nutrition in Amoeba


  1. Food taken in using temporary finger-like extensions of the cell surface

  2. Food particle enclosed in a food-vacuole

  3. Complex substances broken down into simpler ones

  4. Remaining undigested material moved to the surface and thrown out
• Nutrition in Paramoecium


  1. Food taken in at a specific spot

  2. Food moved to this spot by the movement of cilia covering the entire surface
• Nutrition in human beings

  1. Food crushed with teeth

  2. Food wetted with saliva

  3. Saliva contains enzyme salivary amylase that breaks down starch

  4. Food mixed thoroughly with saliva and moved around the mouth by tongue

  5. Peristaltic movements push food forward along the digestive tract

  6. Food enters stomach, mixed with digestive juices

  7. Food enters small intestine, digested by enzymes from liver and pancreas

  8. Digested food absorbed by intestinal villi

  9. Unabsorbed food enters large intestine, water absorbed, waste removed through anus
• Dental caries


  Gradual softening of enamel and dentine caused by bacteria acting on sugars to produce acids
• Brushing teeth after eating removes plaque before bacteria produce acids
• If untreated, microorganisms may invade the pulp, causing inflammation and infection
• Respiration


  1. Break-down of glucose into pyruvate in cytoplasm

  2. Pyruvate converted to ethanol and CO2 (anaerobic respiration)

  3. Pyruvate broken down using oxygen to give CO2 and H2O (aerobic respiration)

  4. Energy released used to synthesise ATP
• ATP


  Energy currency for most cellular processes, energy released when terminal phosphate linkage is broken
• Gas exchange in plants

  1. Gases exchanged through stomata by diffusion

  2. At night, CO2 elimination is major exchange activity

  3. During day, CO2 used for photosynthesis, oxygen release is major event
• Gas exchange in aquatic animals

  1. Oxygen dissolved in water absorbed through gills

  2. Rate of breathing much faster than terrestrial organisms due to lower dissolved oxygen
• Gas exchange in terrestrial animals

  1. Oxygen from atmosphere absorbed by specialised organs

  2. Organs have structure to increase surface area in contact with oxygen-rich atmosphere

  3. Air taken in and out through passages to protect delicate exchange surface
• In human beings, air taken into the body through the nose and mouth
• Dissolved oxygen


  Amount of oxygen dissolved in water is fairly low compared to the amount of oxygen in the air
• Breathing rate


  In aquatic organisms, the rate of breathing is much faster than that seen in terrestrial organisms
• How fish take in oxygen

  1. Take in water through mouth

  2. Force water past gills

  3. Dissolved oxygen taken up by blood
• Respiration in terrestrial organisms

  Use oxygen in the atmosphere
• Respiratory organs in terrestrial organisms

  • Have a structure that increases the surface area in contact with the oxygen-rich atmosphere
  • The exchange surface is fine and delicate
  • Placed within the body with passages to take air to this area
  • Mechanism for moving air in and out of this area
• Human respiratory system


  1. Air taken in through nostrils

  2. Air filtered by fine hairs and mucus

  3. Air passes through throat and into lungs

  4. Rings of cartilage in throat prevent air passage from collapsing

  5. Air passage divides into smaller tubes terminating in alveoli

  6. Alveoli provide surface for gas exchange

  7. Alveoli walls have blood vessels

  8. Breathing in expands chest cavity, drawing air into lungs

  9. Blood brings CO2 to alveoli, O2 taken up by blood
• Lungs always contain a residual volume of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released
• Respiratory pigments


  Take up oxygen from the air in the lungs and carry it to tissues which are deficient in oxygen before releasing it
• Haemoglobin


  Respiratory pigment in humans with high affinity for oxygen, present in red blood cells
• Carbon dioxide transport


  More soluble in water than oxygen, mostly transported in dissolved form in blood
• If diffusion were to move oxygen in our body, it would take 3 years for a molecule of oxygen to get to our toes from our lungs
• The alveolar surface in the lungs, if spread out, would cover about 80 m2
• Smoking destroys the cilia in the respiratory tract, allowing germs, dust, smoke and other harmful chemicals to enter the lungs and cause infection, cough and even lung cancer