bio

• Characteristics of living organisms:

  Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
• Sequence of classification


  • Kingdom
  • Phylum
  • Classes
  • Orders
  • Families
  • Genus
  • Species
• The classification of organisms helps show the evolutionary relationships between them
• Scientists also use the DNA base sequence to help classify organisms
• The similarity in DNA chains shows how closely related two organisms are
• The Five Kingdoms


  • Animals
  • Plants
  • Fungi
  • Prokaryotes
  • Protocists
• Guidance: For this section, learn the five kingdoms' main features
• Viruses are not part of any classification system due to not being considered living things
• New cells are produced by the division of existing cells
• Syllabus 2.1.3: You must be able to identify the cell structures in diagrams and images of plant, animal and bacterial cells
• Magnification does NOT have any units ('x 50' or 'x 5000')
• The diffusion of gases and solutes is important as without it, molecules that are needed for life, for example, glucose and oxygen for respiration, would not be able to get to the places they are required
• The role of water as a solvent in organisms to aid with digestion, excretion, and transport
• Carrier proteins are also used during active transport, embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient
• Active transport is needed when an organism wants to optimise the nutrients it can take up - ion uptake by root hair cells
• DNA

  • Chromosomes are made of a molecule called DNA
  • DNA is also called deoxyribonucleic acid
  • Each chromosome is a very long molecule of tightly coiled DNA
  • Two strands coiled together to form a double helix
  • Each strand contains chemicals called Bases
  • Cross-links between strands are formed by pairs of bases (A and T, C and G)
• pH on Enzymes


  • Enzymes are sensitive to pH
  • Some enzymes work best in an acid, and others in an alkaline
  • Enzymes work best at their optimum pH
• Optimum temperature for enzymes

  The temperature at which they work best, giving the fastest reaction ≈ at 37°C in animals & human bodies
• As temperature increases


  Molecules move faster, more effectively, and frequently collide
• Having more kinetic energy


  Makes them more likely to bind to active sites
• Denaturation of enzymes


  If the temperature is too high, enzyme molecules vibrate too vigorously; the enzyme loses shape and no longer binds with a substrate
• Effect of low temperature on enzymes

  There is not enough kinetic energy for the reaction, so it reacts too slowly
• Optimum pH for enzymes

  Enzymes work best at their optimum pH
• If the pH changes


  The hydrogen bond is broken, denaturing the enzyme, making it no longer fit with the substrate's active site; therefore, no reaction occurs
• Enzymes working in different pH conditions

  • Pepsin in acidic conditions, Amylase in neutral conditions and trypsin in alkalinity conditions
• Photosynthesis


  The process by which plants manufacture carbohydrates from raw materials using energy from light

  
• Carbon dioxide diffuses through the open stomata of a plant leaf, and water is taken up through the roots

  
• Chlorophyll


  A green dye that traps light energy and converts it into chemical energy to form carbohydrates and their subsequent storage
• Uses of the carbohydrates made in photosynthesis

  • Starch as an energy store
  • Cellulose to build cell walls
  • Glucose used in respiration to provide energy
  • Sucrose for transport in the phloem
  • Nectar to attract insects for pollination

  
• Investigation of light


  1. De-starch the plant by keeping it in darkness for 48 hours

  2. Place a stencil over part of a leaf

  3. Place the leaf in sunlight for 4-6 hours

  4. Remove the stencil and test for starch

  5. +ve result = parts which received light turn blue-black

  6. -ve result = parts which didn't receive light remain brown
• Investigation of carbon dioxide

  1. Take two de-starched potted plants

  2. Cover both the plants with bell jars and label them A and B

  3. Inside A, keep NaHCO3 (Sodium Bicarbonate). It produces CO2

  4. Inside B, keep NaOH (Sodium Hydroxide). It absorbs CO2

  5. Keep both set-ups in the sunlight for at least 6 hours

  6. Perform the starch test on both plants

  7. The leaves of Plant A will turn black after the starch test

  8. The leaves of Plant B will remain brown after the starch test

  
• Limiting factors


  Something present in the environment in such short supply that it restricts life processes
• As the amount of light increases


  The rate of photosynthesis increases
• Increasing the amount of light after a certain point


  Does not affect the rate, the limiting factor is now carbon dioxide or temperature
• Structures of a dicotyledonous plant leaf

  • Cuticle
  • Upper/Lower Epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Vascular Bundles
  • Xylem
  • Phloem
  • Stomata
• Processes of digestion


  • Ingestion

  Physical Digestion

  Chemical Digestion

  Absorption

  Assimilation

  Egestion
• Main organs of the alimentary canal

  • Mouth

  Salivary glands

  Oesophagus

  Stomach

  Small intestine (Duodenum, Ileum)

  Pancreas

  Liver

  Gall bladder

  Large intestine (Colon, Rectum)

  Anus
• Types of teeth


  • Incisors

  Canines

  Premolars

  Molars

  
• Structure of a tooth

  Enamel, Cement, Pulp, Dentine

  
• Digestive enzymes


  • Amylase

  Maltase

  Protease (Pepsin, Trypsin)

  Lipase