Biology IGCSE

• Characteristics of living organisms:

  • Movement: An action causing a change in position or place
  • Respiration: Chemical reaction in cells breaking down nutrient molecules and releasing energy
  • Sensitivity: Ability to detect and respond to changes in the environment
  • Growth: Permanent increase in size and dry mass
  • Reproduction: Process that makes more of the same kind of organisms
  • Excretion: Removal of toxic waste products from the body
  • Nutrition: Taking in materials for energy, growth, and development
• Species are groups of organisms that can reproduce to produce fertile offspring
• Binomial Naming System: Internationally agreed system naming species with 2 parts showing the genus and species
• Dichotomous key: Way of identifying an organism by pairs of statements leading to its name
• Animal Kingdom:

  • Have a nucleus, no cell wall or chloroplast
  • Feed on organic substances made by other living organisms
• Plant Kingdom:

  • Have a nucleus, cell walls made of cellulose, often contain chloroplasts
  • Feed by photosynthesis
  • Have roots, stems, and leaves (only some)
• Fungus Kingdom:

  • Usually multicellular, can be unicellular
  • Have nuclei and cell walls not made of cellulose
  • No chlorophyll
  • Feed by digesting waste organic material and absorbing it
• Protoctist Kingdom:

  • Multicellular or unicellular
  • Have a nucleus, may or may not have a cell wall and chloroplasts
  • Some feed by photosynthesis, others on organic substances made by other organisms
• Prokaryote Kingdom:

  • Usually unicellular
  • No nucleus
  • Have cell walls not made of cellulose
  • No mitochondria
  • Circular loop of DNA free in the cytoplasm
  • Often have plasmids
• Vertebrates in Animal Kingdom:

  • Fish, Amphibians, Reptiles, Birds, Mammals
• Invertebrates in Animal Kingdom:

  • Arthropods, Insects, Crustaceans, Arachnids, Myriapods
• Ferns:

  • Plants with fronds, no flowers
  • Reproduce by spores
• Flowering Plants:

  • Reproduce using flowers and seeds
  • Monocotyledons and Dicotyledons
• Viruses:

  • Not considered living organisms
  • Replicate inside living cells
• Cells:

  • Smallest unit from which all organisms are made
• Animal Cells:

  • Cell membrane, cytoplasm, vacuole, nucleus, chloroplasts, mitochondria, ribosomes
• Plant Cells:

  • Cell membrane, cell wall, cytoplasm, vacuole, nucleus, chloroplasts, mitochondria, ribosomes
• Bacterial Cells:

  • Unicellular, no nucleus, cell walls not made of cellulose, may have plasmids
• Specialised Cells:

  • Ciliated Cell, Neurone, Red Blood Cell, Sperm cell, Egg cell, Root hair cells, Palisade mesophyll cell
• Sizes of Specimens:

  • Magnification, micrometer, meter
• Diffusion:

  • Net movement of particles from higher to lower concentration
• Osmosis:

  • Diffusion of water molecules through a partially permeable membrane
• Active Transport:

  • Movement of molecules or ions through a cell membrane from lower to higher concentration using energy
• Carbohydrates, Fats, Proteins:

  • Carbohydrates: Starch, cellulose, sugar
  • Fats and Oils: Lipids, glycerol, fatty acids
  • Proteins: Amino acids, enzymes, antibodies, hemoglobin, keratin
• Structure of DNA:

  • Deoxyribonucleic acid, nucleotides, bases
• Biological Catalysts:

  • Catalysts increase the rate of chemical reactions and are not changed by the reaction
• Metabolic reactions within living organisms are controlled by catalysts called enzymes
• Enzymes are proteins that function as biological catalysts in metabolic reactions
• Different enzymes are needed for each kind of nutrient
• For example, Amylase digests starch into maltose
• Protease digests proteins into amino acids
• Catalase breaks down hydrogen peroxide to water and oxygen
• Enzymes can help break down substances or make larger molecules from small ones
• Enzymes are named according to the reaction they catalyze and often end with '-ase'
• Each type of enzyme has a specific shape with an active site where the substrate binds temporarily
• Enzymes work by allowing the substrate to fit into the active site, forming an enzyme-substrate complex
• Factors affecting enzyme activity include temperature and pH
• Enzymes have an optimum temperature and pH for maximum activity
• Temperature affects enzyme activity by increasing kinetic energy, but above the optimum, it can denature the enzyme
• pH affects enzyme activity by altering the enzyme's shape, leading to denaturation