Biology IGCSE

• MRS GREN


  Characteristics of living organisms: Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, Nutrition
• Movement


  An action by an organism or part of an organism causing a change of position or place
• Respiration


  The chemical reactions in cells that break down nutrient molecules and release energy for metabolism
• Sensitivity


  The ability to detect and respond to changes in the internal or external environment
• Growth


  A permanent increase in size and dry mass
• Reproduction


  The processes that make more of the same kind of organism
• Excretion


  The removal of the waste products of metabolism and substances in excess of requirements
• Nutrition


  The taking in of materials for energy, growth, and development
• Species


  A group of organisms which can reproduce to produce fertile offspring
• Sequence of classification


  • Kingdom
  • Phylum
  • Classes
  • Orders
  • Families
  • Genus
  • Species
• Binomial System of Naming Species


  The scientific name of an organism comprises two parts showing the genus and 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
• Dichotomous keys


  Use visible features to classify organisms, giving a choice of two features to follow until the organism is narrowed down to its genus and species
• Syllabus 1.2.4: Ensure you can construct and use dichotomous keys based on identifiable features
• The Five Kingdoms


  • Animals
  • Plants
  • Fungi
  • Prokaryotes
  • Protocists
• Animals


  • Multicellular ingestive heterotrophs (eat living organisms)
  • Examples: cat, ladybird, newt
• Plants


  • Multicellular photosynthetic autotrophic (make their own food) organisms with a cellulose cell wall and chloroplasts
  • Examples: cactus, oak tree
• Fungi


  • Single-celled or multicellular heterotrophic and saprotrophic organisms with cell walls not made of cellulose, spread by spreading spores in moist/dark/warm environments, most have hyphae and mycelium in structure
  • Examples: yeast, mushrooms
• Prokaryotes


  • Single-celled organisms with no true nucleus or DNA in the cytoplasm, many also have plasmids
  • Examples: E.coli, Salmonella
• Protocists


  • Single-celled organisms with a nucleus, eukaryotes, some are multicellular
  • Examples: Amoeba, seaweed
• Guidance: For this section, learn the five kingdoms' main features
• Main Features of All Animals

  • Multicellular
  • Contains a nucleus but no cell walls or chloroplasts
  • Only feed on organic substances made by other living things
• Mammals


  • Fur/hair on the skin
  • External ears (pinna)
  • Internal fertilisation, giving the birth of young
  • Mammary glands
• Reptiles


  • Thick, dry, scaly skin
  • Usually four legs
  • Internal fertilisation, conception from egg
  • Soft eggs
• Fish


  • Wet scales
  • Streamlined body shape
  • External fertilisation and soft eggs
  • Uses gills to breathe
• Amphibians


  • Smooth, moist skin
  • External fertilisation and soft eggs
  • Gills & Lungs can live on land and water
  • Most have four legs
• Birds


  • Feathers on body and scales on legs
  • Constant internal body temperature
  • Hard eggs
  • Internal fertilisation, birth through eggs
• Syllabus 1.3.3: You must be able to classify organisms using the features identified above
• Arthropod Features


  • Exoskeleton
  • Jointed legs
  • Segmented body
• Crustaceans


  • Have an exoskeleton, one pair of compound eyes
  • Two body segments – cephalothorax, abdomen
  • More than four pairs of legs (10-14 legs)
• Arachnids


  • Two body segments – cephalothorax and abdomen
  • Four pairs of legs (8 legs)
• Myriapods


  • Segmented body
  • One pair of antennae
  • 10+ pairs of legs – 1 or 2 pairs on each segment
• Insects


  • Three body segments – head, thorax and abdomen
  • Three pairs of jointed legs (6 legs)
  • One pair of antennae
  • 1 or 2 pairs of wings
• Ferns


  • Do not produce flowers/seeds
  • They are plants with roots, stems and feathery leaves
  • Reproduce by spores
• Flowering Plants

  • They are plants with roots, stems and leaves
  • Reproduce sexually by means of flowers and seeds
  • Seeds are produced inside the ovary in the flower
• Monocotyledons

  • One cotyledon/One-seed leaf
  • Parallel veins
  • Long Narrow Leaf
  • 3 Flower Parts
  • Scattered Vascular Bundles
• Dicotyledons

  • Two cotyledons/Two-seed leaf
  • Branching veins
  • Broad leaves
  • 4 or 5 Flower Parts
  • Ringed Vascular Bundles
• Viruses are not part of any classification system due to not being considered living things