Biology IGCSE

• Movement


  An action by 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 or sense stimuli in the internal or external environment and to make appropriate responses
• Growth


  A permanent increase in cell number or size or both
• Reproduction


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


  Removal from organisms of the waste products of metabolism, toxic materials, and substances in excess of requirements
• Nutrition


  Taking in of minerals for energy, growth and development; plants require light, carbon dioxide, water and ions; animals need organic compounds and ions and usually need water
• An easy way to remember all the characteristics is MRS GREN:
• Characteristics of living organisms

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Living organisms are made of cells
• Plant cell


  • Cell wall
  • Nucleus
  • Cytoplasm
  • Chloroplasts
  • Vacuoles
  • Cell membrane
• Animal cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
• Plant cell walls are made of cellulose, a type of sugar
• Plant cells have a regular, tight arrangement and cell walls, while animal cells have more irregular shapes
• Nucleus


  Stores the cell's genetic material (DNA) and coordinates the cell's processes, including growth, some reactions, protein synthesis, and reproduction (cell division)
• Cytoplasm


  A clear, jelly-like fluid that supports and suspends the cell organelles and is the site for many metabolic reactions
• Cell surface membrane


  A double membrane that surrounds the cell, separates the contents from the environment, and is semi-permeable
• Cell wall


  A cellulose layer that surrounds the plant cell, giving it structure and shape, and preventing the cell from bursting when it absorbs water
• Chloroplasts


  A double-membraned organelle containing chlorophyll, which converts light energy into chemical potential energy for the cell
• Vacuoles


  Act as a store for nutrients and waste, keep contents separate from cytoplasm, store water to provide support and rigidity
• Ciliated cells


  • Have hair-like cilia that move in a wave-like motion to transport mucus out of the respiratory tract
• Root hair cells


  • Have long finger-like projections to increase surface area for absorption of water and ions
• Palisade mesophyll cells


  • Closely packed, tall, cuboidal cells near the top of leaves that carry out most photosynthesis, with many chloroplasts
• Red blood cells


  • Small, biconcave discs containing haemoglobin to efficiently transport oxygen
• Egg cells/Ovum


  • Female sex cells that fuse with male sex cells to form a zygote and develop into a new organism
• Somatic cells in humans have 46 chromosomes, while sex cells (gametes) have 23 chromosomes
• Sex cells


  In humans: ova and sperm

  In flowering plants: ova and pollen
• Somatic cells


  Body cells that contain a specific number of chromosomes for each species
• Humans have 46 chromosomes in their somatic cells
• Ploidy number


  The number of sets of chromosomes in a cell

  Somatic cells have 2n (diploid)

  Sex cells have 1n (haploid)
• When sex cells fuse, the resulting zygote has the correct number of chromosomes (2n)
• Ovum


  The largest human cell, visible to the naked eye, with layers of padding to protect the DNA
• Ovum


  • Surrounded by follicular cells (corona radiata)

  Surrounded by a jelly coat (zona pellucida) that acts as a barrier to sperm

  Cytoplasm (yolk) contains nutrients for the growing zygote
• Sperm


  Male gametes/sex cells that swim to the ovum to fertilize it
• Sperm


  • Nucleus with haploid DNA

  Tail (flagellum) to help it swim

  Large spiral mitochondrion to produce energy

  Acrosome vesicle with digestive enzymes to burrow through the jelly coat

  Streamlined shape for efficient swimming

  Small size to require less energy
• The process of fertilization can be watched in a video up to 4:07
• Magnification


  The ratio of image size to actual size, calculated using the formula: M = I/A
• Actual size (A)


  The real size of a biological specimen, calculated using the formula: A = I/M
• The syllabus requires using millimetres as units when calculating magnification and actual size
• Chemical elements that make up:

  • Carbohydrates: Carbon, Hydrogen, Oxygen

  Fats: Carbon, Hydrogen, Oxygen

  Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur, Phosphorus