Science

• Multicellular organism


  An organism made up of many types of cell
• Cell


  The smallest unit of an organism
• Tissue


  Group of similar cells that work together to perform a particular function
• Organ


  Group of different tissues working together to carry out a job
• Organ system


  Group of different organs that work together to perform a certain function
• Organism


  Group of organ systems that make an individual
• Hierarchical organisation: Cell -> Tissue -> Organ -> Organ system -> Organism
• Flower


  The reproductive organ of most plants
• Structure of a flower

  • Sepals
  • Stamens
  • Anthers
  • Stigma
  • Ovary
• Sepals


  Protect the unopened flower
• Stamens


  The male parts of the flower (each consists of an anther held up on a filament)
• Anthers


  Produces pollen (male gametes)
• Stigma


  The top of the female part of the flower which collects pollen grains
• Ovary


  Produces the female sex cells contained in the ovule
• The flower is involved in sexual reproduction as it allows for fusion of gametes (pollen and egg) to produce seeds
• Pollination


  Pollen from one flower is transferred to the stigma of another flower
• Methods of pollination


  • Insects
  • Wind
• Insect pollination


  • Petals may be brightly coloured and scented to attract insects
  • Nectary produces sugary nectar to attract insects
  • Pollen is sticky or spikey to attach to insects
• Wind pollination


  • Stamen has long filaments and loose anthers to release pollen into the wind
  • Stigma is outside of flower with feathery structure to catch passing pollen
  • Pollen is smooth and light to be easily carried by the wind
• Methods of seed dispersal


  • Wind
  • Roll or float
  • Animals (outside)
  • Animals (inside)
  • Self-propelled
• Wind dispersal


  • Seeds have lightweight parts, wings or parachutes
• Roll or float dispersal


  • Seeds have a round or buoyant structure to allow them to travel over land or water
• Animal (outside) dispersal


  • Seeds have hooks that attach them to the fur of passing animals
• Animal (inside) dispersal


  • Seeds are surrounded by brightly coloured and tasty fruits. These are eaten by animals, the seeds pass through undamaged and deposited far away.
• Self-propelled dispersal


  • Seeds have pods that burst due to pressure or elasticity and send the seeds
• Plants compete for water, space, light, and minerals in the soil
• Seed dispersal reduces competition between plants of the same species and allows more growth
• Structure of a seed


  • Embryo
  • Food store
  • Seed coat
• Embryo


  The young root and shoot that will become the adult plant
• Food store


  Starch for the young plant to use until it can carry out photosynthesis
• Seed coat


  A tough protective outer covering
• Germination


  Seed begins to develop into a new young plant
• Factors needed for successful germination


  • Water
  • Oxygen
  • Warmth
• Light is not needed for germination
• Germinating seeds use their food stores until the seedlings can produce their own food by photosynthesis
• Water


  Lets the seed swell and the embryo start to grow
• Oxygen


  Needed for aerobic respiration
• Warmth


  Increases growth rate but very high temperatures will damage seeds
• Factors plants compete for


  • Water
  • Space
  • Light
  • Minerals in the soil
• Plants compete for water


  For photosynthesis, to produce glucose eventually used for growth