biology

• biotic factors are living factors
• abiotic factors are non-living factors
• biomass is the mass of material in a living organism
• arrows in food chain show transfer of energy
• producers trap light during photosynthesis and transfer to other animals
• the sun is the source of energy in food chains and webs
• the nucleus controls activities in the cell contains genetic information
• cytoplasm is a jelly like fluid in which most chemical reactions occur
• cell membrane controls the passage of substances in and out of the cell (selective permiability )
• mitochondria are organelles in the cell that are the site for cell respiration
• cell walls made of cellulose strengthens cells and give support (full permiability )
• chloroplasts contain the green pigment chlorophyll, which absorbs light energy to make food by photosynthesis
• a permenant vacoule filled with cell sap , contains salts and sugars , which is important to the cells rigid and to support the plant
• bacteria are single celled living organism (unicellular)
• bacteria cell are much smaller then animal and plant cells
• bacteria cells are 0-00.1mm lengths
• bacteria cells contain:

  cell membrane

  cell wall (non-cellulose)

  cytoplasm

  plasmid
• a plasmid is a ring of DNA that floats in cytoplasm
• some bacteria have slim capsules or flagella (tails) to help them move around
• large multicellular organisms have to overcome problems linked to their size , the bigger the organism the more difficult exchanging and transporting substances between cells
• cells-> tissues-> organs-> organ systems-> organisms
• tissues are made of a group of similar cells that carry out a particular function
• an organ is made up of diffrent tissues all working together
• photosynthesis is an endothermic reaction
• light energy

  carbon dioxide + water----------->glucose + oxygen

  chlorophyll
• light energy

  6Co2 + 6H2o -------------->c6h12o6 = 6o2

  chlorophyll
• leaf structure adaptations:

  each leaf is not in shade of another

  leaves are thin to ensure all cells recieve light

  large surface area for light to fall on leaf

  xylom vessel carries water to leaf
• diffusion is the movement of molecules from an area of high concentration to an area of low concentration down a concentration gradient
• Leaf Structure adaptation

  • Palisade leaf is not in shade of another
  • Leaves are thin to ensure all cells receive light
  • Large surface area for light to fall
• Xylem vessel

  Carries water to leaf
• Diffusion

  The movement of molecules from an area of high concentration to an area of low concentration, down a concentration gradient
• Functions of sections of a leaf

  • Waxy cuticle - physical defence that is transparent and waterproof
  • Upper and lower epidermis - cells have cell walls to act as a physical barrier
  • Palisade mesophyll - main site for photosynthesis (contains cells with many chloroplasts)
  • Spongy mesophyll - main gas exchange surface (lots of air space)
  • Intercellular air space - allows rapid diffusion of gas from palisade to stomata (found in spongy mesophyll)
  • Guard cells - control opening and closing of stomata (found in lower epidermis)
  • Stomata - allows gases to enter and leave the leaf, can be closed to stop water evaporation
• at dawn and dusk the rate of photosynthesis and respiration are equal (compensation point )
• the movement of co2 and oxygen can be determined using hydrogen carbonate indicator
• at normal atmospheric carbon dioxide levels hydrogen carbonate indicator is bright red as the rate of photosynthesis and respiration are equal
• in bright light hydrogen carbonate indicator turns purple because the rate of photosynthesis is greater then the rate of respiration causing carbon dioxide levels to decrease
• in darkness hydrogen carbonate indicator turns yellow because photosynthesis has stopped and respiration continues to produce carbon dioxide causing carbon dioxide levels to increase
• we need food for energy, protection, growth
• a balanced diet is a diet that contributes the correct levels of each food group
• carbohydrates are made up of carbon, hydrogen and oxygen