B3 food and ecosystems

• what two things join together in an enzyme reaction like a 'lock and key ' model


  Substrate and Active Site
• What can become denatured to the enzyme doesn't work?

  active site
• What 3 things affect the rate of reaction?

  temperature, ph, and substrate concentration
• What is an example of a plant that does photosynthesis?


  Green Algae
• What is the word equation for photosynthesis?


  carbon dioxide + water = glucose + oxygen
• What is the symbol equation for photosynthesis?

  6CO2+ 6H20-L-I-G-H-T-C6H12O6+6O2
• what test shows whether photosynthesis is happening or not?


  starch test
• what 3 things affect rate of photosynthesis?

  light intensity, concentration of co2 and temperature
• how would you measure rate of photosynthesis?


  using pondweed and counting bubbles.
• Describe the process of measuring rate of photosynthesis

  put pondweed in a flask in water for a set amount of time, count how many bubbles are produced. Repeat this experiment but use a light source/ dark room/ outside/ inside to show how these factors affect the rate of photosynthesis
• what is diffusion?


  movement of particles from areas of higher concentration to areas of lower concentration
• what is osmosis?


  movement of water molecules across a partially permeable membrane from higher water concentration to lower water concentration
• what is active transport


  movement of particles across a membrane against the concentration gradient from an area of lower concentration to higher. It uses energy
• how are plants roots adapted to taking up water and mineral ions from the soil

  root hair - millions of tiny hairs that provide a large surface area to absorb maximum water
• how can you investigate diffusion?


  get some agar jelly made up of phenolphthalein and dilute sodium hydroxide. Add some hydrochloric acid to the beaker and cut and measure cubes of jelly. time how long it takes the jelly to turn colourless as the acid diffuses into agar jelly. use a stopwatch. vary the concentration of acid and see how it affects the rate of diffusion.
• what is the practical for osmosis?


  potato chunks in sugar solution water, weigh mass of chunks before and after and see if osmosis has occurred. Put one chunk in sugar water and the other in pure water, see how this affects the rate of osmosis.
• What is the role of the Phloem?


  transport food substances, made from living cells and have perforated end plates that allows stuff to enter through. It transports food substances both up and down the stem for growing and storage tissues. This is known as translocation. Sugars enter the phloem by active transport. They are then pushed around by water, which enters the phloem by osmosis
• Xylem


  takes water and ions up. made from dead cells joined end to end with no connecting cell and a lumen down the middle. thick walls are made from cellulose. Strong and stiff which gives support. cell walls are also strengthened by a material called lignin. carries water up the stem to the leaves in the transpiration stream
• What is transpiration


  loss of water from the plant. caused by evaporation and diffusion of water from plant's surface. this creates shortage of water at the leaves which is the why the xylem needs to bring water back upwards to the plant. This is how there is a constant transpiration stream through the plant
• Stomata

  stomata opens and closes dues to guard cells. When guard cells are turgid (swollen with water) the stomata opens whereas when the guard cells are flaccid, the stomata is closed. water moves into the guard cells by osmosis. They allow water vapour to escape during transpiration and also allow co2 and oxygen to diffuse in and out of the cell
• How would you view stomata, xylem and phloem?


  under a microscope- paint two thin layers of nail varnish onto a designated leaf, put a piece of clear sticky tape on top and peal off the varnish slowly. Stick the tape with the varnish onto a microscope slide.
• what would you use to see structure of xy and phlo?

  light microscope
• what 3 things affect transpiration rate?

  increase in light intensity, temperature and air movement
• What can you measure to estimate transpiration rate?

  loss in mass
• What else can you measure to estimate transpiration rate?

  measuring water uptake
• what is the equation for percentage change

  final-initial/initial x 100
• what can you use to measure water uptake?

  potometer- cut a shoot underwater at a slant. make sure no air can enter. sealed tightly with a cap. dry the leaves, allow time for the shoot to acclimatise and then shut the tap. remove the end of the tube until one bubble has formed then put it back into water. record starting position of bubble. start a stopwatch and record the distance moved by the bubble per minute. make sure to keep conditions constant
• what are some examples of abiotic factors that affect an environment

  toxic chemicals and environmental conditions
• what are examples of biotic factors that affect an environment

  availability of food and number of predators and presence of pathogens
• what could you use to study the distribution of small organisms

  quadrat
• what method could you use to estimate population size?

  capture-mark-release-recapture
• what is the equation for population size?

  number in first sample x number in second sample / number in second sample previously marked
• what is used to identify creatures?

  keys and questions
• what would you use to measure distribution?

  transects- when you sample along the length of a transect using a quadrat, this is called a belt transect.
• what are the steps of a belt transect?


  mark out a line in the area you want to study using a tape measure. place a quadrat at the start of the line and count and record how many organisms you find. Then move it down the line for a distance pre decided e.g 2m down the line. repeat this many times and record results
• percentage cover


  e.g if 4/10 squares have organisms in, it is 40% covered. Remember if a square is more than half covered then you count it.
• How would you measure abiotic factors?

  temperature - thermometer

  moisture - soil moisture meter

  light intensity - light meter

  soil ph - indicator liquid
• If you find stonefly larvae in a river, it indicates that a river is clean. Blood worms and sludge worms indicate highly polluted water
• if the air is clean and not polluted, then lots of lichen will be present, especially bushy lichen, whereas crusty lichen do not need cleaner air
• You can catch organisms to test for pollution and other thing in the water by a net or in the air.