Ecology 2 Flashcards
What is a quadrat?
- a square that is divided into smaller squares
- it is used to estimate a population
How do we avoid being biased when measuring populations of an area?
whe sampling, we use coordinates and a random number generator
Describe how we can estimate populations?
- find the area of your quadrat
- find the area of your site
- divide the area of the site by the area of the quadrat - this is your ‘multiplication factor’
- place the quadrat randomly
- count and record the number of organisms
- take at least 10 samples
- work out the mean number of organisms in each quadrat
- multiply up to estimate the total number in the site
What is the percentage cover method?
- quadrats are places and the number of little squares that are covered by plants are counted
- only count squares more than half covered and estimate the others
- divide the total number of squares and multiply by 100 to give a percentage
How can we improve accuracy when measuring populations?
- bigger quadrats
- more quadrats
- random sample sites
Describe the practical on how the temperature effects the rate of decay
1) add phenolphthalein to a boiling tube and with 5 cm^3 milk - indicator that will change in pH
2) add 7 cm^3 sodium carbonate solution to the milk tube - to make sure the mixture is alkali
3) put the tubes in a beaker of 10 degrees celsius and leave for 5 minutes - to make sure all the reagents are at the right temperature
4) add lipase to the milk mixture and start the stopwatch, time until the colour changes from purple to yellow - tell us the rate of reaction
5) repeat steps 1-5 using temperatures of 20- 60 degrees celsius going up 10 degrees celsius each time - temperature is our independent variable
6) keep the volume of lipase the same (1 cm^3), the volume of milk (5 cm^3) the same and the number of drops of indicator the same - they are control variables to ensure the results are valid
