Practicals Flashcards
How and when are quadrats used to measure population of a species?
- Typically used for non moving species; e.g. plants
- Can be Random sampling (avoids bias)
- This can be done by using a tape measure to plot out the habitat as a grid and using a random number generator to plot coordinates
- A large number of quadrats will be randomly placed throughout the habitat to ensure the data collected is reliable
- Can also be non random= Systematic sampling
- Quadrats can be placed one next to each other along a transect.
- Used wherever there is an environmental gradient i.e. the abiotic factors change gradually from one end of the sample to the other
How can different types of transects be used to measure distribution of a species?
Line transect - a tape measure is placed along the line and any species which touch the tape measure will be recorded.
Belt transect - quadrats are placed along the transect one after another, so that each quadrat is touching
Interrupted transect - quadrats are placed at regular intervals along the transect
Describe practical investigating photosynthesis with chloroplast extract
1) Remove 2-3 leaves from a plant and add cold isolation solution. Grind the leaves into the solution using a pestle and mortar.
2) Filter to remove the leafy pieces and centrifuge the filtrate at high speed for 10 minutes.
3) Pour off the liquid so that you just have the solid pellet. Re-suspend in cold isolation solution to form the chloroplast extract. Store on ice until ready to use.
4) Zero a colorimeter using a cuvette just containing chloroplast extract and distilled water.
5) Add a certain volume of chloroplast extract to a series of test tubes. Place a lamp at a certain distance from the tubes.
6) Add a certain volume of DCPIP to each test tube and mix.
7) Straight away, take a sample from the mixture and transfer into a new cuvette. Record its absorbance using the colorimeter. Repeat every 2 minutes for the next 10 minutes.
8) Repeat two more times and calculate a mean absorbance for each time interval.
Describe practical investigating effect of temperature on seedling growth
1) Take seedlings of the same age and plant variety and plant in five trays containing soil. Measure the initial height of each seedling.
2) Place each of the five trays in an incubator set to a different temperature (e.g. 12oC, 16oC, 20oC, 24oC, 28oC)
3) Leave for one week and measure the increase in height of each
4) Calculate growth rate by dividing the change in height by the growth time
Describe practical investigating effect of temperature on brine shrimp hatch rate
1) Place 2g of sea salt in a beaker of 100cm of dechlorinated water
2) Put some brine shrimp eggs on a piece of paper, use wet graph paper to pick them up
3) Use a magnifying glass to count out 40 eggs
4) Place the graph paper into the water and leave until all eggs have dehatched
5) Repeat for 5 beakers
6) Incubate at 0, 5, 15, 25 and 30C, mimicking conditions in the wild
7) Shine a bright light on the beaker to draw hatched larvae towards the light and remove with a pipette
8) Return to incubator and continue counting hatched larvae every 24 hours for a week
Describe practical investigating the effect of temperature on an enzyme-controlled reaction
1) Grind known mass of peas in distilled water + place in boiling tube
2) Add 5cm^3 of hydrogen peroxide to peas
3) Fit the syringe into delivery tube + place delivery tube into boiling tube with bung
4) Place into a water bath of a known temperature
5) Measure volume of gas produced at regular intervals (every 30 second for 5 minutes)
6) Repeat at different temperatures
What is Q10?
Tells us how much reaction rate changes when the temperature is raised by 10 degrees
e.g. at 2, means rate doubles for every 10C increase
How is Q10 calculated?
Rate of reaction at temperature T+10 degrees / rate at temperature T degrees
