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A2 Core practicals (Studying ecology (There are various different sampling…
A2 Core practicals
Studying ecology
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There are various different sampling techniques that you can use for this experiment. For example, frame quadrats can be used to investigate immobile populations like plants. Randomly place the quadrat on the ground and then place the light sensor on the top to measure the light intensity. Identify any plants within the grid and use a vernier caliper to measure the width of the plant. Repeat in areas of light and shade. To know the percentage cover of the plants, count the number of plant species within the quadratic. If it is a 10x10 quadrat then the number of squares counted will act as a percentage.
When using the transect to investigate distribution. If you are using a line transect, the number of plants touching the tape measure are measured.
Controls: temperature, water, humidity, soil, mineral content
Measuring abiotic factors: thermometer for temp, light intensity using a light sensor, rainfall using a rain gauge, humidity using a hygrometer
Effects of exercise on tidal volume, breathing rate etc
A spirometer has an oxygen filled chamber with a moveable lid as a person breathes into a tube the lid moves up and down and the movements are recorded on a rotating drum called a spirometer trace. Carbon dioxide is absorbed by soda lime so that there is only oxygen for the person to inhale from as this oxygen gets used up in respiration.
A person breathes into a spirometer for one minute at rest and recordings are taken. The person then exercises and they breath into a spirometer and recordings are taken again. The recordings are then compared.
Tidal volume: volume of air in normal breath Breathing rate: how many breaths in a minute, respiratory minute respiration: volume of gas breathed in or out in a min. Vital capacity is the maximum amount of air that can be expelled after deepest possible inhalation.
Exercise will increase the breathing volume and rate as there needs to be an increased rate of gas exchange and the body needs the oxygen for muscle contraction. Tidal volume will increase, breathing rate will increase, respiratory minute respiration will increase and so will vital capacity.
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Brine shrimp
Put an equal number of brine shrimps in water baths set at different temperatures. The number of hatched brine shrimp are recorded every 5 hours.
Controls: volume of water, water salinity, oxygen availability
Brine shrimp hatch rate: number of hatched brine shrimp in each water bath divided by the number of hours.
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Gel electrophoresis
There is agarose gel in a tray that has solidified and there are a row of wells at the end, put the gel into a gel box and put the row of wells nearest to the cathode and then add buffer solution. Use a micropipette to add the DNA samples to the wells - make sure the tip of the micropipette is in the solution and just above the opening of the gel, don't stick it in too far or the gel may Pearce. Use a clean micropipette head for each DNA sample. Record which DNA sample is in each well. Connect to a power supply and this will cause the DNA to separate according to length. Run for about 30 mins and then remove from box and remove excess buffer solution. Stain the DNA and the DNA fragments will become visible.
Rate of respiration: a respirometer measures the amount of oxygen taken up in a set period of time. Set up a tube with potassium hydroxide in it to absorb carbon dioxide with woodlice inside and attach a syringe to the top to set the fluid in the manometer. The apparatus is left for a set period of time and during that time there will be a decrease in the amount of oxygen due to oxygen consumption by the woodlice and this will cause the colored liquid in the manometer move, measure the distance of the liquid moved in a given time and this can be used to calculate the volume of oxygen used per minute
Controls: temp, volume of potassium hydroxide
Habituation: measure an animals response to an unimportant stimulus, this can be done with snails: gently brush something soft like a blade of grass along the surface of the snails skin, close to the tentacles and the snail should withdraw them back into his head. Using a stopwatch, time how long it takes for the snail to fully extend its tentacles again after you have touched it. Repeat at regular intervals and record the time it takes for the tentacles to extend every time. If habituation has taken place the snail should re-extend its tentacles quicker the more you repeat the stimulus. If habitation hasn't occurred it will take the snail the same time to re-extend its tentacles. The snail should still remain alert to an unfamiliar stimulus.