A2 PRACTICALS FOR BIOLOGY

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Observing patterns by ecological sampling. Controlled variables?
Abiotic factors, light, temp, soil, water, humidity, o2 concentration, pH, aspect slope angle
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How do you execute random sampling?
Set up grid using tape measure, use random numbers to generate points to place quadrate to collect data
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How do you execute systematic sampling?
Line transect, tape measure laid along several zones to be looked at and quadrate are used to record data at regular intervals
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How do you measure abundance, density?
Density = presence of organisms per quadrate
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How do you measure frequency?
Percentage of quadrate squares containing organisms
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What do you use a pitfall trap for?
To collect invertebrates
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What do you use a sweep net for?
To collect invertebrates in long grass
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What do you use a pooter for?
To collect invertebrates in a container
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What do you use a tullgren funnel for?
To collect organisms from leaf litter
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What do you use a Bearman funnel for?
To collect organisms from water
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Observing patterns by ecological sampling. Possible evaluation issues?
constant changing of abiotic conditions, movement of organism, sampling taken within small amount of time, limitations of only one study, consideration for safety of organisms, disruption of normal habitat, ethics of measuring wild organisms
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The effect of temp of hatching success of brine shrimp. Independent and dependent variables?
Independent: temp Dependent: number of shrimps hatched
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The effect of temp of hatching success of brine shrimp. Controlled variables?
Controlled variables: light intensity, pH, salt content, presence of chlorine from tap water, oxygen concentration
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Optimal temperature for brine shrimp eggs to hatch?
28 degrees, most eggs should hatch between 25 to 30 degrees in this practical
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The effect of temp of hatching success of brine shrimp. Possible evaluation issues?
ethics of hatching shrimp under different conditions, using animals in experiments, may be a difference in light at each sample, fluctuating temps, not accurate salt measurements, may not have counted exactly 40 eggs, may miss seeing some baby shrimp
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What stat test used for correlation?
Spearmans rank
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What stat test used to compare means?
Student t test
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What stat test used to compare medians?
mann whitney - u test
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In what stat tests do you reject null hypothesis if the calculated value is more than the critical value?
student t test and spearmans rank
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In what stat tests do you reject null hypothesis if the calculated value is less than the critical value?
mann whitney u test
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How do you calculate degrees of freedom?
in your table, (columns x rows)-2
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What level of confidence do you ALWAYS refer to when drawing conclusions from investigations?
95% confidence, 0.05 significance level
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DNA gel electrophoresis, outcome of this practical?
DNA will be separated out through the agar gel, with the heaviest (biggest) DNA strands near the wells and the lightest (smallest) will be at the opposite end. The DNA restriction ladder can be used as a “ruler” to measure the size of the fragments
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DNA amplification using PCR, equipment needed?
Thermocycler, DNA sample, taq polymerase, nucleotides, primers
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DNA gel electrophoresis. Equipment needed?
selected restriction enzymes, agar gel, gel tank, electrical supply, micropipettes, DNA sample, loading dye, UV light, camera, buffer solution, DNA restriction ladder
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DNA amplification using PCR, what order of the temperatures?
94, 54, 72
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DNA amplification using PCR, what happened at diff temperatures?
94= denature, break hydrogen bonds, makes DNA single stranded, 54 = bonds form between primers and template strands 72= optimum of taq polymerase, bases placed in position, extending strand from primer
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Effects of different antibiotics on bacteria. Independent and dependent variables?
Independent= antibiotic Dependent = diameter of zone of inhibition
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Effects of different antibiotics on bacteria. Controlled variables?
concentration of antibiotic, amount of antibiotic, disc sir, bacterial species, temp, ruler
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Effects of different antibiotics on bacteria. Incubation time and temp?
48 hours, 30 degrees, upside down
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Effects of different antibiotics on bacteria. Possible evaluation issues?
Ensuring the discs are evenly placed on the petri dish, having good aseptic technique to prevent plate contamination, age of antibiotic, if out of date likely to be less effective, repeats, accuracy of incubation time and temp
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Measuring the rate of oxygen uptake. Controlled variables?
no of organisms, temp, time, amount of soda lime
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Measuring the rate of oxygen uptake. Equipment needed?
Respirometer, soda lime, coloured liquid, organisms, cotton wool, stop clock, marker pen
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Simple respirometer. Adv and d.adv?
d.adv: does not allow you to reset, control tube needed alongside, no scale so measurements are likely to be less accurate, adv: very simple to set up, minimal number of connections makes a good seal easier to obtain
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U tube respirometer. Adv and d.Adv?
d.adv: tendency for connections to leak in elderly models (making the equipment useless) expensive, adv: does not need to have an additional control as a second tube balances out the effects of the changes in temp and atmospheric pressure
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Effects of exercise on tidal volume and breathing rate. Equipment needed?
spirometer, kymograph, disinfectant, eye protection, soda lime
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Define the tidal volume?
The tidal volume is the volume of air breathed in and out in one breath at rest. The tidal volume for most adults is only about 0.5 dm3.
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Define the vital capacity?
Vital capacity is the maximum volume of air that can be breathed in or out of the lungs in one forced breath
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Define breathing rate?
Breathing rate is the number of breaths taken per minute.
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Define minute ventilation?
Minute ventilation is the volume of air breathed into (and out of) the lungs in one minute. Minute ventilation = tidal volume x rate of breathing (measured in number of breaths per minute).
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What is residual air, and what does it prevent?
Some air always remains in the lungs as residual air and cannot be breathed out. Residual air prevents the walls of the bronchioles and alveoli from sticking together. Any air breathed in mixes with residual air.
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Investigating habituation to a stimulus. Independent and dependent variables?
Independent: number of pokes Dependent: retraction time
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Investigating habituation to a stimulus. Controlled variables?
replication using snails of approximately same size and age, equal handling history, drying out
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Investigating habituation to a stimulus. Equipment needed?
1 giant african land snail, 1 dampened cotton wool bud, clean firm surface, stop watch
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Investigating habituation to a stimulus. what happens with repeated stimulation? why does the snail take less time to re-emerge?
repeated stimulation = calcium channels, pre synaptic membrane less responsive, less calcium into pre synaptic neurone, less neurotransmitter, action potential less likely, fewer action potentials produced in post synaptic motor neurone, less respons
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Investigating habituation to a stimulus. Possible evaluation issues?
Snails already handled before the experiment may not react in the same way, determining when a snail has fully re emerged can be hard, lack of moisture may encourage snails to stay longer in their shell, measuring eye stalk length instead
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Other cards in this set

Card 2

Front

How do you execute random sampling?

Back

Set up grid using tape measure, use random numbers to generate points to place quadrate to collect data

Card 3

Front

How do you execute systematic sampling?

Back

Preview of the front of card 3

Card 4

Front

How do you measure abundance, density?

Back

Preview of the front of card 4

Card 5

Front

How do you measure frequency?

Back

Preview of the front of card 5
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