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Practical skills Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

What is a prediction?

A
  • a statement about what you think might happen
  • based on prior knowledge or an underlying hypothesis
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2
Q

What is a hypothesis?

A
  • a statement providing an explanation or prediction, ALWAYS based on prior knowledge and testable by an experiment
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3
Q

State 5 components that should appear in a practical plan:

A
  • Controlled variables
  • Independent variables
  • Dependent variable
  • Improving reliability
  • Safety
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4
Q

How can reliability be improved?

A
  • Repeat experiment 3-5 times and take mean value
  • Identify and exclude anomalies
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5
Q

How do you take safety into account?

A
  • state a hazard and the level of risk
  • state a safety precaution to take
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6
Q

What are some common control variables?

A
  • Temperature
  • pH
  • Volume
  • Concentration
  • Time
  • Mass
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7
Q

What are some sources of error when measuring length?

A
  • Parallax error from vernier callipers
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8
Q

How is a respirometer set up?

A
  • two test-tubes, each with soda lime/KOH (absorbs CO2)
  • so CO2 produced does not increase volume of air
  • oxygen consumption read from fluid level on manometer
  • temperature of surroundings must be kept constant, by a thermostatically controlled water bath
  • pressure is controlled by using a second tube with no organism, but glass beads instead, same mass, temperature, light intensity etc.
  • apparatus should be airtight
  • air must be replaced between each set-up
  • take care when assembling respirometer since capillary tubing can break and cause cuts
  • soda lime is corrosive, wear gloves
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9
Q

Outline the procedure to random sampling:

A
  • Make a grid
  • Random number generator to obtain a set of coordinates
  • Place quadrats at coordinates
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10
Q

What reagents can be used to measure the rate of respiration and photosynthesis?

A
  • Redox indicators; a substance that changes colour when oxidized or reduced
  • become colourless when reduced
  • DCPIP or methylene blue
  • the faster the rate of respiration, more hydrogens released per unit time, faster the dyes reduced
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11
Q

What are two types of quantitative data?

A
  • Continuous data: individual values can have any value between two extremes
  • Discrete data: measurement can only belong to one of a limited number of values
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12
Q

When should histograms be used?

A
  • For continuous data divided into classes
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13
Q

When should bar charts be used?

A
  • when the independent variable is qualitative
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14
Q

What are the two types of qualitative data?

A
  • Ordinal data: values are not numerical, however can be arranged in sequence, CAN BE RANKED
  • Nominal data: values cannot be arranged in sequence, instead each is assigned a distinct category
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15
Q

How does repeating an experiment increase reliability?

A
  • allows identification of anomalies
  • minimize the effects of anomalies when taking a mean
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16
Q

How can temperature be standardized?

A
  • thermostatically-controlled water bath
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17
Q

How can pH be controlled?

A
  • Buffer solution
18
Q

How can accuracy of measurements be improved?

A
  • By using apparatus with smaller divisions, e.g; vernier caliper instead of ruler
19
Q

What is the formula for percentage error?

A

((new value - original value) / original value) x 100

20
Q

State the four statistical tests:

A
  • T-test
  • Chi-squared
  • Spearman’s rank correlation
  • Pearson’s linear correlation
21
Q

When should T-test be used

A
  • to compare two means
  • sets of continuous normally distributed data
22
Q

When is Pearson’s linear correlation used?

A
  • to correlate two sets of continuous, linear and normally distributed data
  • scatter graph indicates there may be a LINEAR relationship
23
Q

When is Spearman’s rank used?

A
  • to correlate ordinal data which can be ranked, NOT continuous
  • one or both variables NOT normally distributed
24
Q

When is chi-squared used?

A
  • to compare the observed against expected values
  • nominal data
  • discontinuous
25
Q

How are degrees of freedom calculated for T-test?

A

(n1 - 1) + (n2 - 1)

26
Q

How are degrees of freedom calculated for Pearson’s linear correlation?

A

No. of pairs of data - 2

27
Q

How are degrees of freedom calculated for Spearman’s rank?

A

No. of pairs of data - 2

28
Q

How are degrees of freedom calculated for chi-squared?

A

No. of categories - 1

29
Q

How is a statistical conclusion written?

A
  • state calculated value is smaller/larger than critical value at p = 0.05
  • there is less/more than 5% probability that results are due to chance alone
  • the results are/are not statistically significant
30
Q

What does standard deviation measure?

A
  • the spread of data from the mean
31
Q

What does standard error measure?

A
  • how close the calculated mean value is to the true mean value
  • reliability of mean calculated
  • formula:
    SE = s / √n
    s = standard deviation
    n = sample size
32
Q

What is the range of error bars?

A

+/– 2 x standard error

33
Q

How is biodiversity assessed?

A
  • Simpson’s Index of biodiversity
34
Q

What does the calculated value of Simpson’s index indicate?

A
  • it is between 0 and 1
  • close to 1: high biodiversity
  • close to 0: low biodiversity
35
Q

How is a 1% sugar solution made?

A
  • 1% sugar solution means 1g of sugar for every 100g of water
  • 1cm3 of water has a mass of 1g
36
Q

How is a 1 moldm-3 sucrose solution made?

A
  • find Mr of sucrose - 342g
  • put 342g of sucrose in 1dm3 volumetric flask
  • add a small amount of distilled water and shake until completely dissolved
  • add more distilled water until 1dm3 mark
37
Q

Outline how chromatography can be used to identify chloroplast pigment:

A
  • extract pigments by crushing leaf in small amounts of solvent (propanone or petroleum ether)
  • filter extract to obtain dark green solution pigments
  • ruler and pencil used to draw baseline 2cm from base of chromatography paper
  • use capillary tube/pipette to place small drop of solution onto baseline and dry
  • place paper in beaker with solvent such as ethanol BELOW baseline
  • put lid to prevent evaporation of solvent
  • pigments will rise, calculate Rf value

Rf = distance travelled by spot / distance travelled by solvent

38
Q

How are factors of photosynthesis measured in aquatic plants?

A

light intensity
- altering distance from lamp

wavelength of light
- using colour filters (ensure same light intensity)

concentration of CO2
- adding different quantities of sodium hydrogencarbonate (NaHCO3) to water surrounding plant

temperature of water surrounding plant
- large container to maintain chosen temperatures

39
Q

How are redox indicators used to determine rate of photosynthesis

A
  • high energy electrons emitted in light dependent reactions
  • electrons picked by electron acceptors and travel along ETC
  • DCPIP and methylene blue take up electrons instead
  • colour change from blue to colourless
  • time taken for indicator to decolourise is an indication of the rate of photosynthesis
40
Q

How do error bars show if data is significant?

A
  • error bars overlap: NO significant difference
  • no overlap: significant difference

Biology (9 decks)

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