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A Level Biology OCR A UPDATED > Module 1 > Flashcards

Module 1 Flashcards

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1
Q

Factors that can be changed in experiment about enzyme rate

A

Temperature
pH
Enzyme concentration
Substrate concentration

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2
Q

When evaluating experimental methods, consider

A

Method limitations
Accuracy
Precision
Reliability
Validity

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3
Q

Method limitation

A
  1. An experimental design flaw or fault in the method that affects the accuracy of the results.
    example, potometer: air buble in xylem
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4
Q

accuracy

A

1.reduced by systemic errors(faulty instruments or flaws in the experimental method, repeate consistently every time the instrument or method is used)
2. random errors(unexpected environmental changes or incorrect use of equipments diferent every time the experiment is carried out. e.g a breeze blowing during potormeter experiment may not blow at the same speed throughout the experiment)

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5
Q

Precision vs Accuracy

A

Precision refers to the ability to take multiple readings that are close to each other, accuracy is the closeness of those measurements to the true value

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6
Q

Constructing a table

A
  1. Draw lines with a ruler to separate cells
    2.Use appropriate headings
    3.Use the correct units and symbols (in the headings, not the cells)
    4.The independent variable should be in the first column
    5.Any dependent variable readings should be in the subsequent columns
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7
Q

Qualitative data or discrete

A

bar charts or pie charts

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8
Q

continuous data

A

line graphs or scatter graphs

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9
Q

Random errors

A
  1. cause unpredictable fluctuations in an instruments reading as a result of uncontrollable factors
  2. affect precision of measurements, causing a wider spread of results about the mean value
  3. Repeat measurements several times and calculate average from them
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10
Q

Systematic errors

A

1.arise from the use of faulty instruments used or from flaws in the experimental method.
2. cosistently repeated everytime the instrument is used or the method is followed, affects accuracy
3. reduce by recalibrating instruments or different instruments should be used. corrections or adjustments should be made to the technique.

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11
Q

Uncertainty

A
  1. the amount of error your measurements might contain
  2. margins of errors use to calculate percentage error
    a. use gas syringe give readings to the nearest 1 cm^3
    b. gas syringe margin of error +/-0.05
    c. +/- sign tells you the range in which the true value lies.
    d. the real volume produced could be up to 0.05 cm^3
  3. percentage error = (uncertainty/measurement) * 100
  4. percentage error less than 5% considered statistically not significant
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12
Q

smaller measuring instruments

A

higher resolution scales due to the smaller graduation on the scale. means have smaller margins of error.

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13
Q

Standard Deviation

A
  1. the measure of the spread or dispersion of data around the mean
  2. Large standard deviation indicates that the results are more spread out
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14
Q

overlap in standard deviations

A
  1. overlap= results not significantly different
  2. no overlap= results significantly different
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15
Q

What are the three types of data

A
  1. Qualitative data (non-numerical data e.g. blood group)
  2. Discrete data (numerical data that can only take certain values in a range e.g. shoe size)
  3. Continuous data (numerical data that can take any value in a range e.g. height or weight)
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16
Q

When are evaluations conducted

A

before conclusions drawn

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17
Q

Ethical concerns with dissections

A
  1. how the animals for dissections are raised and killed
  2. it goes against the religious beliefs of some individuals
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18
Q

Apparatus for dissections

A
  1. Scissors
  2. Scalpel
  3. Tweezers
  4. Dissection board
  5. Paper towels
  6. Biological specimen
  7. Pins
  8. Gloves
  9. Goggles.
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19
Q

Limitations of dissections

A
  1. hard to see some of the smaller, finer structures within organs
  2. specimens do not refelct how the tissue would look in a living organism
  3. If only single specimen dissected then anomalies found within that specimen may be ignored or glossed over.
  4. dissection instruments should be sharp to give good clean cuts with as little damage as possible- blunt instruments are dangerous and will not give precise cuts making internal structures harder to distinguish
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20
Q

Types of sampling

A

random
non random

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21
Q

Sampling equipments

A
  1. Quadrats
  2. Sweeping nets
  3. Pitfall traps
  4. pooters
  5. Tullgren funnel
22
Q

Quadrat method of sampling

A
  1. Apparatus
    -Quadrat
    • Random number generator
  2. Method for choosing sample sites
    • Mark up a grid on a map or a to-scale drawing of the area being studied and label the grid with coordinates
    • Large area to get a representative estimate for the specific habitat/ecosystem
    • Use a random number generator to choose a set of coordinates to avoid sampling bias which could lead to over or under-estimation
23
Q

Getting measurements from quadrats

A
  1. population density
  2. percentage cover
  3. Species frequency
24
Q

Population density

A
  1. place quadrated at generated coordinate
  2. count # of individuals in each quadrat
  3. use running mean to determine the number of quadrats (calculate mean number of individuals per quadrat: 1st 2 quadras, then first 2, then first four and repeat until no further significant change in mean)
  4. calculate estimated population size: divide the whole area by the area of one quadrant, then multipy this value by the mean number of individuals per quadrat.
25
Q

percentage cover

A
  1. plants
    place grid quadrat (10by10). each square of grid quadrat is equivalent to 1% cover.
  2. count number of squares in each quadrat within which the species occupies over half the square.
    • If 30 squares contain the species, the percentage cover is 30%
    • the method is subjective and therefore the same person should make the estimate for all samples to control this variable
26
Q

Frequency

A
  1. place a frame quadrat at multiple coordinates generated
  2. count the number of quadrats that contain the species
    • if 3 out of 10 quadrats that contain the species the frequency is 30%
27
Q

Species density

A
  1. how many individuals of that species there are per unit area.
  2. number of individuals counted across all quadrats is divided
28
Q

Species Frequency

A
  1. Probability that species will be found within any quadrat in the sample area.
  2. # of quadrats that the species was present in divided by the total number of quadrats and then multiplied by 100
29
Q

limitation of using quadrats

A
  1. only used for slow-moving animals and immobile species
  2. frequency technique shows how common a species is but it does not information on the estimated number of individuals or the size of the population
  3. Percentage cover and frequency when used together give a good picture od the distribution if a species. If species ha high mean percentage cover but a low freqeuncy it would suggest the species lives in groups in perferred areas of the habitat.
30
Q

Mark-release-capture method

A
  1. only useful for non-motile organims
  2. Large sample taken, individuals are caught, counted and marked
  3. marked indiviudals returned to their habitat.
  4. When sufficient amount of time has passed another large sample is captured.
  5. # of marked and unmarked individuals counted
  6. proportion of marked to unmarked individuals is used to estimate population size.
    Formula
    N= (n1*n2)/m2
    N= population estimate
    n1= number of marked individuals released
    n2= number of individuals in the second sample
    m2= number of marked individuals in the second sample
31
Q

Assumptions of mark-release-capture

A
  1. given sufficient time to disperse and mix back in fully with the main population
  2. marking does not affect survial rates
  3. remains visible through out
  4. population stays the same during study period(no significant change sin population size due to birth, death)
32
Q

Data loggers

A

tools that allows for quick and efficient gathering of data

33
Q

Computer models

A
  1. used to model effects of natural selection
  2. benefits is that time can be sped up
34
Q

Recording a range of quantitative methods.

A
  1. Mass: digital balance
  2. Time: digital stopwatch
  3. Volume: measuring cylinder
  4. Temperature: a digital thermometer (although water baths have one built-in)
  5. Length should be recorded using a graduated ruler
35
Q

Agar cube increasing in size

A

the volume increases faster than the surface area because the volume is cubed whereas SA is squared. more volume, less surface area diffusion takes longer and less effective. greater SA:V ratio, faster the rate of diffusion.

36
Q

positive and negative change in mass when studying water potential

A
  1. positive percentage change: potato has gained water by osmosis. solution had higher water potential than potato. gain of water makes potato cells turgid.
  2. —% change: solution has lower water potential then potato. more water molecules will move out of the potato cells by osmosis, makes them flaccid decreasing mass of potato cylinder. under microscope cells might be plasmolysed, cell membrane has pulled away from the cell wall.
37
Q

water potential with onion cells

A
  1. solution has lower water potential. water leaves vacuole of cell, volume of cell decreases.
  2. protoplast (living part of the cell inside the cell wall) gradually shrinks and no longer exerts pressure on the cell wall.
  3. as protoplast continues to shrik, it begins to pul away from the cell wall. process known as plasmolysis.
    observed in epidermal strips.
38
Q

factors affecting membrane permeability and structure (beetroot)

A
  1. temperature
  2. solvent concentration
  3. higher permeability of beetroot cell membrane, more of this pigment leaks out of cell.
39
Q

Procedure- factors affecting mem permeability (temperature)

A

Apparatus
- Scalpel
- Cork borer (optional)
- Cutting board
- Ruler
- Digital balance
- Test tubes
- Measuring cylinder
- Water baths
- Digital stopwatch
- Colorimeter
2. using scapel, cut five equal-sized cubes of beetroot. a cork borer could be used. ruler to make sure equal lenghts. digital balance to check that all pieces have the same mass
3. Rinse beetroot pieces to remove any pigment released during cutting
4. add pieces to five different test tube with same volume of water (5cm^3)
5. put each test tube in water bath at different temperature for the same length of time (30 minutes)
6. remove the beetroot pieces, leaving just the colored liquid in the five test tubes
7. use colorimeter. Higher absorbance, more pigment must be released due to greater membrane permeability

40
Q

limitation of method for factors affecting perm

A
  1. Cuvettes may differ in thickness. A thicker (or scratched) cuvette will absorb slightly more light than a thinner unscratched cuvette
    Solution: use the same cuvette for every reading, or repeat the investigation many times and find a mean
  2. The beetroot pieces may not be identical in size and shape, meaning some test tubes could contain slightly more beetroot tissue than others
    Solution: cut the discs as accurately as possible using a scalpel and ruler, and repeat each investigation several times to find a mean
  3. Some parts of beetroot tissue have more pigment in their cells than others
    Solution: conduct several repeats, using different parts of the beetroot and find a mean
41
Q

Biochemical Tests for Reducing Sugars & Starch

A
  1. Benedict’s solution: excess so there is more than enough cu(II)sulfate present
  2. intensity of any color change relates to concentration of reducing sugar. green (low concentration)-brick red (high concentration of reducing sugar present)
  3. use colorimeter: calibrate using blank. set to R
42
Q

Biochemical tests for biological molecules

A
  1. Ethanol for lipids
  2. Biuret for proteins
  3. Benedicts solution and iodine for carbohydrates
43
Q

Biochemical test for lipids

A
  1. Emulsion test.
  2. lipids nonpolar but dissolve in organic solvents such as ethanol.
  3. Apparatus
    -Test tubes
    -Test tube rack
    -Ethanol
    -Pipettes
    -Food sample
    -Mortar and pestle (if food sample is solid)
    -Water
    -Gloves
  4. Add ethanol to sample tested
  5. Shake to mix
  6. decant food + ethanol solution into test tube (water). if lipids present milky emulsion will form. no lipid present, solution remains clear.
  7. Limitation: qualitative test. does not give quantitative value as to how much lipid may be present in a sample.
44
Q

Biochemical tests for proteins

A
  1. Buiret test
  2. reagent contains alkali and copper (II) sulfate which react in the presence of peptide bonds
  3. Apparatus
    -Test tubes
    -Test tube rack
    -Food solution
    -Control solution (containing no proteins e.g. distilled water)
    -Sodium hydroxide
    -Copper (II) sulfate solution
    -Pipette
    -White tile
    -Gloves
  4. Add NaOH to food solution to make solution alkaline
  5. Add a few drops of copper (II) sulfate solution (blue)
  6. repeat steps using the control solution
  7. if color change observed (from blue to lilac/mauve). hold against white tile. protein present.
    9.Limitations: if sample contains amino acids or dipeptides bonds, result negative due to lack of peptide bonds. qualitative.
45
Q

Serial dilutions

A
  1. certain volume of stock solution
  2. Remove some volume add to certain volume of water.
  3. volume of water constant. do continuously.
46
Q

Rate of transpiration

A
  1. Air movement, humidity, temperature and light intensity all affect.
  2. potometer
  3. Apparatus
    -Plant shoot
    -Cutting board
    -Scalpel/scissors
    -Paper towels
    -Potometer
    -Volume scale
    -Beaker
    -Capillary tube
    -Stopwatch
    -Vaseline
  4. cut shoot underwater to prevent air entering xylem
  5. place shoot in tube
  6. Environmental factors
    - Air flow: set up a fan or hair dryer
    - Humidity: spreay water in plastic bag and wrap around the plant
    • Light intensity: change distance of a light source from the plant
    • Temperature: temperature of room (cold or warm room)
47
Q

Investigating with Light Microscope

A
  1. The key components of an optical microscope are:
    • The eyepiece lens
    • The objective lenses
      - The stage
      - The light source
      - The coarse and fine focus
      Other tools used:
      - Forceps
      - Scissors
      - Scalpel
      - Coverslip
      - Slides
      - Pipette
  2. Start with lower power objective leans. prevents damage to lens or coverslip, easier to find what you are lookin for in the field of view.
  3. Preventing the dehydration of tissue
    • add a drop of water to the specimen
  4. Unclear or blurry images
    • switch to lower power objective lens and try using the coarse focus to get a clearer image
    • is specimen thin enough
      - possible cross-contamination with foreign cells or bodies.
48
Q

Preparing a liquid specimen

A
  1. Add few drops of the sample to the slid using a pipette
  2. Cover the liquid/smear with a coverslip gently press down to remove air bubbles
  3. wear gloves to ensure there is no cross-contamination of foreign cells
49
Q

Preparing slide using a solid specimen

A
  1. use scissors to cut a small sample of the tisue.
  2. peel away or cut a very thin layer of cells from the tissue sample to be place on the slide (using a scalpel or forceps)
  3. if needed treat with chemicals to kill/make tissue rigid
  4. Gently place a coverslip on top and press down to remove any air bubbles
  5. Stain may be required to make the structure visible depending on the type of cell being examined
50
Q
A

A Level Biology OCR A UPDATED (25 decks)

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