Quartz 4

Biology Practical Skills

3 min read

Table Plotting

  • For surface area to volume ratio, assume that the table heading says smth like surface area: volume ratio → put down your values as a ratio. Follow the table heading please.

Important

whatever values you want to include in your graph MUST be in the table. vice versa as well

Graph Drawing

  • at least 1 axis has to start from 0
  • at least 5 data points for a good graph. i would recommend myself to do more if time. both curve and line require 5. different from physics*

Bar Graph

  • the space between each bar is not counted in the minimum 50% scale required.

Important

draw point to point graph when there is no relationship between X and Y

Relative Notes for Each Topic

Cells

  • Cells vs Agar Cubes
    • comparison between size, shape, and surface area.
      • Cells have much higher SA than agar cube
      • much smaller than agar cube
      • spherical vs cubical shape

Diffusion

  • Temperature Affecting rate of diffusion: Temperature OF LIQUID, not of each set up. each set up is rather vague

Reproduction in Plants

  • take pollen grains from same flower, not same plant. pollen grains across diff flowers of same plant may vary.

Common Sources of Errors

  • Experiment was only conducted once.

Variables

Temperature

  • temperature kept constant → ensure temperature is kept constant at xx degrees using a thermostat. OR use a water bath
    • do NOT say same location / same room → as the temperature at diff parts of room is different

for ratio, always simplify until it is xxx : 1, no matter decimal or not.

Sources of Error

  • if lets say same source of error for all the set ups, e.g. evaporation occurs in all set ups as there is no lid, then the error is same for all so it will cancel out. thus this cannot be your source of error anymore.
  • this source of error occurs across all set-ups. hence it can be considered a constant that will not interfere with the precision* of results → accuracy however might be impaired due to the presence of the constant source of error that might cause the experimental set up to be different from actual values if you were to conduct the experiment in a real life setting.

e.g. evaporation as source of error

  • occurs across all your set ups, hence all the values will deviate by the same amount.
  • so the results have been balanced out.

If only 2 samples are used → if one of them is the outlier you don’t know which one it is. and also lower sample size affects your reliability as when fewer values are used to calculate mean then the reliability is lower.

Reliability and Accuracy

  • RRRA for reliability → central limit theorem
  • to improve accuracy → usually change instrument or apparatus.

Graph View

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