Practicals Flashcards
A microscopic slide was used to count the amount of red blood cells in a certain volume. When counting, cells that touch top or left are counted, but right and bottom lines are not counted. Why?
To avoid counting the same cells twice.
To be consistent.
To avoid dealing with parts of the cells.
Explain ways the student could improve the quality of her scientific drawing.
No shading. Only use single lines. Add further labels. Don’t allow label lines to intersect. Add magnification.
Scientist used haematoxylin solution to stain lung tissue blue, which stains DNA, instead of iodine solution that stains starch a blue-black colour. Why?
Lung tissue does not contain starch.
DNA is in the nucleus.
When talking about P values, what should you mention?
Significance, and high significance. For example, link with asthma and burned wood is not statistically significant.
Suggest why both percentage change and tumour volume were measured when studying the effectiveness of trexall (2)
Percentage change will allow comparison as rumours may differ in volume. Volume is the best indication of the number of cells in tumour.
Apart from age, gender and general health, give two important factors when choosing patients for this rheumatoid arthritis investigation.
Severity/duration of arthritis
Current/other medication
Type of arthritis (?)
Weight
Ethnicity
What should you remember in an evaluate the data question?
Manipulate data e.g. pain decreases by 4.6 with drug compared to 2 with control group.
Subjectivity measurement
No statistical testing so don’t know if difference is significant.
Explain why the biologist chose to examine 200 cells.
Large sample size so representative sample.
Describe the method to determine surface area of potato cubes on rate of osmosis. Include variables to control (3)
Control temperature.
Ensure all surfaces of the 8 cubes are exposed to the sucrose solution.
Dry cubes before measuring.
Measure mass of cubes at stated time intervals.
