pp

Question 1

how to control temp.

Answer 1

thermostatically controlled room incubator

Question 2

how seeds are treated and then stored in a seed bank

Answer 2

the water content is reduced (1)
* the seeds are x-rayed (1)
* the seeds are kept at {low temperature / dry} (1)

Question 3

what is meant by the term water potential

Answer 3

the ability of water molecules to move out of cell
- water moves from higher to lower WP

Question 4

ref to relevant safety measure

Answer 4

disinfect equipment,
flame equipment (bunsen burner)
lift lid partially,
autoclaving after,
goggles,
gloves,
tie back long hair

Question 5

what is the purpose of placebo affect and double-blind trials

Answer 5

placebo:
* it is used as a control / more validity
* to eliminate a psychological effect of taking the drug
double-blind trials:
* so that {doctor / scientist} does not know if the treatment
contains the (new) drug or not
* to remove bias from results

Question 6

how to increase validity

Answer 6

• everything must be the same except the variable

Question 7

how to reduce measurement errors

Answer 7

repeat measurements {and obtain mean / SD /
identify anomalies} for each concentration / use
callipers to measure length changes / description
of use of ruler to avoid parallax errors

Question 8

properties of sucrose

Answer 8

it {dissolves (completely in water)/is soluble}
* it is {not broken down / not metabolically active / inert}
* it {is not taken up by the carrot /does not cross membrane of cells / has osmotic effect}

Question 9

how do antioxidants reduce heart disease

Answer 9

because (antioxidants
reduce (the quantity of) free
radicals
* that cause damage to {cells / tissues/ blood vessels\endothelium} (1)
* reducing {plaque / atheroma}
formation (1)

Question 10

why pollen tubes grow in same direction from the stigma

Answer 10

the tubes grow towards the {micropyle / ovule / ovary
/ ovum / female gamete} (1)
* {due to chemicals (released by the embryo sac) / it is
chemotropic}

Question 11

safe method to observe the stages of mitosis in these roots

Answer 11

• cut root tip
• (root tips) placed in (warm) acid
• (root tips) then placed in named stain
• (root tip placed on a microscope slide and) {macerated
  / teased / described} / squashed (1)
• use of high power (on a microscope)
• correct ref to safety issue (1)
  e.g. (acetic / ethanoic)
  orcein / toluidine blue
  /methylene blue
  e.g. rinsing tips in water /
  wearing gloves / goggle

Question 12

how to modify an experiment to determine if the diffrences are significant

Answer 12

each treatment should be repeated (1)
* {all conditions / named condition} should be kept
constant (1)
* (mean and) SD calculated / error bars (1)
* look for overlap in SDs / perform t-test (1