methodology

Question 1

why is an insufficient number of values of independent variables e.g. 10C increase each temp, a limitation?

Answer 1

lack of results between intervals so could miss changes and be less accurate. to improve, include more intermediate ranges.

Question 2

why is using different species for an experiment a limitation?

Answer 2

difference state may induce random error so to improve, use large sample of same organism, same species, age and size to make results more representative of population

Question 3

what is the limitation of using a stop watch?

Answer 3

use to a greater agree of resolution e.g. 1.01s to increase accuracy

Question 4

why is lack of control variables a limitation?

Answer 4

not confident in the effect of changing IV is causing the change in the DV, so ,method is not valid. =

Question 5

why is choosing a piece of equipment with low resolution a limitation? e.g. measuring cylinder

Answer 5

measurements are made with high uncertainty. Therefore, using volumetric syringe.

Question 6

how is using a piece of equipment that hasn’t been calibrated correctly a limitation?

Answer 6

introduces systematic error so increases accuracy. Therefore, must check that thermometer reads 0C degrees, and zero on all balances.

Question 7

what is a good method to prove the IV is directly causing the change in the DV?

Answer 7

having a baseline control for comparison.

Question 8

random error contributes to uncertainty. How can we reduce random error?

Answer 8

making more measurements and calculating mean.

Question 9

how to increase accuracy of a practical?

Answer 9

• take more intermediate readings
• take more repeat readings to obtain a more accurate mean

Question 10

list ways in which to improve confidence in findings

Answer 10

• repeat readings
• identify anomalies and repeat experiment to dilute the effect of anomalies.
• calculate standard deviation (less SD, increased confidence)
• conduct statistical test

Question 11

how to improve validity of a practical

Answer 11

• look for gaps in method they have not controlled e.g. pH, temp, species, conc., volume etc…
• listing limitations of practical, and suggesting improvements e.g. thermostatically controlled water baths.

Question 11

what are the 5 aspects of validity?

Answer 11

accuracy
precision
confidence
repeatability
reproducibility

Question 12

what is the process of dissecting bony fish?

Answer 12

• cut away from operculum
• cut one gill out
• put in water
• stain with dye and view on microscope slide

Question 13

what is the process of dissecting insects?

Answer 13

view spiracles with a magnifying class

Question 14

explain the dissection of a stem

Answer 14

• use a scalpel
• stain xylem with methylene blue
• see spiral lignin in microscope

Question 15

what are the precautions you must consider when investigating transpiration rates with a potometer

Answer 15

• healthy shoot
• set up underwater
• seal joints with vaseline
• syringe to reset apparatus
• cut bottom of stem underwater to prevent air bubbles in xylem

Question 16

ways to capture animals (biodiversity)

Answer 16

• pit fall trap
• mark recapture
• tree beating
• sweep net
• pooter

Question 17

why must the leaves be dry in potometer?

Answer 17

to increase water potential gradient

Question 18

describe stratified sampling

Answer 18

number of samples is proportionate to each area - it ensures areas are not missed, divided strata and sample in each.

Question 19

what are two methods of systematic sampling

Answer 19

belt and line transects

Question 20

describe how to produce a cutting of a plant tissue

Answer 20

• cut healthy shoot at an angle
• add hormone auxin
• water soil
• place plastic bag over and spray with water to increase humidity
• remove lower leaved

Question 21

describe micropropagation (tissue culture)

Answer 21

• cut explant
• sterilise
• add nutrient medium + hormones
• forms a callus = which divides to form clones

Question 22

why should a glass slide be placed over a beaker investigating chromatography?

Answer 22

to prevent evaporation of the solvent

Question 23

state the process of thin paper chromatography

Answer 23

1. Grind up the leaves using a pestle and mortar​.
2. Draw a line on the TLC plate with a pencil​ ​about 2cm from the bottom.
3. place a dot of pigment in the middle of the pencil line​.
4. allow dot to dry then add another dot over the first, repeat process until you have a concentrated pigment.
5. add small amount of solvent 1cm from bottom.
6. Place the TLC plate in the beaker​, with a glass over to prevent evaporation
7. calculate rf

Question 24

the further the pigment moves up the TLC plate…

Answer 24

it is more insoluble on the chromatography paper because it’s non-polar so travels further up because it isn’t absorbed as easily

Question 25

the less the pigment moves up TLC plate…

Answer 25

the more soluble the pigment is, it is polar and is more easily absorbed onto the paper so travels slower.