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2019 Unit 5
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Terms in this set (18)
The image below shows the woodland strawberry (Fragaria vesca). This plant was used to test whether light intensity had any effect on the mean thickness of its leaves. Explain why the seeds were taken from a single parent plant and were grown under the same conditions, other than light intensity.
So that the only difference between the measurements would be due to the light intensity/ prevent leaf thickness being affected by other factors
To minimise genetic variation between plants/reference to genetic similarity/ similar {genes/ alleles}
Reject genetically identical
Suggest three environmental conditions that should be controlled when growing plants for this experiment.
Any three × (1) from:
air temperature (1)
soil temperature (1)
temperature unqualified = 1 mark only
(relative) humidity (1)
(named) {mineral/ nutrient} availability (1)
soil pH (1)
water availability/ volume of water (1)
(atmospheric) carbon dioxide/ concentration of carbon dioxide (1)
Why were measurements taken from leaves of the same age?
Same period of exposure / comparable stage of {development/ growth}/ same size/ different ages may have different thickness of leaves
Calculate the mean thickness of the leaves at high light intensity.
1526 / 15 = 101.7μm
Explain why the statistical test chosen was the Student's t test.
to compare {the means of data/ two sets of continuous data / normally distributed data}
State a suitable null hypothesis for this test.
There is no significant difference in the mean thickness of leaves grown at low or high light intensity/any difference in the mean thickness of the leaves is due to chance alone
The number of degrees of freedom is given by the formula: number of degrees of freedom = (n1 - 1) + (n2 - 1)
Where n1 and n2 are the numbers of samples from low and high light intensity respectively. Calculate the number of degrees of freedom to be used in this test.
28
The calculated value of t is 2.386. Using the information provided, state the critical value at a suitable level of significance and draw a conclusion for this experiment.
Critical value = 2.048 (at level of significance of 0.05);Calculated value is greater than the critical value / 2.386 > 2.048;
Reject the null hypothesis;
(Mean) thicknesses of the leaves are significantly different / leaves grown at low light intensity are significantly thinner than those grown at high light intensity / differences in thickness of leaves are not due to chance alone
At a level of significance of 0.005, the critical value of t is 3.047. What would your conclusion be if a level of significance of 0.005 had been used?
Any two for 1 mark
Accept the null hypothesis
As calculated value is less than critical value
(mean) thicknesses are not significantly different / any
difference in (mean) thickness is due to chance
Explain why leaves grown at low light intensity might be thicker than those grown at high light intensity in some species.
{More /larger/multiple layers} of palisade cells
So more {chloroplasts/ chlorophyll/ photosystems / antenna complexes}/ higher concentration of photosynthetic pigments}
Reject wider range of pigments
So more light can be absorbed;
Thinner leaves may result in a lower rate of photosynthesis. Suggest one way that leaves grown at low light intensity might be adapted to overcome this problem, while remaining thin. Explain your answer.
Larger surface area/more {chloroplasts/ chlorophyll}/ different range of pigments/ more movement of chloroplasts
to absorb as much light as possible/ absorb light of a wider range of wavelengths
On Image 1, label structures A and B.
A - cilium / cilia
B - {cell/plasma} membrane
Image 1 is printed at a magnification of ×8000. Calculate the width of structure A at the position labelled W, giving your answer to 2 decimal places.
0.25 micrometers
2 x 1000 / 8000
Explain why the structures in Image 2 appear to be a different shape from structure A in Image 1.
Image 1 shows cilia in a longitudinal/ vertical section (and Image 2 is in transverse section)/ cut in a different plane
Reject different angles
Use the width calculated in to calculate the magnification of Image 2 at the position indicated.
120000
30 x 1000 / 0.25
Explain why an electron microscope, rather than a light microscope, is needed to show the internal detail of structure A.
Size of structures {is below the level of resolution of the light microscope / too small}/ electron microscope able to use a higher magnification
State another site in the human body where cells similar to those in Image 1 would be found.
trachea / bronchus
Describe how the shape of the cells lining the proximal convoluted tubule of the mammalian kidney differs from the columnar epithelial cells shown in Image 1.
Proximal convoluted cells are cuboidal (and cells in Image 1 are columnar)
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Verified questions
COMPUTER SCIENCE
Write a program that asks the user for a positive integer value. The program should use a loop to get the sum of all the integers from 1 up to the number entered. For example, if the user enters 50, the loop will find the sum of 1, 2, 3, 4, … 50. Input Validation: Do not accept a negative starting number.
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Design a function that accepts a list of numbers as an argument. The function should recursively calculate the sum of all the numbers in the list and return that value.
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A useless state in a Turing machine is one that is never entered on any input string. Consider the problem of determining whether a Turing machine has any useless states. Formulate this problem as a language and show that it is undecidable.
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Draw an expression tree for each of the following expressions. a. 3+(2*14)-5, b. 20*(10-5), c. 20*10-5, d. (17%5)*11+3, e. (5+3+2)/4.