all2

Question 1

how the student could have used his slide to find the number of stomata per cm2

Answer 1

• by using a method of determining area of field of view/area seen using microscope
• by counting the number of stomata in field of view
• and using repeats and calculating a mean

Question 2

The stomata on the leaves of pine trees are found in pits below the leaf surface. Explain how this helps to reduce water loss

Answer 2

• water vapour accumulates / increased humidity/ reduced air movement around stomata
• so water potential/diffusion gradient is reduced

Question 3

How blood plasma is different from tissue fluid

Answer 3

-more/larger proteins / less urea/carbon dioxide / more glucose/amino acids/fatty acids/oxygen/ high(hydrostatic) pressure

Question 4

The blood pressure is high at the start of the capillary. Explain how the left ventricle causes the blood to be at high pressure.

Answer 4

-contracts

Question 5

The blood pressure decreases along the length of the capillary. What causes this decrease in pressure?

Answer 5

• loss of fluid/volume

- so friction/resistance of capillary wall

Question 6

Explain the link between a low concentration of protein in blood plasma and the accumulation of tissue fluid

Answer 6

• Water potential (in capillary) is higher/less negative so the water potential gradient is reduced
• therefore more tissue fluid formed at arteriole end
• and less/no water is absorbed into blood capillary
• by osmosis into blood capillary

Question 7

Why it may be more useful to calculate the index of diversity than to record only the number of species present

Answer 7

• measures number of individuals of each species and number of species
• some species only present in small numbers

Question 8

Gas exchange in fish takes place in gills. Explain how two features of gills allow efficient gas exchange

Answer 8

• filaments/lamellae provide large surface area
• thin/flattened epithelium are only one/two cell layers so there is a short diffusion pathway between water and blood
• countercurrent/blood flow maintains concentration/diffusion gradient

Question 9

The scale for plotting body mass is a logarithmic scale. Explain why a logarithmic scale was used to plot body mass.

Answer 9

-so that a large range of values can fit on a graph

Question 10

Describe the relationship between body mass and oxygen uptake

Answer 10

-Decrease in uptake with increase in mass / negative correlation

Question 11

The zoologist measured oxygen uptake per gram of body mass. Explain why he measured oxygen uptake per gram of body mass

Answer 11

• enables comparison

- as animals differ in size/mass

Question 12

Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between body mass and oxygen uptake shown in the graph.

Answer 12

• smaller animals have larger surface area to volume ratio
• so lose more heat per gram of tissue
• and respire more/faster relative to body mass
• and oxygen is used in respiration

Question 13

how the scientists should have treated the control group

Answer 13

• given only saline

- otherwise treated exactly the same way

Question 14

factors which should be considered when deciding the number of mice to be used in this investigation

Answer 14

• ethical consideration, e.g., leads to death/suffering of mice
• large number to improve reliability / reduce sampling error
• number of mice related to cost/space available/animal husbandry

Question 15

What information does standard deviation give about the volume of the tumours in this investigation?

Answer 15

-the degree of spread/variation from the mean

Question 16

ways in which courtship behaviour increases the probability of successful mating

Answer 16

• recognition of same species
• stimulates release of gametes
• recognition of mate/opposite gender
• indication of sexual maturity/fertility

Question 17

A female with a head length of 50 mm selected a mate. Explain how you could use the graph to predict the total head length of the mate selected.

Answer 17

• use line of best fit

- and extrapolate/extend line as required

Question 18

How comparisons of biological molecules in these two species could be used to find out if they are closely related.

Answer 18

• compare DNA
• sequence of bases/nucleotides
• DNA hybridisation
• separate DNA strands / break hydrogen bonds
• mix DNA/strands of different species –the temperature/heat required to separate hybrid strands indicates relationship
• compare same/named protein
• sequence of amino acids /primary structure
• immunological evidence – not a mark
• inject seahorse protein/serum into animal
• obtain antibodies/serum
• add protein/serum/plasma from other seahorse species
• the amount of precipitate indicates relationship

Question 19

How downward movement of the diaphragm leads to air entering the lungs.

Answer 19

• increases volume in lungs/thorax
• lowers pressure in lungs/thorax
• air is pushed in by higher outside pressure, down a pressure gradient

Question 20

Pulmonary ventilation equation

Answer 20

Pulmonary ventilation= tidal volume x ventilation rate

Question 21

Mitochondrion function

Answer 21

-aerobic respiration

Question 22

Why certain structures can’t be seen using an optical (light) microscope

Answer 22

• resolution is not high enough

- the wavelength of light is too long

Question 23

Sucrose monosaccharaides

Answer 23

• glucose

- fructose

Question 24

Lactose monosaccharaides

Answer 24

• glucose

- galactose

Question 25

Osmosis/water potential- diarrhoea (cholera bacteria increases chloride ions into lumen)

Answer 25

- water moves into the gut - so there is a lower water potential of gut lumen - this means water moves down a water potential gradient by osmosis - so not enough water is reabsorbed

Question 26

Non-competitive inhibitors- now imatinib stops uncontrolled cell division in leukaemia

Answer 26

- imatinb is a non competitive inhibitor as it binds to a site other than the active site (allosteric site) - this means that the active site is now the wrong shape and no e-s complex is formed - so the uncontrolled cell division is now controlled

Question 27

blood vessel to which the artificial heart is connected

Answer 27

Aorta

Question 28

why the left ventricle requires the help of the artificial heart but the right ventricle does not

Answer 28

- because the left ventricle pumps the blood further (to the whole body except lungs) - meaning It does most the work and produces a greater force/pressure

Question 29

why the pulse recordings in the doctor’s surgery were taken when the men were lying down

Answer 29

-the patients were at rest in controlled conditions using a standard position

Question 30

why the pulse felt can be used to measure heart rate

Answer 30

- because it is caused by pressure, a surge of blood | - from one contraction of the left ventricle of the heart

Question 31

Why people with AIDS die because they are unable to produce an immune response to pathogens

Answer 31

- because people are infected by other pathogens - which reproduce and cause disease - which can damage cells - and release toxins - and the immune system can’t prevent or stop the events

Question 32

why because HIV shows a lot of antigenic variability a vaccine might not be effective against HIV

Answer 32

-antigen on HIV changes -so specific receptor no longer binds to new antigen OR -there are many different stands of HIV -and it is not possible to make a vaccine for all antigens

Question 33

Ways in which substances can cross the cell surface membrane

Answer 33

``` By osmosis - From a high water potential to a low water potential/down a water potential gradient - Through aquaporins/water channels By facilitated diffusion - Channel/carrier protein - Down concentration gradient By active transport - Carrier protein/protein pumps - Against concentration gradient - Using ATP/energy (from respiration); By phagocytosis/endocytosis - Engulfing by cell surface membrane to form vesicle/vacuole By exocytosis/role of Golgi vesicles - Fusion of vesicle with cell surface membrane ```

Question 34

How atheroma formation increases a person’s risk of dying

Answer 34

- atheroma is fatty material - in the wall of an artery - which causes higher risk of aneurysm - and a higher risk of thrombus formation/blood clot - which could block the coronary artery - so less oxygen/glucose goes to the heart muscle - and reduces respiration - causing a heart attack (myocardial infarction) - or it could block an artery to the brain - causing a stroke

Question 35

type of reaction that would break down these carbohydrates into their monomers.

Answer 35

Hydrolysis

Question 36

Give a feature of starch and explain how this feature enables it to act as a storage substance

Answer 36

1. Coiled / helical / spiral 2. (So) compact / tightly packed / can fit (lots) into a small space 3. Insoluble 4. (So) no osmotic effect / does not leave cell / does not affect water potential 5. Large molecule / long chain 6. (So) does not leave cell / contains large number of glucose units 7. Branched chains 8. (So) easy to remove glucose

Question 37

An arteriole is described as an organ. Explain why.

Answer 37

-Made of (different) tissues / more than one tissue

Question 38

An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow to capillaries.

Answer 38

1. (Muscle) contracts; | 2. (Arteriole) narrows/constricts/reduces size of lumen/vessel / vasoconstriction;

Question 39

A capillary has a thin wall. This leads to rapid exchange of substances between the blood and tissue fluid. Explain why

Answer 39

-Short diffusion distance/pathway;

Question 40

Blood flow in capillaries is slow. Give the advantage of this.

Answer 40

-(More) time for exchange/diffusion (of substances);

Question 41

Kwashiorkor is a disease caused by a lack of protein in the blood. This leads to a swollen abdomen due to a build up of tissue fluid. Explain why a lack of protein in the blood causes a build up of tissue fluid.

Answer 41

1. Water potential (in capillary) not as low/is higher/less negative / water potential gradient is reduced; 2. Less/no water removed (into capillary); 3. By osmosis (into capillary);

Question 42

Classification

Answer 42

-kingdom, phylum, class, order, family, genus, species

Question 43

These results suggest that leopards are more closely related to cheetahs than to pumas. Explain why.

Answer 43

1. More hydrogen bonds (form); 2. Similar DNA sequence(s) / similar base sequence(s) / more complementary bases / more base pairs;

Question 44

what is meant by a genetic bottleneck

Answer 44

1. Drop in population / many killed / only single female left; 2. Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene pool;

Question 45

What is intraspecific variation?

Answer 45

-Variation / differences within the same/a species;

Question 46

Explain why both types of twin were used in this investigation. (schitsophrenia)

Answer 46

1. Identical twins show genetic influence / differences between them show environmental influence; 2. Non-identical twins (also) show an environmental/non-genetic influence;

Question 47

factors that the scientists should have taken into account when selecting the twins to be used in this study.

Answer 47

1. Age; 2. Sex (non-identical twins); 3. Family/medical history (of mental illness); 4. No use of recreational drugs; 5. Ethnic origins;

Question 48

Describe how the students would have returned the air bubble to the start of the capillary tube in this investigation.- potometer

Answer 48

-Open/use tap / add water from reservoir;

Question 49

precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot.

Answer 49

- 1. Seal joints / ensure airtight / ensure watertight; 2. Cut shoot under water; 3. Cut shoot at a slant; 4. Dry off leaves; 5. Insert into apparatus under water; 6. Ensure no air bubbles are present; 7. Shut tap; 8. Note where bubble is at start / move bubble to the start position;

Question 50

A potometer measures the rate of water uptake rather than the rate of transpiration. Give two reasons why the potometer does not truly measure the rate of transpiration.

Answer 50

1. Water used for support/turgidity; 2. Water used in photosynthesis; 3. Water produced in respiration; 4. Apparatus not sealed/’leaks’;