Bio exam questions

Question 1

A student suggested that details of component C could clearly been seen with a very good light microscope

Explain why the student is not correct (2 marks)

(By the way component c is mitochondria)

May 2013 unit 1

Answer 1

The mark scheme says

1- Component C is too small
2-The student would need a microscope with higher resolution
3-The wavelength of light is too long

It says to ignore references about magnification (I’m assuming that’s because it says could not be seen clearly)

Question 2

New growth in a stem or trunk comes from the cambium which is situated between xylem and phloem tissue

Explain why the new branches in fig 3.2 are seen going from a position just under the bark of the cut surface (2 marks)

May 2013 (unit 1)

Answer 2

1. Where cambium/meristem/vascular bundle/xylem/phloem found
2. Mitosis occurs in cambium to produce new cells for growth
   New cells can differentiate in cambium into xylem and phloem (learnt that in differentiation and stem cells)

Question 3

Suggest what lenticels are essential to the survival of large multicellular organisms and explain why similar structure are not found in large multicellular animals (2 marks)

Picture shows small holes in branch

(May 2013 unit 1)

Answer 3

1. Allows oxygen to reach cells under bark
   For aerobic respiration
2. animals transport oxygen in blood/circulatory/or transport system
   Plants do not transport as much oxygen

Question 4

Name a location where growth occurs in plant

Answer 4

Meristem

Tip/apex of root or shoot

Question 5

Explain why fetal haemoglobin curve is on the left of the adult haemoglobin curve

(3 marks)

May 2013 unit 1

Answer 5

1. Fetal haemoglobin has a greater affinity for oxygen than adult haemoglobin
2. This is because the placenta has a low PO2
3. so oxygen is more likely to dissociate from haemoglobin there

Question 6

Sickle cell anaemia is an inherited disorder in which haemoglobin crystallises when the
partial pressure of oxygen (pO2) is low. The red blood cells change shape and oxygen
transport is disrupted.

Treatment with drugs, such as hydroxyurea, can stimulate adults to produce fetal
haemoglobin rather than adult haemoglobin.

Suggest why this treatment might be of benefit to adults with sickle cell anaemia.(2 marks)

May 2013 unit 1

Answer 6

(fetal) haemoglobin may not crystallise as much
(at low pO2) ;

2. So (fetal) haemoglobin can pick up more oxygen at low pO2 (than sickle haemoglobin)

So more oxygen can be transported/delivered
around the body

Question 7

Describe and explain how substances that are dissolved in the blood plasma, such as oxygen
or glucose, enter the tissue fluid from the capillaries.

3 marks + QWC so 4 marks

May 2013 unit 1

Answer 7

There is more hydrostatic pressure in the capillaries than in the tissue,
this makes the capillaries walls leakier.
Fluid is then forced out of the capillaries.
Only small molecules such as glucose and oxygen can leave the capillaries

Plus 1 QWC mark. Also, there are marks for mentioning diffusion and its gradients

Question 8

What is the function of the phospholipid bilayer?

(1 mark)

May 2013 unit 1 part of a larger question

Answer 8

To provide a barrier to large polar molecules, or to only allow small non-polar molecules through

Question 9

Distinguish between the term transpiration and the transpiration stream

3 marks

May 2013 unit 1

Answer 9

Transpiration is the loss of water vapour from stomata

Transpiration stream is the movement of water from roots to leaf

Question 10

Liver cells contain membrane-bound organelles called peroxisomes. These organelles
contain catalase, an enzyme that breaks down hydrogen peroxide to release oxygen
gas.
A student carried out an investigation on catalase using the following procedure:
• two identical sized cubes were cut from a piece of fresh liver
• one cube was frozen overnight and then defrosted
• the other cube was stored in the refrigerator
• both cubes were returned to room temperature and were placed in separate
test tubes containing equal volumes of 2% hydrogen peroxide solution.
The student observed that the cube of the liver that had been frozen and defrosted, bubbled
significantly more than the cube that had been refrigerated.

Suggest an explanation for this result (2 marks)

May 2013 unit 1.

Answer 10

The reason is that when deforested the membrane was damaged (you wrote ice crystals pierced it)

Mark 2

this increases the permeability of the membrane

Question 11

DNA codes for the structure of polypeptides.

State the role of messenger RNA (mRNA)

Answer 11

mRNA carries a section of or copy of a gene

2. out of the nucleus/ transfers to a ribosome

Question 12

Describe the actions of b-lymphocytes in the immune system ( 6 marks)

Answer 12

1. Part of the humoral response ;
2. (B) cell/lymphocyte has antigen receptor / carries antibody on its surface
3. This is specific to / matches / complementary to, only one antigen ;
4. clonal selection happens when
5. the correct macrophage selects the b-lymphocyte
6. with the complimentary receptor
7. Then clonal expansion ;
   by (selected cell) divides by mitosis/clones;
8. (B) cells , differentiate / specialise ;
9. (B cells) form, plasma/effector, cells ;
10. (which) secrete/produce, antibodies ;
11. antibodies are, specific/complementary, to antigen ;
    (B cells) form memory cells
    this (provides) secondary response
    they are long-lasting

Question 13

suggest why adults who have survived malaria may lose their immunity when they leave a malarial area ( 2 marks)

Answer 13

Because
no further exposure means that you lose immunological memory
their b memory cells are limited/may reduce/get lost

Question 14

Explain why the decision was made to conserve the species in captivity (ex-situ) rather than in the wild(in-situ) ( 3 marks)

Answer 14

Note: can probably use this template for any question really

1. Can monitor the health of organisms/prevent disease
2. protection from predation/hunting
3. manipulate breeding
4. reduce competition between organims

Question 15

Explain why the white backed vultures in the captive breeding programme were (3 marks)

• collected from different areas
• housed in seperate centres

Answer 15

1. Maintains genetic biodiversity
2. reduces the risk of inbreeding
3. different races of vultures
4. less likely to risk losing organims (vultures) to disease

Question 16

Outline three reasons why the conservation of the white backed vultures is important (3 marks)

Answer 16

Any of the points below, im guessing it can be generic
maintains biodiversity
 part of food chain / part of ecosystem / part of food web /
scavengers
 have a right to existence / moral reason
 specific religious reason
 give pleasure / beautiful creatures
 ecotourism
 useful product / source of medicine / medical research
 genetic resource
 saves clearing up / remove carcasses
 prevents disease
 keeps , rat / dog , population down

Question 17

Suggest three measures that could be taken in the long term to preserve the numbers of
white-backed vultures, once the captive bred individuals have been released into the wild. ( 3 marks)

Answer 17

Any of the points below 
ban / make illegal , use of this painkiller ;
provide alternative painkillers
 (that do not have the same ecological impact) ;
no hunting / no killing / legal protection,
of white-backed vultures ;
protected areas / sanctuary / reserves ;
provide breeding sites ;
prevent habitat destruction ;
monitoring (of vultures) / tagging ;
feeding programme (for released birds) /
 provide uncontaminated carcasses ;
qualified ref. to education ;
promotion of ecotourism ;
in case the population falls again,
 sperm and egg banks / frozen embryos ;

Question 18

State the type of variation shown in figure 5.2 and describe its characteristics

Type of variation: it’s discontinuous btw

Answer 18

Any points below 
Influenced by single / few, genes 
It is qualitative ;
It has discrete categories 
 There are no intermediates ;
no / small / little , environmental effects ;

Question 19

Outline how a breeding programme could be carried out to produce wheat plants that have both high yield and resistance to mildew (which is a bad fungus that infects them)

Answer 19

artificial selection / selective breeding ;
cross / breed , Iranian / resistant , wheat with ,
high yield / UK , wheat ;
method to prevent self , pollination / fertilisation ;
select , best offspring / offspring with good yield and resistant ;
(back) cross to high yield (UK) wheat / interbreed best offspring
/ interbreed offspring with both characteristics ;
idea of breeding (and selecting) for many generations ;

Question 20

Over a period of time mildew can overcome the resistance bred into the wheat.

Using the theory of natural selection explain how the mildew fungus adapts to overcome resistance

Answer 20

Mark points below

1. There is genetic variation, due to a mutation.
2. Wheat resistance acts as a selection pressure
3. Mildew fungus that has the overcome resistance are more likely to survive
4. The mildew fungus reproduce
5. They will then pass on their successful allele to their offspring
6. increased frequency in the allele

Question 21

An investigation was conducted into the effect of smoking on lung function. One measure of
lung function is peak flow rate.

The peak flow rate is the maximum volume of air expelled from the lung in one minute
(dm3 min–1).

Two male volunteers, one a smoker and one a non-smoker, had their peak flow measured
once a year for seven years.

Using the information above suggests three ways of improving the reliability of this investigation

Answer 21

1. more individuals (male) should be used
2. replicates / repeat measurements (at one time)
3. calculate, mean/average
4. identify/deal with, anomalous results ;
5. take measurements at more frequent intervals;
   controlled variable ;

Question 22

State what benedicts solution tests for and what a positive test is.

June 2010 unit 2

(2 marks)

Answer 22

tests for reducing sugars

blue to red, green, yellow

Question 23

Describe the structure of a triglyceride molecule (3 marks)

June 2010 unit 2

Answer 23

You could draw it or

1. one) glycerol
   3 fatty acids
   ester bond (between glycerol and fatty acid)

Question 24

State three roles of lipids in living organisms

(3 marks)

June 2010 unit 2

Answer 24

(thermal) insulation 
energy, store / source / release 
protection 
membranes / phospholipid bilayer /
 control entry and exit into cells 
(steroid) hormones / named steroid hormone 
buoyancy 
waterproofing 
source of water (from respiration) ;
(electrical insulation) in myelin / around neurones /
 around axons / around dendrons 
aid, absorption / storage / production, of,
 fat soluble / A / D / E / K, vitamins

Question 25

Define the term classification (2 marks)

June 2010 unit 2

Answer 25

A method of grouping organisms (1) can also say classifying/taxa/categories
based on similarities/or differences

Question 26

Human populations with diets high in animal fats have a lower life expectancy than those with
diets high in vegetable oils.

Suggest one difference between lipids from animals and those from plants. (1 mark)

June 2010 unit 2

Answer 26

At room temperature animal lipids are solid
they are saturated
they contain only single bonds

can allow vice versa if talking about plants

Question 27

Suggest what criteria a taxonomist may take into account when classifying a new species (3 marks)

June 2010 unit 2

Answer 27

Anatomical features/morpholpgy/
biochemistry/ cyctochrome C 
genes dna etc 
embryological/behavioural 
idea of shared evolutionary relationship

Question 28

Describe the differences between a classification system based on domains and one based on kingdoms

( 4 marks) June 2010 unit 2

Answer 28

1. 3 domains AND 5 kingdoms ;
2. domains are, bacteria / eubacteria, AND,
   archaea / archaebacteria, AND,
   eukarya / eukaryotes ;
3. kingdoms are prokaryotes AND protoctists
   AND fungi AND plants AND animals ;
4. eukaryotes split into different kingdoms /
   all eukaryotes are in the same domain ;
5. all prokaryotes are in the same kingdom /
   prokaryotes split into different domains ;
6. domain classification based on,
   rRNA / ribosomes / RNA polymerase /
   protein synthesis / enzymes /
   flagella / membrane structure ;

Question 29

The food poisoning outbreak involved the bacterium Escherichia coli 0157 (E. coli 0157) which
had been responsible for contaminating meat products. The meat had been stored at 11 °C
rather than the recommended 5 °C and this led to meat spoilage.

Explain how bacteria cause food spoilage. ( 3 marks)
June 2010 unit 2

Answer 29

1. Bacteria reproduce
2. secrete enzymes
3. which then digest food
4. Bacteria release toxins
5. which causes a change in smell, appearance etc

Question 30

Food normally spoils much faster if stored at temperatures higher than 5 °C.

Explain why food spoils faster at higher temperatures
(3 marks)

Unit 2 June 2010

Answer 30

1. Bacetria reproudce rapidly
2. more bacteria present
3. more toxins are released
4. more enzymes are secreted.

Question 31

Explain why the mRNA molecule is shorter than a DNA molecule

Answer 31

1. mRNA is a copy of a section of gene

2. DNA has many genes

Question 32

Given some context that one enzyme involved in the production of mRNA is inhibited by α-amanitin., then we are told

The Roman Emperor Claudius was poisoned by his wife Agrippina when she gave him
death cap fungus to eat. The death cap fungus contains α-amanitin.

Suggest how the toxin α-amanitin may lead to the death of an organism. (2 marks)

Unit 2 June 2010

Answer 32

1. mRNA production would be inhibited
2. which prevents protein synthesis

(said they would accept translation for second mark and transcription for the first mark)

Question 33

Smoking increases the risk of lung infections.

Explain how the mucus and the cilia in the air passages reduce the chance of developing
lung infections. ( 2 marks)

Unit 2 June 2010

Answer 33

1. Mucus traps microorganism/pathogens/bacteria/virus etc

2. Cillia waft/sweep/move bacteria, pathogens, mucus etc

Question 34

Describe how the structure of an antibody molecule is related to its function. (7 marks)

June 2010 unit 2

Answer 34

1. Structure:Y-shaped molecule / light and heavy chains
   disulfide bonds / 4 polypeptide chains ;
2. Structure: constant region ;
3. Function: marker for / binds to, phagocytes / AW ;
4. Structure: variable region ;
5. Function: (antibody) specificity ;
6. Function: (has) complementary shape to antigen (on pathogen)
7. structure: hinge (region)
8. function: allows flexibility ;
9. Structure: more than one variable region :
10. Function: agglutination / description of agglutination
    or attachment to more than one, pathogen / antigen ;
    neutralisation / blocking pathogen’s binding sites ;
    QWC mark

Question 35

When proteins are heated to a high temperature, their tertiary structure is disrupted.
Explain how this occurs. (3 marks)

June 2010 unit 2

Answer 35

1. Increased kinetic energy
2. the molecule vibrates
3. hydrogen/ionic/hydrophilic- hydrophobic interactions break
4. Causes a change in 3D shape or tertiary structure
5. the protein denatures

Question 36

Before any major development can take place, an Environmental Impact Assessment (EIA)
needs to be carried out. One such development is the proposed extension to the M27 motorway in Hampshire. This extension would cut through an important heathland ecosystem.

Suggest three aspects of this development that would need to be considered when carrying out the EIA. ( 3 marks)

June 2010 unit 2

Answer 36

1. Need to consider how it will affect the biodiversity of heathland
2. consider whether there are rare/endangered species present in
3. consider how rare the habitat is
4. the effect of moving organisms
5. how reducing the size of the habitat will affect life

Question 37

An ecologist carried out a survey of butterfly species on the heathland.

The ecologist walked along a marked path on four different days in June. She counted
• the number of butterfly species
• the number of individual butterflies of each species.

Suggest how this method of collecting data could be improved. (3 marks)

June 2010 unit 2

Answer 37

The mark scheme says

1. collect in a wider area
2. use a sweep net/or take photographs
3. collect at different times of the day
4. could do mark, capture, recapture

Question 38

Suggest the implications of a high value of Simpson’s Index of Diversity on planning decisions. ( 2 marks)

June 2010 Unit 2

Answer 38

1. There is a high biodiversity/species richness/species evenness/ many species present
2. therefore area should not be developed, or development should be modified, or habitat should be conserved, or development should be reconsidered

Question 39

State why Small Heath and Large Heath butterflies both share part of their scientific name. (2 marks)

by the way, they share the same genus so what’s the next mark

June 2010 unit 2

Answer 39

2. have similar features, appearance, behaviour, biochemistry,

or

3. share a common ancestor, have similar phylogeny

Question 40

Before the division of the nucleus of a cell, the genetic material must replicate.

Explain why this is essential. (2 marks)

May 2012 unit 1

Answer 40

1. Each daughter cell are genetically identical/same DNA

2. Each daughter cell have a full copy of DNA/46 chromosomes

Question 41

Explain what is meant by a homologous pair of chromosomes (3 marks)

May 2012 Unit 1

Answer 41

1. One chromosome is from the mother one and from the father
   2 they both carry the same genes ;
   3 they both carry, same / different, alleles ;
   4 (usually) same / similar, length ;
   5 centromere in same position ;
   6 same banding pattern ;
   7 pair up in meiosis / form bivalent ;

Question 42

What is the function of the ciliated tissue

1 mark

Answer 42

To waft mucus or to secrete mucus

Question 43

Suggest a type of extracellular protein that can be secreted at the cell surface membrane

(1 mark)

Answer 43

1. Enzyme, hormone

can accept things like insulin, amalyse, collagen,

Question 44

The pressure fluctuates as the blood flows along the aorta, as shown in Fig. 3.1.
Explain what causes this fluctuation.

(2 marks)

May 2012 unit 1

Answer 44

1. ventricular systole increases pressure
2. Diastole decreases pressure

other marks

3. contraction of ventricle/muscle/wall
4. ventricle

Question 45

State the term used to describe the number of fluctuations per minute ( 1 mark)

May 2012 unit 1

Answer 45

Heart rate

Question 46

Using the information in Fig. 3.1, explain what causes the overall change in pressure as
blood flows from the aorta to the arteries and from the arteries to the capillaries.

(3 marks)

May 2012 Unit 1

Answer 46

1. blood flows into a larger number of vessels ;
2. (total) the cross-sectional area of the arteries is
   greater than the aorta
3. (total) the cross-sectional area of the capillaries is greater than the, aorta/arteries

When you did this it said to ignore any comments about the lumen

Question 47

A student wanted to observe some red blood cells under the microscope. The student placed
a small sample of blood onto a microscope slide and added a drop of distilled water. When viewed at high power, the student observed that the red blood cells had burst.

In a similar procedure using plant epidermis, the student observed that the plant cells did not
burst.

Explain these observations. ( 4 marks)

May 2012 Unit 1

Answer 47

1. the RBC has a lower water potential than distilled water
2. so water moves into the red blood cell by osmosis
3. The cell surface membrane is weak, so it will burst due to pressure
4. For a plant cell the water will also move I to the cell by osmosis
5. because the water potential in the plant cell is lower the water potential outside the cell
6. the inelastic cellulose cell wall prevents the plant from bursting
7. So the plant cell becomes turgid

Question 48

Suggest how the student could modify the procedure to observe red blood cells without them bursting. (1 mark)

May 2012 Unit 1

Answer 48

1. Use a salt/sugar solution

2. Use a solution with a lower water potential than the blood

Question 49

About 1 dm3 of air cannot be expelled from the lungs. This is known as the residual volume.

Suggest why it is not possible to expel all the air from the lungs. ( 2 marks)

May 2012 Unit 1

Answer 49

1. the trachea contains cartilage
2. It would be hard to compress the ribcage or intercoastal muscles
3. bronchioles/alveoli are held open by elastic fibres

Question 50

Sugar molecules are actively loaded into the transport tissue.

Describe how active loading takes place. ( 3 marks)

May 2012 Unit 1

Answer 50

1. Hydrogen ions are loaded into the companion cells
2. the concentration of hydrogen ions is lower outside of the cell than inside
3. The hydrogen ions re-enter the cell
4. and the sucrose molecules flow/move with the H+ ions
5. down the concentration gradient
6. by facilitated diffusion
7. through a co-transporter

Question 51

Suggest why the base sequence in the genes for human antibodies is more similar to that found in a chimp than to that found in a mouse. ( 2 marks)

Mixed question Unit 2 PMT

Answer 51

1. Chimps and humans are common ancestors
2. Common ancestor is more recent
3. Less time for mutations

Question 52

Fungi such as Fusarium venenatum are grown in huge batch cultures to manufacture
protein for food products.

Explain why these cultures are often maintained at the optimum temperature for protein production and not at a temperature above the optimum. ( 8 marks)

Answer 52

So you split the question into 2

First is what happens for the optimum temperature

1. At the optimum temperature molecules have more kinetic energy
2. more frequent successful collisions occur with more energy
3. so more enzyme-substrate complexes form
4. Until Vmax is reached

After passing the optimum temperature

1. at higher temp more molecules have higher kinetic energy
2. this leads to molecules vibrate more
3. this causes hydrogen and ionic bonds to be broken
4. this causes a change in the tertiary structure
5. which leads the active site to lose its shape
6. enzymes become denatured
7. the substrate no longer fits into the active site

Question 53

State what is meant by species richness ( 1 mark)

Answer 53

Number of different species present in an area

Question 54

Describe how the students may have determined the numbers of individuals of each species in each habitat. (5 marks)

Its about insects i think

Answer 54

1. They could have randomly chosen an area to observe, by diving up the habitats (elaborate obvs)
2. then using a sweep net
3. Repeat this same technique in every habitat
4. then classify each insect caught

Question 55

Discuss the role of an EIA as part of a local planning decision. (3 marks)

Answer 55

1. they look at whether there is a need for conservation or whether to maintain biodiversity
2. To see whether there are any endangered animals that need protection
3. they may look at laws to see
4. they plan whether to relocate species

Question 56

Suggest why some conservationists might object to these studies. ( 2 marks)

btw they are talking about EIA studies

Answer 56

1. They believe that habitats should be left alone
2. they don’t want to damage the environment when animals are being studied
3. sampling in the area would mean that they would disturb the natural environment

Question 57

Historically, all organisms were classified into just two kingdoms. In 1988 a five-kingdom system of classification was accepted. In 1990 a three-domain system was proposed.

Discuss, with reference to the Prokaryotes, the reasons why classification systems are not universally accepted and why they change over time. ( 4 marks)

Answer 57

A reason why they change over time is that…

1. New scientific evidence has been found
2. New technology has been developed like new microscopes
3. for examples they have noticed differences between archaea and bacteria in terms of RNA polymerase/histones/membrane structure etc

Not universally accepted because

1. there is a difference of opinion between scientists

Question 58

Staphylococcus aureus is a species of bacterium that is found on the skin.

Describe how variation may arise within a species of bacterium such as S. aureus. (1 marks)

Answer 58

1. Spontaneous mutation

Question 59

Suggest why such variation alters the characteristics of the individual organism. ( 2 marks)

Answer 59

1. It happens because of a change in the DNA structure
2. DNA determines your protein structure
3. so a mutation happens when there is a change in DNA structure

Question 60

Discuss the difficulties that variations arising in S. aureus may cause to the medical profession. ( 4 marks)

Answer 60

1. resistant strains will reproduce quickly
2. so scientists would need to develop new antibiotics because old ones will no longer work
3. they won’t work because s.aurus will be resistent to the antibiotics
4. we will need a wider range of antibiotics to work on several species of bacteria
5. Vaccines will no longer be affected

Question 61

The percentage of people infected with HIV is much higher in Sub-Saharan Africa than in much of Europe.

Suggest three reasons why the percentages are so much higher in Sub-Saharan Africa. ( 3 marks)

Answer 61

1. Lack of education on HIV
2. Poverty
3. there may not be that many condoms available
4. less primary healthcare so people will be less likely to be diagnosed
5. using unsterilised needles
6. could have things like war, rape,

Question 62

Explain why it is useful to collect information, such as that shown in the figure above. ( 4 marks)

I think the figure was about rates of diseases in different countries around the world

Answer 62

1. To keep track of infection rates around the world
2. to see where an epidemic is more likely to spread
3. to help research into what drugs are effective
4. it allows organisations to educate people where ist most needed
5. it allows organisations to give things like aid where needed

Question 63

Explain what is meant by the term endangered species (2 marks)

Answer 63

1. A species that numbers are low/ or habitat reduced/ whose population is critically low
2. At the risk of extinct

Question 64

Suggest why the black rhinonoscouros is going to be extinct ( 2 marks)

Answer 64

1. Hunting
2. poaching
3. shot to prevent damage to farmland
4. killed for horns

Question 65

State two ways in which the CITES agreement is helping to save endangered species, such as the black rhinoceros. ( 2 marks)

Answer 65

1. Ban the sales of ivory
2. have international agreements to protect the rhinos
3. countries can make it illegal to kill rhinos
4. use education or raise awareness

Question 66

Outline the potential benefits to agriculture of maintaining the biodiversity of wild animals and plants.

(4 marks)

Answer 66

1. instead of using insecticides farmers can have natural predators
2. it will be a source of plant variety for cross breeding
3. A source of a variety of foods
4. you can breed resistant to disease or insect crops

Question 67

Describe the molecular structure of glycogen. ( 4 marks)

Answer 67

1. Made from alpha glucose monomers
2. has 1,4 glycosidic bonds
3. has 1,6 glycosidic bonds where branches attach
4. has branching
5. it is a polymer

Question 68

Explain why the part of the antibody molecule incorporating the binding site is often called the variable region. ( 2 marks)

Answer 68

1. it is specific to the antigen
2. as different have different shapes
3. different antibodies fit different antigens
4. have different amino acid sequences

Question 69

Explain why there is a delay between the first infection by the pathogen and the appearance of antibodies in the blood. ( 2 marks)

Answer 69

1. there is a delay due to clonal selection,
2. due to clonal expansion
3. due to antigen-presenting
4. time taken for cells to differentiate
5. production of antibodies
6. there are no b memory cells

Question 70

Suggest two measures, apart from the use of antibiotics, that could be taken in a hospital to combat possible infection with MRSA. ( 2 marks)

Answer 70

1. washing hands bwteen diffnet pateints
2. sterilising equipment
3. isolating patients
4. restricted visiting
5. screen patients at the hospital regularly

Question 71

List three features of organisms belonging to the Kingdom Fungi ( 3 marks)

Answer 71

1. chitin cell wall
2. eukaryotic
3. saprotrophic/heterotophic
4. reproduce by spores

Question 72

State two features that fungi have in common with plants. (2 marks)

Answer 72

1. both have a cell wall
2. both eukaryotic
3. both have membrane-bound organelles
4. both reproduce by spores

Question 73

State two advantages of asexual reproduction to a parasite such as Plasmodium ( 2 marks)

Answer 73

1. only need one gamete
2. reproduce quickly
3. only need one parent

Question 74

In order to reproduce asexually, Plasmodium needs to obtain amino acids from the red blood cells of its host.

Suggest how Plasmodium obtains amino acids from haemoglobin within red blood cells. ( 3 marks)

Answer 74

1. they hydrolyse haemoglobin
2. by using enzymes (proteases)
3. these break the peptide bonds
4. which removes the haem group

Question 75

using fig 1.1 and your knowledge, explain why nitrogen fertiliser needs to be applied to farmland

(June 2011, 3 marks)

Answer 75

fertiliser maintains yield
application of firtiliser replaces lost nitrogen
nitrogen is required for amino acids/ proteins
nitrogen is removed from plant by harvesting

Question 76

Long story short there is a practical with the same disc of potato tuber tissue, it was placed in a solution with different sugar concentrations

State two details of the procedure that must be followed to obtain valid results (2 marks)

June 2016 paper 1

Answer 76

1. discs same , size / thickness / surface area /
   surface area to volume ratio / diameter
   2 same (variety / part , of) potato
   3 no skin on potato
   4 ref to removing excess water before (re)weighing
   5 same , number / amount , of discs (in each solution)
   6 same volume (sucrose) solution
   7 same temperature
   8 cover the tubes

Question 77

Explain how the student could use the data in the table to work out the water potential of the potato tuber tissue

June 2016 paper 1

Answer 77

You would say

1. no change in mass when wp of sucrose is equal to the water potential of the potato
2. say there would be no change in mass between 0.2 to 0.3
3. plot a graph of your results with x being sugar conc and y being wp and with a line of best-fit work out wp

Question 78

June 2016 paper 1

Answer 78

1. Lower water potential inside the root hair cell

2. because root hair cells actively pump minerals into themselves

Question 79

A DNA molecule contains two polypeptide chains

Describe how these chains are held together (3 marks)

June 2016 paper 1

Answer 79

1. Nitrogenous bases are held together by hydrogen bonds
2. Adenine binds to thymine with 2 hydrogen bonds and cytosine to guanine with 3 hydrogen bonds
3. purine binds to pyrimidine
4. phosphodiester bond hold sugar phosphate backbone together

Question 80

state an advantage of using the binomial system to name organisms (1 mark)

June 2016 paper 1

Answer 80

1. it is universal so many people can understand it
2. there is a common name for each species
3. we know what genus or species it belongs to

Question 81

Suggest two reasons why this species is critically endangered in the wild (2 marks)

June 2016 paper 1

Answer 81

1. deforestation

2. hunting

Question 82

The remaining population of the rhinos are small and scattered and isolated, explain how these factors might speed up extinction (2 marks)

June 2016 paper 1

Answer 82

1. hard to find a mate / may be gender imbalance
2. (inbreeding leading to) low genetic diversity /
   small gene pool / genetic bottleneck
   3 .cannot / less likely to , cope with / adapt to ,
   (named) environmental change
   4.all wiped out by the same disease
   5.more vulnerable to , predators / poachers
3. natural disaster could wipe out , one / some ,
   of the small populations

Question 83

Suggest one other way that zoos can contribute to the conservation of rhinos (1 mark)

btw breeding programmes were unsuccessful

June 2016 paper 1

Answer 83

1. they could educate people or raise awareness

2. promote conservation projects

Question 84

Explain why RBCs do not use any of the oxygen they are carrying ( 2 marks)

June 2016 paper 1

Answer 84

1. they lack mitochondria
2. so no aerobic respiration
3. oxygen is bound to haemoglobin
4. moved by mass flow so it doesn’t need ATP

Question 85

Explain why the blood offloads more oxygen to regularly respiring tissues than resting tissues ( 2 marks)

June 2016 paper 1

Answer 85

1. there is an increase in the PCO2
2. so haemoglobin has a lower affinity for oxygen
   or

3. (CO2 results in)
dissociation of carbonic acid / increase of H+
leading to the release of oxygen
4. more oxygen released at same pO2 /
suitable data quote from graph

Question 86

Explain how mass flow in the phloem sap occurs in plants with a vascular system

( 3 marks)

June 2016 paper 1

Answer 86

1. sugar / sucrose / assimilates ,
   in the sieve tube (elements)
   2 (assimilates) enter , sieve tube / phloem (at source)
   and lowers water potential (in sieve tube)
   3 water enters (sieve tube) , by osmosis /
   down water potential gradient / described
   and increases hydrostatic pressure 
   4 (assimilates) leave , sieve tube / phloem (at sink)
   and increases water potential (inside sieve tube) 
   5 water leaves (sieve tube) , by osmosis /
   down water potential gradient / described
   and lowers hydrostatic pressure 
   6 (assimilates) move , from high to low (hydrostatic) pressure / down pressure gradient 

Question 87

Explain how mass flow in the phloem sap occurs in plants with a vascular system

( 3 marks)

June 2016 paper 1

Answer 87

1. sugar / sucrose / assimilates ,
   in the sieve tube (elements)
   2 (assimilates) enter , sieve tube / phloem (at source)
   and lowers water potential (in sieve tube)
   3 water enters (sieve tube) , by osmosis /
   down water potential gradient / described
   and increases hydrostatic pressure
   4 (assimilates) leave , sieve tube / phloem (at sink)
   and increases water potential (inside sieve tube)
   5 water leaves (sieve tube) , by osmosis /
   down water potential gradient / described
   and lowers hydrostatic pressure
   6 (assimilates) move , from high to low (hydrostatic) pressure / down pressure gradient

Question 88

Explain why onion root tips were used to view cells undergoing mitosis ( 2 marks)

June 2017 Paper 1

Answer 88

1. There is meristem

2. this is where you’ll see lots of mitosis happening

Question 89

Describe how the molecule is prepared and secreted by cells of the salivary gland after translation has taken place ( 3 marks)

June 2017 paper 1

Answer 89

1. transport vesicle from RER (must say transport) 
2 modification / processing / folding 
3 in / at , Golgi (body / apparatus) 
4 (packaged into) secretory vesicle (must say secretory) 
5 vesicles move along the cytoskeleton 
6 (vesicle) fuses with ,
cell surface / plasma , membrane 
7 (secretion occurs by) exocytosis

Question 90

Theres a whole bunch of writing so like progesterone can easily diffuse across the plasma membrane, produced in ovaries from cholesterol

Explain why progesterone can move across membranes (2 marks)

June 2017 paper 1

Answer 90

1. It is fat-soluble
2. therefore can diffuse through phospholipids bilayer

must say diffuse through not move passes or across

Question 91

Suggest two ways in which the scientific community are likely to have validated Woose research. ( 2 marks)

Btw he suggested the domain system in 1990

June 2017 paper 1

Answer 91

1. scientific conferences, meetings
2. peer review
3. replication of works
4. looks for supporting evidence

Question 92

DNA ligase is one enzyme involved in the replication of DNA

State two other enzymes involved and describe their functions

June 2017 paper 1

Answer 92

1. DNA helicase
2. it unzips the DNA molecule
3. DNA polymerase
4. forms phosphodiester bonds, or sugar phosphate backbone

Question 93

The cytoskeleton in cells consists of microtubules and microfilaments.

Describe the roles of the cytoskeleton. ( 3 marks)

May 2014 Unit 1

Answer 93

1. To provide support/scaffolding for the cell
2. to transport vesicles around the cell or to hold organelles in place
3. to help the movement of flagella
4. to help the movement of chromosomes
5. helps change the shape of the cell

Question 94

Outline how the organelles in pancreatic cells work together to produce and release these protein molecules from the cells. (5 marks)

May 2014 unit 1

Answer 94

1. Transcription occurs at the nucleus
2. translation occurs at the ribosome
3. vesicles transport protein to Golgi apparatus
4. the Golgi apparatus processes and packages the vesicle
5. a secretory vesicle fuses with the plasma membrane
6. the protein is secreted through exocytosis

Question 95

Explain the meaning of the term tidal volume. ( 2 marks)

May 2014 unit 1

Answer 95

The volume of air in each breath

Question 96

Explain the meaning of the term vital capacity. ( 2 marks)

May 2014 Unit 1

Answer 96

the maximum volume of air that can be breathed in

Question 97

Erythrocytes are full of haemoglobin.

Describe the role of haemoglobin in transporting oxygen around the body. ( 3 marks)

May 2014 Unit 1

Answer 97

1. haemoglobin was a high affinity for oxygen
2. at the lungs oxygen binds with haemoglobin this forms oxyhaemoglobin
3. then at repairing tissues oxygen dissociates from haemoglobin because there is a low po2

Question 98

High concentrations of carbon dioxide in the blood reduce the amount of oxygen transported by haemoglobin.

Name this effect and explain why it occurs. ( 3 marks)

May 2014 unit 1

Answer 98

Bohr shift

2. it reduces the affinity of oxygen for haemoglobin
3. so more haemoglobin acid is formed

more points but I didn’t get them so

Question 99

Suggest what evidence the scientist might expect to see in companion cells, using an electron microscope. ( 2 marks)

May 2014 unit 1

Answer 99

1. many mitochondria
2. many ribosomes
3. many proteins in the plasma membrane
4. plasdostomata

Question 100

Complete the paragraph. ( 5 marks also learn this paragraph)

At step A, charged particles are moved out of the companion cells by the process of
………………………………………………… . This creates a …………………………………………………gradient between the companion cell and its surroundings. At step B, the charged particles and assimilates are co-transported by …………………………………………………
diffusion into the companion cells. The assimilates build up in the companion cells and move by ………………………………………………… into the sieve tube elements at step C.
Assimilates, such as sucrose and …………………………………………………, can be loaded in
this way.

Answer 100

1. active transport
2. concentration gradient
3. facilitated diffusion
4. diffusion
5. amino acids

Question 101

describe the functions of glycoproteins in the cell surface membrane

(Jan 2010, 5 marks)

Answer 101

acting as antigens
recognition of cells as self or non self
cell signalling ( describe it)
receptors as a binding site for hormones
cell adhesion- to hold cells together
forms bonds with water molecules to stabilise membrane

Question 102

describe three steps a student should take when setting up the potometer to ensure that the apparatus works properly

(Jan 2010, 3 marks)

Answer 102

make sure shoot is healthy 
cut shoot under water 
cut at an angle 
check that there are no air bubbles 
leaves need to be dry 
make sure screw clip is tightly shut

Question 103

suggest two possible reasons, other than light and temperature, why the rate of transpiration was lower in the afternoon than in the morning

( Jan 2010, 2 marks)

Answer 103

in the afternoon…

plant is less healthy
stomatal closure
more humid so higher water potential
less air movement

Question 104

explain why potometer only gives an estimate of the rate of transpiration

(Jan 2010, 2 marks)

Answer 104

measures water uptake
not all water taken up is lost
some used for photosynthesis

Question 105

state two other ways in which the wall of an artery is different form the wall of a vein

(Jan 2010, 2 marks)

Answer 105

endothelium is folded
thicker muscle
thicker elastic tissue
thicker collagen

Question 106

explain why hydrostatic pressure of the blood drops as blood moves away from the heart

(Jan 2010, 2 marks)

Answer 106

vessels have a larger total lumen
reduced resistance to blood flow
arteries stretch
loss of fluid from capillaries

Question 107

describe and explain what happens to the blood plasma at point A along the capillary tube

(Jan 2010, 3 marks)

Answer 107

plasma moves out of capillary 
enters tissue fluid
plasma proteins remain in the capillary 
fluid moves down pressure gradient 
hydrostatic pressure greater than water potential

Question 108

describe the methods the student used to:
collect both samples of fleas
find out the proportion of fleas that are resistant
process the data

(classification and evolution 2, 7 marks)

Answer 108

named equipment for collecting from dogs ( pooter, forceps, tweezers, pipette, flea comb, sweep net, sticky traps) 
get large number of fleas 
use several dogs - random sampling 
named container ( tank, jar, boiling tube, petri dish) 
control without flea killer 
leave for a set amount of time 
count number of dead/ live fleas 
calculate % of live/ dead

Question 109

living organisms can be classified into three groups called domains.

outline the features of this system of classification compared to the five kingdoms system

(classification and evolution 2, 3 marks)

Answer 109

based on differences in RNA/ DNA/ nucleus acids
domains more accurately reflect origin of prokaryotes
divides it into bacteria and archaea
(explain differences e.g. RNA polymerase)
domain reflects that there are similarities between eukaryotic kingdoms

Question 110

describe how it’s possible to confirm, over a long period of time, whether two organisms belong to different species or the same species

(classification and evolution 2, 2 marks)

Answer 110

INTERBREED

determine if offspring are fertile
if not, then different species

Question 111

species that are more closely related in evolutionary terms have more genes in common than species that are less closely related

using the information provided, suggest the likely genetic relationship between the three parrot species

(answer more specific to the question)

Answer 111

they are all in the same family
kea and kaka are both in the same genus (nestor)
kea and kaka are more closely related
share more recent common ancestor

Question 112

define the term parasite

( communicable diseases 1, 3 marks)

Answer 112

lives on host
gains food from host
at the expense of the host being harmed

Question 113

suggest two reasons why governments in parts of the world other than tropical areas, are also becoming increasingly concerned about malaria

(communicable diseases)

Answer 113

climate change results in spread to other parts of the world
increased movement of infected people

Question 114

outline the mode of action of antibodies in defending the body against pathogens by describing the process of naturalisation and agglutination

( communicable diseases)

Answer 114

neutralisation:
block bonding site on pathogen
bind to toxins
prevent binding to host cell

agglutination:
clump together
clump is too large to enter host cell
increase likelihood of being consumed by phagocyte

Question 115

explain why the students use of the word ‘immune’ was incorrect

Answer 115

immunity involves lymphocytes that bacteria do not have
correct term is resistant
bacteria are unicellular

Question 116

explain how phagocytes are able to pass from the blood into the tissue fluid

(communicable diseases)

Answer 116

lobed nucleus
can change shape
can squeeze between cells through pores
histamines make capillary walls more leaky

Question 117

describe the process by which a pathogen is destroyed after it has become attached to the surface of a phagocyte

Answer 117

pathogen engulfed by cytoplasm 
phagocytosis 
formation of phagosome 
lysosomes fuse with phagosome making phagolysosome
enzymes are in lysosome
hydrolyse pathogen to amino acid/ sugar
breaks down products into cytoplasm

Question 118

state what a gene codes for

Answer 118

sequence of amino acids

Question 119

state the role of a gene

Answer 119

codes for one or more polypeptide

Question 120

explain how the structure of DNA allows replication

Answer 120

double stranded
both strands act as template
hydrogen bonds easily break and form between bases
purine binds to pyramidine die to different sizes of purines and pyramidines
3 h bonds between C and G
2 h bonds between A and T

Question 121

suggest how changing the sequence of DNA nucleotides could affect the final product that DNA codes for

Answer 121

different sequence of amino acids- primary structure
different tertiary structure
no longer function

Question 122

Outline how the percentage efficiency of energy transfer between producers and herbivores
can be estimated.

Answer 122

herbivore / primary consumer,energy x 100 ; producer energy

last 3 marks

sample primary consumers
sample producers
measure biomass
using a calorimeter

Question 123

Suggest three ways that farmers can maximise the efficiency of the transfer of energy up food chains from primary consumers to humans.

Answer 123

1. keep animals, warm / indoors ;
   2 reduce animal movement ;
   3 feed animals high, protein / energy, food ;
   4 vaccination / (routine) antibiotics, for animals ;
   5 selective breeding / genetic engineering,
   for improved animals ;
   6 slaughter just before, mature / full size ;

Question 124

Define producer

Answer 124

autotrophic/change light energy into chemical energy

Question 125

Define consumer

Answer 125

eats other organisms

Question 126

Define trophic level

Answer 126

level on a food chain

Question 127

What is a dynamic ecosystem

Answer 127

biotic and abiotic factors vary over time

Question 128

Suggest two reasons why the large scale removal of peat from bogs for use in gardens is
discouraged by conservation groups.

Answer 128

1. peat bogs take a long to form

2. reduces biodiversity

Question 129

what is humus

Answer 129

type of soil that contains microorganisms animals etc

Question 130

What does decomposition mean

Answer 130

to break down dead matter

Question 131

What does denitrification mean

Answer 131

denitrification is conversion of nitrates to nitrogen (gas)

Question 132

what does conservation mean

Answer 132

conservation maintains , ecosystem / biodiversity /

species / habitats

Question 133

what does preservation mean

Answer 133

preservation leaves , ecosystems / habitats ,

undisturbed

Question 134

what does niroegen fixtaion mean

Answer 134

nitrogen fixation is the conversion of (atmospheric)

nitrogen into ammonia

Question 135

what does nitrification mean

Answer 135

nitrification is the conversion of ,ammonia / ammonium compounds /ammonium ions , into nitrite / nitrate

Question 136

Resistance to antibiotics has evolved in some pathogenic bacteria, such as MRSA.

Suggest why the resistance of MRSA to existing antibiotics is of major concern to humans.

Answer 136

1. there is a risk of a disease outbreak

2. creating new antibiotics takes time

Question 137

The evolution of antibiotic resistance in bacteria is evidence to support the theory of evolution.

How does fossil evidence support the idea that evolution has taken place?

Answer 137

1. fossil show development of organisms over time
2. these can be dated
3. they can show a sequence of evolution

Question 138

Describe three characteristics of continuous variation.

Answer 138

1. controlled by many types of genes/ influenced by the environment
2. qualitative
3. has no distinct categories

Question 139

Suggest two undesirable consequences of selective breeding

Answer 139

1. inbreeding
2. more suspectable to disease
3. low genetic variety

Question 140

The wild ancestor of the domestic chicken is the red jungle fowl found in the rainforests
of South East Asia.

Explain why it is important to preserve the population of the red jungle fowl.

Answer 140

maintain biodiversity ;
aesthetic (reasons) / tourism ;
ethical (reasons) ;
part of a food chain / web ;
maintain / increase gene pool ;
genetic resource / availability to breed with domestic
chickens

Question 141

what do you do if your t value is above the critical value

Answer 141

you reject the null hypotheses and say the difference (between the means) is significant / not due to chance

Question 142

Describe three steps a student should take when setting up the potometer to ensure that the apparatus works correctly

Answer 142

1. potomtere is airtight
2. there is no water on the leaves
3. cut the shoot underwater
4. cut it at an angle

Question 143

Xerophytes have various modifications that reduce water loss from their leaves.

State two such adaptations that reduce water loss and explain how the reduction in loss is achieved.

Answer 143

1. covered in hair, this traps water vapour
2. thick waxy cuticle, reduces evaporation of from leaves
3. have spikes for leaves, which reduces the surface area
4. sunken stomata traps water vapour
5. rolled up leaves less surface area

Question 144

what does habitat mean

Answer 144

a place where an organism lives

Question 145

what does biodiversity mean

Answer 145

variety of life / the range of living organisms found

or a variety of habitats

Question 146

basically the question talks about the last male Spix Macaw mating with a Blue-winged Macaw

explain why the eggs produced did not hatch

2 marks

Answer 146

different species
different genus
genetically incompatible
(may have) different number of chromosomes
physical / behavioural , reason for reproductive
incompatibility

Question 147

describe three ways in which the sweep net sampling procedure could be designed to try and make sure that a representative sample was obtained

Answer 147

idea of: unbiased method to selecting sampling area
sample many times / AW, and calculate mean / average
standardised sweeping procedure
ensure insects do not escape (before being identified)
method to prevent recounting
sample at different times of, day / month / year / weather
conditions

Question 148

state two of the aims of the CITES agreement

Answer 148

regulate / monitor , trade in selected ,
species / animals / plants / animal products
idea of ensuring trade does not put wild populations at
risk
idea of prohibiting commercial trade in wild plants
idea of allowing trade in artificially propagated plants
idea of allowing trade in less endangered species
subject to permit

Question 149

suggest two factors to be taken into account when selecting individuals for the breeding programme

Answer 149

unrelated individuals
healthy
selecting individuals of the opposite sex for breeding

Question 150

describe three ways in which the sweep net sampling procedure could be designed to try and make sure that a representative sample was obtained

Answer 150

idea of: unbiased method to selecting sampling area ;
sample many times / AW, and calculate mean / average
standardised sweeping procedure
ensure insects do not escape (before being identified)
method to prevent recounting
sample at different times of, day / month / year / weather
conditions

Question 151

In this study, a student placed his quadrat on areas he considered to have the most biodiversity.

Explain what is wrong with this technique

Answer 151

1. sameple he collects will be biased

2. it may be under representative or certain species and over representative of others

Question 152

The Millennium Seed Bank Project (MSBP) is a global conservation programme
conceived, developed and managed by the Seed Conservation Department at the
Royal Botanic Gardens, Kew. The aims of the project are to collect and conserve 10%
of the world’s seed-bearing plants by 2010.
The project aims to make seeds available for research and species re-introduction into
the wild. Scientists working in seed banks have to maintain the viability and genetic
variability of the seeds they store. Samples of seeds stored are germinated to assess
their variability.

Describe how scientists working in seed banks maintain the viability and genetic
variability of seeds.

Answer 152

viability- ensures seeds germinate or collect new seeds that are produced

genetic variability: collect many different types do seeds, collect them from different parts of teh world

Question 153

Zoos and botanic gardens, such as Kew Gardens, are involved in many conservation projects throughout the world.

Outline the problems experienced by zoos and botanic gardens in managing such projects and explain why it is important for such projects to be successful.

Answer 153

Problems

1. capture of species/AW;
   2 numbers of species caught ref to extinction;
   3 ref to named example e.g. elephants;
   4 maintenance of genetic variability/gene pool;
   5 ref to funding;
   6 ref to species ownership/AW;
   7 problems of storage and maintenance;
   8 ref to specific example of problem; e.g. inbreeding/altered breeding/seed
   preparation;

Need for success

10. stop extinction/maintain gene pool;
    11 potential medical benefits;
    12 agricultural benefits/artificial selection;
    13 named example of crop improvement;
    14 ethical/moral responsibility for future generations;

Question 154

state reasons for the domain prokaroytae being split into bacteria and archaea

Answer 154

molecular evidence:
RNA polymerase is different in archaea and bacteria
archaea and eukarya have similar histones
cellular evidence:
bonds of lipids in cell membranes of B and A are different
flagella is different

Question 155

explain the importance of species evenness in determining the biodiversity in a habitat

Answer 155

(measures), abundance / numbers, of individuals in each
species
species evenness is more quantitative than
species richness
high(er) species evenness indicates
high(er) biodiversity
low species evenness indicates, dominance by / high
abundance of, one / few, species
used to calculate (Simpson’s) Index of Diversity

Question 156

suggest what is meant by critically endangered

Answer 156

likely to become extinct / on the verge of extinction /
numbers are not sustainable /
numbers too low for survival of species /
numbers drop below 10% of (original) population

Question 157

describe how it is possible to use selective breeding to improve the overall disease resistance of a crop such as potatoes in both the short and long term

7 marks

Answer 157

cross / breed, with disease resistant variety
method to test offspring for disease resistance
select , best offspring / offspring with
resistance
(inter)breed, offspring with resistance / best
offspring
(continue process) for (many) generations
idea of avoid breeding, closely related
individuals to preserve genetic diversity
(regularly back) cross with, wild variety
idea of preserving rare varieties in case they
are needed in the future

Question 158

suggest two reasons why the number of species identified is likely to be lower than the actual number of species present on earth

Answer 158

idea that:
not all , areas explored / species yet discovered ;
microscopic / small / nocturnal / camouflaged , species
difficult to see
sampling might miss rare species
organisms mistakenly identified as one species may
actually be two (or more) species
concept of species is difficult to define

Question 159

state two aims for each of the conventions

RIO & CITES

Answer 159

CITES 2 max
regulate / monitor / prevent , trade in , selected / certain
endangered , species
ensure (international) trade does not endanger , wild
populations
prohibit (commercial) trade in wild plants
allow trade in , artificially propagated plants
allow (some) trade in less endangered , wild species /
organisms / animals and plants
Rio Convention 2 max
sustainable use of , organisms / habitats / ecosystems ;
share genetic resources
share access to , scientific knowledge / technology ;
idea of promoting (named) ex situ conservation
method(s)
idea of raising profile of (biodiversity) with , governments
public bodies / general public
idea of international cooperation (on biodiversity issues)

Question 160

suggest how organic fertilisers improve yield of plant crops

Answer 160

broken down by, decomposers / bacteria / fungi
add (named) mineral(s) to soil
nitrate and phosphate and potassium / NPK
specific use of (any) named mineral
lack of (named) , mineral(s) / nutrient(s) / ion(s), is
limiting factor (for growth)
example of way in which soil quality is improved

Question 161

explain how excessive use of inorganic fertilisers on farmland can cause a reduction in its biodiversity

Answer 161

(fertiliser) promotes growth of, one / few, (plant)
species
other (plant) species , out-competed (as a result
of competition from crop species)
idea of disruption of food chains
idea of reduction in , soil quality / humus , over time so
plants cannot grow

Question 162

explain why a reduction in biodiversity may present problems for agriculture in the future

Answer 162

loss of genetic , diversity / variation (in wild
population)
environment / agricultural requirements, may change
(in future)
(lost) genes / alleles , may have been useful
e.g. of gene useful to agriculture
fewer pollinators
loss of (pest) predators

Question 163

outline an advantage of using a seed bank as opposed to adult plants in order to conserve an endangered plant species

Answer 163

most plants produce an excess
(so) can be collected (from wild) without damaging
(wild) , plants / organisms / population / habitat
take up little space
able to store, large numbers / more species
easy / cheaper, to transport
idea of remaining viable for long periods
less susceptible to, disease / pests / environmental
change

Question 164

suggest why its important to ensure that for each species, the seeds in a seed bank have been collected from several different sites in the world

Answer 164

(maintain / increase) genetic variation / gene pool
reduced chance of (future), disease / environmental
change, affecting (whole) population
reduces chance of inbreeding
maintain, geographical variation / varieties / races /
strains / subspecies

Question 165

suggest why bacteria cannot break down agrose (polysaccharide)

Answer 165

(bacteria) do not, make / have, correct enzyme (to digest agarose)
agarose, does not fit / not complementary to, active site
(of bacterial enzymes)

Question 166

suggest how the effects of insecticide use on a population of mosquito could be measured and state the steps that should be taken in order to produce valid and reliable results

Answer 166

Field investigation
(sampling) before and after insecticide treatment
idea of , unbiased / random, sampling of population
example of sampling technique
(sampling in) different, times / weather
large number of samples taken
idea of standardised sampling procedure
idea of preventing counting same individual more than
once
idea of capture – recapture
calculate mean / calculate standard deviation / apply
statistical test

Question 167

state what is meant by the term recessive

Answer 167

only expressed , when homozygous /

in absence of dominant (allele)

Question 168

outline the events that lead to genetic variation in gametes and in the plant grown from seed

Answer 168

mutation 
meiosis 
cross(ing)-over 
between non-sister chromatids 
(in) prophase I 
independent / random , assortment / segregation 
(in) metaphase 
idea of random , fertilisation / fusion of gametes

Question 169

outline the role of decomposers in breakdown of leaves

Answer 169

bacteria / fungi 
idea of external digestion 
by , enzymes / named enzymes 
absorption of breakdown products 
release of carbon dioxide and water 
(breakdown of protein) makes ,
 ammonium , ions / compounds
or NH4+

Question 170

State why the structure of enzyme molecules allows them to be detected in solution using the biuret test

Answer 170

(enzymes are) globular, proteins / polypeptide;

hydrophilic / water soluble, (R-)groups on outside (of enzyme

Question 171

With reference to Fig. 2.1, discuss the factors that may have affected the size of the elk population:
before 1995
after 1995

7 marks

Answer 171

idea that population size is determined by limiting factor(s);
Before 1995, population increases due to
2 example of factor that is not limiting population
Before 1995, population levels off because
3 reaches carrying capacity;
Before 1995, population becomes limited by
4 intraspecific competition for named resource;
5 interspecific competition for named resource;
Population can decline at any time/ dips, due to
6 severe weather / natural disaster;
7 decrease before 1995 not due to wolves (as none present);
8 decrease after 1995 (probably) due to wolves;
9 idea that effect of wolves on population may be debatable

Question 172

Outline how the percentage efficiency of energy transfer between producers and herbivores can be estimated.

Answer 172

a sample of) producers collected;
(a sample of) herbivores /primary consumers collected;
(collected from) the same area;
(measure) biomass / dry mass (of individual or population);
energy content calculated of producer and herbivore;
use of calorimeter / described

Question 173

Describe the differences between the following biological terms:

a) pioneer community and a climax community
b) decomposition and denitrification
c) conservation and preservation
d) nitrogen fixation and nitrification

Answer 173

pioneers arrive, before climax / earlier
pioneer community (usually) has, less / lower, biodiversity

decomposition is break down, dead matter / waste
denitrification is conversion of nitrates to nitrogen (gas)

conservation maintains, ecosystem / biodiversity / species / habitats
preservation leaves, ecosystems / habitats, undisturbed

nitrogen fixation is the conversion of (atmospheric) nitrogen into, ammonia / ammonium compounds / ammonium ions
nitrification is the conversion of, ammonia / ammonium compounds / ammonium ions, into nitrite / nitrate

Question 174

The woodland in the figure can supply timber continuously, sustainably and economically.

Discuss some social, aesthetic and ethical benefits of managing woodland in this way compared to coniferous monoculture

4 marks

Answer 174

social
amenity / recreation / (eco)tourism;
educational benefit (to visitors / children);
improve (mental) well-being;

aesthetic
landscape more attractive / AW (for local people / visitors);

ethical
(continuous management) better for local employment;
duty of care for, habitat / environment / biodiversity / food webs /ecosystems;

Question 175

Why is it important to calibrate a colourimeter

Answer 175

idea that values are, all measured to the same standard /

comparable / accurate / valid

Question 176

State how the student could reduce uncertainty of their data

Answer 176

use more, accurate / precise apparatus / described

Question 177

What is meant by the term autoimmune disease

Answer 177

-abnormal immune response

against bodies own tissues

Question 178

Scientists often use natural substances to help them develop new medicines

State two possible sources of such natural substances

Answer 178

Plants

Microorganisms

Question 179

Suggest how water is lost from the cut stem when all the leaves were treated with petroleum jelly

Answer 179

Evaporation from the leafs upper surfaces

Question 180

Suggest two possible sources of error in an investigation involving a potometre

Answer 180

• Leaks in apparatus
• shoots not cut underwater
• error reading mensicus

Question 181

Explain why onion root tips were used to view cells undergoing mitosis

Answer 181

• roots tips have meristem tissue

- cell division, growth, replication

Question 182

Suggest a stain that the student could have used to highlight the nucelli of these cells

Answer 182

Methylene blue, acetic orcein, toluidine blue

Question 183

Explain why mammals store glycogen instead of glucose

Answer 183

• Can store lots of energy
• metabolically inactive
• glycogen is insoluble so won’t change wp of cells
• compact

Question 184

Describe how the molecule is prepared and secreted by cells of the salivary gland after translation has taken place (3 marks)

Answer 184

1.transport vesicle from RER 
2. modification / processing / folding 
3. in / at , Golgi (body / apparatus) 
4 .(packaged into) secretory vesicle 
5. vesicles move along the cytoskeleton 
6. (vesicle) fuses with ,
cell surface / plasma , membrane 
7. (secretion occurs by) exocytosis 

Question 185

How does the fluid mosaic model describe the structure of plasma membranes (2 marks)

Answer 185

1. phospholipid bilayer
2. describe the structure of the bilayer, so hydrophilic heads face out towards the environment and hydrophobic tails face inwards away from the environment
3. phosphlipds/proteins move around
4. protiens are randomly scattered

Question 186

Why can progesterone move across the membrane (2 marks)

Answer 186

1. Progesterone is fat soluble/lipid/hydrophobic

2. diffuses through phospholipid bilayer

Question 187

ATP is made up of a phosphate groups and two other molecules

Name the two other molecules

Answer 187

1. Adenine

2. ribose sugar

Question 188

State how the structure of the cell surface membrane allows potassium ions to enter or leave a cell

Answer 188

-protein channels

Question 189

In 1990, Carl Woese suggested a new top level taxon to the current system of classification of living organisms, which he termed a domain. He used his results from studying RNA to organise organisms into three distinct groups.

Name the cell component that appears in organisms of all three domains that Woese
suggested.

Answer 189

Ribosomes

Question 190

Explain the meaning of semi conservative replication (1 mark)

Answer 190

The DNA molecule has has 1 old and one new strand

or

Each strand acts like a template strand

Question 191

DNA ligase is one enzyme involved in the replication of DNA.

State two other enzymes involved and describe their functions. ( 4 marks)

Answer 191

DNA polymerase (1) 
forms phosphodiester bonds/joins sugar-phosphate backbone/joins adjacent nucleotides (1)

DNA helicase (1)
unzips the DNA molecule /breaks hydrogen bonds between base pairs (1) 

Mark scheme says to ignore unwinds DNA strand

Question 192

The protease enzyme bromelain can be extracted from pineapples. A student investigated the effect of changing the concentration of the enzyme and measured the time taken to break down the protein gelatine.

State three variables that the student would need to control in order to make the results of this investigation valid. ( 3 marks)

Answer 192

1. temperature
2. pH
3. concentration of , protein / gelatine
4. volume / mass / surface area , of , protein / gelatine
5. volume of , protease / bromelain / enzyme
6. same source of , enzyme / gelatine
7. same reaction end point