Edexcel Extension Biology B3 extended answer Q's

Review of question structure in edexcel exams

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1. Question

Agrobacterium tumefaciens and Bacillus thuringiensis are both used to increase crop yields in different ways.
Describe how each of these bacteria are used to modify plants to increase crop yield. (5)

 

Question is two fold - they are asking you describe both processes!

1 Mark will come from identifying the common feature, the rest will come from describing the differences between the two.

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1. Answer

1. to make crops herbicide /pest resistant / drought resistant/eq ;
Agrobacterium tumefaciens:
Maximum of 3 marks
2. Agrobacterium tumefaciens is used as a vector / to transport genes into (crop) plant;    3. gene for desired characteristic /named characteristic e.g. herbicide resistance / gene for larger fruit identified / cut out;  4. gene put into plasmid/Agrobacterium (tumefaciens) ;  5. which infects/put into plant ;  6. plant produces crown gall (will accept tumour);  7. (crown gall) is used /tissue culture used to grow new plants (with desired characteristic);

Bacillus thuringiensis:
Maximum of 3 marks
8. Bacillus thuringiensis produces toxin/pesticide/ is a source of the gene for producing toxins / pesticides  9. gene cut out of bacterium / B.thuringiensis ; ONLY CREDIT THIS POINT ONCE  10. gene put into plasmid /vector that takes the wanted gene into plant cells ; ONLY CREDIT THIS POINT ONCE  11. gene (for toxins) incorporated into DNA/genome/eq of crop plant /plant produces pesticide so less eaten/insects killed;

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2. Questions

1. Explain what is meant by the term ‘anthropomorphic’ (2)

2. Suggest two reasons why humans keep animals as pets. (2)

3. Suggest one reason why plant extracts are carefully tested before use on humans (1)

4. What is the natural source of quinine? (1)

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2. Answers

1. Any two of:
• Companionship / Entertainment, Reduce stress / Health benefits, protection, Assist with work, Status, Products eg eggs, milk.

2.• Give a definition:
Giving animals/non-human objects human characteristics:
• Give an example:
Cartoon animals speaking/driving.

3.One of:
• May be toxic, May have side-effects, Could be harmful, May cause allergic reactions, To test if it is effective.

4. The bark of the cinchona tree

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3. Question (Variations of this Q are very common)

Describe the stages in the production of soy sauce (4 marks)

Only 4 marks so only requires 4 key points, however, you will not loose marks for including additional points.

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3. Answer

Any four in the correct sequence from:

• cook soya bean;
• mix with (ground) roasted wheat;
• ferment with Aspergillus ;
• brine is added;
yeast and/or Lactobacillus added;
• second fermentation/refermentation;
• filtered;
• pasteurisation;
• use sterile bottle

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4. Questions

1. Describe some ways that the supply of artemisinin could be increased.(3)

2.Explain how prebiotics benefit the human body. (3) They are expecting an explanation as to their role in the body and how this benefits the body - not just what prebiotics are.

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4. Answers

1. Any three from:
• Grow more Artemisia
• Use genes from Artemisia to genetically modify other plants
• GM/ selectively breed Artemisia to increase concentration of
Artemisinin/ grow faster
• Improve efficiency of extraction technique
• use GM micro organisms to produce Artemisinin
• Tissue Cluture
• use of transgenic animals

2. • Increase/stimulate the growth of (friendly) bacteria;
• Decrease the growth of bad bacteria;
• Health benefits related to above e.g reduction of toxins from bad bacteria/increasing B
vitamins from good bacteria;

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5. Question

 a). Name the type of behaviour demonstrated by ducklings following their parent. (1)

 

 

b). Explain how this type of behaviour can help the duckling survive. (3)

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5. Answers

 

a). imprinting ;
maternal /paternal/parental

b). Any three from:
1. stays near parent ;
2. less likely to be preyed on ;
3. taken to a food supply ('given food' would not be credited)
4. learn (species specific) behaviour from parent; (copies parent would be credited)
5. credit one example of
e.g. how to fly / attract mate;

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6. Questions

The first stage in making yoghurt is adding a starter culture of microorganisms to milk.

a). Name the microorganisms that are used in the starter cuture. (1)

b). Describe how these microorganisms change the milk into yoghurt (3).

c). Explain why prebiotics are added to some yoghurts (2) - 2 marks - again they are expecting more than just the definition of what prebiotics are, an explanation of their benefits will be needed as well.

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6. Answers

a). bacteria /Lactobacillus (bulgaricus/acidophilus /sp)/Streptococcus (thermophilus/lactis/cremoris/sp);

b). Any three from:
1. bacteria multiply ;2. produce lactic acid 3. lowers pH/ makes
more acidic;4. milk thickens /coagulates / clots /solidifies/ sets (curds would not be credited); 5. Streptococcus and lactobacillus work together ; 6. both produce other chemicals/acetaldehydes that give yoghurt its distinctive flavour/ taste ;

c).Any two from:
1. contain oligosaccharides ; 2. we can’t digest oligosaccharides ; 3. (the oligosaccharides) can be used by (beneficial) bacteria (to multiply) ; 4. (that) outcompete the harmful bacteria ;

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7. Questions

a). Suggest one reason the peacock would display his plummage. (1)

b). Suggest how this type of behaviour increases the chances of survival of a species. (3) -Ensure your answer relates to species survival not individual survival

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7. Answers

a). attracting a female / mate / courtship; scaring away/feels threatened

b). Any three from:
1. (female) selects the fittest / healthiest /best genes / attractive features (of male) e.g. big tail ;
2. increases the chances of mating/reproduction;3. young inherit ‘best / good’ genes 4. young have good characteristics / named characteristic 5. idea of survival of the fittest ( referred to individual / orspecies) ;6. appears larger ; 7. predator / male competitorsscared away ;8. young protected / peacock less
likely to be eaten ;

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8. Question

Pheromones are chemicals that are made by an animal and released into the air.
Some moths can detect pheromones from 10 km away. ALWAYS READ THE INFO THEY GIVE WITH THE Q CAREFULLY!
(a) (i) Describe how the concentration of the pheromone changes as it spreads out from the female moth.
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(1)
(ii) How does the male moth use this change to find the female moth?
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(1)
(b) Explain why it is important that pheromones from female moths usually only affect males of the same species.(2 marks - again, how does this befit species)
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8. Answers

a i).the pheromone becomes less (concentrated)/
particles are further apart/more spread out/
concentration weaker/less dense; (1)

(a) (ii) flies up a concentration gradient (low to high);
(1)
(b) Any two from:
1. many other chemicals/pheromones around;
2. would not know which way to go/confused/
would fly to wrong species.
3. wouldn’t find a mate/mating not successful/
no point in female – female attraction;

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9. Question (Variations of this Q are very common)

Malaria is a disease caused by the malaria parasite.
(a) Quinine is an effective anti-malaria drug.
What is the natural source of quinine?

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(1)
(b) Scientists are now testing artemisinin as a possible treatment for malaria. It is extracted from the plant Artemisia annua. At the moment it is very difficult to  get sufficient artemisinin to use as a treatment for lots of people.
(i) Suggest one reason why plant extracts are carefully tested before use on
humans. (1)
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(ii) Describe some ways that the supply of artemisinin could be increased. (3) (Ensure you relate this to identified issues with production)
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9. Answers

(a) the bark of the cinchona tree;
(b) (i) may be toxic/have side-effects/harmful/allergic reactions/ to see if it is effective; (1)

(b) (ii) Any three from:
1. grow more Artemisia;
2. use genes from Artemisia to genetically modify
other plants;
3. genetically modify/selectively breed Artemisia to
increase concentration of Artemisinin/grow faster;
4. improve efficiency of extraction technique;
5. use GM micro organisms to produce Artemisinin;
6. tissue culture;
7. use of transgenic animals;

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10. Question

A breakfast cereal for children is marketed as the first cereal to contain prebiotics.
(a) Name the food group to which most prebiotics belong. (Hint: Remeber: prebiotics are sugars - just because we cannot digest them does not change the food group you find sugars in)
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(1)
(b) Explain how prebiotics benefit the human body. (3)
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10. Answers

a). carbohydrates/ oligosaccharides; (1)

(b) increase/stimulate the growth of (friendly) bacteria; decrease the growth of bad bacteria; health benefits related to above e.g reduction of toxins from
bad bacteria/increasing B vitamins from good bacteria;

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11. Question

Some people now want to choose the sex of their baby.
(a) Explain how being allowed to choose the sex of babies may affect the human
population. (Again asking for impact overall, not impact upon individuals)
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(1)
(b) Discuss the ethical implications of choosing the sex of your baby.
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(Ethical Q's come up on almost all papers, they enable you to gain mark based on your ability to discuss multiple issues and communicate your opinion well).

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11. Answers

a). imbalance of sexes/change in gene pool; (1)

b) Any two from:
1. wrong to interfere with nature/qualified groups eg reference to Catholics;
2. cultural variations favour one gender;
3. a family which already has daughters may wish to have a son or vice versa/parents should have the right to choose;
4. ‘slippery slope’ leading to more genetic selection;
5. may lead to discrimination for one sex/ one sex not valued as another;
6. use to avoid sex linked genetic diseases;
7. reference to increased number of terminations of babies of unwanted gender;

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12. Question

Many people like to have a dog as a pet. They buy the dog as a puppy and train it. The puppy can learn through conditioning.
(a) Use an example from dog training to help explain what is meant by the term
‘conditioning’. (4) (They have stated what is required to gain full credit - if you do not include an example you will NOT gain full marks for this Q)
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(4)
(b) Describe how an animal’s parents and early experiences in life impact on the way it behaves as an adult.
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(4) (Again, requirements spelled out in the Q - do not ignore these guidelines)

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12. Answers

Any four from:
1. puppy shows desired behaviour e.g sit at curb/ORA;
2. desired behaviour is rewarded e.g given biscuit/ORA;
3. this reinforces behaviour/ORA;
4. desired behaviour increased and becomes the norm;
5. credit correct reference to operant conditioning;
[Ignore references to Pavlov’s dogs as not ‘training’ to modify natural behaviour]
(b) Any four from:
1. some behaviour is inherited/innate;
2. imprinting;
3. learn from copying parents/owners/adults;
4. allow offspring to learn species specific
behaviour e.g bird song;
5. this allows it to cope socially;
6. increased chance of courtship
7. increase chances of survival e.g finding food;
8. habituation to stimuli in early life (will reduce unnecessary behaviours);
9. credit correct reference to parents ‘teaching’ children/offsprings;
(4)

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13. Question

Explain how recombinant DNA technology (this is just a different term for GM/GE)can be used to make large amounts of useful products such as human insulin. In your answer, refer to sticky ends and how restriction enzymes and ligase are used. (6 mark Q, 2 - 3 of them require you to explain the role of the terms in the Q, USE THE ADDITIONAL GUIDANCE IN THESE Q's)
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(Total 6 marks)

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13. Answer

Any six from:
1. human insulin gene identified/removed/cut out ;
2. restriction enzyme used to cut out gene ;
3. plasmid taken from bacterium ;
4. same restriction enzyme used to cut plasmids ;
5. (insulin) gene sealed/joined to plasmid using ligase;
6. sticky ends allow (complementary) bases/genes to match up/join together;
7. plasmid inserted into bacterium ;
8. in a fermenter bacterium multiplied/grown;
9. ref to (qualified) optimum conditions
10. insulin separated / purified / extracted /collected;
accept section of DNA for gene ‘restriction enzyme’ in question so must be qualified
accept bacterial DNA for plasmid
‘ligase’ in question so must be qualified
‘sticky ends’ in question so must be qualified
accept named condition eg temperature, pH
Maximum of 4 marks if the
order is confused

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Comments

Stars122

WOW this helped me allot on what i had to learn thanks sooooooo much :) 

Kamila

these questions are really good, they helped me learn thank you!!!!!!!!!!!!

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