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Past papers - biology > Wednesday 18th January 2012 > Flashcards

Wednesday 18th January 2012 Flashcards

1
Q

Describe the function of a chloroplast. 2 marks

A
  • Absorbs sunlight
  • For photosynthesis
  • Produces carbs/ sugars/ lipids/ proteins
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2
Q

Describe what happens during anaphase that results in the production of two genetically identical cells. 2 marks

A
  • Sister chromatids

- To opposite poles

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3
Q

Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA and other had only 4.2 units. 2 marks

A
  • 8.4 - cells with twice DNA content as the DNA had replicated.
  • 4.2 = DNA not replicated
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4
Q

How many units of DNA would you expect to be present in a gamete formed in this animal as a result of meiosis?

A

2.1

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5
Q

A scientist carried out breeding experiments with catfish from different populations. Describe how the results could show that the catfish belong to the same species. 1 mark

A

Fertile offspring produced

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6
Q

The variety of colours displayed by catfish is important in courtship. Give 2 ways in which courtship increases the probability of successful mating. 2 marks

A
  • Recognise opposite sex
  • Recognise same species
  • Synchronises mating
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7
Q

Explain how this mutation leads to the formation of non-functioning PAH. 3 marks

A
  • Change in amino acids
  • Change in hydrogen bonds
  • Alters active site of enzyme
  • Substates can’t bind as they are no longer complementary so no E-S complexes can form.
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8
Q

One mutation causing phenylketonuria was originally only found in one population in Central Asia. It is now found in many different populations across Asia. Suggest how the spread this mutation may have occurred. 1 mark

A

Interbreeding - reproduction between individuals from different populations

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9
Q

Vancomycin acts on the cell wall - explain why vancomycin does not affect human cells. 1 mark

A

Human cells don’t have cell walls

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10
Q

Tetracycline acts on ribosomes - how does tetracycline prevent bacterial growth. 1 mark

A

Affects protein synthesis

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11
Q

Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain how. 3 marks

A
  • Mutation occurs
  • Resistant allele
  • Resistant bacteria survive and reproduce
  • Vertical gene transmission
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12
Q

Use your knowledge of gene transmission to explain how the gene was passed from one species of bacterium to another. 3 marks

A
  • Horizontal gene transmission
  • Via conjugation
  • Plasmid copied
  • Plasmid transferred to s.aureus
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13
Q

Scientists can use protein structure to investigate the evolutionary relationships between different species. explain why. 2 marks

A
  • Amino acid sequences
  • Close the amino acid sequence the closer the relationship.
  • Protein structure related to DNA base sequence.
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14
Q

Comparing the base sequence of genes provides more evolutionary information than comparing the structure of proteins. Explain why. 2 marks

A
  • More bases than amino acids
  • Introns
  • More than once code for each amino acid.
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15
Q

Explain the importance of taking a large number of samples at each site. 1 mark

A
  • Produces a more reliable mean
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16
Q

Explain the importance of taking samples at random. 1 mark

A
  • Removes bias
17
Q

Explain the effect of developing this golf course on the index of diversity of insects. 3 marks

A
  • Increase in variety of plants
  • More habitats
  • Greater variety of food sources
18
Q

Root pressure moves water through the xylem. Describe what causes root pressure. 3 marks

A
  • Active transport by endodermis
  • Ions into xylem
  • Lowers water potential in xylem
  • Water enters by osmosis
19
Q

Explain how oxygen is loaded, transported and unloaded in the blood. 6 marks

A
  • Haemoglobin carries oxygen
  • In red blood cells
  • At high potential of oxygen
  • Unloads to respiring cells
  • At low potential of oxygen
  • Unloading linked to higher oxygen
20
Q

The larvae in this investigation were kept at a temperature of 17 degrees, why was it important that the larvae of both species were kept at the same temperatures? 2 marks

A
  • Allows comparison
  • Different temperature affects enzymes
  • Different temperature affects metabolism
  • Different temperature affects amount of dissolved oxygen.
21
Q

Apart from age, suggest two factors that the scientists should have considered when selecting volunteers for this trial. 2 marks

A
  • Sex
  • Health
  • Ethnicity
22
Q

In analysing the results of the investigation, the scientists took into account the age of the volunteers. Suggest why. 1 mark

A

Age affects risk of cancer

23
Q

Tea and coffee contain caffeine. A newspaper reported the results of this investigation under the headline ‘ Caffeine helps cut cancer risk’. Explain why scientists could not support this view solely on the basis of this investigation. 4 marks

A
  • Correlation does not mean causation
  • Tea/coffee contains other substances
  • Contain different amounts of caffeine
  • No control group
  • Only one type of cancer studied
  • Further studies required.
24
Q

Describe how the control group should have been treated. 2 marks

A
  • Treated the same

- No caffeine

25
Q

Volunteers who drank the same concentration of caffeine solution often had different concentrations of caffeine in their blood. Suggest one reason for the difference in concentration of caffeine in the blood of volunteers. 1 mark

A
  • Absorb different amounts
  • Broken down by enzymes
  • Difference in metabolisms
26
Q

The investigation showed that caffeine reduces the blood flow to certain parts of the brain. Suggest one way in which this could lead to a reduced risk of brain cancers. 1 mark

A
  • Less oxygen to cancer cells

- Reduced spread of cancer cells

Past papers - biology (17 decks)

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