Jan 2005 U3

GCE Edexcel GCE Biology / Biology (Human) (6103/03)

January 2005

Biology / Biology (Human) (6103/03)

Edexcel GCE

Mark Scheme

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

General Principles Symbols used in the mark scheme Symbol ; semi colon eq / oblique {} curly brackets () round brackets [] square brackets

Meaning of symbol Indicates the end of a marking point. Indicates that credit should be given for other correct alternatives to a word or statement, as discussed in the Standardisation meeting. It is used because it is not always possible to list every alternative answer that a candidate may write that is worthy of credit. Words or phrases separated by an oblique are alternatives to each other. Indicate the beginning and end of a list of alternatives (separated by obliques) where necessary to avoid confusion. Words inside round brackets are to aid understanding of the marking point but are not required to award the point. Words inside square brackets are instructions or guidance for examiners.

Crossed out work If a candidate has crossed out an answer and written new text, the crossed out work can be ignored. If the candidate has crossed out work but written no new text, the crossed out work for that question or part question should be marked, as far as it is possible to do so. Spelling and clarity In general, an error made in an early part of a question is penalised when it occurs but not subsequently. The candidate is penalised once only and can gain credit in later parts of the question by correct reasoning from the earlier incorrect answer. No marks are awarded specifically for quality of language in the written papers, except for the essays in the synoptic paper. Use of English is however taken into account as follows: • the spelling of technical terms must be sufficiently correct for the answer to be unambiguous e.g. for amylase, ‘ammalase’ is acceptable whereas ‘amylose’ is not e.g. for glycogen, ‘glicojen’ is acceptable whereas ‘glucagen’ is not e.g. for ileum, ‘illeum’ is acceptable whereas ‘ilium’ is not e.g. for mitosis, ‘mytosis’ is acceptable whereas ‘meitosis’ is not • candidates must make their meaning clear to the examiner to gain the mark. • a correct statement that is contradicted by an incorrect statement in the same part of an answer gains no mark – irrelevant material should be ignored.

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6103/03 January 2005

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

Question 1

Maximum mark

(a)

1. Use inorganic materials / eq ; 2. {Make / eq} organic materials / eq ; 3. Reference to {photosynthesis / using light} ; 4. Reference to {chemosynthesis / using energy from chemicals} ; 2 marks

(b)

1. Production of {organic material / biomass / new tissue / named example} ; 2. Idea of energy incorporated into a trophic level; 3. KJ m-2 year-1 / kg m-2 year-1 / per (unit) {area / volume} per (unit) time / eq ; 4. Reference to {gross / net} productivity ; 2 marks

(c)

1. {Harvesting / using} {trees / forest} in such a way as not to {destroy / reduce / use it up} ; 2. (To ensure supply) over a (relatively) long period of time (minimum 5 years) ; 3. Cutting timber at the same rate as it can be {grown / regenerated / replanted / eq} ; 4. Credit suitable example of management programme e.g. {coppicing / selective felling / pollarding / replanting} ; 2 marks Total 6 marks

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6103/03 January 2005

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

Question 2

Maximum mark

(a) (i) 1. Reference to all decrease ; 2. The bigger the mesh, the greater the breakdown / leaves in the 5 mm mesh {broken down / eq} more quickly than the other bags ; 3. Leaves in the air broke down the least ; 4. In {1 mm / 5 mm mesh} no change after {Nov 1989 / May 1990} but 0.05 mm continued to break down over entire period / eq ; 5. In first six months, leaves remaining in 5 mm mesh was {half / eq} that remaining in {0.5 mm / 1 mm} mesh / any other valid comparison ; 6. Comparison of 0.05 in air and 0.05 in soil ; 7. Credit for suitable comparative manipulation of data e.g. 19% more leaves were broken down in 5 mm mesh compared with 61% in 1 mm mesh ; 4 marks (ii) 1. {Soil animals / organisms / microorganisms / decomposers} {responsible for the breakdown of the leaves / feed on the leaves} ; 2. The bigger the mesh, {the more animals / larger animals} are able to enter the bags to feed on the leaves / eq ; 3. Credit a specific example, e.g. worms cannot enter the bags with smaller mesh ; 4. Bag in the air had least breakdown because {fewer / no} {soil animals / organisms / microorganisms / decomposers} could get at the leaves / reference to {lack of moisture / dry air} / eq ; 2 marks

(b)

The higher the nitrogen content {the greater the breakdown / eq} ; {Soil animals / microorganisms / decomposers} {more numerous / breed more / grow more} in leaves with higher nitrogen content OR leaves with more nitrogen were more {palatable / nutritious} / reference to lignin / eq ; 2 marks

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6103/03 January 2005

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

Question 2 continued (c)

Maximum mark

1. Decomposition affected by {climate / weather} ; 2. {Hot / wet} climate increases rate of decomposition so leaves are broken down quickly ; 3. Pine needles {do not break down quickly / harder to break down} (so build up on forest floor) ; 4. Rainforest leaves may have high nitrogen content so are broken down more ; 5. Reference to {temperature / pH} and enzyme activity ; 6. Pine needles {may contain inhibitory chemicals / are thick / are waxy / are fibrous / eq} ; 3 marks

(d)

1. {Bacteria / microorganisms / fungi} in soil {breakdown / putrefy / decompose} leaves / reference to bacterial decomposition ; 2. Releasing {ammonia / ammonium} ; 3. {Nitrosomonas / reference to nitrifying bacteria [allow ONCE]} {converts / oxidise} {ammonia / ammonium} to nitrite ; 4. {Nitrobacter / reference to nitrifying bacteria [allow ONCE]} {converts / oxidise} nitrite to nitrate ; [Maximum 2 marks if any reference to nitrogen fixation or Rhizobium] 3 marks Total 14 marks

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6103/03 January 2005

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

Question 3

Maximum mark

(a)

1. {Sulphur dioxide / nitrogen oxides} ; 2. (Produced by) burning {fossil fuels / named fossil fuel} ; [Do not allow CO2] 3. {Dissolve / eq} in {moisture / rain / clouds} (in air) ; [Do not allow for CO2] 4. {Falls / precipitated} as {acid rain / acidic rain} / makes rain acidic ; 5. With pH less than 5 ; 6. Pass into soil and drain into streams that feed into rivers / fall directly on rivers ; [Maximum 3 marks if neither sulphur dioxide nor nitrogen oxides mentioned] 4 marks

(b)

1. Mussel + hoglouse ; 2. Able to {tolerate / survive in} {pH lower than 5 / in acidified rivers} ; 3. Less competition / more {food / space} in context ; 4. {Fewer eaten / less predation} ; 3 marks

(c)

1. In non-acidified rivers {catch goes up / eq} and {catch falls / eq} in acidified rivers ; 2. Both more or less the same until 1940 ; 3. Both show similar pattern until {1960 / 1970} / reference to particular change compared between quoted years ; 4. Both show some fluctuations ; 5. Comparative manipulated data ; 3 marks

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6103/03 January 2005

January 2005

GCE Biology / Biology (Human) Unit 3 – 6103/03

Question 3 continued (d)

Maximum mark

1. Reference to eggs affected ; 2. So fewer fish hatch / eq ; 3. Increased aluminium ; 4. (Increases) mucus production by gills ; 5. Reduced oxygen uptake / eq ; 6. Reference to other heavy metals ; 7. Reference to enzyme inhibition (linked to heavy metals) ; 8. Reference to food chain effects ; 9. Specified food chain effect ; 4 marks

(e) (i)

125 – 5 = 120 then (120 ÷ 5) x 100 ; [accept alternative correct methods] = 2400 (%) ; 2 marks

(ii)

Rivers {flow / eq} and lakes (more or less) have {stationary water / eq} ; {Lime / neutralised water} {washed away in rivers / not washed away in lakes} ; Reference to more acidic water enters rivers from streams (after lime washed away) ; 2 marks Total 18 marks

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6103/03 January 2005