Download Humans - their origins and adaptations June 2014

A-LEVEL
HUMAN BIOLOGY
HBIO2
Mark scheme
2405
June 2014
Version: 1.0 Final
Mark schemes are prepared by the Lead Assessment Writer and considered, together with the
relevant questions, by a panel of subject teachers. This mark scheme includes any amendments
made at the standardisation events which all associates participate in and is the scheme which was
used by them in this examination. The standardisation process ensures that the mark scheme covers
the students’ responses to questions and that every associate understands and applies it in the same
correct way. As preparation for standardisation each associate analyses a number of students’
scripts: alternative answers not already covered by the mark scheme are discussed and legislated for.
If, after the standardisation process, associates encounter unusual answers which have not been
raised they are required to refer these to the Lead Assessment Writer.
It must be stressed that a mark scheme is a working document, in many cases further developed and
expanded on the basis of students’ reactions to a particular paper. Assumptions about future mark
schemes on the basis of one year’s document should be avoided; whilst the guiding principles of
assessment remain constant, details will change, depending on the content of a particular
examination paper.
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
1 (a)
Marking Guidance
1. Glucose;
Mark
Comments
2 max
1. Ignore sugar,
carbohydrates, protein and
phosphocreatine
2. Glycogen;
3. Triglycerides/fats/lipids;
Ignore references to type of
respiration.
4. ATP/Adenosine triphosphate;
1 (b)
2
Requires
oxygen
Produces
carbon
dioxide
Releases
most
energy



x
x
x
One mark for each correct row
Blank boxes mean a cross
;;
1 (c)
1. Oxidised to carbon dioxide and water;
2. Converted to glycogen/glucose;
3. Converted to protein;
4. Excreted in sweat/urine;
2 max
1. Accept converted/broken
down
2. Ignore use of oxygen in
this context
4. Accept descriptions of
excretion, reject secretion and
excretion in faeces.
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
2 (a)
Marking Guidance
Mark
1. Deoxyribose;
2
2. Phosphate/PO43-/H3PO4-;
2
Pro
Thr
1. Accept phonetic spelling
2. Reject Phosphorous/P
2 (b)
Arg
Comments
Cys
Ala
All five correct = 2 marks
Four correct = 1 mark
;;
2 (c) (i)
Allele/s;
1
Accept phonetic spelling
2 (c) (ii)
Locus;
1
Accept loci
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
Marking Guidance
Mark
Comments
3 (a)
Heart rate × stroke volume;
1
Accept × as description eg
multiplied by
3 (b)
Box 1. Carbon dioxide;
4
One mark per correct answer
Box 3. Chemoreceptors;
Box 4. Medulla ((oblongata)/cardiovascular
centre;
Box 5. SAN/sinoatrial node/SA node;
Box 1. Accept hydrogen ions/
H+
Box 4. Reject respiratory
centre.
Box 4. Cardiac (control) centre
is neutral
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
4
Marking Guidance
1. Homo sapiens;
Mark
Comments
4
2. Australopithecus;
3. Homo habilis;
4. Homo neanderthalensis;
4. accept Homo neanderthalis
and Homo neanderthals
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
5 (a)
Marking Guidance
Mark
Comments
2
1. Accept descriptions of
‘pairing’ e.g. purine with
pyrimidine.
1. Each base only pairs with one
other/one specific base;
2. Adenine pairs with thymine/cytosine
with guanine;
1. Reject references to
active sites.
2. Accept A-T/C-G.
5 (b)
1. Two strands with complementary
base pairing;
2
max
2. Large number of hydrogen bonds
(between
strands/nucleotides/bases);
2. Reject strong bonds
between strands/
nucleotides/bases.
3. Helix/coiling reduces chance of
molecular damage / protects H
bonds/bases;
3. Ignore references to
compaction.
4. Strong sugar-phosphate backbone;
5 (c)
1. DNA strands separate/hydrogen
bonds broken/helix unwinds;
4 max
Q
2. Each strand forms a template/is
copied/DNA is replicated once;
3. Role of DNA polymerase;
4. Each new strand contains
radioactive/labelled thymine;
5. Each new chromosome/DNA
molecule is made of 1 old/original
and 1 new/labelled strand;
Reject each new strand is
made of one old and one
new strand.
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
6 (a)
Marking Guidance
Mark
2.24/2.2/2.237;
1
Comments
Reject % as units
Reject 2.23
6 (b)
1. Parents may be less than 2 years
old;
2 max
2. (and therefore parents) might not
have been diagnosed yet/may
develop HD later in life;
Reject any reference to HD
gene.
3. (Offspring) may have been
overfed;
6 (c)
German shepherd;
6 (d)
For
Accept HD might be
recessive / parents might be
heterozygotes/carriers for 1
mark.
1
3
max
1. Parents without HD have the
lowest percentage of offspring with
HD;
2. (Selective breeding) reduced
percentage in German
shepherds/Labradors (a lot);
3. (Qualified) animal welfare;
2. and 5. Accept suitable
use of data
3. For example, dogs in
less pain
Against
4. Can (still) be caused by excess
food consumption/in some breeds
feeding may have a bigger effect;
5. Not work in bulldog/little difference
in St. Bernard/only shows 4
breeds of dog;
6. (Selective breeding can) decrease
(genetic) diversity/variation;
Ignore ideas relating to
sample size
6. Accept descriptions such
as less alleles in the
gene pool
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
7 (a) (i)
Marking Guidance
1. Overall without schizophrenia identify
a higher percentage of/more facial
expressions correctly;
Mark
2 max
2. (With schizophrenia and without) get
most correct with happiness / little
difference/about the same level correct
for happiness;
Comments
1. Accept converse for
schizophrenia
Accept the use of data for
mark points 3 and 4
3. Neither recognise disgust very well;
4. Biggest difference for fear;
7 (a) (ii)
1. Each group is different size;
2
2. Allows groups to be compared;
7
(b)
1. Can judge if other people are a
threat/e.g. anger means stay away /
likely to be helpful/friendly/e.g. happy
means approachable;
3 max
1. Accept use of numbers
from the stem
Accept allows deaf to
communicate
2. Allows communication without
talking/e.g. when quiet is needed on a
hunt;
3. Allows communication between
different language groups;
4. Helps bonding with parents;
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
8 (a)
Marking Guidance
1. All (members) of the same species;
Mark
2
2. In an area/the same place;
8 (b) (i)
1. Mutation (occurred);
Comments
Accept examples of areas,
e.g. in a habitat/ecosystem
5
2. (Allowing) gene/allele/protein for citrate
usage (to be produced);
3. Ability to use citrate advantageous /
those that use citrate have increased
chance of survival/reproduction;
4. (Bacteria) pass on gene/allele/ability to
use citrate;
5. Increase the allele frequency/proportion
of bacteria that can use citrate;
8 (b) (ii)
(chance of correct) mutation is rare/mutation
is random;
1
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
Marking Guidance
9 (a) (i)
81.25%/81.3/81%;;
9 (a) (ii)
1. Lower diversity of plants/few species of
plants/less variety of plants;
Mark
2
Comments
Allow one mark for answers
that clearly show change
divided by starting value, e.g.
130/160
3 max
2. Few sources/types of food/feeding
sites/only oil palm/one food source;
2. Ignore less food
3. Loss of habitat;
3. Accept niches
4. Fewer (species of) herbivore so few
(species of) carnivores;
5. Aspect of machinery used to clear
forest, e.g. vibration causing migration;
9 (b)
The graph only shows number of
species/does not show (total) number of
butterflies;
9 (c)
Yes
1. Graph shows reduction in bird species
(from rubber to oil palm) would not be as
great (as natural forest to oil palm);
2. Butterfly species would (actually)
increase (from rubber to oil palm);
No
1
2 max
No mark for yes or no
If student has not scored mark
point 1 or 2 accept biodiversity
from rubber to oil palm
remains the same.
Accept use of data from the
graph for mark points 1 and 2
3. Only one of each area studied;
4. Only shows data for birds/butterflies;
5. Loss of biodiversity has already occurred
creating a rubber plantation;
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
Question
Marking Guidance
10 (a)
Mark
2
Comments
One mark for each correct
column
Phylum
Class
Order
Family
Ambystoma
mexicanum/
Ambystoma
mexicanum/A.
mexicanum
;;
10 (b) (i)
Change/alteration in the base sequence (of
DNA/gene);
1
10 (b) (ii)
1. Chemical carcinogens/named example;
2
2. Radiation/named example;
10 (c)
(During prophase)
1. Chromosomes
coil/condense/shorten/thicken/become
visible;
6 max
Accept correct examples of
viruses, e.g. HPV
No marks for naming the
stages
2. (Chromosomes) appear as (two sister)
chromatids joined at a centromere;
(During metaphase)
3. Chromosomes line up on the
equator/centre of the cell;
4. (Chromosomes) attached to spindle
fibres;
5. by their centromere;
(During anaphase)
6. The centromere splits/divides;
7. (Sister) chromatids/chromosomes are
pulled to opposite poles/ends of the
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
cell/separate;
(During telophase)
8. Chromatids/chromosomes
uncoil/unwind/become longer/thinner;
10 (d)
1. The sequence of bases/a gene/allele on
DNA determines the order of amino
acids (in a polypeptide/protein);
3 max
2. The gene is copied into (a molecule of)
RNA;
1. Genetic
information/material is
neutral
3. Direction of RNA movement
must be clear.
3. RNA leaves the nucleus;
4. RNA associates with a ribosome;
4. Accept rough endoplasmic
reticulum
5. RNA brings amino acids to the ribosome
and joins them in the correct order;
10 (e) (i)
To show that the extract was the factor
causing the reactivation of tumour
suppressor genes /stopping the growth of
tumours / to see if tumours stopped growing
anyway / to compare/see what would
happen with no treatment;
1
Unqualified comparison / due
to other factors is neutral.
10 (e) (ii)
1. Injected with salt solution/saline only;
2
1. Placebo is neutral
2. Other conditions kept the same/same as
the experimental group;
10 (f)
For
1. Less experimentation on humans / mice
may have similar metabolism/are also
mammals;
3 max
2 max if only discuss
arguments for or against
Q reject rats once.
2. (proteins in amphibians are very similar
to those in humans) therefore might not
cause immune response;
3. (Potential treatment/cure as) no growth
of tumours/cancer in mice (after 60
days);
3. Ignore references to
human suffering
Against
4. Don’t know if it works on humans/mice
tumours may be different/may have
harmful side effects in humans;
5. Qualified ethical argument regarding
killing of animals;
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MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2014
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