Download A-level Human Biology Mark scheme Unit 02 - Humans - their

A-LEVEL
Human Biology
HBIO2
Mark scheme
2405
June 2016
Version: 1.0 Final
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relevant questions, by a panel of subject teachers. This mark scheme includes any amendments
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2
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Additional
Comments/Guidance
Answers
Mark
1(a)
Centromere;
1
1(b)
They are alleles (of the gene);
Accept they have a different base
sequence/mutation.
1
1(c)(i)
There are (four) chromatids /
(each) chromosome consists of
two chromatids;
Accept there are four
chromosomes
1
1(c)(ii)
(Each new copy/DNA molecule)
consists of one new and one
original/old/template strand;
Accept each strand is a template
(for new DNA strands)
1
Total
4
3
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Answers
2(a)
(a group of similar organisms
that) can reproduce to give fertile
offspring;
2(b)
Organisms cannot
interbreed/reproduce with another
group;
Additional
Comments/Guidance
Mark
1
Reject any reference to
inbreeding
1
Accept examples that cause
reproductive isolation, e.g.
organisms cannot interbreed due
to physical differences.
2(c)
1. Predation;
2. Disease;
3. Competition;
Accept suitable examples for
each
2 max
Accept (sudden) environmental
change/suitable named example
2(d)
Mutation/change in base
sequence (of allele);
2(e)
More red blood
cells/haemoglobin;
Accept suitable named mutation
1
1
Total
6
4
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Additional
Comments/Guidance
Answers
Mark
3(a)(i)
Homo;
Reject ‘Homo sapiens’
1
3(a)(ii)
(Homo) habilis/(Homo)
erectus/(Homo) neanderthalensis;
Ignore ‘neanderthal’
1
Accept (Homo) neanderthalis
3(b)(i)
(tools in Group A) have not been
shaped (as much)/sharpened;
Accept clear converse for group B
tools.
3(b)(ii)
1. Chipped against other
stones/used one stone as a
hammer (to hit another stone);
2. Making sharp flakes;
3. Used bones to sharpen
edges;
MP 1 & 2 - Accept knapping of
flints
3(b)(iii)
Accept one suitable example of
use, e.g.
1
2 max
1 max
1. To cut/scrape meat (off
bones)/cleaver;
2. For hand-axes/spearheads;
3. Killing animals;
Total
6
5
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
4(a)
4(b)(i)
Additional
Comments/Guidance
Answers
1. Deoxyribose;
2. Phosphate/PO43-;
AUGAAU;
Mark
2
2. Reject phosphorus/P
2. Accept Pi
Ignore reference to bases
If read from the right accept
GUUCAU
1
Ignore bases after first 6
4(b)(ii)
4(c)
5;
1
1. Different genes;
2. Different (DNA) base
sequences;
2
OR
3. Mutations;
4. Cause differential
survival/selective advantage;
Total
6
6
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Additional
Comments/Guidance
Answers
Mark
5(a)(i)
Metaphase;
1
5(a)(ii)
4.8 hours/4 hours 48 minutes/288
minutes;;
Allow one mark for 68 x 24
340
2
5(b)
DNA replication;
Accept synthesis of protein/of
ATP/of cytoplasm/of organelles.
1
5(c)
1. To attach to
centromeres/chromosomes /
align chromosome along the
equator;
2. To pull
chromatids/chromosomes
apart/to opposite poles/ends
(of the cell);
2
Total
6
7
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Answers
6(a)
1. To allow comparison between
the groups/male and female;
2. As there may have been
different numbers in each
group/different numbers of
male and female;
6(b)
Factor:
Additional
Comments/Guidance
1. Accept allows comparison with
non-overweight people.
1. Neutral easier to compare
1. Ignore unqualified comparisons
Mark
2
2
Waist-to-hip ratio;
Explanation:
It shows the highest relative risk
in both males and females;
6(c) (i)
Men at a (significantly) higher
risk;
6(c) (ii)
1. Increased (relative) risk in all
categories;
2. Sample size unknown;
3. (however,) other factors can
cause colon cancer / (table
shows) risk (which) is not a
certainty;
1
Accept no SD values, so do not
know if differences between
overweight and non-overweight
people are real.
Total
3
8
8
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
7(a)
Answers
Statement
7ai
7aii
7aiii
;;;
Additional Comments/Guidance
Mark
3
Number from
Figure X
4
2
3
7(b) (i)
1. Aortic body;
2. Carotid body/sinus;
3. Medulla;
1. Neutral aorta.
2. Neutral carotid artery.
2
max
7(b) (ii)
1. Lack of oxygen increases
anaerobic respiration/
production of blood lactate;
2. (Chemoreceptors) detect fall
in pH;
3. Send increased frequency of
impulses to respiratory centre;
4. Increased frequency of
impulses to
intercostals/diaphragm;
Accept hypoxia / low pO2 detected
by carotid bodies for MP1 and 2.
3
max
3 & 4 Reject
signals/messages/information.
3 & 4 Must have idea of
increase/more.
Total
8
9
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Additional
Comments/Guidance
Question
Answers
8(a)
Letter Q placed on or near where
larvae penetrate the skin;
1
8(b)
1. Travel up the
airways/trachea / coughed up
(to the pharynx/throat);
2. (And) are swallowed/move
down oesophagus;
2
8(c)
1. (Put sample on slide and)
use microscope;
2. (to) look for eggs;
2
8(d) (i)
Attaching to (host) small
intestine;
1
8(d) (ii)
The hookworm feeds on the
hosts blood;
Accept the hookworm attached
with hooks which damages the
lining of the small intestine
Mark
1
Q Reject feeds ‘off’ the hosts
blood
8(d) (iii)
Increased chance that eggs will
survive / infect new human / to
allow eggs to reach new hosts /
more chance of completing life
cycle;
1
Total
8
10
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
9 (a) (i)
9 (a) (ii)
Additional
Comments/Guidance
Answers
1. As the farm size increases,
the number of species of
butterflies decreases;
2. Due to fewer plant
species/types of plant for
them to feed on / less variety
of food sources;
2. Ignore less food for butterflies.
1.78:1;
Accept 1.8:1 or 1. 7̇: 1
Mark
2
1
Reject 1.7:1
9 (a) (iii)
Yes (no mark)
1. Small farms do have more
species;
2. No overlap of SDs between
small and large farms (so)
differences are
significant/real;
2 max
2. Accept suitable use of data
No (no mark)
3. No idea of numbers of each
species;
4. Accept suitable economic
argument, e.g. government
money could be better spent
elsewhere;
5. May not be true in countries
other than Italy
9 (b) (i)
Negative correlation/description;
Accept (they are) inversely
proportional /description of
inverse proportionality.
11
1
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
9 (b) (ii)
Additional
Comments/Guidance
Answers
1. To reduce the number of
species;
2. Which might compete with
their crop/the hay in the
meadow;
Mark
2 max
OR
3. To get more hay/increase
yield of hay;
4. Frequent cutting stimulates
growth;
OR
5. To get more hay/increase
yield of hay;
6. To feed animals (and make
more profit);
Total
8
12
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
10 (a)
10 (b)
Additional
Comments/Guidance
Answers
1. (Determine) the base
sequence (of genes/and look
for similarities/differences);
1. Immunological;
2. Anatomical;
Mark
1
Accept fossil evidence/examples
of fossil evidence for one mark
2
Neutral behavioural and
embryological
10 (c) (i)
Blocks/absorbs/dissipates UV
(light) / lower risk of
mutation/(skin) cancer/burning;
1
10 (c) (ii)
1. The sun is weaker/less UV
(light) (in more northern
latitudes);
2. (Lighter skin means) more UV
(light) can be absorbed;
3. To make more vitamin D;
3
10 (c) (iii)
10 (d)
1. Enough vitamin D from
diet/fish;
2.and 3. Reject ideas relating to
absorbing vitamin D from sunlight
Accept (in summer) high levels of
UV are reflected by snow, (dark
skin) protects them (from this
reflected light);
The results of preference/(sexual)
attraction (when choosing mating
partner);
1
1
13
MARK SCHEME – A-LEVEL HUMAN BIOLOGY – HBIO2 – JUNE 2016
Question
Answers
Additional
Comments/Guidance
10 (e) (i)
1. More food/more regular food
supply/food sources;
2. Can store food in times of
plenty/for times of
shortages/in winter
3. Do not have to move to new
areas to find food / follow
animals;
4. Larger
populations/communities
form/settle / increased
reproduction;
5. Develop social
structures/different
roles/specialists
6. Develop the use of tools/skills;
7. Allow development of
culture/trade;
10 (e) (ii)
1.
Relevant reference to
small population size;
2.
Relevant reference to
inbreeding/gene flow;
10 (e) (iii)
1. Small samples might not be
reliable/representative (of all
(European humans);
2. Trend not followed with
Greenlanders/humans living
coastal regions;
3. Does not show that evolution
is happening now;
4. No fossils/skeletons showing
transitions between dark and
light/changes in pigmentation
mentioned/hair/skin/eyes;
Mark
6 max
2
Total
3 max
20
14