Jan 2013 Unit 2 Flashcards
An arteriole is described as an organ. Explain why.
made up of more thatn one type of tissue
An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow
to capillaries.
- (Muscle) contracts;
2. (Arteriole) narrows
A capillary has a thin wall. This leads to rapid exchange of substances between the
blood and tissue fluid. Explain why
Short diffusion distance
Blood flow in capillaries is slow. Give the advantage of this.
(More) time for exchange/diffusion
Kwashiorkor is a disease caused by a lack of protein in the blood. This leads to a
swollen abdomen due to a build up of tissue fluid.
Explain why a lack of protein in the blood causes a build up of tissue fluid.
1. Water potential (in capillary) not as low/is higher/less negative / water potential gradient is reduced; 2. Less/no water removed (into capillary); 3. By osmosis (into capillary)
They found that hybrid DNA from a leopard and a
cheetah separated into single strands at a higher temperature than hybrid DNA from a
leopard and a puma.
These results suggest that leopards are more closely related to cheetahs than to
pumas. Explain why.
- More hydrogen bonds (form);
2. Similar DNA sequence
Use this information to explain what is meant by a genetic bottleneck.
1.Drop in population / many killed / only single female left; 2. Idea of reduced/low genetic variation/diversity / reduction in (variety of) alleles / smaller gene poo
The fertility of cheetahs is low. The proportion of abnormal sperm cells produced is
higher in cheetahs than in other members of the family Felidae. Suggest an
explanation for this.
Inbreeding / closely related cheetahs
breed;
4. High chance of inheriting allele / high
frequency of allele
What is intraspecific variation?
Variation within a species
Explain why both types of twin were used in this investigation.
1. Identical twins show genetic influence / differences between them show environmental influence; 2. Non-identical twins (also) show an environmental/non-genetic influence
What do these data suggest about the relative effects of genetic and environmental
factors on the development of schizophrenia?
Genes play a greater role
Suggest two factors that the scientists should have taken into account when selecting
the twins to be used in this study
- Age;
- Family/medical history (of mental
illness)
Describe how the students would have returned the air bubble to the start of the capillary tube in this investigation.
Open/use tap
Give two precautions the students should have taken when setting up the potometer to
obtain reliable measurements of water uptake by the plant shoot.
- Seal joints / ensure airtight / ensure watertight;
- Cut shoot under water
Ensure no air bubbles are present
A potometer measures the rate of water uptake rather than the rate of transpiration.
Give two reasons why the potometer does not truly measure the rate of transpiration.
- Water used for support/turgidity;
2. Water used in photosynthesis;
Explain the relationship between the number of leaves removed from the plant shoot
and the mean rate of water uptake.
Less surface area;
Fewer stomata;
Less transpiration
Mycolic acids are substances that form part of the cell wall of the bacterium that
causes tuberculosis. Mycolic acids are made from fatty acids. Isoniazid is an antibiotic
that is used to treat tuberculosis. The diagram shows how this antibiotic inhibits the
production of mycolic acids in this bacterium.
- Cell wall not formed / production inhibited;
- Lower water potential in bacterium;
- Water enters and causes
lysis/expansion
Human cells also produce fatty acids. Isoniazid does not affect the production of these
fatty acids.
Use information in the diagram to suggest one reason why isoniazid does not affect
the production of fatty acids in human cells.
human cells have a different enzyme
A mutation in the gene coding for enzyme B could lead to the production of a
non-functional enzyme. Explain how.
- Change in base sequence (of DNA/gene);
- Change in amino acid sequence /
primary structure (of enzyme); - Change in hydrogen/ionic/ disulphide
bonds
Using isoniazid to treat diseases caused by other species of bacteria could increase
the chance of the bacterium that causes tuberculosis becoming resistant to isoniazid.
Use your knowledge of gene transmission to explain how.
- Resistance gene/allele;
- On plasmid;
- (Spread by) horizontal transmission;
Suggest one ethical argument for maintaining biodiversity.
Prevent extinction
Suggest one economic argument for maintaining biodiversity
tourism
Explain the relationship between the percentage of original forest area remaining and
the percentage of bird species that have become extinct.
1. Fewer plant species / decrease in plant diversity; 2. Fewer habitats/nesting sites; 3. Fewer niches; 4. Fewer food sources/varieties;
The ecologists noted that the species of birds surviving on the coldest islands had a
larger body size than those surviving on warmer islands.
Explain how a larger body size is an adaptation to a colder climate.
- (Larger birds have) a low(er) SA:VOL;
- (So) less heat loss / more heat
retained;
Describe how DNA is replicated.
- Strands separate / H-bonds break;
- DNA helicase (involved);
- Both strands/each strand act(s) as (a)
template(s); - (Free) nucleotides attach;
- Complementary/specific base pairing /
AT and GC; - DNA polymerase joins nucleotides (on
new strand); - H-bonds reform;
- Semi-conservative replication / new
DNA molecules contain one old strand
and one new strand
Explain how the doctor could have recognised which cells were in interphase when
looking at the tissue samples.
- No visible chromosomes/chromatids;
2. Visible nucleus
Which tissue sample, C or D, was taken from a cancerous tumour?
Use information in the table to explain your answer.
1. Lower % (of cells) in interphase / higher % (of cells) in mitosis/named stage of mitosis; 2. (So) more cells dividing / cells are dividing quicker;
Describe one way the scientists could have allocated the patients to each group.
Random;
number generator
What do the standard deviation bars suggest about the difference in the mean increase
in FEV1 between Group 1 and the other groups? Explain your answer.
- (Differences) are real/significant/not
due to chance; - (As) bars/SDs do not overlap;
What do the data suggest about the ‘placebo effect’ in this investigation? Explain your
answer.
- No/slight (placebo) effect;
2. Group 2 and 3 results are similar
On each occasion that a patient’s FEV1 was measured, a doctor repeated the
measurement several times. Explain why
- (Allows) anomalies to be identified
- (Makes) average/mean (more)
reliable;
Suggest why all the patients were allowed to continue with their normal asthma
treatment in this investigation.
- Unethical/unfair not to treat patients;
- Dangerous / could cause an asthma
attack
Suggest why the patients were told to stop their normal asthma treatment 24 hours before their FEV1 measurements were taken.
1. Ensures normal treatment does not affect results / improvements are only due to the spray; 2. (As) normal treatment is short-lived/ effective for less than 24 hours/ (24h) is long enough for normal treatment to wear off;
The scientists concluded that the data obtained for the Improvement Scores were less
reliable than the data obtained measuring FEV1. Suggest why they concluded this.
1. (Improvement scores) are qualitative / subjective/rely on own judgement/ different patients may assess symptoms differently; 2. Some patients may lie/exaggerate/want to please doctors;
Group 3 reported the lowest mean Improvement Score. Suggest one explanation for
this.
- Not blind / patients knew they were not
receiving treatment/ patients did not
receive treatment; - (So) more likely to underestimate/give
lower scores / did not expect to
improve / less improvement
