FT - 06 Genetics and Evolution
Q1.There are two forms of peppered moth, dark and pale.
Birds eat the moths when the moths are resting on tree bark.
Pollution in the atmosphere may:
•
kill lichens living on tree bark
•
make the bark of trees go black.
(a)
Draw a ring around the correct answer to complete the sentence.
carbon
dioxide.
Lichens are very sensitive to air pollution caused by
nitrogen.
sulfur dioxide.
(1)
The photographs show the two forms of peppered moth, on tree bark.
Tree bark covered with lichens
Tree bark made black by pollution
© Kim Taylor/Warren Photographic
(i)
The dark form of the peppered moth was produced by a change in the genetic material of a pale moth.
Use one word from the box to complete the sentence.
characteristic
clone
mutation
A change in genetic material is called a ...............................................................
(1)
(ii)
In the 19th century, pollution made the bark of many trees go black.
Explain why:
•
the population of the pale form of the moth in forests decreased
•
the population of the dark form of the moth in forests increased.
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(3)
(c)
(i)
The larvae (young) of the peppered moths eat the leaves of birch trees.
The diagram shows the food chain:
birch trees → peppered moth larvae → birds
Draw a pyramid of biomass for this food chain.
Label the pyramid.
(2)
(ii)
Which two reasons explain the shape of the pyramid you drew in part (c)(i)?
Tick (
) two boxes.
Some material is lost in waste from the birds
The trees are much larger than peppered
moth larvae
Peppered moth larvae do not eat all the
leaves from the trees
The trees do not use all of the Sun’s energy
(2)
(Total 9 marks)
HT - 06 Genetics and Evolution
Q2.
The following passage is adapted from an article by Martin Kelly in The Independent
newspaper.
Thanks to the test tube banana
Specially bred resistant varieties may save African crops from disease
A banana is a fruit, but it has no seeds. And if there are no seeds how do the plants
reproduce? At one level the answer is easy; centuries of selective breeding have
resulted in varieties with plenty of tasty flesh but few bitter inedible seeds, and
propagation is carried out by means of root corms.
Most bananas we eat are thus actually 'clones' of a few successful plants, as is also
the case with the potato. Banana clones are genetically identical to their parents, so
growers can be completely sure their fruits will be big and tasty.
Genetic variability of these cloned plants is extremely low. Resistance to new
diseases, therefore, is almost nil; witness the spread of potato blight through Ireland
in the 1840s.
The issue goes well beyond our high streets and supermarkets. The banana has a
larger relative called a plantain, which is starchy rather than sweet and is a staple
food of more than 60 million Africans. Bananas and plantains are being ravaged by
a new fungal disease called Black Sigatoka. The commercial planters that produce
the bananas we buy in supermarkets have little problem here; they can afford to buy
chemicals to spray their crops. African subsistence farmers, forced to rely on
'organic' methods can only sit by and watch their plants die.
Several governments have turned to the International Institute for Tropical
Agriculture (IATA) for help. IATA is in Africa, but is not of Africa. It is internationally
funded with levels of staffing and equipment that enable advanced bio-technological
techniques to be used. However, even with genetic engineering, to breed resistant
varieties is a long-term project and Black Sigatoka is not going to wait. IATA
scientists have had to divide their energies between two approaches: an interim
solution and the development of resistant varieties.
The interim solution was easily found in a group of 'cooking bananas' which were
resistant to Black Sigatoka disease and which could, to some extent, be substituted
for plantain in the diet. These, however, were only found in localised areas and the
first problem facing IATA was to obtain enough plants from the few available plants
of resistant varieties to supply the needs of the affected farmers.
a)
Explain how selective breeding may have been used to produce bananas with tasty flesh.
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(2)
(b)
Explain, as fully as you can, why “Genetic variability of these cloned plants is extremely
low” compared with natural populations.
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(4)
(c)
Explain, as fully as you can, how IATA scientists might be able to “obtain enough plants
from the few available plants of resistant varieties to supply the needs of
affected farmers”.
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(3)
(d)
Explain, as fully as you can, how IATA scientists may use genetic engineering to produce
varieties of banana resistant to Black Sigatoka disease.
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(4)
(Total 13 marks)
M1.(a)
sulfur dioxide
1
(b)
(i)
mutation
1
(ii)
pale form now (more) easily seen (by predators) or dark form now less easily
seen (by predators)
accept ref to camouflage
1
so pale form (more) likely to be eaten or dark form less likely to be eaten
1
so dark form (more likely to) breed / pass on genes
or
pale form less likely to breed / pass on genes
1
(c)
(i)
pyramid of three layers of diminishing size
either way up
1
three labels in food chain order
award 2 marks only if the pyramid is correctly labelled
accept trees / birch
accept (peppered) moth(s) / larvae
1
(ii)
some material is lost in waste from the birds
1
peppered moth larvae do not eat all the leaves from the trees
1
[9]
M2.
(a) select for breeding;
the plants with the sweetest taste
each for 1 mark
2
(b)
natural population has a wide range of variations;
because it has a large number of alleles;
selective breeding reduces the number of alleles;
cloning perpetuates this reduced number of alleles
each for 1 mark
4
(c)
3 of:
reference to cuttings;
reference to tissue culture;
reference to hormones;
cloning
each for 1 mark
3
(d)
4 of:
cut genes for disease resistance;
from chromosomes of ‘cooking banana’;
introduce into chromosomes of ‘ordinary banana’;
tissue culture to produce disease resistant plants/clone;
enzymes cut chromosomes
each for 1 mark
4
[13]