Topic 6 - Inheritance, Variation
and Evolution EXAM COMPLETE
QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED
ANSWERS) |ALREADY GRADED
A+
Darwin suggested the theory of natural selection.
Explain how natural selection occurs. [3 marks]Tip - identify at
least three different points. - ✔✔ANSWER✔✔-Variation exists
between organisms within the same species (due to random
mutations). Described answers of variation within a species will
be awarded. [1 mark]
The organism that survive are the most suited to a particular
environment. [1 mark]
The genes/alleles/mutations from a successful organism will be
passed on to their offspring. [1 mark]
The scientists cannot be sure that this is the full range of fossil
shell widths for this species. Why? [1 mark]
Tip - the fossil record is not complete, so it cannot be assumed all
have been found. - ✔✔ANSWER✔✔-Only a small sample was
examined, for example 49 shells in total. This was not a
representative number and could not be considered enough
evidence. It may also suggest that not all fossils have been found.
,What is the chance of having a female child? Give the reason for
your answer. [2 marks] - ✔✔ANSWER✔✔-Calculation explained -
4 possible offspring and 2 have XX therefore 2 divide by 4 = 0.5
You will be marked correctly for using equilvalent alternatives to
0.5, such as , 50%, 1:1, 50:50, or 1 in 2. [1 mark]
2 (out of 4) boxes are XX or half of the sperm contain an X-
chromosome. [1 mark]
The dodo bird lived on the island of Mauritius. It was a large,
flightless bird which had no predators.
People came to the island, bringing hunting dogs with them.
Suggest why there are no dodos living today. [4 marks]
Tip - consider generalised ideas about what causes extinction of
any species. Use the information in the question. -
✔✔ANSWER✔✔-The four marks will be given by implementing
the following points:
dodos have become extinct [1 mark]
dodos were easily hunted by humans/caught by dogs [1 mark]
introduction of a new predator caused many dodo birds to be
eaten [1 mark]
dodo birds were not frightened of humans, and so they were easy
to catch for food [1 mark]
The herring gull (larus argentatus) and the lesser black-backed
gull (larus fuscus) are two species of gull that are now found in
the UK, but the two species cannot interbreed with each other.
Scientists believe that these two species have evolved from a
common ancestor.
The map shows a view of the Earth from above the North Pole.
The map also shows where these two species are found.
Suggest an explanation for the development of these different
species. [6 marks]
,Tip - consider why maps are used to help you. What other factors
affect variation in species? - ✔✔ANSWER✔✔-The six marks will
be given by implementing the following points:
the organisms in the original ancestral species of seagulls must
have become isolated or separated [1 mark]
this isolation could have been created by a geographical barrier,
such as a sea or a mountain [1 mark]
there was pre-existing genetic variation within these isolated
populations of seagulls due to the presence of different alleles [1
mark]
possible changes in the environmental conditions such as climate
or the introduction of new predators or even the limitation of
certain food types can affect species [1 mark]
would lead to natural selection acting upon these isolated
populations [1 mark]
successful organisms will pass on certain allele(s) to their
offspring and so these different alleles are passed on in the
different environments therefore these differences lead to inability
to interbreed [1 mark]
Sample question 4 - Higher
Embryos can be screened for genetic disorders. Many people
would favour the use of embryo screening for cystic fibrosis but
not for polydactyly.
Compare the issues involved in the use of embryo screening for
cystic fibrosis and for polydactyly. You should use your
knowledge and understanding of the process and the two
conditions.
Tip - six-mark questions are sometimes marked in a different way
to other questions. A level format is used, and so science must be
included as usual. Refer back to the question 'compare' is saying
you must talk about cystic fibrosis and polydactyly. -
✔✔ANSWER✔✔-Level 3 (5-6 marks): A clear, balanced and
, detailed description of the issues involved in screening for both
conditions, giving pros and cons for each condition.
Tip - key points are in bold, to show you how to improve your
answer.
Examples for cystic fibrosis points to be made in the response:
reduce number of people with cystic fibrosis (in population)
reduce health-care costs
allows decision / emotional argument eg allows people to make
choices about termination
Examples against cystic fibrosis points to be made in the
response:
possible damage / risk to embryo / fetus / baby
possible harm / risk to mother
(may) have to make ethical / moral / religious decisions
Examples for polydactyly points made in the response:
cures 'disfigurement'
but condition not life threatening
so risks to fetus / mother unjustified
The students measured the growth of the duckweed by counting
the number of leaves.
Suggest a better method of measuring the growth of the
duckweed. [1 mark]
Tip - suggest possible ways to measure growth. Think about other
examples from your topics. - ✔✔ANSWER✔✔-By recording the
mass or weight of the leaves this would allow data to be collected
for a number of duckweed leaves. [1 mark]
Ignore dry or fresh leaves, for this example this is unimportant
here.
Or other sensible methods for example, such as the measuring
the length of roots would be acceptable. Ignore 'size' of roots -
and Evolution EXAM COMPLETE
QUESTIONS AND CORRECT
DETAILED ANSWERS (VERIFIED
ANSWERS) |ALREADY GRADED
A+
Darwin suggested the theory of natural selection.
Explain how natural selection occurs. [3 marks]Tip - identify at
least three different points. - ✔✔ANSWER✔✔-Variation exists
between organisms within the same species (due to random
mutations). Described answers of variation within a species will
be awarded. [1 mark]
The organism that survive are the most suited to a particular
environment. [1 mark]
The genes/alleles/mutations from a successful organism will be
passed on to their offspring. [1 mark]
The scientists cannot be sure that this is the full range of fossil
shell widths for this species. Why? [1 mark]
Tip - the fossil record is not complete, so it cannot be assumed all
have been found. - ✔✔ANSWER✔✔-Only a small sample was
examined, for example 49 shells in total. This was not a
representative number and could not be considered enough
evidence. It may also suggest that not all fossils have been found.
,What is the chance of having a female child? Give the reason for
your answer. [2 marks] - ✔✔ANSWER✔✔-Calculation explained -
4 possible offspring and 2 have XX therefore 2 divide by 4 = 0.5
You will be marked correctly for using equilvalent alternatives to
0.5, such as , 50%, 1:1, 50:50, or 1 in 2. [1 mark]
2 (out of 4) boxes are XX or half of the sperm contain an X-
chromosome. [1 mark]
The dodo bird lived on the island of Mauritius. It was a large,
flightless bird which had no predators.
People came to the island, bringing hunting dogs with them.
Suggest why there are no dodos living today. [4 marks]
Tip - consider generalised ideas about what causes extinction of
any species. Use the information in the question. -
✔✔ANSWER✔✔-The four marks will be given by implementing
the following points:
dodos have become extinct [1 mark]
dodos were easily hunted by humans/caught by dogs [1 mark]
introduction of a new predator caused many dodo birds to be
eaten [1 mark]
dodo birds were not frightened of humans, and so they were easy
to catch for food [1 mark]
The herring gull (larus argentatus) and the lesser black-backed
gull (larus fuscus) are two species of gull that are now found in
the UK, but the two species cannot interbreed with each other.
Scientists believe that these two species have evolved from a
common ancestor.
The map shows a view of the Earth from above the North Pole.
The map also shows where these two species are found.
Suggest an explanation for the development of these different
species. [6 marks]
,Tip - consider why maps are used to help you. What other factors
affect variation in species? - ✔✔ANSWER✔✔-The six marks will
be given by implementing the following points:
the organisms in the original ancestral species of seagulls must
have become isolated or separated [1 mark]
this isolation could have been created by a geographical barrier,
such as a sea or a mountain [1 mark]
there was pre-existing genetic variation within these isolated
populations of seagulls due to the presence of different alleles [1
mark]
possible changes in the environmental conditions such as climate
or the introduction of new predators or even the limitation of
certain food types can affect species [1 mark]
would lead to natural selection acting upon these isolated
populations [1 mark]
successful organisms will pass on certain allele(s) to their
offspring and so these different alleles are passed on in the
different environments therefore these differences lead to inability
to interbreed [1 mark]
Sample question 4 - Higher
Embryos can be screened for genetic disorders. Many people
would favour the use of embryo screening for cystic fibrosis but
not for polydactyly.
Compare the issues involved in the use of embryo screening for
cystic fibrosis and for polydactyly. You should use your
knowledge and understanding of the process and the two
conditions.
Tip - six-mark questions are sometimes marked in a different way
to other questions. A level format is used, and so science must be
included as usual. Refer back to the question 'compare' is saying
you must talk about cystic fibrosis and polydactyly. -
✔✔ANSWER✔✔-Level 3 (5-6 marks): A clear, balanced and
, detailed description of the issues involved in screening for both
conditions, giving pros and cons for each condition.
Tip - key points are in bold, to show you how to improve your
answer.
Examples for cystic fibrosis points to be made in the response:
reduce number of people with cystic fibrosis (in population)
reduce health-care costs
allows decision / emotional argument eg allows people to make
choices about termination
Examples against cystic fibrosis points to be made in the
response:
possible damage / risk to embryo / fetus / baby
possible harm / risk to mother
(may) have to make ethical / moral / religious decisions
Examples for polydactyly points made in the response:
cures 'disfigurement'
but condition not life threatening
so risks to fetus / mother unjustified
The students measured the growth of the duckweed by counting
the number of leaves.
Suggest a better method of measuring the growth of the
duckweed. [1 mark]
Tip - suggest possible ways to measure growth. Think about other
examples from your topics. - ✔✔ANSWER✔✔-By recording the
mass or weight of the leaves this would allow data to be collected
for a number of duckweed leaves. [1 mark]
Ignore dry or fresh leaves, for this example this is unimportant
here.
Or other sensible methods for example, such as the measuring
the length of roots would be acceptable. Ignore 'size' of roots -
