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LIFE SCIENCES
GRADE 12
PAPER 1
LEARNER RESOURCE
2
REVISION QUESTIONS
1.1
DNA and RNA
The diagram below represents a part of a molecule. Study the diagram and
answer the questions that follow.
1
2
3
G
4
A
5
KEY:
A – Adenine
G – Guanine
Part of a molecule
1.1.1
Identify the molecule in the above diagram.
1.1.2
Label the parts numbered 1 and 5 respectively.
1.1.3
What is the collective name for the parts numbered 2, 3 and 4?
1.1.4
What is the significance of this molecule being able to replicate itself?
1.1.5
Tabulate THREE structural differences between DNA and RNA
3
1.2
Analysis of DNA samples from a patient with an illness showed that therewere
two different types of DNA present. One was double-stranded human DNA and
the other was single-stranded virus DNA. The two types of DNA were isolated
and put into separate test tubes. The analyses of the nitrogenous base
composition of each test tube is shown in the table below.
Test tube 1
Test tube 2
Adenine
22.1
31.1
Nitrogenous base composition (%)
Cytosine
Guanine
27.9
27.9
31.3
18.7
1.2.1 Which test tube (1 or 2) contains virus DNA?
1.2.2 Explain your answer to QUESTION 1.2.1
Thymine
22.1
18.9
4
1.3
A woman was found stabbed to death in a hotel.The police found a few
strands of hair in one of her hands. There was also skin tissue under her long
nails.
Forensic scientists took blood samples from three suspects to compile DNA
fingerprints. DNA fingerprints were also compiled from the victim's blood and
the hair and skin tissue found in the victim's hands.
The following diagram shows the DNA fingerprints of the hair sample, the skin
tissue sample and blood from the victim and the three suspects.
Blood samples
Skin
Hair
Victim
Suspect 1
Suspect
DNA fingerprints compiled by the forensic scientists
1.3.1
Did the DNA from the hair and skin tissue come from the same
person?
1.3.2
What conclusion can you make from QUESTION 1.3.1 about the possible
number of people involved in the murder?
1.3.3
Which of the three suspects might have been involved in the murder?
1.3.4
Give a reason for your answer to QUESTION 1.3.3.
1.3.5
Do you think that the DNA evidence on its own is enough to convict
a suspect?
1.3.6
Give a reason for your answer to QUESTION 1.3.5.
1.3.7
Explain whether the collection of DNA from every citizen in South
Africa to create a DNA fingerprint database is a good idea or not.
5
PROTEIN SYNTHESIS
1.4
The diagram below shows part of a mRNA (messenger RNA) molecule
U
A C
1
C
G
2
A U
A A
3
1.4.1 How many codons are shown in the diagram of this section of
mRNA?
1.4.2 Write down the complementary base sequence of the DNA strand that formed codon 1
of the mRNA strand in the above diagram.
1.4.3 Explain the purpose of a specific sequence of codons in a mRNA
molecule.
1.4.4 A tRNA (transfer RNA) molecule carries complementary bases for
a particular codon.
(a)
Write down the complementary base sequence of a tRNA for
codon 1 in the mRNA sequence shown in the above diagram.
(b)
Briefly describe the role of tRNA molecules in the translation process of protein
synthesis
1.4.5 Describe the effect/impact that gene mutations might have on the formation of proteins.
6
1.5
1.5.1
The diagram below shows the sequence of nitrogenous bases of a
strand of DNA which codes for part of a protein molecule.
GTT
ATG
TGG
Write down the mRNA codon sequence that reads from left to right from the DNA
sequence above.
1.5.2
The following diagram shows the anticodons of nine different tRNA
(transfer RNA) molecules each carrying a particular amino acid.
VALINE
GLYCINE
ALANINE
CAA
CCC
CGU
PROLINE
METHIONINE
TRYPTOPHAN
GGU
ACC
PHENYLALANINE
SERINE
ASPARAGINE
AAA
UCA
UUA
UAC
Anticodons of nine different tRNA molecules each carrying
a particular amino acid
Select and write down from the above diagram the amino acids (in the correct
sequence) that would be required for the base sequence of mRNA
shown below.
UUU
GUU
AUG
7
1.6
The diagram below represents a part of the process of protein synthesis.
W
X
X
U A A
U A A
C A G
V
Y
U A A
C A U G U C A U
U G C U
Z
Representation of a part of the process of protein synthesis
1.6.1
Name the part/stage of protein synthesis that is illustrated in the diagram
above.
1.6.2
Name the organelle labelled W.
8
1.6.3
The table below shows the base triplets of mRNA that correspond to the
different amino acids.
mRNA
CAU
AUU
GUC
CUU
GCU
CCU
CGA
AMINO ACID
histidine
isoleucine
valine
leucine
alanine
proline
arginine
With reference to the diagram in QUESTION 1.6 and the table above:
(a)
Name the amino acid labelled X.
(b)
State the base sequence of the molecule labelled Y.
(c)
What collective name is given to the triplet of mRNA bases that
correspond to each amino acid?
(d)
How would the composition of the protein molecule change if the
base sequence at Z was CGA instead of GCU?
1.6.4
Use the information in the table to write the DNA base sequence that
would correspond with the amino acid histidine.
9
MEIOSIS
1.7
The diagram below represents a process taking place during meiosis.
C
D
B
A
Diagram representing a process taking
place during meiosis
1.7.1
Provide labels for parts A, B, C and D.
1.7.2
Name the process in meiosis that is illustrated in the diagram above.
1.7.3
State ONE importance of the process named in QUESTION 1.7.2
1.7.4
Draw a diagram of the structure labelled A to show its appearance
immediately after the process named in QUESTION 1.7.2.
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1.8
The following diagram represents a phase of meiosis.
A
B
Diagram representing a phase of meiosis
1.8.1
Provide labels for parts A and B.
1.8.2
How many chromosomes will there be in each cell formed from this cell at the end of
meiosis?
1.8.3
How many chromosomes were present in the phase before the one represented in the
diagram?
1.8.4
Give TWO reasons why meiosis is biologically important.
1.8.5
Tabulate FOUR differences between meiosis and mitosis.
1.9
Polyploidy refers to an organism, usually a plant, which has more than the diploid set of
chromosomes in the nucleus e.g. triploid plants have 3 sets of chromosomes and
tetraploid plants have 4 sets of chromosomes. Polyploidy is rare in animals but more
common in plants.
1.9.1
1.9.2
Why are polyploids not commonly found in animals.
Name TWO reasons why farmers grow polyploidy plants.
11
GENETICS
1.10
Learners want to investigate eye colour in fruit flies (Drosophila
melanogaster). Fruit flies can have red (R) eyes or white (r) eyes. Red eye
colour is dominant and white eye colour is recessive.
Male fruit flies, homozygous for red eye colour, were bred with female fruit
flies, homozygous for white eye colour.
Show how the possible phenotypes and the genotypes of the F1 generation
for eye colour may be obtained.
1.11 Study the family tree below which shows the inheritance of sex and type of earlobes
over four generations of a family. In humans, free earlobes (F) is dominant over
attached earlobes (f).
A
C
KEY:
B
D
E
F
Male with attached earlobes
Male with free earlobes
Female with attached earlobes
Female with free earlobes
Pedigree diagram showing inheritance of sex
and type of earlobes
12
1.11.1 How many members of the family have free earlobes?
1.11.2 What proportion of offspring in the fourth generation are females with attached earlobes?
1.11.3 If the genotype of person A is FF, what will be the genotype of person B?
1.11.4 Give a reason for your answer to QUESTION 1.11.3.
1.11.5 Persons E and F are twins. Were they produced from a single fertilised egg cell or from
two separately fertilised egg cells?
1.11.6 Explain your answer to QUESTION 1.11.5.
1.11.7 Is it possible for individuals C and D to have a child with free earlobes?
1.11.8 Explain your answer to QUESTION 1.11.7.
13
1.12
Cystic fibrosis is an inherited disorder of the human body caused by a recessive gene.
This disorder affects mucus production causing blockage of tiny air passages in the
lungs. Study the pedigree diagrams below and answer the questions that follow.
Family 2
Family 1
Gg
father
22
Thandi
Gg
mother
GG
or 3
Gugu
Gg
father
Gg
Sipho
1
mother
gg
Sam
KEY:
Normal male
Normal female
Male affected by cystic fibrosis
Female affected by cystic fibrosis
Pedigree diagrams showing inheritance of cystic fibrosis
1.12.1
Name the genotypes represented by 1 and 3 in the diagrams
respectively.
1.12.2
What is Thandi's genotype?
1.12.3
Does Thandi suffer from cystic fibrosis?
1.12.4
Thandi and Sipho intend getting married. Show, using a
pedigree diagram and the key above, ALL the possible
genotypes of any sons they might have.
1.12.5
Explain what Thandi and Sipho should consider before
deciding whether to have children or not.
14
1.13
Study the diagram below and answer the questions that follow.
1
2
8
9
16
17
3
10
18
4
11 12
19
20
5
6
7
13
14
15
21 22
23
Karyotype of a person
1.13.1 Is this the karyotype of a male or a female?
1.13.2 Give a reason for your answer to QUESTION 1.13.1.
1.13.3 How many chromosomes does this person have? Name the genetic disorder that this
person has.
15
1.14
The diagram below shows the steps of an experiment in which a large
number of genetically identical frogs were developed from unfertilised frog
eggs. The nucleus of each unfertilised egg was destroyed and replaced by a
nucleus obtained from a body cell from frog X.
Unfertilised frog egg cell
Frog X
Nucleus
destroyed by
ultraviolet
radiation
AA
Body cell
taken from
frog X
BB
Tadpole
Frog
Experiment to show how genetically identical frogs were
developed from unfertilized frog eggs
16
1.14.1
The diploid number of chromosomes in the above frogs is 26. How
many chromosomes are present in the nucleus of the following
cells?
(a)
Cell A
(b)
Cell B
1.14.2
Why can an egg containing a nucleus from the body cell of a frog
develop into a tadpole?
1.14.3
Explain why all the frogs produced from the treated eggs are
genetically identical.
1.14.4
Name the method of producing genetically identical offspring as shown in
the diagram.
1.14.5
State ONE reason why some people might:
(a)
Favour the process shown in the diagram
(b)
Be against the process shown in the diagram
17
The graph below shows the results of an investigation into the frequency of blood
groups in a small human population.
Proportion of population (%)
1.15
Proportion of each blood group in a small
population
50
45
40
35
30
25
20
15
10
5
0
ABAB
A A
B
O
B
O
Blood groups
1.15.1
Which blood group has the lowest frequency in the population
investigated?
1.15.2
State ONE reason why it is suitable for the results of this investigation to
be represented in the above type of graph.
1.15.3
Using the information provided, construct a table to show the data that was
used to draw the graph.
18
1.16
Study the diagrams below that show some breeding experiments on
mice. A single pair of alleles showing complete dominance controls
coat colour (white or grey) in these mice.
Female
1
Male
Female
2
3
Male
4
Offspring
Offspring
Offspring
Female
Female
Male
Female
Results of breeding experiments
1.16.1
State which sex chromosomes would be present in the gametes of parent
mouse 2 and mouse 3, respectively.
1.16.2
If mice 3 and 4 had a second set of offspring, what is the percentage
chance that the first mouse born would be female?
1.16.3
Which of the parent mice (1, 2, 3 or 4) is likely to be homozygous
dominant for coat colour?
1.16.4
State why mouse 3 can only be heterozygous for coat colour.
19
1.17
Haemophilia is a sex-linked hereditary disease that occurs as a result of a recessive
allele on the X- chromosome. Study the family tree below and answer the questions
which follow. (Use the symbols H for normal and h for haemophilia above the
gonosomes where applicable, e.g. XHXh )
Albert (male)
(haemophilic)
Carol (female)
(haemophiliac)
Beatrice (female)
(normal; carrier)
Eckhardt (male)
(haemophiliac)
Fiona (female)
(normal; carrier)
1.17.1 Write down the genotypes of each member of the family pedigree
diagram.
1.17.2 If Albert and Beatrice had a 4th child, Damien (male) , what would be the
probability in percentage that he would be a haemophiliac?
1.173 Should Fiona marry Fred who is a haemophilia sufferer, what would be the chance
that their daughter, Helen, will be a Haemophilia sufferer as well? Show your answer
with the help of a punnet square.
1.18
1.18.1
1.18.2
1.19
In humans, the gene for curly hair is dominant over that for straight
hair. Use
the letter H to represent the gene for curly hair and the letter h to represent the
gene for straight hair.
Explain why the statement below is TRUE:
A person with curly hair may be heterozygous or homozygous for
this characteristic
Show diagrammatically, by means of a genetic cross, how a man
with curly hair, who marries a woman with curly hair, may have a
child with straight hair.
Insulin is the smallest known protein and contains51 amino acids. Using biotechnology,
scientists have genetically modified bacteria so that they produce human insulin.
1.19.1 State THREE advantages of producing human insulin by genetic
modification.
1.19.2 Give TWO reasons why some people might be against genetic modification.
20
1.20
A fingerprint is a useful way of identifying people and classifying them into groups. A
fingerprint is taken by rolling the right index finger onto an inkpad and then on a piece
of paper.
During a discussion of this topic, a group of learners asked the
following question:
''Which one of the five main types of fingerprints is most common amongst the
learners of this school?''
1.20.1 State any FOUR steps in the planning process that must be
considered when planning an investigation to answer the question
above.
1.21
The table below shows the results obtained by first crossing a pure-bred
blackfurred mouse with a brown furred mouse. The gene for black fur is
dominant over the gene for brown fur.The F1 generation was used as
parents (consisting of 4 breeding pairs) of the F2 generation.
Parents
F1 generation
F2 generation
Offspring of 1st breeding pair
Offspring of 2nd breeding pair
Offspring of 3rd breeding pair
Offspring of 4th breeding pair
Number of black mice
1
8
Number of brown mice
1
0
8
7
5
4
0
1
3
4
1.21.1
From the data, calculate the phenotypic ratio of the mice with black f
fur and the mice with brown fur in the F2 generation.Show ALL
your workings.
1.21.2
Suggest why it is better to use the four sets of offspring to calculate the ratio
rather than using only one set
1.21.3
Draw bar graphs on the same system of axes to represent the
phenotypic results of the F2 generation offspring of each breeding
pair shown in the table above.
21
MORE GENETIC CROSS EXAMPLES
1.22
a Couple has 3 sons and the woman is pregnant again .Show diagrammatically,
by means of a genetic cross what the percentage chance is for them to have a
baby girl.
1.23
In an experiment to show co-dominance, cows with white fur (W) were
crossed with bulls with red fur (R). All the offspring of the F1-generation have
roan fur (RW). A roan fur consists of patches of white and patches of red fur.
Roan cows and roan bulls were crossed and the results are given below.
Genotype
Number of offspring
1.23.1
RR
120
RW
240
WW
120
Give the ratio of the different phenotypes shown in the above table.
Use the information in the table above to draw a pie-chart showing the
proportions of the different genotypes.
Explain why the cows and bulls with genotype RW have roan fur and not
only red or only white fur.
22
COMPLETE DOMINANCE e.g. two
individuals with pure – breeding
contrasting characteristics are crossed.
P1
P1

phenotype
genotype
INCOMPLETE DOMINANCE e.g. red
flowered plants crossed with white flowered
plants
phenotype
Red x White
genotype
RR x WW
EXAMPLES OF GENETIC CROSSES
Tall x Short
TT x tt

(Mendel’s Law of Segregation)
Meiosis
(Mendel’s Law of Segregation)
Meiosis
Gametes
Gametes
T
R
W

t

Gametes
Fertilisation
Fertilisation
Gametes T
t
Tt
t
Tt
or
T
Tt
Tt
W
W
F1
F1
or
genotype: Tt
(Principle of dominance)
Phenotype: Tall
R
RW
RW
R
RW
RW
genotype: RW
Phenotype: Pink 
(Offspring have intermediate forms of traits of parents)
 (Individuals of F1 all display the dominant characteristic)
Sex – linked diseases eg. Haemophilia cused by a recessive allele on
CO - DOMINANCE e.g. Cows with white fur crossed
with bulls with red fur.
P1

phenotype
genotype
Red x White
RR x WW
P1
(Mendel’s Law of Segregation)
Meiosis
Gametes
the
X-chromosome. Caused excessive bleeding. Males have only one Xchromosome – they mainly suffer from this disorder. Cross a heterozygous
mother with a haemophiliac father.
R

F1
(Mendel’s law of Segregation)
Meiosis
W

Fertilisation
phenotype Non haemophiliac x haemophiliac
genotype
XHXh x XhY
Gametes
Gametes R
W
RW
W
RW
genotype: RW
Phenotype: Roan (both red and white)
or
R
RW
RW
(Both alleles are equally dominant and are expressed in the phenotype)
XH , Xh
Xh ,Y 

Gametes XH
Xh
XHXh
Y
XHY
genotype: XHXh ; XhXh XHY XhY:
phenotype: Two haemophiliac(1F + 1 M);
Two non-haemophiliac(1F + 1 M)
Fertilization
F1
or
Xh
XhXh
XhY
23
EVOLUTION
REVISION
1.1
Tens of thousands of years ago, the animals that evolved into giraffes were not
as tall as modern giraffes. Over a long period of time, the necks of giraffes
became longer. They could reach leaves high in the trees and reach down for
water.
Ancestral giraffe
Modern giraffe
Ancestral and modern giraffes feeding
1.1.1
Describe how the long necks of modern giraffes would have been explained
by the following:
(a)
(b)
1.1.2
Darwin
Lamarck
Explain why Lamarck's theory is not accepted.
24
1.2
The different species of finches (A, B, C and D) below are found on different
Galapagos Islands and are thought to have originated from a seed-eating
ancestral species from the mainland of South America. They resemble each
other with respect to their internal body structure but differ with respect to the
shapes and sizes of their beaks and hence their feeding habits.
Buds and fruit
Leaves
A
B
Insects
Larvae/Worms
Ancestral seedeating species
from the mainland
C
Some of the finch species from the different Galapagos
islands
1.2.1
1.2.2
1.2.3
Explain what is meant by geographical isolation of
population.
Why do you think the different finch species became
adapted to eat different food types?
Describe how new finch species were formed on the
different islands
25
1.3
Study the diagrams below showing a process of evolution. DIAGRAMS 1, 2
and 3 show the sequence of events that occurred in rabbit populations over
many thousands of years.
River
1
Gene flow
Land slide
2
River
Population A
Population B
River
3
No
gene flow
occurs
Species X
Species Y
1.3.1 Name the evolutionary process represented by the sequence of
events shown in DIAGRAMS 1, 2 and 3 above.
1.3.2 Describe the process stated in QUESTION 1.3.1 using the
diagrams above.
1.4
26
Study the three diagrams (A, B and C) below that show a mechanism used
to explain evolution.
A
B
C
Roots
Offspring
Time
The structural adaptation of cacti over time
1.5
1.6
1.4.1
From a comparison of pictures A and B, describe the feature of
the cacti that have enabled them to survive long periods of hot,
dry weather conditions.
1.4.2
Name the mechanism put forward by Darwin to explain his
theory of evolution that is illustrated in these diagrams.
1.4.3
Use the three diagrams above to explain the mechanism
mentioned in QUESTION 2.1.2.
Describe how each of the following contributes to genotypic variation within
a species:
1.5.1
Meiosis
1.5.2
Mutation
1.5.3
Sexual reproduction
Describe how speciation occurs when a population becomes separated by
a geographical barrier.
27
1.7
1.8
Both Darwin and Lamarck proposed theories to explain the origin of new
species.
1.7.1
State the FOUR observations upon which Darwin based his theory.
1.7.2
Tabulate TWO differences between Lamarck's and Darwin's
theories.
Study the diagram of a duck's foot below.
Webbed foot of a duck
1.8.1
Ancestors of ducks did not have webbed feet. In terms of natural selection,
explain how the webbed feet could have evolved.
1.8.2
The following questions refer to Lamarck's explanation of evolution:
(a) Describe the idea proposed by Lamarck to explain evolution.
(b) State why Lamarck's explanation is not accepted by most scientists today.
1.9
Read the following passage:
The cichlid fishes of Lake Malawi have evolved from one ancestor
into more than 400 species over time. There are not many barriers in
the lake that would stop gene flow and breeding between populations.
Scientists think that the speciation process of the fish happens by
sexual selection in which random mutations give rise to new colour
patterns in male fishes. Female cichlid fishes prefer the new colour
patterns and accordingly choose a mate on this basis.
1.9.1 What type of speciation occurs in cichlid fishes ?
1.9.2 Briefly explain the type of speciation mentioned in Question 1.9.1
1.9.3 What type of reproductive isolation occurs in cichlid fishes?
1.9.4 Explain how reproductive isolation occurs in the cichlid fishes.
28
1.10
Study the following diagrams which
in evolution
show different stages (1 to 4) of a process
1.10.1 Name the evolutionary process that resulted from the continental
drift shown.
1.10.2 Describe how the original population of species A split to become two species
as indicated in the diagrams above.
29
ADDITIONAL QUESTIONS
GENETICS
1.1
Study the diagram below which shows three generations of snapdragon plants
and answer the questions which follow.
Use the following symbols for the contrasting alleles:
W – for white flowers
R – for red flowers
A
B
C
Diagram showing inheritance of colour of snapdragon flowers
KEY:
Snapdragon with pink flowers
Snapdragon with red flowers
Snapdragon with white flowers
1.1.1
State the kind of dominance shown in the diagram above.
1.1.2
Use the symbols R and W and write down the genotypes of each of
the following snapdragon plants:
30
(a) A
(b) B
(c ) C
1.2
1.3
1.4
(2)
(2)
(2)
Haemophilia is a sex-linked disease caused by the presence of a recessive
allele (Xh). A normal father and heterozygous mother have children.
1.2.1
Represent a genetic cross to determine the possible genotypes
and phenotypes of the children of the parents mentioned in
QUESTION 2.1.
1.2.2
What are the chances of the parents having a child that will be a
haemophiliac male?
1.2.3
Explain why the father is not a carrier for haemophilia.
The risks and benefits of using biotechnology have been the subject of
considerable debate in recent times. State the following:
1.3.1
THREE disadvantages of genetic engineering
1.3.2
THREE advantages of genetic engineering
Height of humans is a trait that is controlled by more than one gene. The
Grade 12 learners at a girl's school did an investigation to determine the
height of the Grade 12 learners.
The results of the investigation are shown in the table below.
Height (cm)
Number of
girls
150–151 152–153 154–155 156–157 158–159 160+
5
18
30
24
14
2
31
1.4.1
Plot a histogram using the information in the table above.
1.4.2
Name this type of inheritance that is controlled by more than one
gene.
1.4.3
How is the type of inheritance, named in QUESTION 2.3.2,
different from that of inheritance due to one gene?
1.4.4
State TWO other possible variables/factors that might have an
influence on the height of a person.
1.5
The questions below are based on DNA profiling/fingerprinting.
1.5.1
What is DNA profiling?
1.5.2
DNA evidence of a murder suspect was found at the scene of a
crime.
Give TWO possible reasons why the suspect might be found not
guilty in court, by referring to the DNA evidence.
1.6
The questions below are based on protein synthesis.
1.6.1
Describe the role of DNA during transcription in protein synthesis.
1.6.2
The diagram below shows the sequence of nitrogenous bases of a
small part of a strand of DNA which codes for part of a protein
molecule.
CGG
TAT
CCT
Write down the mRNA codon sequence that reads from left to
right from the DNA sequence above.
32
1.6.3
The table below shows the tRNA anticodons and their
corresponding amino acids.
ANTICODONS OF
tRNA
CAA
CCC
CGU
AAA
UUA
UAC
GGU
ACC
UCA
GGG
CCA
AMINO ACIDS
Valine
Glycine
Alanine
Phenylalanine
Asparagine
Methionine
Proline
Tryptophan
Serine
AGU
Select and write down from the table above, the amino acids (in the
correct sequence) that would be required for the base sequence of
mRNA shown below.
1.7
Describe the mechanisms by which meiosis contributes to genetic variation and
describe how abnormal meiosis leads to Down's syndrome and polyploidy. Also
describe the advantages of polyploidy in agriculture.
NOTE:
NO marks will be awarded for answers in the form of flow charts or
diagrams.
33
EVOLUTION
1.8
The peppered-moth, Biston betularia, has two phenotypes for body colour,
dark (blackish) and pale (whitish). The trunks of the trees on which the moths
rest are black in polluted environments compared to the white trunks of trees
in unpolluted environments. In both unpolluted and polluted environments,
birds are the predators of the moths.
An investigation was carried out to determine the number of dark and pale
peppered-moths present in polluted and unpolluted environments using a
sampling technique.
The results of the investigation are shown in the table below.
TYPE OF ENVIRONMENT
Polluted
Unpolluted
DARK MOTHS
150
30
PALE MOTHS
40
170
1.8.1
Formulate a hypothesis for the above investigation.
1.8.2
Suggest THREE factors that might have decreased the validity of
this investigation.
1.8.3
Using the table and your understanding of natural selection,
explain the results for the polluted environment.
1.9
Describe how sympatric speciation occurs.
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