SECONDARY SCHOOL IMPROVEMENT
PROGRAMME (SSIP) 2015
GRADE 12
SUBJECT:
LIFE SCIENCES
TEACHER NOTES
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TABLE OF CONTENTS
SESSION
TOPIC
PAGE
1
DNA: Code of Life
4 - 19
2
Meiosis
19 - 31
3
Reproduction in Vertebrates
32 - 35
3
Human Reproduction Part 1
35 - 44
4
Human Reproduction Part 2
44 - 55
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Note to Teachers:
Please make sure that you cover these tips on exam techniques with the learners.
Where possible, when going through the solutions to the questions, point out the
relevant components please, so that it becomes second nature.
When answering questions in an exercise, test or exam:
 Read the question first and underline the operative words so that you are clear
about what is being asked of you.
 Take careful note of the mark allocation, as this will guide you to the number of
facts that you need to write. Do not waste time writing 5 facts when the examiner
only asked for 2. They will only mark the 1st two answers.
 Answer the question as if you are answering someone whom you like, is
intelligent but knows nothing about Life Science – then you will not leave anything
out.
 Please note: an examiner will never ask 2 questions with the same answer. If
you have written the same answer then one of them is definitely wrong. Please
re-read each of the questions and you will see that each one requires a different
answer.
 When you are asked to write your ‘view’ or ‘belief’ or ‘what do you think….’ Then
only write one type of view. For example: What is your view on abortion? Here
you must be either pro-abortion or anti-abortion. You must not write about both
views. You must take a stance on one view.
 When you are asked to debate something – then you are required to look at the
issue from both sides and you will be expected to provide both sides for marks.
 If you are asked to ‘tabulate’ – then you must answer in the form of a table. You
will be penalized if your points are not listed in a table format.
 When you are asked to compare two things, then rather use the table format.
This way you will remember to write equally about both of the factors.
When answering questions with diagrams:
 Study the diagram and write missing labels in on the diagram itself FIRST.
 Now read through the questions and answer each one.
 If you do not know the answer, then write the number on your answer page, look
at the mark allocation and leave enough lines to write the answer in later, i.e.: if
the mark allocation is 2, then leave two lines open.
Graphs and Pie charts:
 Make sure that you know the difference between a line graph, bar graph, histogram
and a pie chart.
 Make sure that you practice the skill of graphing and representing data from a
table as a graph.


Always provide a heading for your graph and label the x and y-axis which include the
units of measurement like 0C, seconds, years, number of organisms etc.
The independent variable is graphed on the x-axis (controlled by the researcher e.g.:
time, temperature). The dependent variable is graphed on the y-axis and will be the
results obtained.
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
Make sure that you are able to read information from a graph accurately. Use a
ruler and draw lines on the graph – through the x and y-axis so that your readings
are accurate.
Calculations:
 You will be expected to do calculations in a test and exam.
 Make sure that you have a calculator.
 Make sure that you understand how to calculate the average, the difference
between and percentage.
 Generally, the examiner will ask you to show your calculations. You must write
out your calculation step by step, otherwise you will only be awarded a mark for
the answer – if it is correct.
SESSION NO: 1
TOPIC: DNA: THE CODE OF LIFE
Teacher Note: Please ensure that the learners understand that the nucleus is an
organelle located in a cell. Go through the structure of DNA and RNA very carefully.
They MUST understand the structure and combination of the complimentary bases or
they will not be able to answer exam questions based on Protein Synthesis. Please
emphasize that Thymine is only in DNA and Uracil is only in RNA. Before starting
with the questions, write DNA: G-C and T-A AND RNA: G, A, C and U on the
board. Refer to this while working through the questions.
1.
2.
3.
Introduce session – 10 minutes and go over the exam technique tips
Typical exam questions and solutions – 55 minutes
(Questions that are not completed must please be included with Homework)
Notes on Content – 25 minutes
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 5 minutes
(Taken from NSC Feb/Mar 2013 Paper 1)
The diagram below shows part of a DNA molecule in a nucleus just before cell
division.
(NOTE: The structure of the DNA and RNA molecule is very important and is
often examined. Make sure that you know the labels of each component.
Remember to label the diagram first and then move on to the questions. )
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1.1.
Identify the parts labelled:
a) 3
b) 4
1.2.
Identify the nitrogenous bases labelled:
a) 1
b) 2
1.3.
(1)
(1)
(1)
(1)
Explain why the diagram above represents replication and
not transcription.
(Replicate means to make another identical molecule – to ‘copy’)
(2)
QUESTION 2: 5 minutes
(Taken from NSC Feb/Mar 2013 Paper 1)
Ribonuclease is an enzyme made up of 127 amino acids.
2.1.
What is the minimum number of DNA bases needed to code for amino acids
of this enzyme?
(1)
2.2.
The sequence of DNA bases coding for seven amino acids in the enzyme
ribonuclease is:
GTT
TAC TAC TCT
TCT
TCT
TTA
(Remember that the mRNA codon will always be opposite to the DNA
code. Also remember that Thymine is only found on DNA and that on
RNA, Thymine is replaced with Uracil)
The number of each type of amino acid coded for by this sequence of DNA
bases, is shown in the table below.
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The first amino acid in this enzyme is Gly, which is coded for by GTT in DNA. Use
the DNA base sequence and the table above to work out the sequence of the
remaining amino acids, in this part of the enzyme.
(3)
QUESTION 3: 6 minutes
(Taken from NSC Nov 2012 Paper 1)
The diagram below shows a short section of a DNA molecule.
(A reminder first to label the diagram and then to move on to questions)
3.1.
Identify part C and part D respectively.
(2)
3.2.
Name the type of bond that joins A and B.
(1)
3.3.
Give ONE visible reason for identifying the above molecule as DNA.
(1)
3.4.
Name TWO structures in a non-dividing human cell, where DNA is found. (2)
QUESTION 4: 12 minutes
(Taken from NSC Nov 2012 Paper 1)
The first 7 triplets of nitrogenous bases that form part of the gene coding for one
chain of the haemoglobin protein that makes up red blood corpuscles in humans is
shown below.
4.1.
How many of the following are coded for in the DNA template sequence
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above:
a)
Nitrogenous bases
b)
Different types of tRNA molecules that are required to form the
polypeptide from this piece of DNA
c)
Amino acids
(1)
(1)
(1)
4.2.
Write down the mRNA sequence from triplet number 4 to triplet number 6 for
the DNA template above.
(3)
(Remember: A=T/U and G=C for the DNA templates TGA – GGA – CTC)
4.3.
Using the table below, determine the amino acid sequence coded
by triplet number 4 to triplet number 6.
(3)
4.4.
th
If the T in the 6 triplet of bases changed to A in the DNA template above:
th
a)
Write down the new amino acid (using the table above) that this 6
triplet now codes for
(1)
(Remember: A=T/U and G=C)
b)
State the type of gene mutation that has occurred
(1)
QUESTION 5: 10 minutes
(Taken from NSC Nov 2011 Paper 1)
The questions below are based on protein synthesis.
5.1. Describe the role of DNA during transcription in protein synthesis.
(4)
5.2.
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.
Write down the mRNA codon sequence that reads from left to right from
the DNA sequence above.
(3)
(A reminder that a codon is made up of 3 bases and can also be called a
triplet base. A=T/U and G=C)
5.3.
The table below shows the tRNA anticodons and their corresponding amino
acids.
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(Note: The anti-codon is the opposite to the mRNA and is, therefore, the
same as what was coded on the DNA)
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.
(3)
QUESTION 6: 5 minutes
(Taken from NSC Nov 2011 Paper 1)
The questions below are based on DNA profiling/fingerprinting.
6.1.
What is DNA profiling?
(1)
6.2.
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.
(4)
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QUESTION 7: 12 minutes
(Taken from NSC Feb/Mar 2011 Paper 1)
The diagrams below represent the process of protein synthesis.
(A reminder first to label the diagram and then to move on to questions – assist
the learners with this task.)
7.1.
Identify compound M and organelle R.
(2)
7.2.
Write down the sequence of the FIRST THREE nitrogenous bases on the
DNA strand that led to the formation of Z.
(2)
7.3.
Name the part/stage of protein synthesis that is illustrated in O.
7.4.
The table below shows the base triplets of DNA and the amino acid each
codes for.
(1)
(Remember that Thymine is only found on DNA and that on RNA,
Thymine is replaced with Uracil so: A=T/U and G=C)
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With reference to the diagram in QUESTION 7 and the table above:
a)
Name the amino acid labelled P.
b)
State the base sequence of the molecule labelled Q.
c)
What name is given to the triplet of tRNA bases that codes for
each amino acid?
d)
Describe how the composition of the protein molecule
changes if the base sequence at X is UGU instead of UCA.
(2)
(2)
(1)
(2)
SECTION B: NOTES ON CONTENT
Terminology & definitions:
 Base pairing: Purines pair with Pyrimidines - adenine (A) always bonds to
thymine (T) and guanine (G) with cytosine (C) in DNA molecule, to ensure the
precision of DNA replication
 Codon: the corresponding three-base sequence on the mRNA, required to
specify one amino acid in a protein chain that is comlementary to the bases of the
DNA template. If the DNA is C-G-T, then the codon will be the complimentary
G-C-A carried by the mRNA
 Anticodon: a set of three bases (three-base sequence) on the tRNA that
correspond (and are complementary) with the codon on the mRNA. If the codon
is G-C-A then the anticodon will be C-G-U (Remember: In RNA, Thymine is
replaced with Uracil)
 Chromatid: is one half of a chromosome and consists of a protein core
surrounded by DNA. The DNA carries the hereditary characteristics. When two
chromatids are joined by a centromere = a chromosome
 Chromatin network: visible as thread-like structures in the nucleus of an inactive
cell
 Chromosome: a structure made up of two chromatids joined by a centromere
that that carries the hereditary characteristics within the DNA
 Chromosome mapping: the plotting of the relative positions of certain genes
with respect to the positions of the other genes, in the same linkage group
 DNA: (deoxyribonucleic acid) located on the chromosomes in the nuclei of all
living cells and carries the hereditary information of the organism. The DNA
molecule is a double helix (twisted) strand. The four nitrogenous bases can be
arranged in any order, as long as a purine is attached to a pyrimidine. A weak
hydrogen bond holds the complementary nitrogenous bases together. The
combination of nitrogenous bases is the code system for the messages from the
DNA. Adenine always only joins to Thymine and Guanine always only joins to
Cytosine (ALWAYS: A-T and G-C)
 DNA Replication: takes place to produce two new identical DNA molecules.
(Process: DNA unspirals; weak hydrogen bonds break; each separate strand of
DNA attracts a new complimentary nucleotide partner; results in DNA containing
half the original molecule and a new complimentary half. It is an exact copy of the
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











origibal DNA.) The process occurs during Mitosis and ensures that the same
genetic information is carried to the new cell so that growth, repair and
replacement can take place.
DNA gene sequence: determines the mRNA sequence in transcription and
therefore the protein sequence in translation, during the process of protein
synthesis
Frameshift mutation: a codon is substituted, altering the gene expression of the
codons so that a different amino acid is translated from the original resulting in
different proteins
Gene: a unit of sequenced pieces of DNA that carry the genetic information that
will determine the hereditary characteristics of an organism.
Genetic code: is encoded in the DNA and mRNA sequences. The genetic code
will determine translation during protein synthesis. The genetic code determine
the organism’s genotype (sequence of genes) and the phenotype (physical
appearance and characteristics) of the organism.
Nitrogenous bases: this is a nitrogen containing molecule that has the
properties of a base e.g.: purines and pyrimidines, which forms the main protein
part of the nucleotide
Non-coding DNA: separates genes to minimize the effects of mutations;
regulates gene expression and may be used to identify shared sequences that
could show evidence of common ancestry and evolution.
Nucleotide: the building block of RNA and DNA. Each nucleotide consists of a
pentose sugar, a phosphate ion and a nitrogenous base (purine or pyrimidine)
Point mutation: one or more nitrogenous bases are deleted from the codon or
replaced (e.g.: sickle cell anaemia) or when additional nitrogenous bases are
included into the DNA.
Polyploidy: (poly = many and ploidy = the number of complete sets of
chromosomes in a biological cell) is where cells have multiple pairs of
chromosomes beyond the basic set and refers to the changes in the gene
frequency and the chromosome numbers – altering the species at a genetic
level.
RNA: (ribose nucleic acid) a single strand, located in the nucleoplasm and
cytoplasm. The RNA molecule is always a single strand of nucleotides containing
both purines and pyrimidines. Remember that the RNA contains Uracil instead of
Thymine (A, G, C and U). RNA is responsible for protein synthesis.
o Messenger RNA (mRNA): responsible for carrying the genetic code that is
transcribed from DNA, to specialized sites of the ribosomes where the
information is translated for protein synthesis
o Ribosomal RNA (rRNA): form the ribosomes and produce the proteins,
based on the information received from the tRNA.
o Transfer RNA (tRNA): carries specific amino acids to the mRNA codon,
during the production of proteins
Transcription: the enzyme controlled process where the base sequence of
chromosomal DNA is transferred to mRNA (codon), to form a complimentary copy
of three bases on the DNA strand
Translation: the process where the code on a mRNA is coded to the tRNA
(anticodon) and results in a specific sequence of amino acids, to form a specific
protein
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Structure of nucleic acids: (Make sure learners know this well)
Each nucleic acid consists of a number of basic building blocks called nucleotides.
Each nucleotide consists of three parts: 1 phosphate ion, 1 pentose sugar and 1
nitrogenous base.
phosphate
ion
deoxyribose
sugar
nitrogenous base
Nitrogenous bases are divided into two complementary groups: Purines and
Pyrimidines. DNA forms a double strand where purines will only bond with
pyrimidines (weak hydrogen bond holds them together). DNA contains Thymine and
RNA contains Uracil instead of thymine. The other nitrogenous bases are found in
both DNA and RNA. (Draw this schematic on the board)
Adenine
Purines
Combination is ALWAYS:
Guanine
Nitrogenous
bases
Pyrimidines
Cytosine
Guanine
(Purine)
Cytosine
(Pyrimidine)
Adenine
(Purine)
Thymine
(Pyrimidine)
Thymine (on
DNA) or
Uracil (on RNA)
Difference between DNA and RNA: (Impress on Learners to learn this well)
RNA
DNA
Ribose pentose sugar
Deoxyribose pentose sugar
Single strand of nucleotides
Double strands of nucleotides
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Strand is unwound
Strands form a helix (twisted)
Strand is short – codons and anticodons
consisting of three bases only
Strands are long and contain many
triplets
Contains the nitrogenous bases adenine,
guanine, cytosine and uracil
Contains the nitrogenous bases adenine,
guanine, cytosine and thymine
Protein synthesis process: (Go through this process thoroughly. It is a problem
generally, but when the learners understand the difference between transcription and
translation, they will have no problem with protein synthesis)
Step 1: Transcription: the enzyme controlled process where the base sequence of
chromosomal DNA is transferred to mRNA (codon) using free RNA nucleotides from
the nucleoplasm, to form a complimentary copy of three bases on the DNA strand.
Example: DNA = CTG, mRNA = GAC (Always complimentary bases A-T and G-C).
mRNA will carry the coded message from the DNA for protein synthesis into the
cytoplasm and attach to a ribosome.
Step 2: tRNA has an anticodon that picks a specific amino acid and carries it to the
ribosome where the mRNA codon determines the anticodon fit. Example: the mRNA
codon of GAC will only accept the tRNA anticodon of CUG. The original triplet
sequence on the DNA strand was CTG. (Remember that RNA contains Uracil in
place of Thymine on the DNA, so codons and anticodons will only ever contain
Uracil).
Step 3: Translation: the tRNA releases the amino acid into the correct place on the
polypeptide chain (poly = many peptides). Amino acids are joined by peptide bonds
to form the required protein molecule.
Each protein is formed specifically to the genetic code stored on the DNA in the
nucleus of every cell in the organism. Any change during this coding process will
result in a mutation.
Example of base triplet, codon and anticodon combinations:
(Perhaps do a couple of other examples on the board so that learners remember that
the DNA codes for the amino acid and that mRNA will be complementary (but with U
not T) and mRNA is complementary to tRNA (which is the same as the original DNA
triplet except with T and not U)
Amino Acid
Base triplet of
DNA
* Contains
Thymine not Uracil
Codon of mRNA
Anticodon of tRNA
* Each Codon is
complementary
(opposite) to the
DNA base triplet
but contains Uracil –
not Thymine
* Each Anticodon is
complementary
(opposite) to the
Codon and similar to
the DNA base triplet
but contains Uracil –
not Thymine
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Alanine
CGA
GCU
CGA
Histidine
GTC
CAG
GUC
Valine
CAT
GUA
CAU
Serine
AGA
UCU
AGA
DNA fingerprinting: (Remind learners to use a ruler horizontally when comparing
DNA profiles. This will help them identify the same markers)
All living organisms have DNA with the same basic chemical structure. The
difference between us all is the order of the nitrogenous base sequences. A DNA
profile is designed by using DNA probes. A selection of DNA sequences within the
DNA profile forms what is termed the VNTR pattern for that individual. Forensic
scientists are able to compare the DNA profiles to a sample that is provided from a
crime scene. DNA profiling is very acurate.
Sequencing of DNA: (This is very important for speciation and also Genetics and
inheritance. Please make sure the learners grasp the importance of DNA
sequencing. It is the individual and species recipe for all organisms)
A species is a group of organisms that are similar in appearance, share the same
DNA sequences, perform the same mating rituals and interbreed. When the DNA
sequence is altered, genes mutate by accident. If the mutation is beneficial, it will
become a fixed mutation and be passed to the next generation, resulting in new
strains and species. If a mutation is bad, it results in the death of the individual and is
termed a lethal mutation. When a mutation has no immediate effect on the
individual it is termed a neutral mutation and is passed on to the next generation.
When the environment changes, the neutral mutation may assist the organism to
adapted and cope with the change. The sequence of DNA and the number of
chromosomes found in different species, provides evidence of relationships between
groups of organisms. The DNA sequencing of all mammals suggest phylogenic
relationships.
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1: 10 minutes
(Taken from various NSC exams)
(Note: When answering multi-choice questions:
1. Read the question while covering the answers.
2. Think of the correct answer.
3. Look for your answer.
4. Write the letter down on your answer sheet.
BUT: If you do not know the answer after point 1 and 2, then:
3. Look at the options.
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4. Try to think of why an option is wrong for the question and cross it out. If
there is an option that you don’t know, write a ? next to this option.
5. If you still do not know the answer, then select the ? option)
1.1.
What percentage of adenine bases is present in a DNA molecule with 2 000 bases, if
400 of the bases are cytosine?
(REMEMBER THE RULE: G = C and A = T/U)
A
B
C
D
1.2.
20%
30%
40%
60%
The diagram below shows changes in cell mass and DNA mass during two
cell cycles.
It can be concluded from the graph that during the cell cycle ...
A
the interphase is the longest phase.
B
the cell is dividing between 24 and 36 hours.
C
replication takes place between 0 and 12 hours.
D
cytokinesis takes place at 12 and 36 hours.
1.3.
The result of profiling various DNA samples in a criminal investigation is
shown below.
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Which conclusion about the crime could the DNA analyst draw?
A
Only suspect X was involved.
B
Only suspect Y was involved.
C
Suspects X and Y were both involved.
D
Neither suspect X nor Y was involved.
(Hint: use a ruler to line the different markers up so that you can see any
corresponding VNTR patterns.)
1.4.
DNA sequences are now routinely used to determine how closely related
different species are to each other. The table below shows DNA sequences
from the amylase gene of four different organisms.
Based on this information alone, which TWO organisms are most closely
related?
A
Organism 1 and Organism 2
B
Organism 2 and Organism 3
C
Organism 2 and Organism 4
D
Organism 3 and Organism 4
1.5.
As DNA was extracted from cells of E. coli it was analyzed for its nitrogenous
base composition. It was found that 38% of the bases are cytosine. What
percentage of the bases is adenine?
A
12
B
24
C
38
D
62
QUESTIONS 1.6 to 1.8 are based on the diagrammatic representation below of a
part of two different nucleic acid molecules found in the cells of organisms during a
stage in the process of protein synthesis.
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1.6.
The diagram above illustrates the process of ...
A
replication.
B
transcription.
C
translation.
D
mutation.
1.7.
The process illustrated above occurs in the …
A
cytoplasm.
B
centrosome.
C
ribosome.
D
nucleus.
1.8.
An observable difference between molecule 1 and molecule 2 is that …
A
molecule 1 is double stranded and molecule 2 is single stranded.
B
molecule 1 contains deoxyribose sugars and molecule 2 contains
ribose sugars.
C
molecule 1 has thymine and molecule 2 has uracil.
D
molecule 1 is longer than molecule 2.
1.9.
The mRNA sequence from a portion of a DNA template GATCAA is …
A
CTAGTT
B
CUAGUU
C
AGCTGG
D
AGCUGG
(REMEMBER THE RULE: G = C and A = T/U)
1.10. RNA differs from DNA in that it …
A
has thymine and a phosphate group.
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B
C
D
has a deoxyribose sugar and cytosine.
is a double stranded molecule.
has uracil and a ribose sugar.
(10 x 2) = (20)
QUESTION 2: 15 minutes
(Taken from NSC Nov 2012 Paper 1)
During their work to establish the structure of DNA, Watson and Crick were
interested in the proportion of nucleotides in the DNA of skin cells from a particular
organism. They considered the results from three different samples done in the same
laboratory, as shown in the table below.
2.1.
2.2.
2.3.
2.4.
Why did Watson and Crick consider results from three samples?
What is the ratio of adenine to thymine in the overall experiment?
Give a reason for your answer to QUESTION 2.2.
Draw a pie chart illustrating the percentages of the different nucleotides in
sample 1. Show ALL working.
SECTION D:
1.1
1.2.
1.3.
(8)
SOLUTIONS FOR SECTION A
(a) deoxyribose
(1)
(b) phosphategroup (1)
(a) Guanine(1)
(b) Guanine
(1)
The formed complementary strand contains thymine/
Both strands of DNA molecule are being used as a templateAny (1 x 2)
2.1.
2.2.
381 
(Met-
3.1.
C- deoxyribose/(sugar)
D- phosphate 


(2)
(weak) hydrogen bond

(1)
It is doublestranded/base pairs are present/(ladder -like)
(Mark first ONE only)
3.2.
3.3.
(1)
(1)
(1)
 - (Arg-Arg-Arg)  - Asn  (3)
3.4.
nucleus/chromosomes/chromatin/mitochondrion
4.1.
a)
b)
c)
21
6
7 


(1)
(2)
(3)
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4.2.
4.3.
4.4.
ACUCCUGAG(sequence must be correct) (3)
threonineprolineglutamate(sequence must be correct) (3)
a)
valine 
(1)
b)
pointmutation (1)
5.1.




DNA codes for a particular protein/polypeptide/amino acid sequence
One strand is used as a template 
To form mRNA
DNA cannot leave nucleusAny (4)
5.2.
5.3.
GCC AUA GGA (in sequence) (3)
Glycine Proline Serine (in sequence) (3)
6.1.
Process by which the DNA of a person/organism is mapped/
DNA sequence of an individual is determined/barcode pattern of DNA(1)
6.2.
- Suspect was framed by leaving DNA evidence at the scene/swopping
specimens at the lab
- Human error during DNA profiling process
- Suspect had an identical twin who has the same DNA profile
- The DNA evidence of the accused was at the scene before
the crime was committed(Mark first TWO only) Any 2 x 2 (4)
7.1.
M – DNA
R – Ribosome (2)
AGT  (2)
Transcription (1)
a)
Threonine(2)
b)
CCG(2)
c)
Anticodon(1)
d)
A different protein may form because it has cysteine
instead of serine/have different amino acids (2)
7.2.
7.3.
7.4.
SESSION NO: 2
TOPIC: MEIOSIS
Note: Briefly revise Mitosis. You must understand the difference between Mitosis
and Meiosis. You must understand the relevance of the crossing over in Prophase 1
as this forms the basis and grounding for genetic variation and hereditary
characteristics in the sections on Genetics and Reproduction. Learn the relevance of
diseases and syndromes resulting from mutations caused during meiosis.
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 10 minutes
(Note: When answering multi-choice questions
1. Read the question while covering the answers.
(Taken from various NSC Paper 1)
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2. Think of the correct answer.
3. Look for your answer.
4. Write the letter down on your answer sheet.
BUT: If you do not know the answer after point 1 and 2, then:
3. Look at the options.
4. Try to think of why an option is wrong for the question and cross it out. If
there is an option that you don’t know, write a ? next to this option.
5. If you still do not know the answer, then select the ? option)
1.1.
The nucleus of the somatic cells of a human contains:
A. 46 identical chromosomes
B. 23 different chromosomes
C. 46 pairs of chromosomes
D. 23 pairs of chromosomes
1.2.
Mitosis is responsible for the following in plants and animals
A. growth and repair
B. gamete formation
C. reduction division
D. genetic variation
1.3.
The number of chromosomes in a zygote….
A. diploid
B. half the number in a gamete
C. haploid
D. triploid
1.4.
Karyokinesis begins during which phase?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
1.5.
The most important reason for meiosis to take place is…..
A. the production of four gametes per mother cell to improve the chances of
fertilization being successful
B. the doubling of the chromosome number of each cell
C. the production of haploid gametes to ensure that the chromosome number
is diploid after fertilization
D. the production of a diploid number of chromosomes in the gamete
1.6.
During the process of meiosis….
A. two identical daughter cells result
B. four identical daughter cells are formed
C. the chromosome number remains the same
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D. four unidentical daughter cells result
1.7.
Cytokinesis is the …...
A. division of the nucleus
B. fusion of the nuclei
C. division of the cytoplasm
D. cytoplasmic streaming
1.8.
When daughter cells with 20 chromosomes are formed by cell division, the
following will result:
A. 20 chromosomes after mitosis; 20 chromosomes after meiosis
B. 20 chromosomes after mitosis; 10 chromosomes after meiosis
C. 40 chromosomes after mitosis; 20 chromosomes after meiosis
D. 10 chromosomes after mitosis; 10 chromosomes after meiosis
1.9.
Place the following steps that occur in meiosis in order:
1. crossing over of the chromatids 2
2. lining up of paired chromosomes at the equator 3
3. pairing of homologous chromosomes 1
4. complete separation of chromatids 4
A. 1, 2, 3, 4
B. 2, 3, 4, 1
C. 3, 1, 2, 4
D. 4, 1, 2, 3
(With this type of question: read through options 1 to 4 and tick those that
are correct and apply to the question. Cross those that do not. Select your
answer from the ticked options)
1.10. Why does crossing over /chiasma take place during meiosis?
A. to ensure that the chromosomes divide evenly
B. to ensure that characteristics from the mother are transferred to the father
C. to ensure that cell division can take place
D. to ensure that that genetic variation is passed on to all offspring
(10 x 2) (20)
QUESTION 2: 7 minutes
(Taken from NSC Feb/March 2013 Paper 1)
Study the diagrams below representing various phases of meiosis in an organism.
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2.1.
2.2.
Which diagram (A, B or C) represents meiosis I?
(1)
Suggest why the chromosomes in diagram B will be genetically different
from that of the parent cell at the beginning of meiosis.
(1)
(Hint: crossing over in meiosis I – why is this relevant?)
2.3.
How many chromosomes will each daughter cell have at the end of this
cell division?
(1)
Give TWO reasons why this type of cell division is important.
(2)
2.4.
QUESTION 3: 8 minutes
(Taken from NSC Nov 2012 Paper 1)
The diagram below shows crossing over in a pair of homologous chromosomes.
3.1.
Identify the point X and part Z respectively.
(2)
3.2.
Give ONE observable reason why the chromosomes above are regarded as
homologous.
(1)
3.3.
Give ONE reason why crossing over is important.
(1)
3.4.
Name ONE other process occurring during meiosis that has the same
importance as crossing over.
(Hint: this takes place during metaphase)
(1)
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3.5.
If a mouse egg cell contains 20 chromosomes, how many chromosomes will
there be in its skin cell?
(1)
QUESTION 4: 20 minutes
(Taken from NSC Nov 2011 Paper 1)
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.
(17)
Synthesis (3)
(20)
(Hint: look at the underlined words in the question. This will tell you what you
must cover in the essay.)
QUESTION 5: 15 minutes
(Taken from NSC Feb/Mar 2011 Paper 1)
Study the following diagrams representing different phases of meiosis.
5.1.
Label structures A, B and C.
(3)
5.2.
Which phase is represented by:
(a) Diagram 1
(b) Diagram 2
(1)
(1)
5.3.
Write down the numbers of the diagrams to show the correct sequence in
which the phases occur.
(2)
(Hint: IPMAT)
5.4.
Tabulate THREE differences between the first and second stages of meiosis.
[Hint: Remember to give the table suitable headings/captions. Always
compare the same characteristics in each of the columns)
(7)
Name and explain TWO processes/mechanisms that ensure that the
gametes produced at the end of meiosis are genetically different from each
other.
(4)
5.5.
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SECTION B: NOTES ON CONTENT
Terminology & definitions
Autosomes: chromosomes that are not sex chromosome. There are 22 pairs of
autosomes in a diploid cell.
Centriole: an organelle in the cytoplasm of the cell, which forms the spindle pole
during meiosis and mitosis.
Centromere: structure that holds two chromatids together to form a chromosome.
Chiasma: crossover of chromatids during meiosis I, resulting in a mixing of the
maternal and paternal alleles of the homologous chromosome.
Chromatid: one half of a chromosome consisting of a protein core surrounded by
DNA that carries the hereditary characteristics. Two chromatids are joined by a
centromere to form a chromosome.
Chromosome: a structure made up of two chromatids joined by a centromere that
that carries the hereditary characteristics within the DNA.
Diploid number (2n): complete chromosomal number represented in pairs, which is
characteristic of an organism.
Gametes: haploid cells (n) which contain half the chromosome number of the diploid
generation. Egg cells and sperm cells are haploid and necessary in sexual
reproduction where the fusion of the two gametes results in a new individual.
Gene: the unit of heredity transmitted in the chromosome, which controls the
development of the characteristics.
Gonosomes: sex chromosomes. There are one pair of sex chromosomes in a
diploid cell: the XX chromosomes in females and XY chromosomes in males.
Haploid number (n): half the number of chromosomes present in the human cells
(23) and present in gametes after meiosis has occurred.
Homologous chromosomes: a pair of chromosomes containing 23 pairs of similar
chromosomes with genes for the same characteristics or traits.
Karyotype is a set of chromosomes from a human cell that shows the chromosomes
arranged in pairs, according to numbers. Pair 1 is always the largest while pair 22 is
the smallest. The female karyotype will have XX as pair 23 and the male will show
XY as pair 23.
Maternal: from the mother / female parent.
Meiosis: a process of cell division whereby the chromosomal number is halved for
the production of haploid gametes (sperm cells and egg cells).
Mitosis: a process of cell division where the resulting daughter cells have the same
diploid chromosomal number as the original parent cell.
Non-disjunction: is when the chromosome pairs do not separate properly during
meiosis in anaphase specifically. So, the homologous chromosomes do not separate
in meiosis I or failure of the sister chromatids to separate during meiosis II, resulting
in an imbalance. Chromosomes with one chromosome missing from one of the pairs
is called monosomy and one gaining a single chromosome is called trisomy,
example: Down’s syndrome.
Paternal: from the father / male parent.
Polyploidy: (poly = many and ploidy = the number of complete sets of
chromosomes in a biological cell) is where cells have multiple pairs of
chromosomes beyond the basic set and refers to the changes in the gene frequency
and the chromosome numbers – altering the species at a genetic level.
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Somatic cells: normal diploid body cells.
Spindle fibres: micro-tubules that form during cell division which radiate out from the
centrosomes and draw the chromosomes to the poles.
Variation: the morphological and physiological differences that can be seen between
members of the same species.
Zygote: the resulting cell after fertilization has occurred.
The Process of Meiosis
For sexual reproduction to take place, a haploid male gamete will fuse with a haploid
female gamete during fertilisation. The result is a diploid zygote.
haploid
half




+ haploid
= diploid
+
= whole
half
Each gamete contains half of the chromosomal number of the body cells. This
means that each gamete must contain one set of the double set of
chromosomes in the original cell nucleus.
The process of meiosis takes place so that each gamete contains one
complete set of chromosomes.
The zygote will contain two complete sets of chromosomes – one from the
male gamete and one from the female gamete.
The growth and development of the zygote will then occur by the process of
mitosis.
In humans, each body cell contains 46 chromosomes (diploid). One set of 23
chromosomes will come from the mother in the egg cell (haploid female gamete).
The second set of 23 chromosomes will come from the father in the sperm cell
(haploid male gamete). When there are two sets of chromosomes, the nucleus is
diploid (2n) and complete. When we refer to one set of chromosomes in the gamete,
it is called haploid (n). Haploid represents 23 chromosomes and diploid represents
46 chromosomes.
The 23 pairs of chromosomes that result in a zygote are divided as follows:
 22 pairs of autosomes
 1 pair of sex chromosomes / gonosomes represented by
XX in females
XY in males
The two steps of the meiosis process:
 Meiosis I (first meiotic division): this is called reduction division where the
chromosome number in the nucleus is halved. The resulting gametes are
haploid.

Meiosis II (second meiotic division):this process is similar to mitosis. The
haploid gametes duplicate so that in males, four sperm cells result. In females,
one gamete forms the egg cell and the three remaining gametes provide
nutrition for the egg cell.
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Differences between Meiosis I and II
The process of Meiosis simplified:
Original diploid cell
(46 chromosomes)
Reduction division
Meiosis I
Haploid gamete
(23)
Duplication
Haploid
Gamete
Haploid gamete
(23)
Duplication
Meiosis II
Haploid
Gamete
Takes place in
the male and
the female
reproductive
organs
Haploid
Gamete
Haploid
Gamete
THEN
Haploid female gamete
(Egg cell)
Haploid male gamete
(Sperm cell)
Fertilisation
Diploid zygote
(46)
Significance of Meiosis
The process of meiosis takes place to:
 Produce haploid gametes from diploid chromosome pairs, in preparation for sexual
reproduction
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



the formation of haploid sperm cells during meiosis is called spermatogenesis
the formation of haploid egg cells during meiosis is called oogenesis
Ensure that the chromosome number remains the same in the offspring as in the adult (n
+ n = 2n)
Ensure genetic variation when crossing over takes place during Prophase I
In animals:
 male gametes/spermatozoids are produced in the testes
 female gametes/egg cells are produced in the ovaries
In plants:
 special cells in the pollen sacs of the anthers divide by meiosis to produce the
pollen grains containing the male gametes
 a specialised cell in the ovule divides by meiosis to produce the embryo sac
containing the egg cell
Where process
occurs
Mitosis
Meiosis


In every living organism, in
the somatic (body) cells

Why process
occurs

Production of genetically
identical cells, which
specialise and differentiate
for growth, repair and
replacement of cells
Mitosis will take place as
binary fission in unicellular
organisms during asexual
reproduction

Reduction division resulting
in haploid gametes for
sexual reproduction so that
the chromosome number
will remain the same in the
offspring as in the adult (n +
n = 2n) once fertilisation
takes place



The transformation of the
chromatin network to
chromosomes
Karyokinesis takes place
Cytokinesis takes place
The transformation of the
chromatin network to
chromosomes
Karyokinesis takes place
Cytokinesis takes place


One nuclear division
No crossing-over



Daughter chromosome is
pulled to opposite poles


Two identical cells are
produced with identical

Similarities
Differences
Specialised cells in the
testes and ovaries of
animals
Specialised cells in the
anthers and ovules in plants



Two nuclear divisions
Crossing-over takes place to
ensure a different
combination of genes when
genetic information is
exchanged
Daughter chromatids do not
separate, one entire
chromosome of each
homologous pair is pulled to
the pole – each
chromosome pair separates
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chromosomes to the original
cell

independently
Four cells are produced,
each containing half the
original number of
chromosomes in the
gametes
Polyploidy: (poly = many and ploidy = the number of complete sets of
chromosomes in a biological cell) is where all cells have multiple pairs of
chromosomes beyond the basic set. Polyploidy refers to the changes in the gene
frequency and the chromosome numbers – altering the species at a genetic level.
When chromosomes are different, bivalents cannot be formed properly during
meiosis, so gametes cannot be produced. In animals, a polyploidy hybrid mule
results when a donkey is crossed with a horse. A mule is infertile and cannot produce
gametes for sexual reproduction. Polyploidy is common in plants and does not affect
reproduction but it does result in a new species. Sometimes, sterile polyploid crops
are preferred, like in the cultivation of many seedless fruit varieties. These crops are
propagated using asexual techniques such as grafting, cuttings and stolons.
Polyploidy in crop plants can be induced by treating seeds with a chemical called
colchicine – it inhibits chromosome segregation during meiosis. So, half of the
gametes will contain no chromosomes, while half will contain double the usual
number of chromosomes. The resulting embryos will have double the usual number
of chromosomes and be tetraploid instead of diploid. This type of genetic
manipulation in animal cells would be fatal. The results are plants that are bigger,
tougher and faster growing.
Down’s syndromes
Sometimes changes take place in the chromosome number during meiosis. Each
nucleus should contain 23 chromosomes after meiosis but if one nucleus contains 22
while the other has 24, it creates problems and is called non-disjunction. When either
of these resulting gametes joins with a normal gamete, the result could be: 23 + 22 =
45 or 23 + 24 = 47 chromosomes. If this happens, abnormalities like Down’s
syndrome result. The Down’s syndrome baby has 47 chromosomes. The mother’s
egg cell has 24 chromosomes + the father’s sperm cell that has 23 chromosomes.
The child will have 45 autosomes, with three number 21 chromosomes instead of the
normal pair and one pair of sex chromosomes. Women over the age of 40 have a
1/12 chance of producing gametes that have 24 chromosomes.
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1: 2 minutes
(Taken from NSC Nov 2013 Paper 1)
1.1. The diagrams below represent six different phases of meiosis taking place in a
cell with four chromosomes.
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The correct sequence of the different phases in which the above-mentioned
division takes place is …
A
1, 2, 3, 4, 5, 6.
B
6, 2, 5, 4, 1, 3.
C
3, 5, 4, 2, 6, 1.
D
3, 4, 5, 6, 1, 2.
(2)
QUESTION 2: 25 minutes
(Taken from NSC Feb/March 2012 Paper 1)
Describe how point mutations, frame-shift mutations and meiosis contribute to
genetic variation.
(17)
Synthesis: ( 3)
(20)
NOTE: NO marks will be awarded for answers in the form of flow charts or
diagrams.
SECTION D:
SOLUTIONS FOR SECTION A
1.1. D
1.2. A
1.3. A
1.4. B
1.5. C
1.6. D
1.7. C
1.8. B
1.9. C
1.10. D
2.1.
2.2.
2.3.
2.4.
(20)
Diagram A


(1)
Crossing over took place/ there was exchange of genetic material / there
was random assortment of chromosomes  (Any 1)
(1)
2
(1)
It increases genetic variation
Reduces the number of chromosomes by half
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Results in formation of gametes
Ensures that the chromosome number remains constant within species
(Mark first TWO only)
(2)
3.1.
3.2.
3.3.
3.4.
3.5.
X – chiasma 
Z - centromere



(2)
The chromosomes are of the same structure / size/ shape/ length
Crossing-over is taking placeany (Mark first ONE only) (1)
It increases genetic variation/produces recombinant gametes
(Mark first ONE only)
(1)
Random arrangement of chromosomes/independent assortment
(Mark first ONE only)
(1)
40/20 pairs
(1)
4.
Possible answer
Crossing – over 
- Homologous chromosomes/bivalents pair up
- Each chromosome has 2 chromatids
- Chromatids overlap/cross over
- Points at which crossing-over takes place are referred to as chiasma
- Genetic material is exchanged between non-sister chromatids
- After the process of crossing-over chromosomes have genes from its
homologous partner 
-This means that each gamete formed will have a mix of genes from maternal
and paternal parents
- Brings about variation in the gametes formed and also the offspring
Max (5)
Random arrangement of chromosomes at the equator 
- Each pair of homologous chromosomes may line up either way on the
equator of the spindle 
- Independently of what the other pairs are doing / independent assortment
-This means that gametes will have differing number/mix of maternal and
paternal chromosomes 
Max (3)
Down’s syndrome
- In meiosis 1 the chromosome pair 21 does not separate  or
- In meiosis II  the chromatids of chromosome 21 do not separate/ centromere
does not divide
- Referred to as non-disjunction
- One gamete will have an extra copy of chromosome number 21  / two copies
of chromosome number 21
- If this gamete fuses with a normal gamete /gamete with 23 chromosomes
- The resulting zygote will have 3 copies of chromosome number 21
instead of 2 / zygote has 47 chromosomes leading to Down’s syndrome
Max (4)
Polyploidy
- During meiosis I
- There is a lack of separation of ALL homologous chromosomes/nondisjunction
- One gamete will inherit the diploid set of chromosomes
- When a diploid gamete is fertilized by a normal haploid gamete
- The zygote/offspring will have 3 sets of chromosomes/triploid
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- In the similar way, tetraploid and other polyploid offspring could be formed 
Max (3)
Advantages of polyploidy in agriculture
- Forms seedless varieties of fruit such as watermelons/bananas/some apples
- Polyploidy cells are bigger / produce larger flowers/fruits/storage organs
- Infertile plants become fertile e.g. wheat
- Plants may be more healthy/resistant to diseases
Max (2)
Content (17)
ASSESSING THE PRESENTATION OF THE ESSAY
Synthesis (3)
(20)
5.1.
5.2.
5.3.
A - Chromatid/chromosome
B – Centromere
C – Spindle fibre /spindle thread
(3)
(a) Metaphase 2
(b) Prophase I 

(2)
Diagram 2, Diagram 3, Diagram 1, Diagram 4
(2)
5.4.
(Mark first THREE only)
any 3 x 2 + 1 table
(7)
5.5. Crossing over
 Pieces of chromatids/groups of genes are exchanged between
 homologous chromosomes
 Random/independent assortment of chromosomes
 Maternal and paternal chromosomes assort themselves randomly/independently
on either side of the equator during metaphase (4)
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SESSION NO: 3
TOPIC 1: REPRODUCTION IN VERTEBRATES
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 10 minutes
1.1.
1.2.
(Taken from various sources)
Discuss how the reproductive strategies of birds are essential to their
survival.
(5)
Differentiate between precocial and altricial development.
(6)
QUESTION 2: 22 minutes
(Taken from various sources)
2.1.
Tabulate the differences between oviparous, viviparous and ovoviviparous
organisms. Provide two examples of each type of organism.
(15)
2.2.
Differentiate between external and internal fertilization.
(4)
2.3.
Discuss the difference between parental care in birds and parental care
in mammals.
(4)
SECTION B: NOTES ON CONTENT
Diversity of reproductive strategies in some animals
Different groups in the animal kingdom have developed reproductive strategies to
ensure reproductive success and survival of the species. In order for sexual
reproduction to take place, two individuals (one male and one female) must come
together so that fertilization can occur.
Courtship: in animal species, courtship is a ritual for mate selection and mating. The
male will generally initiate the courtship but the female selects her mate based on his
‘display’. The courtship rituals may include complicated dances, soft pecking and
head rubs, singing, noise making, fancy flying patterns, croaking, mock-fighting, real
fighting and displays of ‘good looks’. Note that courtship rituals can result in
behavioural isolation, which results when animals behave differently during mating
rituals. Females will not become responsive to the male, so no mating will take place.
Examples of courtship: Frogs croak; male reptiles are brightly coloured and ‘dance’
around the female; birds: singing, peacocks display their tail feathers and weaver
bird males build a nest; mammals: females come into oestrus and release
pheromones
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External versus internal fertilization:
 External fertilization: egg cell and the sperm cell fuse outside of the female’s
body. Egg cells are generally inside the egg structures. The female lays her eggs
and the male deposits his sperm cells over the eggs. Examples are frogs and
many species of fish.
 Internal fertilization: egg cell fuses with the sperm cell inside the female’s body.
In some fish, most reptiles and all bird species, reproduction is internal but
fertilization is cloacal because eggs are produced. In mammals, copulation takes
place when the male inserts the penis (copulatory organ) into the vaginal cavity
of the female. Fertilization takes place in the fallopian tubes.
Embryo Development: Once fertilization has taken place, the diploid zygote
develops into an embryo. This development takes place in an egg or in the uterus.
 Viviparous: the embryo develops inside the uterus. A placenta nourishes the
embryo. The female gives birth to live young when the gestation period is
complete.
 Oviparous: Eggs with shells are laid outside the female’s body into a nest and
continue to develop, hatching when development is complete.
 Ovoviviparous: The fertilized eggs remain in the oviduct of the female. The
eggs have no shell and embryo feeds off the yolk (no placenta). When
development is complete, the female gives birth to live young.
 Amniotic Egg: the amniotic egg has a porous leathery or hard eggshell to
prevent the egg from drying out. There are three membranes: the amnion
(protects embryo during development), chorion (transfers nutrients from the
albumen to the embryo) and allantois (respiration and for waste disposal from
embryo).
Examples: Insects – eggs are not amniotic; Fish and amphibians: eggs are jellylike without a shell for external fertilization; Reptiles – amniotic eggs when
oviparous: Birds: amniotic eggs.
Amniotic Egg Diagram
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• Precocial and Altricial:
o Precocial: young are mature and able to move directly after birth or hatching.
They are able to fend for themselves and feed without parental care.
Examples: insects
o Altricial: young are born helpless, cannot protect, feed themselves or fend for
themselves. Examples: Insects, fish, amphibians, reptiles and some bird
species like ducks, chickens, geese and plovers are precocial. Birds species
like doves, finches, hawks and eagles and all mammals are altricial.
 Parental Care: Parents look after offspring to provide comfort, warmth, to feed
and protect them. Examples: Insects, fish, amphibians and Reptiles – no parental
care. Precocial and altricial birds – parental care and mammals – long periods of
protective nurturing where social behaviour and survival techniques are taught.
SECTION D:
SOLUTIONS FOR SECTION A
1.1.
Singing, flying patterns, wing dragging around the female. Peacocks
open up their pretty tail feathers and make a clucking noise to attract
females. Male weaverbirds build a nest, which is inspected by the female. If
she likes his construction, she will allow him to mate.
Internal fertilisation but cloacal. Oviparous. Produce Amniotic eggs
Nesting, nurturing and protective parental care until offspring is able to
fend for itself 
Any 5
(5)
1.2.
Precocial: young are mature and mobile directly after birth or hatching.
They are able to fend for themselves and feed without parental care.
Altricial: young are born helpless, cannot protect or fend for themselves(6)
2.1.
Oviparous
Eggs contain shell
Viviparous
No eggs with a shell
Eggs are laid outside
the female body
Eggs are not laid or kept
inside the oviduct of the
female
Embryo develops inside
the uterus
Eggs are incubated to
complete development
of embryo in a nest
Eggs hatch outside the
females body when
development is
complete
Fish/Amphibians/Most
reptiles/Birds. Any 2
Ovoviviparous
Eggs do not have a
shell
The eggs remain inside
the oviduct of the female
Embryo develops inside
the egg in the oviduct
Female gives birth to
live young
Eggs hatch inside the
oviduct and the female
gives birth to live young
Any 2 examples of
mammals
Any 2 examples of
reptiles
Any 3 differences (3 x 3) = (9)
Any 2 relevant examples of each (2 x 3) = (6)
(15)
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2.2.
External fertilisation:
Internal fertilisation:
2.3.
Egg cell and sperm fuse outside the female’s body
Water is required
Egg cell and sperm cell fuse inside the female’s body
Water is not required 
(4)
Birds: Short period of nurturing and protection, parental care until the
offspring can fend for themselves then left alone
Mammals: Long period of nurturing and protection, some mammals remain
with parents in a herd even though they are able to fend for themselves (4)
TOPIC 2:
HUMAN REPRODUCTION PART 1
Teacher Note: Please make sure that the learners know and understand:
 The male and female reproductive systems – structure versus function
 Definitions of gametogenesis, oogenesis and spermatogenesis
 The menstruation cycle, events in the ovarian cycle and the uterine cycle
 Hormonal control for sperm production and menstruation, negative feedback
mechanisms
 Fertilization process, implantation, foetal development and birth.
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 10 minutes
(Taken from NSC Nov 2012 Paper 2)
Study the diagram of the male reproductive system below.
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1.1.
Write down the LETTER (A to G) and the NAME of the following:
a)
The part where meiosis takes place
(2)
b)
The part that transports semen and urine to the outside of the body (2)
c)
The part where immature sperm cells are stored
(2)
1.2.
Name the male hormone that is responsible for the development of
secondary sexual characteristics during puberty.
(1)
Write down the LETTER (A to G) of the following:
a)
The part where the hormone mentioned in QUESTION 1.2 is
produced
b)
The part which is cut surgically during male sterilization
(1)
(1)
1.3.
QUESTION 2: 10 minutes
(Taken from NSC Feb/Mar 2011 Paper 1)
The diagram below represents the female reproductive system.
2.1.
Label structures A, B and C.
(3)
2.2.
State THREE functions of D.
(3)
2.3.
Fertilization usually takes place at Y. Why will a blockage at X:
a)
Prevent fertilization at Y
b)
Not necessarily lead to infertility
(1)
(2)
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SECTION B: NOTES ON CONTENT
Terminology & definitions
Afterbirth: the mass of placenta and membranes that are expelled from the uterus
after the birth of a baby
Amnion: fluid-filled sac where the embryo develops in the uterus
Amniotic fluid: fluid surrounding the foetus in the amnion
Circumcision: religious rite or surgical procedure where the foreskin of the penis is
removed.
Co-joined twins: Sometimes the separation of the egg into two (monozygotic twins)
is not complete, resulting in the twins remaining joined at areas and they may even
share internal organs. The co-joined twins are called Siamese twins.
Copulation: the insertion of the male reproductive organ into the female reproductive
organ to transfer sperm to the egg cell
Corpus luteum: structure that results when the Graafian follicle releases the egg cell
during ovulation. The corpus luteum also secretes progesterone if the egg is
fertilized
Cowper’s glands: located just below the prostrate gland in male mammals and
secretes a sticky fluid to assist with movement of the sperm cells.
Dizygotic or fraternal twins: (di = two) when more than one egg is released during
ovulation and fertilized. The developing foetuses share the same uterus, but each
foetus has a separate placenta and their own amnion.
Epididymis: a long convoluted tube that stores sperm cells while they mature and
reabsorbs them after four weeks if they are not ejaculated.
Fallopian tube (also called the oviduct): a muscular tube, lined with a mucus
secreting ciliated epithelium joining each ovary to the uterus. Fertilization takes place
in this tube.
Fertilization: fusion of two haploid gametes (sperm cell and egg cell) to form a
diploid zygote
Follicle stimulating hormone: (FSH) produced by the anterior lobe of the pituitary
gland and causes the maturing of the follicle surrounding the oocyte and stimulates
the supply of nutrients
Gametogenesis: the formation of gametes
Gonadotrophic hormones: hormones secreted by the pituitary gland to control
reproductive cycles and processes in males and females
Implantation: when the blastula attaches to the lining of the uterus after about six
days after fertilization has taken place
Internal fertilization: fertilization that occurs inside the body of the female, inside the
Fallopian tube
Invitro fertilization (IVF): This is when one or more eggs are fertilized outside the
woman’s body and transferred into the uterus for development and growth.
Luteinising hormone (LH): a hormone produced by the anterior lobe of the pituitary
gland that stimulates the release of oestrogen into the bloodstream which causes
ovulation
Menstrual cycle: this cycle begins with menstruation and continues for 28 days. It is
controlled by hormones to co-ordinate the release of the mature egg cell with the
readiness of the uterus for implantation, if fertilization takes place
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Menstruation: when there is no fertilization, the lining of the uterus is shed to
prepare for the next cycle. This results in a flow of blood that lasts for approximately
5 days
Monozygotic or maternal twins: (mono = one) when one egg is fertilized and the
egg separates into two structures, identical twins will result. The twins have the same
sex and be identical in genetic inheritance and appearance. The placenta will be
fused with a common embryonic membrane.
Oestrogen: a hormone secreted by the ovaries, causing ovulation
Oogenesis: the process to produce haploid egg cells in the follicles of the ovary
Ovaries: female reproductive organs which release egg cells.
Placenta: a structure that grows from the wall of the uterus to prevent direct contact
of the mother’s blood with that of the foetus.
Pregnancy: it is the development of the embryo inside the uterus. It can also be
called gestation.
Progesterone: a hormone secreted by the corpus luteum when the egg cell is
fertilized to ensure pregnancy
Prostate gland: gland of the male reproductive system situated just below the
urinary bladder. It secretes most of the seminal fluid.
Seminal vesicle: located in the male reproductive system and stores sperm until
ejaculation.
Sertoli cell: an elongated nurse cell in the tubules of the testes that supports and
provides nutrition to maturing sperm cells.
Spermatogenesis: diploid cells in the seminiferous tubule of the testes undergo
meiosis to form haploid sperm cells
Umbilical cord: links the placenta to the developing foetus
Urogenital system: the male reproductive system and the urinary system link so
that both semen and urine pass out of the body through the urethra.
Vas deferens: the tube that carries sperm cells and seminal fluid into the penis
during ejaculation
Vasodilation: is the increase of blood volume causing the penis to become erect.
The erect penal tissue closes the valve of the urethra to prevent the possibility of
urination during ejaculation of the sperm cells.
Male reproductive system:
The male reproductive system is closely related to the urinary system. Together, the
two systems are called the urogenital system.
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Diagram of the male reproductive system
Please learn the function of each of the following structures very well:
Structure
Two glandular
testes
Function
Responsible for the production of the sperm and the male sex
hormone called testosterone
Testosterone is responsible for:
 the secondary sexual characteristics when the males
mature like a deeper voice, pubic hair and facial hair.
 rapid physical growth at puberty
 the maturation of reproductive organs and production of
Scrotal Sac (bag
of skin)
Seminiferous
tubules
sperm
Holds the testis and hangs outside of the abdominal cavity to
regulate the temperature of the testes at 35 C. The scrotal sac
can contract into the body when it is cold or relax and hang
away from the body if the temperature is high.
Each testis consists of about a thousand coiled seminiferous
tubules lined with germinal epithelium. Contains the Leydig
cells, the spermatogonia and cells of Sertoli
Leydig cells
Diploid
spermatogonia
Produce testosterone
Undergoes Spermatogenesis - produces haploid
spermatozoa/sperm cells
Cells of Sertoli
Nutrition for the developing sperm cell
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Vas efferentia
Epididymis (6m
long coiled tube)
Vas deferens
Seminal vesicle (a
short glandular
tube)
Prostate gland
Cowper’s gland
Penis (consists of
masses of erectile
tissue that
surrounds the
urethra)
Transfers collected sperm to epididymis
Tube stores about 5000 million sperm per cm3 until the sperm
mature and are able to swim
Tube that connects each testis from the epididymis to the
urethra, just after the urethra leaves the bladder
Tube secretes mucus and a watery alkaline fluid containing
fructose, an energy source for the sperm during ejaculation
Secretes mucus mixed with a slightly alkaline fluid during
ejaculation to increase motility of the sperm cells and
neutralizes the possible acidity of the vagina
Secretes an alkaline fluid directly into the male’s urethra to
neutralize acidity caused by urine residue
During sexual stimulation, blood flows into the erectile tissue
causing the penis to become erect for insertion into the vagina
during sexual intercourse. Semen (sperm and fluid) is
ejaculated directly into the vagina (internal fertilization)
Female reproductive system:
Unlike the male urogenital system, the female has separate external openings for
excretion and reproduction.
Diagram of the female reproductive system
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Please learn the function of each of the following structures very well:
Structure
Ovaries (two almondshaped ovaries are
located inside the
abdominal cavity)
Function
The germinal epithelium produces the egg cells. Produce
the sex hormones oestrogen and progesterone. Once
female matures sexually, an egg cell is produced each
month and released during ovulation.
Fallopian tubes (a tube Egg cell moves along the fallopian tube to the uterus.
that connects the
Fertilization and the first stages of mitosis take place in the
ovaries to the uterus)
fallopian tube.
Uterus (a hollow,
muscular, pear-shaped
structure about 7,5 cm
long and 5 cm wide,
located inside the pelvic
cavity behind the
bladder)
Cervix
Vagina (a muscular
tube 8 to 10 cm long,
with elastic tissue and a
folded lining, connecting
the external area with
the uterus)
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1:
1.1.
5 Minutes
(Taken from various sources)
In mammals, fertilization takes place in the
A
B
C
D
1.2.
Perimetrium: outer layer - protection
Myometrium: middle layer - smooth muscle that contracts
during childbirth
Endometrium: inner layer consists of glands and a very
good blood supply to provide nutrition and protection for
developing foetus in pregnancy. Layer breaks away
during menstruation.
Opening between the Vagina and uterus. A mucus plug
develops in the cervix during pregnancy.
Links from the outside to the uterus. Able to stretch when
penis is inserted during copulation and childbirth process
because it forms the birth canal.
Fallopian tubes
vagina
uterus
ovary
The fusion of an egg cell and a sperm cell is known as
A
copulation
B
cleavage
C
fertilization
D
ovulation
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1.3.
Fertilization occurs when the….
A
sperm penetrates the ovum
B
sperm makes contact with the ovum
C
nucleus of the sperm fuses with the nucleus of the ovum
D
fertilization membrane has formed around the ovum
1.4.
Which of the following pairs indicates a reproductive structure and its function
accurately?
A
Fallopian tube – production of sperm
B
Vagina – fertilization
C
Uterus – development of the embryo
D
Testes – production of the ovum
1.5.
Which ONE of the following represents the correct order of the parts
through which spermatozoa pass?
A
Testis → vas deferens → epididymis → ureter
B
Vas deferens → seminal vesicles → ureter → urethra
C
Testis → epididymis → vas deferens → urethra
D
Vas deferens → prostate gland → urethra → ureter
(5 x 2) = (10)
QUESTION 2: 10 Minutes
Match column A with the statements in column B:
(Taken from various sources)
(10)
QUESTION 3: 10 Minutes
(Taken from NSC Feb/Mar 2013 Paper 2)
The diagram below shows the structure of the female reproductive system.
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Give the LETTER and NAME of:
3.1.
The part that breaks down when the levels of progesterone and oestrogen
drop
(2)
3.2.
The part that plays a role during copulation
(2)
3.3.
The part where the zygote will be formed
(2)
3.4.
The part where the Graafian follicles develop
(2)
SECTION D:
1.1.
1.2.
SOLUTIONS FOR SECTION A
(a) F 
testis/seminiferous tubules (2)
(b) C 
urethra  
(2)
(c) D 
epididymis 

(2)
testosterone 
(1)
1.3.
a)F
b)B
2.1.
A – Fallopian tube
B – Ovary
C – Vagina
(1)
(1)
2.2.
- Encloses and protectsthe developing embryo/foetus
- Forms part of the placenta
- Which provides for the nutrition/ gaseous exchange/excretion of the
embryo
- Allows for implantation/attachment of the embryo
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- Contracts during labour for child birth
(Mark first THREE only)
2.3.
a)
b)
The sperms will be prevented from reaching the ovum/
prevents the ovum from travelling along the Fallopian tube
The egg produced in the other ovarycan still be fertilized
in the other Fallopian tube
SESSION NO: 4
TOPIC: HUMAN REPRODUCTION PART 2
SECTION A: TYPICAL EXAM QUESTIONS
QUESTION 1: 16 minutes
(Taken from NSC Feb/March 2013 Paper 2)
(NOTE: Please make sure that you are able to read information from a table
and draw the representing graph. Know the different types of graphs and
when they are applicable.)
Study the information in the table below showing the growth of a foetus in the uterus
of a woman.
1.1.
Between which TWO months did the foetus grow the most?
(2)
1.2.
Draw a line graph to represent the data from the table above.
(7)
(Hint: The age of the foetus is the independent variable and is graphed
on the x-axis. The length of the foetus is the dependent variable and is
graphed on the y-axis)
1.3.
State ONE general conclusion that can be drawn from the data about the
growth of the foetus in the uterus.
(2)
1.4.
State TWO functions of the amniotic fluid that surrounds the foetus during
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1.5.
its development.
(2)
Name and describe the stage that signals the start of the natural birth
process once the foetus is fully developed.
(3)
QUESTION 2: 10 minutes
(Taken from NSC Feb/March 2013 Paper 2)
The diagram below represents a developing foetus in a human body.
2.1.
Identify the parts labelled:
a)
X
(1)
b)
Y
(1)
2.2.
State ONE function of the fluid labelled Z.
2.3.
Explain how the part labelled V is structurally suited to perform its function
during the process of birth.
(2)
2.4.
Name TWO systems in the baby's body that take over the functions of
part W once the baby is born.
2.5.
(1)
(2)
Explain what prevents another ovum from being produced while the foetus
is developing in a human body.
(2)
QUESTION 3: 15 minutes
(Taken from NSC Nov 2011 Paper 2)
Study the graph below of a menstrual cycle and the influence of the different
hormones on it.
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3.1.
On which day does ovulation take place?
(Hint: ovulation is when the egg cell is released)
(1)
3.2.
Between which days does menstruation take place?
(1)
3.3.
State ONE function of FSH during the menstrual cycle.
(Hint: learn the functions of FSH and LH)
(1)
3.4.
Describe the functional relationship between progesterone and FSH.
(2)
(Hint: this is the negative feedback mechanism that controls ovulation
and menstruation. Make sure you know it)
3.5.
Account for the change in the thickness of the endometrial lining between
day 14 and day 21.
(2)
3.6.
Did fertilization take place within the 28-day cycle illustrated in the graph? (1)
3.7.
Give TWO reasons for your answer to QUESTION 3.6.
(2)
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SECTION B: NOTES ON CONTENT
Terminology & definitions: See Session 3, Topic 2
Gametogenesis
Gametogenesis is the process to produce haploid gametes by meiosis. When
sperm are produced, the process is called spermatogenesis and when female
gametes are produced, it is called oogenesis. Both processes occur in the germinal
epithelium of the gonads.
Spermatogenesis: is the process to produce sperm. It takes place at a rate of
approximately 120 million sperm per day. The process starts at the onset of puberty.
The first division takes place in the germinal epithelium and produces
spermatogonia that undergo the first meiotic division to form haploid secondary
spermatocytes. After the second meiotic division, the spermatids are produced.
Cells of Sertoli provide food for the developing rows of spermatids. The spermatids
pass into the seminiferous tubules to mature.
Sperm are very small cells of about 2,5 µm in diameter and 50 µm long. Each sperm
cell consists of a head with a nucleus, a short neck and a long tail. The tail assists
with swimming and orientating the sperm when they cluster around an egg.
Hormonal control of spermatogenesis:
The hypothalamus releases gonadotrophin releasing hormone (GnRH) which
stimulates the pituitary gland to release two hormones jointly called
gonadotrophins. The two gonadotrophins are:
 follicle stimulating hormone (FSH) which stimulates spermatogenesis
 luteinising hormone (LH) which stimulates the synthesis of the hormone
testosterone by the Leydig cells in the testes.
Oogenesis: diploid cells in the ovary undergo meiosis to form a primary follicle
consisting of haploid cells. One cell develops into an ovum, which is contained in the
Graafian follicle and released each month once the female undergoes puberty.
The developing follicle moves to the surface of the ovary as it increases in size. The
protuberance bursts releasing the egg cell to the exterior of the ovary. This process is
called ovulation. The egg cell enters the infundibulum, which contains the fimbriae
of the fallopian tube. When the egg has been released, the Graafian follicle changes
into the corpus luteum. If the egg cell is fertilised in the fallopian tube, the corpus
luteum secretes progesterone. If the egg cell is not fertilised, then the corpus luteum
degenerates.
Hormonal control of oogenesis:
 Hormones are released to control the menstruation cycle, which lasts about 28
days in females. Usually only one egg is released per cycle. The menstruation
cycle affects both the ovaries and the uterus at the same time.
 Gonadotrophin releasing hormone (GnRH) stimulates the anterior pituitary
gland to release follicle stimulating hormone (FSH) into the blood.
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




FSH is transported to the target organ, the ovaries where it stimulates the
development of the follicle.
Granulosa cells in the developing follicle produce oestrogen, which has two
target organs namely the uterus and the anterior pituitary gland. In the uterus, the
development of the endometrium, which is the lining of the uterus, will result.
This is to prepare the uterus for pregnancy because the embryo will implant into
the endometrium. Oestrogen inhibits the secretion of FSH by the anterior
pituitary gland so that no further follicles are produced. This is why only one egg
is produced at a time. High oestrogen levels will trigger the secretion of
luteinising hormone (LH).
LH is released into the blood and is transported to the target organ, the ovary and
causes ovulation. Ovulation is the release of the secondary oocyte from the
Graafian follicle. Each month one egg is released from one ovary at a time. LH
stimulates the ‘empty’ Graafian follicle to develop into the corpus luteum.
The corpus luteum continues to secrete oestrogen and progesterone.
Progesterone has two target organs, namely the uterus and the anterior pituitary
gland. In the uterus, thickening of the endometrium is maintained and glandular
activity is stimulated. In the anterior pituitary gland, the release of LH and
oestrogen is inhibited. The release of progesterone causes the slight rise in
temperature just after a female has ovulated.
Should fertilisation not take place, the corpus luteum degenerates, causing the
levels of oestrogen and progesterone to decrease. The endometrium starts to
break down and tear away from the walls of the uterus, causing the bleeding
associated with menstruation. This phase lasts for about five days.
Sexual intercourse/copulation
Terrestrial organisms generally reproduce by internal fertilisation. The process of
inserting the sperm cells into the vagina of the female is called copulation. The
penis must become erect before insertion as the blood volume increases. This
involves the stimulation of the parasympathetic nervous system, which results in
vasodilation of the arterioles entering the penis. The smooth muscles of the
epididymis, vas deferens, seminal vesicles, Cowper’s gland and prostate respond by
contracting. This causes rhythmic, wave-like contractions that result in the
ejaculation of the semen into the vagina. The semen increases the normally acidic
vaginal pH to pH 6. Sperm is deposited inside the vagina, close to the cervix. Sperm
travels through the cervix, uterus and into the fallopian tubes. The swimming of the
sperm is assisted by the cilia in the uterus and fallopian tubes. The sperm take about
4 to 8 hours to reach the egg and can survive for 2 to 3 days. However, the sperm
remains highly fertile for 12 to 24 hours with female sperm living longer than male
sperm.
Conception
The sperm cell must mature more before it can fertilise the egg cell. This process is
called capacitation, and it takes place while the sperm cell is in the female genital
tract. When the head of the sperm cell comes into contact with the jelly coat around
the egg cell, enzymes are released from the acrosome of the sperm, to soften the
glycoproteins around the egg. Only the head and the middle portion of the sperm
enter the egg. The tail is discarded, as it is no longer required. The egg cell
immediately forms a fertilisation membrane around itself. This prevents any other
sperm cells from entering it.
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Fertilisation: (zygote  morula blastocyst embryo)
The process of fertilisation is when the haploid egg cell and the haploid sperm cell
fuse to form a diploid zygote. The diploid zygote contains 46 chromosomes in the
nucleus (23 from the sperm cell and 23 from the egg cell). This new zygote will
contain genes from both parents and develop into an embryo. The embryo will
develop into a foetus where, after 40 weeks of development, the baby will be born to
ensure the continuation of the species.
Fertilisation occurs inside the fallopian tube. After fertilisation, the zygote is moved
by muscle contractions in the fallopian tubes and pushed towards the uterus. This
takes about three days. The zygote undergoes mitosis and divides to form a solid
ball called the morula. The morula develops into a blastula. The blastula attaches to
the lining of the uterus after about six days and this is called implantation. The
female is now pregnant. The trophoblast is the outer layer of the blastula, which
develops into the chorion. The chorion has finger-like outgrowths that grow into the
endometrium called chronionic villi. These outgrowths anchor the developing
embryo and increase the surface area for the absorption of nutrients.
Diagrammatic representation of ovulation to implantation
Gestation
Gestation (pregnancy) means the development of the embryo inside the uterus. The
embryo develops into a foetus over a period of 40 weeks. At the end of this period,
the woman will give birth to a baby. Development is from a diploid zygote after
fertilization, to an embryo, to a foetus and finally a baby is delivered and born.
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Development of the placenta and amnion
The placenta is a combination of cells from the foetus and the mother, which
develops from about 12 weeks of pregnancy. It allows for the exchange of a number
of substances:
 Nutrients, oxygen and hormones move between the mother and the foetus.
 Carbon dioxide and nitrogenous wastes pass from the foetal blood to the
mother’s blood so that it can be excreted.
 Antibodies from the mother ensure passive immunity against diseases.
The placenta ensures that there is no direct link between the mother’s blood and that
of the developing foetus. Just as required substances move across the placenta to
the foetus, so do harmful substances like nicotine from cigarette smoking, alcohol,
drugs and viruses like Rubella (German measles), Hepatitis B and HIV.
The amnion is a membrane that develops around the embryo. The amnion fills with
amniotic fluid, which protects the embryo by cushioning it and also regulates the
embryo’s body temperature. The amnion expands as the foetus grows and
eventually fills the whole uterus cavity. At the onset of labour, uterine contractions
cause the amnion to burst and the amniotic fluid is released. We say the woman’s
‘water has broken’ and this indicates that the birth process has begun.
The embryo in the amnion
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Birth
The process of birth is called parturition.
Labour: The walls of the uterus begin to contract, indicating the onset of labour.
These contractions are caused by the release of a hormone called oxytocin,
secreted by the posterior lobe of the pituitary gland of the mother. The amniotic fluid
is released as the amnion bursts and the cervix dilates.
Expulsion: The uterine contractions force the baby down through the pelvic bones
and through the vagina (birth canal). As the head appears, it is called crowning. The
head comes out first. The baby is turned sideways and then the shoulders and body
moves through the canal. The umbilical cord connecting the baby to the placenta is
cut and tied off.
Afterbirth: The mother will undergo more contractions to expel the placenta. The
placenta is now called the afterbirth. Note: the umbilical cord has a very good
supply of stem cells.
SECTION C:
HOMEWORK QUESTIONS
QUESTION 1: 8 minutes
(Taken from NSC Feb/March 2012 Paper 2)
The diagram below represents the events leading to the development of the
foetus in the human uterus.
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Identify the following:
1.1
Part labelled 1
1.2. Cell labelled 2
1.3. Cell labelled 3
1.4. Structure labelled 4
1.5. Part labelled 5
1.6. Fluid labelled 6
(6)
QUESTION 2: 12 minutes
(Taken from NSC Feb/March 2012 Paper 2)
Study the graph below showing the hormonal changes during pregnancy.
2.1.
Identify the following structures:
a)
b)
2.2.
2.3.
2.4.
2.5.
A
B
(2)
State the following:
a)
Where prolactin is produced
b)
The function of prolactin
(2)
Explain the significance of the levels of oestrogen and progesterone
dropping towards the end of pregnancy.
(2)
Explain what will happen if structure A breaks down at the end of the
first week of pregnancy.
(2)
Suggest the role of oxytocin around week 40 of pregnancy.
(1)
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SECTION D:
1.1.
SOLUTIONS FOR SECTION A
4 and 5(2)
1.2.
(7)
NOTE:
If the wrong type of graph is drawn:
- Marks will be lost for ‘correct type of graph'
If axes are transposed:
- Marks will be lost for labeling and scaling of X-axis and Y-axis
1.3. The length of the foetus increases with age(2)
1.4. Control the temperature changes
Prevents drying out/dehydration of the foetus
Allows free movement 
Acts as shock absorber
(Any 2) (2)
1.5. Labour (1)
- The uterine muscles
- contract and relax pushing the baby forward
- Cervix dilates
(Any 2)
(2)
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2.1.
2.2.
(a) Umbilical cord
(1) 
(b) Cervix/endometrium/uterus wall
(1)
It provides the fluid medium for the free movement of the foetus
It acts as a shock absorber
It protects the foetus against dehydration
It protects the foetus against temperature changes
Promotes lung development
Holds waste
(Any answer – mark first one only)
(1)
2.3.
Uterine walls consist of strong muscles which contract and relax to push the
foetus / afterbirth forward
any (1 x 2) (2)
2.4.
Respiratory / gaseous exchange system
Digestive system
Excretory system (Mark only first two answers)
2.5.
(2)
High levels of progesterone inhibits the secretion of FSH
(2)
3.1
Day 14 (1)
3.2
Day 0–6/day 0–7 (1)
3.3
Stimulates follicle development in the ovary/stimulates secretion
of oestrogen (1)
3.4
An increase in progesterone level inhibits the release of FSH (2)
3.5
- Corpus luteum starts to secrete progesterone
- Progesterone continues to thicken the lining of the uterus wall/
endometrium (2)
3.6
No (1)
3.7
- Corpus luteum has degenerated
- Progesterone level decreased
- FSH level starting to rise
(Mark first TWO only) (2)
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