HOW TO …
LIFE SCIENCES GRADE 12
TEACHER’S GUIDE
TERM 1
Author: MD Watson
With assistance of:
J Brümmer
A Esterhuizen
C van Heerden
LIFE SCIENCES Grade 12
TEACHER’S GUIDE
TERM 1
A.
Steps involved in planning
B.
Prefixes and suffixes
1.
Scientific skills
2.
Summary of variables
3.
The code of life: DNA, RNA and Protein synthesis
4.
Meiosis
5.
Reproduction in vertebrates
6.
Human Reproduction
1
A. STEPS INVOLVED IN PLANNING FOR EFFECTIVE
TEACHING AND LEARNING
1. Get resources ready:
A. Exam Guidelines
B. ATP
C. Diagnostic report
D. Topic resources
A. Exam Guidelines:
Use guidelines to determine the following:
●
●
●
●
How many hours/periods per topic
How many marks for topic/ paper 1 and 2
Depth and width of content
Sub-topics allocated to
B. ATP
Preparation for lesson:
● Study the textbook against the exam guidelines to become familiar with the
content required on the topic.
● What prior knowledge is required for the topic/subtopics?
● What terminology is relevant to the topic and how will you teach this
terminology?
● What diagrams are relevant to the topic and how will you get learners familiar
with structure, functions and adaptations relevant to each diagram?
● What practical work is relevant and what resources/preparations are required
for the practical?
● What opportunity is there to develop the broad principles of scientific
investigations on this topic?
Planning for informal assessment:
●
●
●
●
●
●
●
●
What activities will you compile for each sub-topic?
How will learner activities allow for multi exposure to concepts?
How will prior knowledge be assessed?
What activities will you use to get the learners actively involved in the learning
process?
What opportunities will there be to encourage learning through
reading/writing/speaking?
Are there simple diagrams in this topic that learners can draw to practice?
What opportunity is there for drawing graphs and what data can you compile
from which graph can be drawn in the relevant topic? Allow learners to mark
one of the graphs to get them familiar with the criteria.
Is there any opportunity for performing calculations in this topic?
2
● Have you collected articles/case studies relating to the given topic
to use in teaching and assessing?
● What opportunity is there for learners to practice writing a paragraph?
● In what conscious way will you get learners familiar with the action verbs used
in questions especially as it relates to the given topic?
● Have you compiled a balanced SBA task of good standard based on the
relevant topic?
● What is your plan for monitoring learner’s written work?
● How will knowledge of each lesson be recapped at the start of the next lesson?
C. Diagnostic report
● Examine how topics have been assessed through the years?
● What errors, misconceptions, and strategies are highlighted in the report
● Study the memoranda of past exam questions to see how answers to certain
concepts/process have been structured and how marks have been distributed.
D. Topic resources
● Use more than ONE textbook and the internet.
● Past papers and memos cannot always be taken as the alpha and omega
since they evolve over the years.
3
B.
4
1. SCIENTIFIC SKILLS
A. GRAPHS
Graphs are a way of recording the relationship between two things / factors that can change in
picture form. These factors that change in relation to each other are called variables.
Graphs are therefore a way of recording large amounts of information in a simple form that can
easily be understood. Graphs make it easier to interpret trends.
Depending on the information we want to record, we can use different types of graphs. The
most common graph is the (jagged) line graph; we will also deal with bar graphs, histograms
and pie graphs.
Before we start, we need to learn the terminology linked to graphs. The following terms are
common to most graphs:
Axis (pl. axes):
The vertical axis is the y-axis
The horizontal axis is the x-axis
Origin:
The point where the x- and y-axis cross meet.
THERE MUST BE A ZERO AT THE ORIGIN.
Independent variable:
always goes on the x-axis.
This is the variable that we can control / change so that we can see what happens.
Dependent variable:
always goes on the y-axis.
This is the variable that depends on the independent variable i.e. it changes as we change the
independent variable / the variable that is measured.
Scale: This is the way we determine how to plot the information on the graph and we have to
take readings from the graph and carefully consider it before we start the graph. We need to
make sure that our scale covers all the figures that we have to plot. The scale starts at 0 and
must be kept constant e.g. 5, 10, 15, 20 or 10, 20, 30 etc. The scale must also be clearly
marked on the axes.
Heading:
All graphs must have a heading that includes the information on both axes i.e.
both variables. The question will guide you to write the heading. The heading must say what
type of graph it is. The heading must not have the units. The heading must be underlined.
Labels:
Each axis must be correctly labelled – always include units (if there are any)
Plotting points:
Plot the points and clearly mark them on the graph with a dot.
Use a ruler to join the plotted points.
5
1. LINE GRAPHS:
Line graphs are used when we compare two different number values.
1.1.
Draw two graphs on the same set of axes showing the changes in heart rate of two boys,
John and Thabo, as they run over a certain distance.
Distance run (m) John’s heart rate
Thabo’s heart rate
(beats per minute) (beats per minute)
0
60
70
100
75
80
200
85
90
400
100
110
800
120
115
1500
120
130
1.2.
What is the relationship between exercise (running further and further) and heart rate
(heart beats per minute)?
1.3.
Translate the information in the table into a line graph on the same set of axes. It gives
the % male and female cigarette smokers aged 16 and over from 1972 until 1982.
Year
1972
1974
1976
1978
1980
1982
Percentage cigarette smokers
Males aged 16 & over Females aged 16 & over
52
41
51
41
46
38
45
37
42
37
38
33
What trend can you infer from the two graphs:
(i)
about smoking in general and
(ii)
comparing smoking in males and smoking in females?
2. BAR GRAPHS / CHARTS:
Bar graphs are used when one of the variables is given in numbers.
Remember:
•
•
•
•
•
•
•
bar graphs have separate bars like the bars in a prison
bars are always the same size (width) – measure and draw with a ruler
spaces between the bars are always the same size
do not draw bars against the y-axis
scale must be clearly marked and the number written next to the mark
it is strongly advised that a key be used. e.g. A, B, C or 1, 2, 3.
Do not write in the bars.
6
2.1. Translate the information in the table below showing the number of learners in a class
of 35 who like different types of sports, into a bar graph.
Types of sports
Soccer
Rugby
Basketball
Netball
Volleyball
Cricket
Number of learners who like the sport
8
5
6
10
2
4
2.2. Which sport is liked the least? ____________________________
2.3. Which sport is liked the most? ____________________________
3. HISTOGRAMS:
Histograms are used when information is presented in continuous groups. These are
similar to bar graphs BUT THERE ARE NO SPACES BETWEEN THE BARS.
Remember:
•
•
•
•
•
bars are always the same size (width) – measure and draw with a ruler
draw bars against the y-axis
scale must be clearly marked and the number written next to the mark
it is strongly advised that a key be used. e.g. A, B, C or 1, 2, 3.
Do not write in the bars.
3.1. Translate the following information showing the rainfall (mm) per month for Tshwane
in 2004 into a histogram.
Month of the year Rainfall (mm)
January
200
February
350
March
210
April
100
May
50
June
10
July
0
August
0
September
10
October
150
November
200
December
280
7
4. PIE GRAPHS / CHARTS:
How to draw a pie chart:
1. Add the numbers to get a total.
2. Convert to %.
3. Convert % to degrees.
Example.
Convert the following table to a pie chart.
Different food types
Lipids
Proteins
carbohydrates
No. of portions
10
20
40
Step 1 – Add number of portions together to get a total
10 + 20 + 40 = 70
Step 2 – Convert each food type to %.
Lipids –10 X 100 = 14%
70
1
Proteins – 20 X 100 = 29%
70
1
Carbohydrates – 40 X 100 = 57%
70
1
14 + 29 + 57 = 100%
Make sure you round off correctly till you get 100% then proceed to next step.
Step 3 - Convert the % to degrees by multiplying by 3, 6 OR 360/100.
Lipids - 14 % X 3,6 = 50 degrees
Proteins – 29 % X 3,6 = 105 degrees
Carbohydrates – 57 X 3,6 = 205 degrees
50 + 105 + 205 = 360
Add all degrees and once you have 360 degrees then you may proceed to draw the circle.
8
Remember to use a key for the pie chart.
Do not write any numbers in the pie chart.
4.1. Draw a pie chart above to show the proportion of carbon, hydrogen and oxygen in a
carbohydrate. The proportion of C:H:O is 1:2:1.
4.2. Translate the information showing the number of learners who like different
type of fruits into a pie graph.
Types of fruits No. of learners who like
the fruits
Kiwi
10
Apples
5
Pears
15
Oranges
10
SCIENTIFIC DIAGRAMS:
Remember:
1. Diagrams must be drawn with a pencil.
2. Draw sharp, clear and solid lines.
3. No shading or colour.
4. Diagrams must be 10 lines big or a third of the page big.
5. Labels should be printed in lowercase unless a structure is the name of a person e.g.
Golgi apparatus.
6. Labels must be one below each other.
7. Label lines should be drawn with a ruler and should be parallel.
8. Heading should include: Drawing of ………… what it is …………. which view i.e. L/S or a
C/S ………….. fresh material / seen under a microscope ……………. with magnification
e.g. A line diagram of a cross section of a dicot root as seen under a microscope X200.
(Section of diagram and magnification must be include only if relevant to diagram)
9. Heading must be underlined.
10. You may be asked to draw annotated diagrams. These are diagrams with labels and
functions or labels and descriptions of the structures.
9
Study the micrograph below. Draw a C/S of this nucleus on the next page. DO NOT TRACE
THE DRAWING!! Label it.
TABLES
1. A table must have a heading which includes the variables that are in the table
i.e. A table of ….
2. The heading must be underlined.
3. A table must have columns and rows. (horizontal and vertical lines)
4. Each column must have a heading and units. (if applicable).
5. Table must have a frame or border (drawn in pencil and with a ruler)
10
THE SCIENTIFIC METHOD
Steps of the scientific method
Ask a question: The scientific method starts with a question about something that you
observe:
How, Why, When, What or Where?
Construct a hypothesis: A hypothesis is an educated guess about the outcome of the
experiment:
If ____________________ (I do this) ______, then _____(this) ____will happen.
You must state your hypothesis in a way that you can easily measure or test. Include both the
dependent and independent variable and the relationship between the variables in the
hypothesis.
Test your hypothesis by doing an experiment: your experiment tests whether your hypothesis is
true or false. It is important for your experiment to be a fair test. You conduct a fair test by
making sure that you change only one factor at a time while keeping all the other conditions the
same.
You should also repeat your experiments several times to make sure that the first results were
not just an accident (if possible).
Variables
Independent variable: a variable/factor that you choose to control in the experiment.
Dependent variable: a variable/factor that you measure in an experiment.
Fixed variables: Variables/factors that stay the same throughout the experiment.
Begin with the word same…
Aim
To determine / To investigate …. . The aim must include the 2 variables.
Apparatus
List all apparatus/ chemicals/equipment you will use in the experiment. You may be asked to
draw the apparatus as it should be set up.
Method
The method is written in steps and is numbered. It is short and simple and written in third
person, as a set of instructions.
Results/Observation
A table is best used to record results. The observation can include what you have seen, heard
or smelt. You may be asked to draw a graph in the results.
Discussion
State the results. Discuss the results. Why it happened and what caused it to occur? Was the
hypothesis true or false? Was it a fair test? How could you have improved the experiment?
Conclusion
Refer back to aim. It is a short statement.
11
EXAMPLE OF A SCIENTIFIC WRITE-UP
Investigative question
Do plants on a windowsill, grow towards light?
Hypothesis
If plants are placed on a windowsill, then plants will grow towards light.
Aim
To investigate if plants on a windowsill grow towards light.
Dependent variable: growth of a plant
Independent variable: amount of light
Fixed variables: same size pot plant, same amount of water, same amount of soil,
same time intervals, same type of plant, same temperature.
Apparatus
• 2 pot plants (same size and type, same amount of soil and water)
• windowsill near light
• dark cupboard
Method
1. Collect 2 pot plants.
2. Place one pot plant on a windowsill.
3. Place the other pot plant in a dark cupboard.
4. Leave for 2 weeks.
5. Record the observations.
Observation
A table of the growth (direction) of 2 pot plants in the dark and on the windowsill (different
amount of light)
Pot plant in dark
No change
Pot plant on windowsill
Entire plant grew towards light
Discussion
The pot plant on the windowsill grows towards light. Plants need light for photosynthesis. The
hypothesis is supported.
How could you have improved the experiment?
Evaluation
The experiment is not a fair test as I could have used many plants and could have increased the
sample group.
Conclusion
Plants on a windowsill do grow towards light.
12
EXERCISE: DESIGNING AN EXPERIMENT USING THE SCIENTIFIC METHOD:
PRACTICE EXERCISE:
Your teacher put forward the hypothesis that males are stronger than females. To test this she
takes her class into the playground where they decide to test her hypothesis by finding out
who can throw an object the furthest. Study the pictures below showing how they complete the
test and what the result shows.
Result: ………………………………………………………………............................................
Conclusion: ……………………………………………………………........................................
Was the teacher’s hypothesis correct? …………………………………………………………..
Do you agree with the outcome of this experiment? ……………………………………………
Give reasons for your answer above: .…………………………..............................................
………………………………………………………………………………………………………………
……………………………………………………………………………………………………
Is this a fair test? ………………………..
How could you change this experiment to make it a fair test?
(Hint: variables)……………………………………………………………………………..……….
………………………………………………………………………………………………………………
……………………………………………………………………………................................
Name the independent variable(s) in this experiment:
………………........................................................................................................................
……………………………………………………………………………………………..…………
Name the dependent variables(s): …………………………………………………................
Write down the experiment to test this hypothesis.
Do this on a separate sheet of paper.
13
HOMEWORK EXERCISE
1. DESIGNING AN INVESTIGATION USING SCIENTIFIC METHOD:
Observation: Mrs Nthuli has two different kinds of pots in her kitchen. The food always seems
to cook quicker when she uses the aluminum pots than when she uses the enamel pots.
Write a scientific report with the following headings:
• Hypothesis
• Aim
• Apparatus
• Variables
• Method
• Results (including a suitable graph)
• Conclusion
• Evaluation
2. PLANNING STEPS
2.1 The blood bank wants to carry out an investigation to determine the distribution of blood
groups of 1 200 learners in a high school. They decide to use a sample to do their investigation
in order to save costs and time. They also want to get a reliable result.
2.1.1. State any FOUR planning steps that the blood bank should put in place to do this
investigation, before they draw blood from the learners, using a syringe.
(4)
2.1.2. State THREE precautions that the blood bank should take when drawing blood from
the learners.
(3)
(7)
Answers
2.1.1
• Determine sample size✓
• Determine the venue✓
• Take random samples✓
• Arrange necessary equipment✓
• Arrange trained personnel ✓
• Inform school of day and time research will take place✓
• Draw up a table to record information✓
(4)
2.1.2
• Personnel should wear gloves✓
• Sterilise the learners’ arms✓
• Use new sterile syringes for every learner that is tested✓
• Apply pressure to stop the bleeding✓
• Monitor the learners after drawing the blood✓
(3)
(7)
14
CALCULATIONS
(1)
AVERAGES
To calculate the average: Add together the set of quantities and then divide by the
number of quantities that were added.
Example:
(2)
The average of 2, 4, 6 and 8
2+4+6+8 = 20
20 ÷ 4 = 5 is the average.
PERCENTAGE INCREASE AND DECREASE
% Increase or decrease = difference
first
Example 1.
X 100
A High School for Girls had 200 girls in 2004. The numbers have
increased to 350.
Calculate the percentage increase of girls in the school.
% increase = difference
first
150
200
Example 2.
X
100
=
X 100
75 % increase
Nadine weighed 55 kg when she was 16 years old. At 21 years she weighs
49 kg.
What is the percentage decrease in her mass?
% decrease = difference
first
X 100
6
55
11 % decrease
X
100
=
15
Example 3.
Mass of different materials recycled for the years 2004 and 2010
Type of
material
Paper
Glass
Plastic
Wood
Mass (in millions of tons)
2004
2010
2,5
3,0
1,0
1,7
0,4
0,6
0,8
0,9
Calculate the percentage increase in the mass of paper recycled from 2004 to 2010. (2)
Answer
Percentage increase = Difference X 100
First
3,0 – 2,5 X 100 ✓
2,5
1
= 20 %✓ (2)
(3)
OR
0,5 X 100
2,5
1
RATIOS
Simplify the numbers to its simplest form.
Remember the order of the ratio is given in the question.
Example 1
14 boys and 16 girls
7: 8
Example 2
Morgan has 9 cows, 3 dogs and 27 cats on her farm. What is the ratio of
animals in her farm?
3: 1: 9
(4) TRENDS
As the one variable increase or decrease, so too does the other variable increase/ decrease/ no
change.
Year
2003
2004
2005
2006
Total amount of solid waste
(millions of tons)
1,49
1,59
1,80
1,93
Amount of recyclable material
in solid waste (millions of tons)
0,78
0,82
1,20
1,30
Describe the general trend in the total amount of waste produced and the amount of recyclable
materials dumped from 2003 to 2006.
(5)
16
Answer
The total amount of solid waste produced increased✓ from 1, 49 to 1, 93 ✓ in 2003 to 2006
and the amount of recyclable material increased ✓ from 0, 78 to 1,30✓ in 2003 to 2006. ✓
(5)
May mention words like increase, decrease, becomes constant or stable.
Describe the increase or decrease by using the words: steady, slow or drastic.
Use the numbers as well to show the increase or decrease.
(5)
RELATIONSHIPS
As the one variable increase or decrease, so too does the other variable increase or
decrease.
Do not use words such as directly and indirectly proportional.
Amount of nitrate fertiliser
added to crop (kg/hectare)
0
225
425
650
700
750
Yield of grass
(100 kg/hectare)
8
14
18
20
20
19
Describe the relationship between the amount of fertiliser added and the yield of grass. (3)
Answer
As the amount of nitrate fertiliser increases✓ so too does the yield of grass increase✓ up to
a certain point. ✓ (3)
17
1
3.
The code of life:
DNA, RNA and PROTEIN SYNTHESIS
INDEX
3.1
Examination guidelines
A
Revision guidelines
B
Misconceptions
3.2
Terminology
C
Teaching Tips
3.3
Learning Templates 1 – 4
3.4
Mind maps 1 – 2
3.5
Marking guidelines on questions
3.6
Activity 1 – 5
D
Teaching tool on extraction of DNA
3.7
Investigation 1: DNA extraction
3.8
Activity 6
19
3.1 EXAMINATION GUIDELINES 2021
DNA: THE CODE OF LIFE
Paper 2: 27 marks
Term 1
CONTENT
2 weeks
ELABORATION
Introduction
Revision of the structure of the cell with an emphasis on the ribosome,
cytoplasm and the parts of the nucleus
Two types of nucleic acids: DNA and RNA
DNA: location,
structure and
functions
•
Nucleic acids consist of nucleotides
Location of DNA:
•
Present in the nucleus (nuclear DNA) – makes up
genes on chromosomes
•
Present in mitochondria (mitochondrial DNA)
Present in chloroplasts (plants)
Brief history of the discovery of the DNA molecule (Watson & Crick,
Franklin & Wilkins)
Structure of DNA
•
The natural shape of the DNA molecule is a double helix
•
Each strand of the helix is made up of a sequence of DNA
nucleotides
Three components of a DNA nucleotide:
•
Nitrogenous bases linked by weak hydrogen bonds:
o Four nitrogenous bases of DNA: adenine (A), thymine (T),
cytosine (C), guanine (G)
o Pairing of bases in DNA occur as follows: A: T and G: C
•
Sugar portion (deoxyribose in DNA)
•
Phosphate portion
Stick diagram of DNA molecule to illustrate its structure
Functions of DNA:
•
DNA makes up genes which carry hereditary information
•
DNA contains coded information for protein synthesis
DNA replication
Process of DNA replication:
•
When in the cell cycle it takes place
•
Where in the cell it takes place
•
How DNA replication takes place (names of enzymes not required)
•
The significance of DNA replication
DNA profiling
Interpretation of DNA profiles
Uses of DNA profiles
20
CONTENT
RNA: location,
Structure and
function
ELABORATION
Location of RNA:
mRNA is formed in the nucleus and functions on the
ribosome
tRNA is located in the cytoplasm
Structure of RNA
A single-stranded molecule consisting of nucleotides
Three components of an RNA nucleotide:
•
Nitrogenous bases
o Four nitrogenous bases of RNA:
o adenine (A), uracil (U), cytosine (C), guanine (G)
•
Sugar portion (ribose in RNA)
•
Phosphate portion
Stick diagram of mRNA and tRNA molecules to illustrate their structure
Function of RNA:
RNA plays a role in protein synthesis
Protein synthesis
The The involvement of DNA and RNA in protein synthesis:
• Transcription
o The double helix DNA unwinds.
o The double-stranded DNA unzips/weak hydrogen bonds
break to form two separate strands.
o One strand is used as a template
o to form mRNA
o using free RNA nucleotides from the nucleoplasm.
o The mRNA is complementary to the DNA.
o mRNA now has the coded message for protein synthesis.
mRNA moves from the nucleus to the cytoplasm and attaches to the
ribosome.
• Translation
o Each tRNA carries a specific amino acid.
o When the anticodon on the tRNA
o matches the codon on the mRNA
o then tRNA brings the required amino acid to the ribosome.
o (Names of specific codons, anticodons and their amino
acids are not to be memorised.)
o Amino acids become attached to each other by
peptide bonds
o to form the required protein.
Simple diagram to illustrate transcription and translation in protein
synthesis
21
A. REVISION GUIDELINES
PAPER
TOPIC
P2
DNA – THE CODE
OF LIFE
(27 marks)
CONTENT
History of DNA
•
•
Structure of DNA
and RNA
Differences
between DNA and
RNA
DNA replication
Protein synthesis
•
DNA profiling
•
•
•
KEY POINTS TO FOCUS ON DURING
REVISION
Roles played by Rosalind Franklin and
Wilkens on the structure of DNA
Watson and Crick come up with the
double helix shape of the DNA
Identify using diagrams
Distinguish when asked only nucleotides or
the complete structure
•
•
Describe in the correct sequence
Role of DNA & RNA in protein synthesis:
✓ Transcription and
✓ Translation
as
stipulated
in
Examination Guidelines
Emphasise:
• Mutations: note that the codons,
anticodons, and the amino acids that
change must be mentioned. Refer to the
example given in the question
• For Replication and Transcription see
Diagnostic Report P163
Interpretation of diagrams of DNA profiling
Refer to DNA profile bars or DNA bars
and NOT just black bars or just DNA e.g.,
DNA profile bars of suspect A compare
with the DNA profile bars of the blood on
the glass
Emphasise:
• The use of DNA profiling to determine
paternity. Also compare this with using
blood groups
• At a crime scene to identify the suspect
and not to solve the crime
22
B. MISCONCEPTIONS: DNA and RNA
MISCONCEPTION
Do not understand that
components of nucleotides
are the same for all species
Unable to perform the
required calculation with the
different nitrogenous bases.
Candidates were not exposed
to the role of Franklin and
Watson in the discovery of
DNA.
RECOMMENDATION
Explain to learners like all countries have telephone
numbers from 0-9 all species have only four nucleotides.
Candidates did not receive
credit for functional
differences between DNA
and RNA since the question
specifically asked for
structural differences
Confused with the terms:
transcription, translation, and
replication.
There are differences between DNA and RNA based on
their location, their structure, and their function. Learners
should be taught how to distinguish among these and to
be aware of what is required by the question.
Cannot distinguish between
the roles of mRNA and tRNA
Used the terms codon and
anticodon with the wrong
RNA molecule.
Structure of the different
RNAs
Candidates used the terms
nucleotides and nitrogenous
bases in the incorrect
context.
Candidates incorrectly
identified the peptide bond as
occurring between
nucleotides, instead of being
between adjacent amino
acids. They also incorrectly
identified the bond as being a
polypeptide between two
amino acids and not more
than two
Explain the paring of the bases and the number of each
to take in consideration when doing the calculations.
Show learners the video of the history of DNA and let
them complete the worksheet. Franklin took the Xray,
Wilken gave the Xray to Watson and Crick and they
used it to determine the natural shape of DNA.
After completing DNA and RNA let the learners draw a
table to distinguish between the three, indicating the
process, where does it take place, involvement of DNA,
RNA or both, product formed.
The role of the nucleic acids should appear in the order
of their involvement i.e., DNA followed by mRNA and
then tRNA
The process of protein synthesis should be taught to
learners using appropriate diagrams. Teachers must
make use of the Mind the Gap Study Guide to assist
learners
RNA structure the plan should have included the general
structure of RNA, then the structure of messenger RNA
and transfer RNA. Make use of the work sheet.
A molecule that contains nitrogen and has the chemical
properties of a base.
Amino acids are monomers for proteins (P for peptide
to bind amino acids to form protein.)
A hydrogen bond is a common type of chemical bond
between two nitrogen bases. E.g., adenine and thymine
are bonding to one another with a hydrogen bond.
23
3.2 TERMINOLOGY
TERM
Amino acid
Anticodon
Base triplet
Centromere
Chromatid
Chromatin
Codon
DNA profile
DNA profiling
DNA Replication
DNA
Double helix
Gene
Genome
Hydrogen bond
Interphase
Messenger RNA
(mRNA)
Mitochondrial DNA
Monomere
Mutation
Chromosomal
mutation
Gene mutation
EXPLANATION
The monomer of a protein molecule
The three adjacent nitrogenous bases found on tRNA molecule that will
determine which amino acid will be brought to the ribosome.
The three adjacent nitrogenous bases found on a DNA strand.
The structure that holds the two chromatids together to form a chromosome
The individual threads that form a chromosome
Tangled network of chromosomes located within the nucleus before division
Three adjacent nitrogenous bases found on the mRNA that code for a specific
amino acid.
Barcode pattern formed by the base sequence of prepared, processed DNA
The process where a specific DNA pattern, called a DNA profile, is obtained
from a person or sample of bodily tissue.
The formation of an exact copy of the DNA in a cell
Deoxyribonucleic acid (DNA) consists of genes that characterise for all the
traits
DNA is made up of two strands that are twisted together. (the natural shape of
DNA)
Segment of a DNA molecule that codes for a specific characteristic.
It is a full set of genes/ all the genes found in a particular organism.
A weak bond which links nitrogenous base pairs in the DNA molecule.
Phase of the cell cycle during which DNA replication occurs
A type of RNA involved in protein synthesis. DNA is transcribed into mRNA.
The type of DNA found only in the mitochondrion
A single unit that makes up a larger molecule.
A sudden and relatively permanent gene / chromosomal change
Changes in the chromosome number or structure of the chromosomes
Is a change in the sequence of a nitrogenous base/nucleotides in
DNA/monomers
Nitrogenous bases
The (adenine and guanine) and (thymine, cytosine, and uracil) that construct
DNA and RNA molecules.
Nucleolus
Structure in the nucleus responsible for forming ribosomal RNA
Nucleoplasm
That part of the protoplasm within the nucleus
Nucleotide
A monomer (building block) of DNA and RNA (nucleic acids), consisting of a
nitrogenous base, a deoxyribose/ribose sugar, and a phosphate group.
Peptide bond
A bond between two adjacent amino acids
Ribosome
An organelle where protein synthesis takes place. (translation)
RNA (ribonucleic acid) A nucleic acid that occurs as a single strand which contains uracil.
Synthesis
Is an anabolic process where monomers are combined into macro molecules
Transcription
The synthesis of mRNA from a DNA template.
Transfer RNA (tRNA)
An RNA molecule that carries amino acids to the ribosomes to form a protein.
Translation
The process of converting the information carried by mRNA to the correct
sequence of amino acids at the ribosome
24
C. TEACHING TIPS for the CODE OF LIFE
While teaching make sure that: (for active learning)
•
•
•
•
•
Learners have their own notebooks
Highlighters (bear in mind the likes and dislikes of either left-brained or right brained
learners in you class. Read about it because you as a teacher should know how to
treat the learner accordingly. (Your left-brainers will not use highlighters)
Learners making notes
#1
#2
Interconnect notes of different topics
#3
Chunking: A way of dealing with or remembering information by separating it into
small groups.
DNA:
RNA:
Phosphate
Phosphate
Deoxyribose
Deoxyribose
Thymine, Adenine, Guanine, and cytosine
Uracil, Adenine, Guanine, and cytosine
Type of teaching technique
Learners must LISTEN
Learners must READ
Learners must TALK or DO
Facts to highlight during teaching:
➢
➢
➢
➢
➢
➢
➢
Start with revision of the cell
Show pictures with emphasis on the nucleus
It has pores (link it with a golf ball) to let substances go through
Nucleoplasm and the nucleolus are suspended in the nucleus
Chromatin network is the chromosomes before division (think of a bll of wool)
Chromosomes carries genetic information
DNA supplies the code for protein synthesis
Interesting facts
DNA is about 2 meters long and wrapped around proteins called histones (to have enough
space in a nucleus per cell)
DNA (deoxyribonucleic acid) It has one O2 molecule less than RNA. (De - means absent,
oxy represents oxygen)
RNA (ribonucleic acid) one O2 more than DNA
(DNA is the recipe book for protein synthesis)
25
What is a gene?
(A page in the recipe book e.g., protein for blood clotting = a gene)
It is a segment of DNA that control heredity traits that determine how an organism looks
like and how it function.
Wat is the function of a gene?
•
•
Carriers the genetic code (in the form of genes) for the synthesis of proteins
It controls heredity traits that determine how an organism looks like and how it
function.
Remember DNA is a polymer (huge in complexity not size)
Monomer = Nucleotides
Simulation for nucleotides:
Let’s make milkshakes:
•
•
•
Let’s build nucleotides
What do we need?
What do we need?
Milk (holds everything together)
Ice cream
Flavour
Phosphate
Sugar
4 types of nitrogenous basis
26
Adenine
Thymine (Always Together) 2 Hydrogen bonds
Guanine
Cytosine (Good company) 3 Hydrogen bonds
A and G
T and C
Large molecules (Purines)
Small molecules (pyrimidines)
27
3.3 LEARNING TEMPLATES 1 -4
LEARNING TEMPLATE 1
28
LEARNING TEMPLATE 2
29
LEARNING TEMPLATE 3
30
LEARNING TEMPLATE 4
31
MIND MAP 1
1
MIND MAP 2
DNA replication
The double helix DNA molecule unwinds
Weak hydrogen bonds between the two
strands break. The molecule unzips
Free DNA
nucleotides
attach to
the
individual
strands
Each strand serves as a template to form a
new strand
Two genetically identical DNA molecules are
formed
WHY?
During mitotic cell division, one mother cell divides into two daughter cells.
•
•
It is essential that DNA makes identical copies of itself before cell division to ensure
each daughter cell contains the same genetic information as the mother cell.
Each daughter cell has identical DNA composition to the mother cell.
WHERE?
In the cell nucleus
WHEN?
During the Interphase of the cell cycle
HOW?
33
3.5 MARKING GUIDELINES
THE LOCATION, STRUCTURE AND FUNCTIONS OF A DNA MOLECULE
- The DNA is in the nucleus/chromosome/genes/mitochondria/chloroplast
- DNA is a nucleic acid
- It is double stranded
molecule
- and arranged in the form of a helix
- consisting of building blocks called nucleotides
The three components of a nucleotide are as follows:
- Nitrogenous bases
- Phosphate portion
- Deoxyribose sugar portion
(in DNA)
- 4 nitrogenous bases are A, T, C, G
- adenine (A) binds with thymine (T) 
and cytosine (C) binds with guanine (G)
- by weak hydrogen bonds
- Sections of DNA carry hereditaryinformation
- DNA contains coded information for protein synthesis

STRUCTURAL DIFFERENCES BETWEEN DNA AND RNA.
DNA
Double stranded
molecule
Has a helixshape
One of the nitrogen bases is thymine
Contains deoxyribose
sugar
A longermolecule
Paired bases
RNA
Single strandedmolecule
Is a straight molecule
The nitrogen base uracilin place of thymine
Contains ribosesugar
A shortermolecule
Unpaired bases
DNA REPLICATION
- The DNA- double helix molecule unwinds
within the nucleus
- Weak
hydrogen bonds between the two strands break/ the molecule unzips
- Each strand serves as a template
to form a new strand
- Free DNA nucleotides
attach to the individual strands
- with complementary nitrogenous bases
pairing/ (A to T and C to G)
- Two genetically identical DNA molecules
are formed

EXTRACTING DNA (practical work)
SUBSTANCE
Onion, strawberry, wheat germ etc.
Dishwashing liquid
Salt
Meat tenderizer, pineapple juice, contact
lens solution
Alcohol/ methylated spirits
FUNCTION
Source of DNA
Breaks down cell membranes
Combines with nucleic acid to form visible
crystals, since DNA is not visible
Contains enzyme to break down the histone
proteins
DNA is NOT soluble in these solvents and
will therefore appear as a stringy or cloudy
mass
• Grating the onion, increases the surface area for the dishwashing liquid, salt and
tenderizer to act on.
• Placing the beaker in hot water allows for the cell breakdown to occur faster
34
TRANSCRIPTION IN PROTEIN SYNTHESIS
- The double helix DNA unwinds.
- The double-stranded DNA unzips/weak hydrogen bonds break to form two separate
strands. 
One strand is used as a template
to form mRNA
using free RNA nucleotides from the nucleoplasm.
The mRNA is complementary to the DNA. 
mRNA now has the coded message for protein synthesis. 
TRANSLATION IN PROTEIN SYNTHESIS (Apply to example)
mRNA moves from the nucleusto the cytoplasm and attaches to the ribosome
When the [anticodon on the tRNA] 
matches the [codon on the mRNA]
Then tRNA brings the required amino acid
to the ribosome
Amino acids are joined by peptide bonds
to form the required protein
HOW A GENE MUTATION INFLUENCES THE STRUCTURE OF A PROTEIN (Apply to
example)
- A mutation is a change in the nucleotide/nitrogenous base sequence
- of a DNA molecule/a gene
- since mRNA is copied from the DNA molecule
- during transcription
- This will result in a change in the codons
- As a result, different tRNA
molecules
- carrying different amino acids
will be required
- The sequence of amino acids changes
- resulting in the formation of a different protein
- If the same amino acid 
is coded for
- there will be no change
in the protein structure
USES OF DNA PROFILING / ANALYSIS
- To investigate crimes / resolve disputes
- To identify organisms from their remains
- To identify family relationships other than paternity
e.g. siblings or cousins
- To test for the presence of specific alleles
/ genes that cause a genetic disorder
- To establish matching tissues for organ transplants
35
3.6 ACTIVITIES 1 - 5
THE CODE OF LIFE: Revision of the cell
Activity 1
1.
MEMO
Study the following diagrams and answer the questions:
Diagram X
1.1
Diagram Y
Identify the organelle (number and name) in Diagram X that is represented by
Diagram Y.
(2)
Nucleus√
1.2
Identify label D and give its function.
(2)
Ribosomes are the site for protein synthesis√
1.3
Name the two nucleic acids present in Diagram Y.
(2)
DNA√
RNA√
1.4
Give the significance of the organelle represented in Diagram Y.
(3)
Carries the genetic material√ which contains the hereditary characteristics of an
organism√ Controls the structure and metabolic reactions of the cell√
1.5
Identify the following labelled organelles and give the function of each.
Label
Name of organelle
Function of organelle
number
(6)
5
Mitochondria√
Releases energy during cell respiration√
7
Centriole√
Forms the spindle fibres during cell division√
TOTAL 15
36
THE CODE OF LIFE: History of DNA and location in a cell
Activity 2
1.
MEMO
Study the following pictures and answer the questions.
A
CrCrickC
1.1
Maurice Wilson Rosalind Franklin
Watson and Crick
D
Identify the scientists who took the X-ray photo in diagram A.
(2)
Maurice Wilson✓ and Rosalind Franklin✓
1.2
Diagram A is a photo of an X-ray. Briefly discuss the history of the discovery of
based on the X-ray by referring to the involvement of these scientists.
DNA
(3)
Rosalind Franklin took the X-ray photo✓, Wilson gave the photo to Watson and Crick✓ without
Rosalind Franklin’s permission. Using the photo, Watson and Crick built the DNA structure.✓
1.3
What reward did Watson and Crick receive for their pioneering with the discovery
the DNA structure?
of
(1)
Nobel price✓
1.4
Why was Rosalind Franklin not acknowledged for her discovery?
(2)
She died at the age of 32✓. The Nobel price is not awarded posthumously✓.
37
2.
Study the picture.
2.1
Identify the structures represented by labels 6 and 7 collectively.
(1)
Chromosome✓
2.2
Where is the cell is this structure found?
(1)
In the nucleus✓
2.3
Identify the significance of these structures in life?
(2)
Carries genetic material✓ with hereditary characteristics✓
2.4
2.5
How many of these structures are present in ONE:
2.4.1
human somatic cell? 46✓
2.4.2
sex cell? 23✓
Name the TWO nucleic acids found in a cell? Indicate the specific location of
each nucleic acid in the cell.
(2)
(6)
DNA = nucleus,✓mitochondria,✓ chloroplast✓
RNA = nucleus,✓cytoplasm,✓ribosome✓
TOTAL 20
38
THE CODE OF LIFE: Structure of DNA
Activity 3
MEMO
ACTIVITY 1: Building the different nucleotides
Adenine nucleotide
Thymine nucleotide
Cytosine nucleotide
Guanine nucleotide
39
THE CODE OF LIFE: DNA replication
Activity 4
MEMO
DNA replication occurs during interphase of the cell cycle and involves making of an
identical copy of DNA. The process occurs within the nucleus before mitosis and meiosis
and is controlled by enzymes.
40
Complete the process of DNA replication by writing the numbers in your workbook explaining
steps 1 to 4.
1
The DNA double helix unwinds
2
Weak hydrogen bonds between the
two strands break/ the DNA double
helix unzips
3
Each original DNA strand serves as a template
Free DNA nucleotides attach to the individual
strands to form a complimentary DNA strand/
nitrogenous bases A-T and C-G
4
Two genetic identical DNA molecules are formed.
(4)
41
1.
Number the steps of DNA replication in the correct order (1, 2, 3, 4 and 5):
3.
3 Each original DNA strand serves as a template on which its complement
is built.
The DNA double helix unwinds.
Two identical DNA molecules are formed.
Week hydrogen bonds between nitrogenous bases break and two DNA
strands unzip (separate).
Free DNA nucleotides build a DNA strand onto each of the original two DNA
strands by attaching to their complementary nitrogenous bases.
(5)
1.
5.
2.
4.
2.
Copy the table in your workbook. Show the complimentary base pairing that would
occur in the replication of the short DNA molecule below. Use two different coloured
pencils (or different pens, markers, etc.) to show which strands are the original and
which are newly synthesized. Also indicate the nitrogenous bases.
Original Original
DNA
DNA
strand 1 strand 2
Original
DNA
strand 1
(copy
from left)
New DNA
strand
+
+
+
+
+
+
+
+
+
+
+
A
T
A
T
C
G
C
G
C
G
C
G
T
A
T
A
G
C
G
C
A
T
A
T
T
A
T
A
C
G
C
G
G
C
G
C
T
A
T
A
New DNA
strand
(copy
from left)
Original
DNA
strand 2
A
T
C
G
C
G
T
A
G
C
A
T
T
A
C
G
G
C
T
A
(10)
3. When and where does DNA replication take place?
(2)
Nucleus✓ interphase✓
4. Why is the process of DNA replication important?
(1)
To ensure that after the cell has divided, each of the two daughter cells contain the
same DNA as the mother cell.✓
5. Give TWO functions of DNA.
(2)
Carries the hereditary characteristics✓
Controls the structure and function of the cell✓
TOTAL 24
42
THE CODE OF LIFE: DNA profiling
Activity 5
1.
MEMO
The diagram below is a representation of the DNA profiles of a family. Number 1
represents the mother, number 2 the father and number 3 to 6 the children. One
of the children is adopted. 2 children are from the original parents, and another is
only the child of one parent.
DNA profile compiled by forensic scientists.
1.1 Which profile (3 to 6) represents the original children from both parents? (2)
3✓ and 5✓
1.2 Which biological specimens from the human body could probably be used to
compile the above profile?
(3)
Blood✓, hair✓, skin✓, saliva✓, semen✓, urine✓
1.3 Which child is adopted? Give a reason for your answer.
(3)
4✓
None of the DNA profile bars of child✓ (number 4) compares with number 1
(mother) or number 2 (father). ✓
1.4 One of the children has only one parent. What is the gender of that parent?
(1)
Female✓
1.5 Except for the example above, give other uses of DNA profiles.
(3)
To identify crime suspects in forensic investigations✓,
to determine the probability and/or causes of genetic defects✓, tracing
missing persons✓, to establish the compatibility of tissue types
for organ transplant✓
TOTAL: 12
43
D. TEACHING TOOL FOR THE EXTRACTION OF DNA
Investigation 1:
Background Information to DNA extraction practical
(http://www.wetheteachers.com/files/0/53221225405059.doc)
DNA extraction is a fundamental procedure in scientific laboratories around the world. By
extracting DNA and studying just it alone (separated and purified from the other cell parts and
substances), scientists can learn how DNA encodes the instructions for all life processes.
DNA of course is important in the study of heredity (passing of traits through genetic material
from generation to generation) and the treatment of all genetic diseases. It can be used for
identification of individuals through DNA fingerprinting (matching patterns of the bases).
All life forms and even most viruses have DNA as their genetic material that they inherit from
the previous generation. In DNA can be found the information that controls what our cells
become, how they function and the cell’s life cycle. Multicellular organisms have different
types of cells.
Each cell type only uses the code from genes for their specific cell type even
though every body cell contains approximately 25,000 genes located over 23
pairs of chromosomes in their nucleus.
Changes in gene structure, called
mutations, that have that allowed organisms to survive in their environment is how evolution
occurs.
In this practical you will be extracting DNA from wheat germ (other material such as onions or
bananas can also be used)
Why is water temperature important?
The heat softens the phospholipids (fats) in the membranes that surround the cell and the
nucleus. It also denatures the deoxyribonuclease enzymes (DNase) which, if present, would
cut the DNA into such small fragments that it would not be visible. Denatured enzymes and
DNA unravel, lose their shape, and thus become inactive. Enzymes denature at 60° Celsius,
and DNA denatures (falls apart) at 80° Celsius.
44
Detergent/Soap
Detergent contains sodium laurel sulfate, which
cleans dishes by removing fats and proteins. It
acts the same way in the DNA extraction,
pulling apart the fats (lipids) and proteins that
make up the membranes surrounding the cell
and nucleus. Once these membranes are
broken apart, the DNA is released from the cell.
Soap molecules and grease molecules are
made of two parts:
•
Heads, which like water
•
Tails, which hate water.
Both soap and grease molecules organize
themselves in bubbles (spheres) with heads
outside to face the water and tails inside to hide from the water.
When soap comes close to grease, it captures it, forming a greasy soapy ball.
A cell's membranes have two layers of phospholipids (fat) molecules with proteins going
through them.
When detergent comes close to the cell,
it captures the lipids and proteins, breaks
the cell and nuclear membranes and
releases the DNA.
Why use concentrated alcohol/methylated spirits?
Watch carefully as the DNA precipitates or separates and moves through the alcohol layer
with small bubbles attached to the strands. The DNA released from the cell nucleus is
dissolved in the water/detergent/wheat germ solution and cannot be seen. DNA precipitates
out of solution in alcohol, where it can be seen as white mucous-like strands. Besides
allowing us to see the DNA, the alcohol separates the DNA from the other parts of the cell,
which are left behind in the water solution. You should use 70-95% isopropyl, ethyl alcohol,
or methylated spirits –that is very concentrated (less water). Why cold ethanol? The cold
temperature keeps the DNA from breaking apart (dissolving) so easily. DNA is very thin and
fragile.
45
3.7 INVESTIGATION 1: Extraction of DNA from wheat germ
MEMO
Material needed
-
2,5 ml wheat germ
50 ml water
5 ml dishwashing liquid
50 ml methylated spirits/alcohol
glass or plastic beaker
teaspoon
toothpick or wooden skewer
Method
- Add 2,5 ml wheat germ to the beaker.
-
Add 50 ml water to the beaker and stir gently with a teaspoon.
-
Add 5 ml dishwashing liquid to dissolve the lipids in the nuclear membrane and
release the DNA strands. Again, stir gently.
-
Carefully add 50 ml methylated spirits to the mixture. It should form a layer on top of
the water.
-
The white DNA strands do not dissolve in the methylated spirits and will float to the
upper layer. Remove the threads of DNA using the toothpick or wooden skewer.
-
Wash hands thoroughly and clean up the workstation.
Worksheet
1. Give a suitable aim for the investigation
To extract DNA from wheat germ✓✓
(2)
2. Variables.
(a) List the dependent variable
(1)
DNA✓
(b) List the independent variable
(1)
Amount of (wheat germ) ✓
(c) List ONE variable that must be kept constant
(1)
Temperature✓
46
3. List THREE safety precautionary measures that should be considered during
this practical activity.
•
•
•
•
(6)
Methylated spirits is flammable, so keep it away from an open flame.
Do not ingest the methylated spirits. Methylated spirits contains a substance that would
induce vomiting.
Ensure that the workspace is kept clean during this practical activity. Dishwashing liquid is
slippery, and learners could slip and fall, causing serious injuries such as broken bones.
Do not fool around with sharp objects such as toothpicks and wooden skewers. If a
person is accidentally poked in the eye, for example, damage to the eye could result in
blindness.
4. Make one recommendation for improving this method of extracting DNA from wheat
germ.
(2)
•
Place the methylated spirits in a fridge before the practical activity, so that its temperature
is colder than that of the water. This would ensure that distinct layers are formed.
5. Analysis of the results
5.1 Describe the appearance of the wheat germ DNA that you pulled out of the
beaker.
(2)
....................................................................................................
………………………………………………………………………..
5.2 What was the purpose of adding the dishwashing liquid?
…………………………………………………………………………
…………………………………………………………………………
(2)
5.3 Describe ONE precaution you took when adding the dishwashing liquid. (2)
………………………………………………………………………...
………………………………………………………………………...
6. State ONE reason why it is not advisable to stir the wheat germ-alcohol mixture too
vigorously?
(2)
……………………………………………………………………………
……………………………………………………………………………
7. What conclusion can be drawn from this experiment?
…………………………………………………………………………...
……………………………………………………………………………
(2)
47
8. Questions
8.1 Why should the wheat germ be stored at moderate temperate conditions, not
be exposed to very high or very low temperature before being used.
Explain your answer.
(2)
…………………………………………………………………………………..
…………………………………………………………………………………..
…………………………………………………………………………………..
8.2
Suggest ONE way in which the excess foam may be removed?
(2)
…………………………………………………………………………………..
…………………………………………………………………………………..
8.3
Why should cold ethanol/methylated spirits be used?
(2)
………………………………………………………………………………...
…………………………………………………………………………………
8.4
Suggest a reason why should fresh wheat germ be used in the experiment.
(2)
………………………………………………………………………………..
………………………………………………………………………………..
TOTAL:
(33)
48
3.8 Activity 6
THE CODE OF LIFE: Structure of RNA
Activity 6
MEMO
Question 1
Study the diagram below of an RNA molecule and answer the questions that follow.
R
R
R
R
R
1.1
Give THREE reasons why this is an RNA molecule.
(3)
Single strand✓
Ribose Sugar✓
Uracil✓
1.2
Draw a labelled diagram of the third nucleotide as indicated in the above diagram (3)
Ribose
Uracil
Phosphate
1.3
Which nitrogenous base from DNA is being replaced by uracil in RNA?
(1)
Thymine✓
49
QUESTION 2
2.1
The diagram below shows two types of RNA found in a cell.
Draw the diagram and complete the table.
(6)
Number 1
Number 2
Type of RNA
mRNA✓
tRNA✓
Position in cell
Nucleus✓
Obtain the code for protein
synthesis from DNA✓
cytoplasm✓
Carries a specific amino acid
to the ribosome✓
Function
2.2 Draw a stick diagram of number 1 and 2.
(4)
m-RNA√
√
2.3
What is the main function of RNA in a cell?
(1)
Synthesize proteins✓
50
QUESTION 3
Study the diagram of an RNA molecule below and answer the questions that follow.
3.1
Identify molecule 1 and 3.
(2)
1 - DNA✓
3 - mRNA✓
3.2
Which process is taking place at number 2?
Why does this process take place?
(2)
Transcription✓ to get the code for protein synthesis✓
3.3
Give the NAME and the NUMBER of the organelle mentioned in QUESTION 3.2
where the process takes place.
(2)
4✓nucleus✓
3.4
Briefly describe the above process.
(6)
The double helix DNA unwinds ✓
The double-stranded DNA unzips/weak hydrogen bonds break to form two
separate strands✓
One strand is used as a template✓
to form mRNA✓
using free RNA nucleotides from the nucleoplasm✓
The mRNA is complementary to the DNA✓
mRNA now has the coded message for protein synthesis✓
51
3.5
Draw the following table and complete the differences between DNA replication
and the process mentioned in QUESTION 3.2.
(6)
Template
Product
Nucleotides
Nitrogenous
base pairs
that are
formed
DNA Replication
2 DNA strands✓
2 identical DNA molecules✓
DNA Nucleotides✓
A=T
C=G✓
Transcription
1 single DNA strand✓
1 mRNA strand✓
RNA Nucleotide✓
A=U
C=G✓
QUESTION 4
Study the diagram below and answer the questions that follow:
4.1
Identify the process above. Where does this process take place?
(2)
Translation✓ in the cytoplasm of the cell✓
4.2
Which organelle is represented by number 3? Give the function of this
organelle.
(2)
Ribosome✓ site of protein synthesis✓
4.3
Identify the labels numbered 4 and 5 respectively. Explain the relationship
between these two structures.
4
5
(4)
protein/polypeptide✓
tRNA✓ the tRNA carries a specific amino acid ✓to ribosome
to form a specific protein✓
52
QUESTION 5
(Make a copy of this diagram in your workbook)
Study the diagram below and answer the questions that follow.
Diagram A
Key for amino acids (AA stands for amino acids)
mRNA
GUU
GUC
CAU
GCU
AUU
5.1
Amino Acid
Leucine
Valine
Histidine
Alanine
Isoleucine
Complete strand 1 by making use of all the information provided.
(mRNA as formed on strand 2). Draw strand 1 in your workbook and complete the
nitrogenous bases from left to right.
(4)
C
A
T
A
T
T
G
T
C
G
T
T
G
C
T
G
T
A
T
A
A
C
A
G
C
A
A
C
G
A
G
U
A
U
A
A
C
A
G
C
A
A
C
G
A
Key for amino
acids (AA stands
for amino acids)
ISO
VAL
HIS
LEU
ALA
53
5.2
Indicate whether each of the descriptions in COLUMN I apply to A ONLY,
B ONLY, BOTH A AND B or NONE of the items in COLUMN II. Write A only,
B only, both A and B or none next to the question numbers (5.2.1 to 5.2.5) in
the ANSWER BOOK.
(5 x 2)
(10)
COLUMN A
5.2.1
mRNA is synthesized during …
5.2.2
tRNA
5.2.3
One amino acid is equal to this number of
codons.
5.2.4
tRNA carries the amino acids to the ……
5.2.5
A polypeptide is a sequence of
A:
B:
A:
B:
A:
B:
A:
B:
A:
B:
COLUMN B
Transcription
Translation
Codon
Anticodon
ONE
THREE
Ribosome
Nucleus
Amino acids
Proteins
QUESTION 6
6.1
Tabulate the structural differences between DNA and RNA.
(7)
6.2
Name TWO similarities between DNA and RNA.
(2)
Both nucleotides consist of a phosphate, a sugar and a nitrogenous base✓
Both molecules are found in the nucleus✓
Both consist of the nitrogenous basis cytosine, guanine, adenine✓
(9)
TOTAL 62
54
4.
MEIOSIS
INDEX to TEACHER’S GUIDE
4.1
Examination guidelines
A
Revision guidelines
B
Misconceptions
4.2
Terminology
C
Teachings tips
4.3
Learning Templates 1 – 2
4.4
Mind maps 1 – 2
4.5
Marking guidelines
4.6
Activity 7 – 12
55
4.1 EXAMINATION GUIDELINES 2021
56
A. REVISION GUIDELINES
PAPER
P2
TOPIC
MEIOSIS
(21 marks)
CONTENT
Why, where, when
and how it occurs
Significance of
meiosis
(Write a sentence
and not only a
word e.g. gametes)
KEY POINTS TO FOCUS ON DURING
REVISION
Identify the MAIN characteristics of each
phase and note the numbers e.g., Anaphase 1
or Metaphase 2 / II
• Explain crossing over
✓ Homologous
chromosomes
form
bivalent and NOT chromosomes only definition of homologous chromosomes
✓ Parts of non-sister chromatids cross
over and exchange material
• The process using diagrams with labels
Emphasise:
• If question asks to draw diagrams of a
phase, shading must be according to what
is in the question, with labels
•
•
•
Differences
between meiosis I
and meiosis II
•
Abnormal meiosis:
Non-disjunction &
Down syndrome
•
Production of haploid gametes
The halving effect of meiosis overcomes
the doubling effect of fertilisation, thus
maintaining a constant chromosome
number from one generation to the next
Mechanism to introduce genetic variation
through crossing over and random
arrangement of chromosomes on the
equator
Especially in the different phases. E.g., In
metaphase I homologous chromosome
pairs align and in metaphase II single
chromosomes align
Non-disjunction of chromosomes at
position 21 during Anaphase in humans to
form abnormal gametes with an extra copy
of chromosome 21
57
B. MISCONCEPTIONS
Misconceptions
Learners could describe crossing
over and random arrangement but
could not indicate how it create
variation.
Recommendations
It is recommended that teachers let learners
draw a table
Processes in meiosis that contribute to variation
Process
Description
How does it
contribute to
variation
Crossing over
occurs during
prophase I
Homologous
chromosomes
non-sister –
chromatids/adjacent
chromatids overlap
at points called
chiasma /chiasmata
Genetic material is
exchanged
resulting in new
combinations of
genetic different
chromosomes
with genetic
material both
parents
Random
arrangement
Homologues
chromosomes
arrange randomly
on the equator
during Metaphase 1
and single
chromosome
arrange randomly
on the equator
during Metaphase 2
This result into
genetic different
gametes
Beyond a description of the events of
meiosis, learners need exposure to questions
requiring higher order thinking. This will allow
them to interpret illustrations representing
non-disjunction or the effects of nondisjunction.
Teachers should account for the
• Due to non-disjunction during meiosis;
occurrence of Down syndrome
the homologous chromosome pair at pair 21
using a clear cause-effect
fail to separate during Anaphase 1. • The
sequence
resulting ovum may therefore have an extra
Learners are unable to apply the
chromosome at chromosome pair number
knowledge of non-disjunction when 21.
a diagram is given.
• If this ovum with 24 chromosomes fuses
with a normal sperm having 23 chromosomes
the resulting zygote will have 47
chromosomes/ extra chromosome at number
21 and
• leading to a child with Down syndrome
Candidates provided the label
Teachers should provide learners with
prophase rather than prophase 1.
multiple opportunities to label diagrams of
different phases of meiosis. Blank diagrams
provided in the Mind the Gap Study Guide
can be used for this purpose. The name of
the phase must indicate if it is a part of
meiosis I or meiosis II. For example,
prophase I is a phase in meiosis I, whereas
prophase II is a part of meiosis II.
58
Marks are lost because candidates
were unable to identify the phases
and to determine the number of
chromosomes that will occur in a
daughter cell/gamete. This type of
question is often asked, and
candidates are meant to apply
their response to the chromosome
number given in the example and
not assume that it is for a human
cell. Once again learners confused
similar sounding terms, e.g.,
centromere and centrosome,
chromosomes with chromatids
Learners cannot identify the main
events during meiosis.
Learners must be able to identify: • The
phase represented in diagrams, with
reasons. When a phase is asked, candidates
will only be credited if they indicate whether it
is from stage I or II e.g., Metaphase I. • The
correct sequence of phases • The structures
represented • Functions of each structure •
Site of meiosis in plants and humans •
Chromosome number in parent and daughter
cells. Meiosis is best taught using diagrams
with the correct labels and describe what
happens during that specific phase.
The same as above
59
4.2 TERMINOLOGY
TERMS
(Alphabetical)
EXPLANATION
Anaphase I
Phase in meiosis in which chromosomes are pulled apart
Anaphase II
Phase in meiosis in which chromatids are pulled apart
Bivalent
A pair of homologous chromosomes involved in crossing over
Centrioles
Structures that form spindle threads during meiosis
Centrosome
Structure that splits to form two centrioles in animal cells during meiosis
Chiasma
Point of overlap of chromatids during crossing over
Chromatids
The two strands that make up a chromosome
Crossing over
The exchange of genetic materials between the non-sister chromatids of
homologous chromosomes
Diploid
Chromosome condition describing the presence of two sets of
chromosomes in each cell
DNA replication
Process by which a single stranded chromosome becomes double
stranded
Down syndrome
Genetic disorder caused by the presence of an extra chromosome on
chromosome pair 21
Haploid
Chromosome condition describing the presence of a single set of
chromosomes in each cell.
Homologous
Chromosomes that are identical in shape/height/length and size, with the
same location of the centromere and position of genes
Interphase
Phase during which DNA replication takes place
Karyotype
The complete diploid set of homologous chromosomes arranged according
to their shape, size and numbering possessed of a body cell
Meiosis
The type of cell division that results in halving of the chromosome number
Meiosis
Cell division producing daughter cells that are not similar
Metaphase I
Phase in meiosis in which chromosomes line up at the equator in pairs
Metaphase II
Phase in meiosis in which chromosomes are arranged singly at the equator
Mitosis
Cell division producing identical cells
Non-disjunction
Non-separation of chromosomes or chromatids during meiosis
Prophase I
Phase in meiosis in which crossing over occurs
Spindle threads
Structures to which chromosomes are attached during Metaphase I and
Metaphase II
Telophase I
Phase in meiosis in which two cells are formed having half the
chromosome number as the original
Telophase II
Phase in meiosis in which four cells are formed having half the
chromosome number as the original cell
60
C. TEACHING TIPS
Facts to highlight during teaching:
Start with revision of the CELL CYCLE during mitosis link DNA replication with the S phase
(Although the cell cycle is only during mitosis it is important to understand the
Interphase)
Interphase consist of:
➢ G1 Phase (Period of cell growth before DNA replication)
➢ S (synthesis phase where DNA replication occur)
➢ G2(The period after DNA replication and the cell prepares itself for division
Mitosis
The following Phases:
➢ Prophase
➢ Metaphase
➢ Anaphase
➢ Telophase
Cytokinesis
➢ Splitting of cytoplasm
➢ Explain why Meiosis takes place
➢ 1. Ensure an offspring with the correct amount of chromosomes
➢ 2. Leads to variation due to swopping of genetic material and random
Arrangement (role play with six learners, two learners each forms a
chromosome and let them change positions while holding hands let
the rest of the class count the different positions of learners to explain
the huge amount of possibilities (remember what can happen if it is 46
chromosomes.)
61
3. Forms haploid reproductive cells in animals(gametes) and spores and
gametes in plants
➢ Explain the form, position, and size of chromosomes using a karyotype
➢ Mnemonic: I Prefer Milk And Tea Interphase, prophase, anaphase and telophase
(REMEMBER interphase is NOT part of the meiosis phases)
46
2n
Chromosomes
DNA Replication
92
Chromosomes
2n
Halving
n
n
Second division
n
n
n
n
62
Unreplicated chromosome/
Daughter chromosome
Replicated chromosome
Homologous chromosomes have …
•
•
•
•
the same shape,
size/length/height.
The same position of
genes/alleles
The same genes coding for
the same characteristics
The same location of the
centromere
Sister chromatids are identical in every
way. Sister chromatids only appear
before the point of cell division (S phase
of interphase)
63
4.3 LEARNING TEMPLATES
MEIOSIS 1
64
MEIOSIS II
65
4.4 MIND MAPS
FIRST MEIOTIC DIVISION (MEIOSIS I)
66
SECOND MEIOTIC DIVISION (MEIOSIS II)
Prophase 2
• Each cell formed during meiosis I now divides again.
• A spindle forms in each of the new cells.
Prophase 2
Metaphase 2
• Individual chromosomes line up at the equator of each cell, with
the centromeres attached to the spindle fibres.
Metaphase 2
Anaphase 2
•
•
The spindle fibres start to contract.
The centromeres split and daughter chromosomes/
chromatids are pulled to the opposite poles of each cell.
Anaphase 2
Telophase 2
•
The daughter chromosomes/chromatids reach the poles
and a new nucleus forms.
•
The cell membrane of each cell constricts and the
cytoplasm divides into two cells.
nucleus
•
•
Four haploid daughter cells are formed.
•
The daughter cells are genetically different from each
Each daughter cell has half the number of chromosomes
of the original cell.
other.
Telophase 2
67
An easy way to remember the events of meiosis is to use the word mnemonic
IPMAT.
Letter
Phase
event
i
interphase
i for in between: The part of the
life cycle of the cell that is in
between cell divisions.
P
Prophase
P for preparation: The
chromosomes prepare for meiosis
by untangling and becoming clearly
visible. Homologous chromosome
pairs are formed. Crossing over
also takes place.
Metaphase
M for middle: The chromosomes
move to the ‘middle’ (equator).
A
Anaphase
A for apart: The
chromosomes/chromatids move
apart/move to the poles.
t
telophase
t for terminal: The final phase of
meiosis I/ meiosis II.
M
68
4.5 MARKING GUIDELINES
STRUCTURE AND ARRANGEMENT OF CHROMOSOMES IN A NORMAL HUMAN
KARYOTYPE
- Each chromosome comprises two chromatids
- held together by a centromere
- There are 23 pairs/46 chromosomes in
- human somatic cells/body cells
- which are arranged into homologous pairs
- that are similar in length
- carry genes for the same characteristics
- have alleles of a particular gene at the same lociand
- have the same centromere position
- Each somatic cell has 22 pairs/44 autosomesand
- a pair/2 gonosomes/sex chromosomes/X and Y chromosomes
- Autosomes are arranged in pairs from largest to smallest
in a karyotype
- Males have XY chromosomes
- Females have XX chromosomes
- The X chromosome is larger than the Y chromosome

BEHAVIOUR OF THE CHROMOSOMES DURING THE DIFFERENT PHASES OF MEIOSIS
I
- During prophase
I
- Homologous chromosomes pairup/bivalents form
- Crossing over and exchange of genetic material occurs
- Between non-sister chromatids of homologous chromosomes/adjacent chromosome
pairs
- During metaphase
I of meiosis
- homologous chromosomes/chromosome pairs are arranged
- at the equatorof the cell
- in a random
way
- with the centromeres of chromosome attached to the spindle fibres
- During anaphase 
I
- chromosome pairs separate/chromosomes move to opposite poles
- During telophase 
I
- the chromosomes reach the poles of the cell

EVENTS THAT LEAD TO DOWN SYNDROME
- Non-disjunction occurred/A homologous pair of chromosomes
- at position 21
- homologous chromosomes failed to separate
- during anaphase
- resulting in one gamete with 24 chromosomes
/ an extra chromosome /
chromosomes at position 21
- The fertilisation of this gamete with a normal gamete/gamete with
23 chromosomes /1 chromosome at position 21
- results in a zygote with 47 chromosomes
- There are 3 chromosomes/an extra chromosome at position 21/ this is Trisomy 21
69
HOW MEIOSIS CONTRIBUTES TO GENETIC VARIATION
• Crossing over
- Occurs during prophase 1
- Homologous chromosomes form a bivalent
- Non-sister chromatids of homologous chromosomes/adjacent chromatids overlap
- at points called chiasma/ chiasmata
- Genetic material is exchanged
- resulting in genetically different chromosomes from both parents
• Random arrangement of chromosomes
- Occurs during metaphase I / II
- Each pair of homologous chromosomes 
/each chromosome
- may line up randomly
on the equator
- so that they separate in a random/ independent manner 
- allowing the gametes to have different combinations of maternal and paternal
chromosomes 
- resulting in new combinations of genetic material in different gametes

HOW MUTATIONS CONTRIBUTE TO GENETIC VARIATION
Two types of mutations:
•
•
gene mutation and
chromosome mutations
- A gene
mutation occurs
- as a result of a change in sequence of nitrogenous bases
in the DNA molecule
- A chromosomemutation occurs as a
- result of a change in the structure of a chromosomeOR
- a change in the number of chromosomes during meiosis

- Mutations that occur in sex cells
- are passed on to the new generations
- creating new characteristics
70
4.6 ACTIVITIES
MEIOSIS: Mitosis revision
Activity 7
MEMO
QUESTION 1
1.
Study the diagram below
1.1
Name phases A to D.
(4)
A – Interphase✓
B – Telophase✓
C – Metaphase✓
D - Anaphase✓
1.2
Name structure X in diagram A?
(1)
Centrosome✓
1.3
Place the diagrams in the correct sequence of occurrence. Only use
the letters.
(2)
A, E, C, D and B✓
1.4
Is the above mitosis taking place in a plant or an animal cell? Give a
reason for your answer.
(2)
Animal cell✓ - Invagination✓
1.5
Give the biological importance of mitosis.
(3)
Repair damaged tissues,✓ growth,✓ asexual reproduction✓
71
QUESTION 2
2.
Give the correct biological term for the following statements.
2.1
In which phase of mitosis does the cell resulting in daughter cells to become
visible?
Telophase✓
2.2
During which phase of mitosis does centromeres divide and the daughter
chromosomes move toward their respective poles?
Anaphase✓
2.3
What is the phase called where chromatin condenses to form
chromosomes?
Interphase✓
2.4
What is the name of the structure that connects the two sister chromatids?
Centromere✓
2.5
The two structures that a chromosome consist of and is connected by a
centromere?
Sister chromatids✓
2.6
What is the step of cell division where 2 identical daughter cells are formed?
Telophase✓
2.7
In which phase of the cell cycle does the cell prepare itself to grow in
size making organelles and copying DNA?
Interphase✓
2.8
What forms across the center of a plant cell near the end of telophase?
Cell plate✓
2.9
What is the division of the cytoplasm called?
Cytokinesis✓
2.10
During this phase chromosomes line up in the middle of the cell.
Metaphase✓
(10)
QUESTION 3
3
Draw a labelled diagram of a replicated chromosome.
(4)
A replicated chromosome ✓
Chromatid ✓
Centromere ✓
Correct drawing ✓
TOTAL 26
TOTAL
72
MEIOSIS: Meiosis I
Activity 8
MEMO
QUESTION 1
Some cells in our bodies are formed during mitosis and others during meiosis. Complete the
table below
(12)
1.1
Functions
Product formed after
these processes.
Number of cells
produced
The final chromosome
number in each cell.
(Humans)
1.2
Mitosis
Repair or replace of
damaged cells✓
Meiosis
To reduce the
chromosome number by
half✓
Growth of cells✓
Exchange of genetic
material✓
Asexual reproduction✓
Production of gametes
in animals and spores in
plants (n) ✓
Identical body cells✓
Gametes✓
2✓
4✓
46✓
23✓
According to your findings in the above table, define meiosis.
(3)
A type of cell division that results in four daughter cells✓ each with half the
number of chromosomes✓ of the parent cell, as in the production of gametes
and plant spores✓
73
QUESTION 2
The following diagram represents human karyotype.
Z
2.1
Identify:
2.1.1 Chromosome pair 1 to 22.
autosome✓
2.1.2 Chromosome pair 23
gonosome✓
2.1.3 Chromosome pair Z
Homologous chromosomes✓
2.2
2.3
Is this karyotype representative of a male of female?
Explain your answer.
Female✓
The gonosome/chromosomes pair 23 have two X chromsomes✓✓
(3)
(3)
Give the definition of …
2.3.1 Homologous chromosomes
(2)
The same size and shape/length/height of chromosomes✓. Not structure
Same position of genes/alleles✓
Genes coding for the same characteristics✓
Location of centromere✓
2.3.2 Karyotype
The complete diploid✓ set of chromosomes arranged according to their
shape, size and numbering✓ according to homologous pairs✓
(3)
74
2.4
How many chromosomes will there be in …
2.4.1 a human somatic cell?
46✓
(1)
2.4.2 a human gamete?
23✓
(1)
2.4.3 Down syndrome somatic cells?
47✓
(1)
2.4.4 Gametes of a Down syndrome female?
23✓ and 24✓
(1)
QUESTION 3
Study the micrograph below of Meiosis I.
A
D
B
C
E
3.1.1 Identify phase A to E.
(5)
A – Interphase ✓
B – Prophase ✓
C – Metaphase ✓
D - Metaphase✓
E - Anaphase✓
3.1.2 Describe the movement of chromosomes in diagram E.
(4)
Homologous chromosomes separate when the spindle fibres contract✓
and chromosome separate✓/pulled to the opposite pole✓
TOTAL 39
75
MEIOSIS: Meiosis II
Activity 9
MEMO
QUESTION 1
The diagrams below represent a cell in two different phases of meiosis.
1.1.
Which phase is represented in:
1.1.1 Diagram 1
Prophase I✓
(1)
1.1.2 Diagram 2
Metaphase 2✓
(1)
1.2
Provide labels for:
1.2.1 A
centriole✓
(1)
1.2.2 B
Nuclear membrane✓
(1)
1.2.3 C
Homologous chromosomes✓
(1)
1.3
Give the functions of the parts labelled:
1.3.1 A
Forms spindle fibre✓
1.3.2 D
Carries genetic material ✓
Responsible for the structure and metabolic functions of the cell✓
(2)
76
1.4
Are the cells in diagram 2, haploid or diploid?
Haploid✓
(2)
1.5
Name the process that would have caused variation in structure D.
(1)
Crossing over✓
Random arrangement of chromosome on the equator during metaphase ✓
TOTAL 10
77
MEIOSIS: Compare Meiosis I and II
Activity 10
MEMO
QUESTION 1
The diagram below represents some phases of meiosis in an animal cell.
1.1
1.2
Identify the following parts in diagram 3:
1.1.1
A
centromere✓
(1)
1.1.2
B
centriole✓
(1)
1.1.3
C
chromatid✓
(1)
Identify the phases in diagram 1 to 4.
1 – Telophase I✓
2 – Anaphase I✓
3 – Anaphase II✓
4 – Anaphase I✓
(4)
78
1.3
1.4
Tabulate the differences between diagram 2 and diagram 3.
(7)
Diagram 2 / Anaphase I✓
Diagram 3 / Anaphase II✓
Chromosomes are pulled towards the
poles✓
Daughter chromosomes/chromatids are
pulled to the poles✓
Whole centromere connects with
spindle fibre✓
Half centromere connects with spindle
fibre✓
Draw a diagram representing the phase before diagram 4.
Metaphase I✓
Chromosomes on the equator✓
(5)
Spindle fibre✓
✓fiber
Centromere✓e
Correct diagram ✓
1.5
Tabulate the differences between Meiosis I and Meiosis II.
(11)
TOTAL 30
79
MEIOSIS:
Abnormal meiosis and importance of meiosis
Activity 11
MEMO
QUESTION 1
The diagram below represents the distribution of chromosome pair 21 in gametes at the end
of meiosis I in ‘n male.
1.1
Explain why the gametes in diagram C and D does not contain any
chromosomes?
(3)
During meiosis the chromosome pair 21 does not separate✓/
There is non-disjunction✓
Two gametes (A and B) will have an extra chromosome✓number 21
and therefore the other gametes (C and D) do not have a chromosome 21✓
1.2
When gamete A is part of fertilisation, describe how it would result in
Down-syndrome.
(3)
If this gamete (A) which have an extra chromosome✓
fuses with a sperm with 23 chromosomes✓
the resulting zygote will have an extra chromosome/ three chromosomes/47
chromosomes at chromosome pair number 21✓
1.3
The chromosomes in diagram A and B are different from each other, because
of crossing over.
1.3.1
Identify the phase of meiosis when crossing over takes place.
Profase I ✓
(1)
1.3.2
Discuss the process of crossing over.
(5)
-
Occurs during prophase I✓
Homologous chromosomes from a bivalent✓
Non- sister chromatids of homologous chromosomes overlap✓
at points called chiasma✓/ chiasmata
Genetic material is exchanged✓
resulting in new combinations of genetic material ✓from both parents
80
QUESTION 2
The diagrams below represent two phases of meiosis.
2.1
Identify the phase represented by:
2.1.1 Diagram 1
Metaphase II✓
2.1.2 Diagram 2
Anaphase II✓
(2)
2.2
Name the part labelled B.
Chromatid✓
(1)
2.3
Describe what happens during the phase illustrated in diagram 1.
Single chromosomes✓ arrange randomly along the equator✓
(2)
2.4
In Diagram 2 the part circled and labelled A is an abnormality during the
process of meiosis.
2.4.1 Name this abnormality.
Non-disjunction✓
(1)
2.4.2 What genetic disorder would result in humans if this abnormality
occurred in chromosome pair no 21?
Down syndrome✓
(1)
TOTAL
19
81
MEIOSIS: Differences between mitosis and meiosis
Activity 12
MEMO
QUESTION 1
Study the table below with the differences between mitoses and meiosis.
Write the numbers 1.1 – 1.8 in your workbook and give the correct answer next to the
number.
(8)
MEIOSIS
Meiosis involves 2 cell divisions
1.2
1.3
Differs according to gender
2 phases
1.5
Half the number of chromosomes to the
parent cell
1.7
Cells responsible for genetic
variation in reproduction (gametes)
MEIOSIS
Meiosis involves 2 cell divisions
1.2 Meiosis gives rise to sex cells
1.3 Cells produced are haploid
Differs according to gender
2 phases
1.5 4 daughter cells formed
Half the number of chromosomes to the
parent cell
1.7 All cells formed are genetically
different to each other and parent cell
Cells responsible for genetic variation
in reproduction (gametes)
MITOSIS
1.1
Gives rise to somatic cells
Cells produced are diploid
Has no gender specification
1.4
2 daughter cells
1.6
Genetically identical to each
other and parent cell
1.8
MITOSIS
1.1 Mitosis involves 1 cell division
Gives rise to somatic cells
Cells produced are diploid
Has no gender specification
1.4 1 phase
2 daughter cells
1.6 Same number of chromosomes
formed as in parent cell
Genetically identical to each
other and parent cell
1.8. Cells responsible for growth
and repair (somatic cells)
QUESTION 2
Name THREE similarities between mitosis and meiosis.
(3)
- Both are cell division processes.
- Both require DNA replication during interphase before the division phase
begins to provide sufficient genetic material for daughter cells.
- Both processes show the following phases: prophase, metaphase, anaphase
and telophase.
- In both cases the chromatin network forms chromosomes in early Prophase.
TOTAL
11
82
5.
REPRODUCTION IN VERTEBRATES
INDEX to TEACHER’S GUIDE
5.1
Examination guidelines
A
Revision guidelines
B
Misconceptions
5.2
Terminology
C
Teachings tips
5.3
Learning Templates 1 – 4
5.4
Mind map 1
5.5
Marking guidelines
5.6
Activity 13 – 16
83
5.1 EXAMINATION GUIDELINES 2021
A. REVISION GUIDELINES
PAPER
TOPIC
P1
REPRODUCTION
IN
VERTEBRATES
(8 marks)
CONTENT
Diversity in
reproductive
strategies
•
•
KEY POINTS TO FOCUS ON DURING
REVISION
Focus on strategies given in the 2021
Examination Guidelines
Altricial and Precocial: Remember it is all
about energy when is the most and less
energy required (before birth of after birth)
B. MISCONCEPTIONS
MISCONCEPTIONS
Learners struggle to distinguish
between ovipary, ovovivipary
and vivipary.
Learners don’t know the
advantages and disadvantages
of all the terminology in
reproductive strategies.
Learners don’t know the
RECOMMENDATIONS
Let the leaners study the terminology with the 4-block
method.
The meaning of the
word:
e.g. ovi means egg/ova
and parous means
reproducing in a
specific manner
Image
Definition
Development of a
fertilized egg that has
been laid outside the
body.
Use in a sentence
Ovipary is the
development of an
offspring from a hatched
egg.
Use a table with three columns and write on the left-hand
side ovipary and on the righthand side vivipary in the
middle column is a combination of the left and righthand
side.
Use columns to explain all the terminology and
immediately add the advantages and disadvantages
Give a drawing to learners and let them study the labels
84
amniotic egg with it functions.
Learners don’t know the
difference between precocial
and altricial.
together with the functions.
Use a table. Explain that the word pre means before.
Altricial think about A to Z (the organism must start with A
and move to Z before it can be a full-grown independent
organism.
5.2 TERMINOLOGY
Biological term
Allantois
Altricial development
Amniotic egg
External fertilisation
Internal fertilisation
Ovipary
Ovovivipary
Precocial
development
Vivipary
Description
The structure in the amniotic egg that stores wastes
The reproductive strategy when hatchlings of birds for example
are not able to move and feed themselves
A type of egg where the embryo develops inside a fluid-filled
sac which is surrounded by a shell
A type of fertilisation in which the nucleus of a sperm fuses with
the nucleus of an ovum outside the body of the female
A type of fertilisation in which the nucleus of a sperm fuses with
the nucleus of an ovum inside the reproductive system of
the female
The reproductive strategy involving the laying of eggs
Producing young by means of eggs which are hatched within
the body of the parent
The reproductive strategy when hatchlings of birds are able to
move and feed themselves
A type of reproduction in humans for example where the foetus
develops inside the uterus
Zygote
The diploid cell formed by the process of fertilisation
Parental care
Any behaviour that contributes to offspring survival, such as
building nests, providing good or defending offspring from
predators.
Albumin
Egg-white that stores proteins and provides embryo with water
Chorion
Amnion
Yolk sac
The outermost membrane surrounding an embryo, where
gaseous exchange is taking place.
Surrounds embryo except on the ventral side which acts as a
shock absorber
Encloses yolk that provides nutrients to the embryo
85
C. TEACHING TIPS
While teaching make sure that: (for active learning)
•
•
•
•
•
Learners have their own books
Highlighters (bear in mind) the likes and dislikes of the either left-brained or right
brained learners in you class. Read about it because you as a teacher should know
how to treat the learner accordingly. Your left-brainers will not use highlighters)
Learners making notes
#1
#2
Interconnect notes of different topics
#3
Chunking
Learners must LISTEN
Type of teaching technique
Learners must READ
Learners must TALK or DO
Facts to highlight during teaching:
➢
➢
➢
➢
➢
➢
➢
➢
➢
Why is reproduction taking place?
1. Passing on of genes
2. Survival of species
Offspring must be viable to survive successfully
That happens by the
1. Structure
2. Function
3. and behaviour of an organism
Reproduction strategies is all about energy expenditure
EXTERNAL FERTILIZATION
Mostly aquatic environment
Because there is no interaction
between the two genders
pheromones plays a huge role
because it safes energy not having
courtship etc.
Chemotaxis the sperm and the ovum
are chemically attracted to one
another due to the external
environment
Large number of eggs are released,
more energy used
Large number of offspring
No parental care
INTERNAL FERTILIZATION
No water needed
Due to interaction between two
genders pheromones plays a very
small role
The sperm and egg is in a protective
environment and will reach one
another.
Fever ova are released
Less energy used
Few offspring
Good parental care
86
Ovipary (egg bearing)
Ovovivipary (egg and life)
Vivipary (life bearing)
These three strategies are all about where the embryo will develop
How the embryo receives nutrients
Yolk of an egg is the
Yolk of an egg is the
Baby is fed by placenta and
nutrients (large amount of nutrients (small amount of
umbilical cord
yolk)
yolk)
There is no physical
There is no physical
Directly connected t the
connection between the
connection between the
mother and gives birth alive.
mother and the embryo
mother and the embryo.
egg is laid outside the
Egg stays inside mother body
mother’s body.
and give birth alive.
A lot of energy is needed A lot of energy is needed
during development
during development
How longer the incubation period how larger will the egg
yolk be.
A lot of energy is needed
after the birth
AMNIOTIC EGG:
It is like a small incubator which provides oxygen, required temperature and nutrients for a
developing embryo.
It contains 3 extra embryonic membranes:
1. Amnion surrounds the embryo = Shock absorber
2. Allantois grows form embryos intestines = contains all waste products
3. Chorion = helps with gaseous exchange
The yolk sac is energy rich food = nutrients for the baby.
The more the embryo develops the smaller the yolk sac becomes and the larger the allantois
gets.
87
PRECOCIAL
Energy expenditure is prenatal
‘p’ for before
Usually, wild animals
Ground birds
Long on nests large eggs
A lot of energy usage before birth
Fully developed not a lot of parental
care
ALTRICIAL
Energy expenditure is postnatal
‘a’ for afterwards
Usually, domesticated animals
Nests above the ground
Not long on nests small eggs
Lot of energy after birth
Not fully developed a lot of parental
care
88
5.3 LEARNING TEMPLATES
Template 1
INTERNAL FERTILIZATION
EXTERNAL FERTILIZATION
Advantages
Advantages
Disadvantages
Disadvantages
89
Template 2
Ovipary
Ovovivipary
Vivipary
90
Template 3
91
Template 4
PRECOCIAL
ALTRICIAL
Advantages
Advantages
Disadvantages
Disadvantages
92
MIND MAP
93
5.5 MARKING GUIDELINES
EXTERNAL FERTILISATION AND INTERNAL FERTILISATION
-
-
External fertilisation:
The sperm cell fertilises the egg cell OUTSIDE the body of the female.
Water is always required, physical contact not required. E.g. fish, frogs
Disadvantages:
Chances of fertilisation is very reduced and large amounts of sperm need
to be produced
Resulting zygote is not well protected from predators
Internal fertilisation:
The male deposits the sperm inside the body of the female, where fertilisation occurs
inside the female reproductive system. E.g. Birds and
mammals
Disadvantages: copulatory organ required Advantages:
Chances of fertilisation increased and small amounts of sperm need to be
produced
Resulting zygote is well protected inside the female body.
OVIPARY, OVOVIVIPARY AND VIVIPARY
Ovipary- Eggs are laid and development of the embryo takes place outside
the mother’s body. (with internal or external fertilisation)
Disadvantage: Eggs may be preyed on by predators
Ovovivipary- Internal fertilisation and the eggs are retained inside the mother’s body
and obtain nourishment from the egg yolk. The young hatch inside the mother’s body
and are then born.
Advantages: Increased chance of offspring being produced, well developed offspring
produced. Protection from predators.
Vivipary- Internal fertilisation and the young develop inside the uterus of the
mother and obtain nourishment from the mother’s placenta.
Advantages: Increased protection for developing embryo
-
-
AMNIOTIC EGG
Has extra-embryonic membranes: chorion, amnion, allantois and yolk sac
Chorion: allows oxygen to enter and CO2 to leave through to the shell and
out - Amnion: membrane enclosing the amniotic cavity which contains
amniotic fluid which protects the embryo against mechanical damage.
Allantois: stores waste produced by the embryo; also functions in gaseous
exchange
Yolk sac: provides nourishment to the embryo
Shell: prevents dehydration and gives protection
94
PRECOCIAL AND ALTRICIAL DEVELOPMENT
Precocial
1. Eyes are open when they hatch
2. Body is covered in soft feathers
called “down”
Altricial
1. Eyes are closed when they hatch
2. Bodies are not covered by “down”
3. Able to move soon after hatching
4. Able to feed themselves
5. Independent of their parents
6. Eggs provide high energy to
developing embryos
3. Unable to move soon after hatching
4. Unable to feed themselves
5. Dependent on parents
6. Eggs provide less energy to
developing embryos
95
5.6 ACTIVITIES
RERODUCTION IN VERTEBRATES: Internal and external fertilisation
Activity 13
1.
MEMO
Draw the table in your workbook and complete it.
Internal Fertilization
External Fertilization
Humans
Frogs
The male deposits its
sperm inside the
reproductive organs of the
female and fertilisation
occurs inside the female’s
reproductive organs
The sperm fertilises the egg outside
the body of the female, usually in
water
Inside
Outside
Inside the mother
Into water
Sperm placed inside the
mother
Sperm sprayed on to the eggs
Diagram
Examples of your won
Description
Fertilization takes place
inside or outside the
mother body
Fertilised eggs released
into water or stay inside
the mother
Sperm sprayed on to the
eggs or sperm place
inside mother
Few or many egg
produce
Young develop inside or
outside mothers’ body
Most or some of the eggs
get fertilize
Most of few of the
offspring survive
Eggs or offspring looked
after, or not looked after
by parents.
Parents prepare a safe
place to stay or no place
Few
Many
Young develops inside the
mother’s body
Most of the eggs are
fertilize
Most of the offspring
survive
Offspring are looked after
Young develops outside the mother’s
body
Some of the eggs are fertilize
Parents prepare a safe
place to stay
Parents don’t prepare a safe place to
stay
Few of the offspring survive
Eggs or offspring are not looked after
by parents
96
2.
Draw the table in your workbook and complete it.
Advantages
Disadvantages
Internal Fertilization
External Fertilization
•
Ensures that the
sperm cell meets the
ovum
•
•
Developing embryo is
protected from
predators and
removed from harsh
environments
No additional energy
is needed for parental
care or formation of a
protective layer.
•
No need for a male to
have a special organ
to insert the sperm
into the female’s
body.
•
Chances of
fertilisation are
enhanced by
courtship display by
fish.
•
Does not use much
energy
•
Chances are very slim
for a sperm cell to
meet the ova of same
species.
•
Predators eat the
sperm and ova before
fertilization can occur
•
Strong currents carry
sperm cells away
before fertilization can
occur
•
Reproduction must
take place in water
otherwise gametes or
fertilized eggs will
dehydrate
•
Fewer eggs are
produced.
•
The animal must
have a copulatory
organ to insert the
sperm cells into the
female body.
97
RERODUCTION IN VERTEBRATES: ovi-, ovovivi- and vivypary
Activity 14
1.
MEMO
Draw the table in your workbook and complete it.
Ovipary
•
•
•
•
•
Refers to egg laying
animals
Eggs are protected by a
hard shell, while others
are protected by a jelly
like layer after
fertilisation.
Development does not
occur inside the body
The development of an
organism is completed
inside the egg after it has
been laid
Examples: frogs, insects,
birds, and marine
animals
Ovovivipary
•
•
•
•
•
•
•
•
•
Advantages
•
•
Eggs and sperm cells are
produced in large
numbers to increase
chances of survival to
adulthood.
Much energy is invested
for parental care.
Parental care
ensures survival
to adulthood.
Animals that do not lay
eggs but keep them in their
bodies until they hatch.
The body temperature is
necessary for them to
hatch.
There is no connection
between the embryo and
the mother.
Examples: sharks, lizards,
cockroaches, and some
snakes
Advantages:
The young one is protected
from cold and predators to
ensure survival
The young one can develop
to a fairly large size before
birth
Among some snake
species, females bear live
young
This method of
reproduction may be
beneficial to snakes that
live in cold climates,
because the pregnant
female can bask in the sun
to keep her developing
offspring warm.
Vivipary
•
•
•
Advantages
•
The offspring are advance
in their development when
they are born alive, so the
young can mor likely
defend themselves in the
wild.
Refers to animals that
give birth to live young
ones.
There is a connection
between the developing
foetus and the mother.
Examples: most
mammals like human
beings, whales, and
kangaroos.
Advantages
•
•
•
The temperature is
regulated by the mother
The mother provides
nutrition for the young
one
Mortality rate is lower
Parental care
ensures survival
to adulthood.
98
•
2.
Disadvantages
Disadvantages
Mortality rate is high.
•
Disadvantages
•
Fewer individuals are born,
and it takes more energy
for the females to carry the
egg inside
•
Number of off springs
produced is few.
More energy is used to
provide parental care.
Redraw the table in your workbook and complete it.
OVIPARY
OVOVIVIPARY
1
2

3

VIVIPARY

Salmon

4

5
6

7


99

8
Anaconda
9

10
Adders

11
Rinkhals
12

13

14

15

100
RERODUCTION IN VERTEBRATES:
Amniotic egg
Activity 15
MEMO
QUESTION 1
1.1
What is an amniotic egg?
A type of egg where the embryo develops in an amnion. The shell be calcium
based or leathery.
(2)
1.2
Name THREE types of animals that have amniotic eggs.
Some snakes, chickens, and some mammals.
(3)
QUESTION 2
Study the diagram. Draw the table in your workbook and complete it.
Name
A
B
C
Amnion
Amnon cavity with
amnion fluid
Allantois
D
E
Albumen
Yolk sac with yolk
F
Calcium based
shell
Embryo
Airbag
Chorion
H
K
L
(18)
Functions
Consists of amnion fluid.
The amnion protects the embryo from mechanical shock and
supports hydration.
The allantois stores nitrogenous wastes produced by the
embryo and also facilitates respiration.
Gives water and proteins to the embryo
Blood vessels in the yolk sac transport yolk nutrients to the
circulatory system of the embryo.
Protect the embryo and allow gaseous exchange
Develops into a specific organism
Acts as a shock absorber when the egg is laid
The chorion facilitates exchange of oxygen and carbon dioxide
between the embryo and the egg’s external environment.
Total 23
101
RERODUCTION IN VERTEBRATES:
Precocial and altricial development
Activity 16
MEMO
QUESTION 1
Study the diagram. Draw the table in your workbook and complete it.
Meaning
Advantages
Altricial
Hatchlings are poorly developed
when they hatch. They are unable to
feed on their own, they cannot
move. Brain size and intelligence
increases after hatching
•
•
•
•
•
Disadvantages
•
•
•
Examples
•
Rapid growth (fed large
nutrient-rich food items by
parents)
chicks become independent
relatively quick.
minimizes young mortality.
allow the brain to grow well in
size.
capable of growing into an
ultimately more developed
state
(18)
Precocial
Hatchlings are quite well
developed when they hatch –
eyes are open, they can move
and feed. Brain size and
intelligence remains the same
throughout their lives
• Young ones are relatively
mature and can move
around after they are born
or hatch.
• Their eyes are open, and
have good eyesight
• They can go out to search
food for themselves.
• Have strong skeleton, and
their body is either covered
by feathers (birds) or
hair(mammals).
• Mammals can regulate
their body temperature.
Young ones are unable to
move after birth and are
helpless.
They do not have feathers
(birds) and blind.
They need to be fed and kept
warm.
•
Birds need their parents to
keep them warm, but this
lasts for a short period.
Owls kangaroos, cats, dogs,
and humans.
•
Birds, cattle, sheep,
antelopes, buffalo,
elephants, hippos, and
giraffe.
102
6.
HUMAN REPRODUCTION
INDEX to TEACHER’S GUIDE
6.1
Examination Guidelines
A
Revision Guidelines
B
Misconceptions
6.2
Terminology
C
Teaching Tips
6.3
Learning Templates 1 - 7
6.4
Mind maps 1 - 2
6.5
Marking guidelines
6.6
Activities 17 – 25
103
6.1 EXAMINATION GUIDELINES 2021
HUMAN REPRODUCTION
Term 1
3 weeks
Paper 1: 41 marks
CONTENT
ELABORATION
Introduction
❑
Structure of the male
reproductive system
❑
❑
Functions of the testis, epididymis, vas deferens, seminal vesicle, prostate
gland, Cowper's gland, penis and the urethra
Structure of the
female reproductive
system
❑
Structure of the female reproductive system, using a diagram
❑
Functions of the ovary, Fallopian tubes, uterus lined by endometrium,
cervix, vagina with its external opening and the vulva
❑
Structure of the ovary, using a diagram, showing the primary
follicles, the Graafian follicle and the corpus luteum
Main changes that occur in male characteristics during puberty
under the influence of testosterone
Puberty
Gametogenesis
❑
Revision of the schematic outline of the human life cycle to show the
role of meiosis, mitosis and fertilization
Structure of the male reproductive system, using a diagram
❑
Main changes that occur in female characteristics during puberty
under the influence of oestrogen
❑
Formation of gametes (gametogenesis) by meiosis
•
Male gametes formed by spermatogenesis
•
Female gametes formed by oogenesis
❑
Spermatogenesis:
•
Under the influence of testosterone
•
diploid cells in the seminiferous tubules of the testes undergo meiosis
•
to form haploid sperm cells
❑
Structure of a sperm, using a diagram
❑
Functions of the parts of a sperm cell (acrosome, head with haploid
nucleus, middle portion/neck with mitochondria and a tail)
❑
Oogenesis:
•
Diploid cells in the ovary undergo mitosis
•
to form numerous follicles.
•
At the onset of puberty
•
and under the influence of FSH,
•
one cell inside a follicle enlarges and undergoes meiosis.
•
Of the four cells that are produced, only one survives to form a
mature, haploid ovum.
•
This occurs in a monthly cycle.
❑
Structure of an ovum, using a diagram
❑
Functions of different parts of an ovum (jelly layer, haploid nucleus,
cytoplasm)
104
CONTENT
Menstrual cycle
ELABORATION
❑
The menstrual cycle includes the uterine and ovarian cycles
❑
Events in the ovarian cycle:
•
Development of the Graafian follicle
•
Ovulation
•
Formation of the corpus luteum
❑
Events in the uterine cycle:
•
Changes that take place in the thickness of the endometrium
•
Menstruation
❑
Hormonal control of the menstrual cycle (ovarian and uterine cycles)
with reference to the action of FSH, oestrogen, LH and progesterone
Negative feedback mechanism involving FSH and progesterone in
controlling the production of ova
❑
Fertilisation and
development of
zygote to blastocyst
Implantation,
gestation and the
role of the placenta
❑
Definition of copulation and fertilization
❑
Process of fertilization
❑
Development of zygote → embryo (morula and blastula/blastocyst)
→ foetus
❑
Definition of implantation
❑
The role of oestrogen and progesterone in maintaining pregnancy
❑
Structure of the developing foetus in the uterus, using a diagram
❑
Functions of the following parts:
•
Chorion and chorionic villi
•
Amnion, amniotic cavity and amniotic fluid
•
Umbilical cord (including umbilical artery and umbilical vein)
•
Placenta
105
A. REVISION GUIDELINES
P1
HUMAN
REPRODUCTION
(41 marks)
Male reproductive
system
Female
reproductive
system
Puberty
•
•
•
•
•
Spermatogenesis
& oogenesis
•
Ovarian &
Menstrual cycles
(incl. hormones &
negative feedback)
•
•
•
•
Development of
the zygote to a
blastocyst
(blastula)
•
Structure of the male reproductive system,
using a diagram, with labels and functions
(only parts given in Examination Guidelines)
It is good to know the adaptations of the parts.
Structure of the female reproductive system,
using a diagram with labels and functions (only
parts given in Examination Guidelines)
It is good to know the adaptations of the parts.
Definition & main characteristics (male &
female)
Exactly as stated in the Examination
Guidelines
Refer to Mind the Gap (MTG) for the structure
of the ovary, using a diagram/graph, showing
the primary follicles, the Graafian follicle, and
the corpus luteum
Includes the uterine and ovarian cycles and
days per month
The role, the gland which secretes FSH,
oestrogen, progesterone & LH in these
processes
Negative feedback between progesterone
and FSH
Order in the development of structures as
well as difference between morula and
blastocyst
Morula
A solid ball of cells
resulting from
division of a fertilized
ovum, and from
which a blastula is
formed
Development of
the foetus during
gestation
Blastula
Is a hollow sphere of
cells surrounding the
blastocoele
produced during the
development of an
embryo
Learners tend to think that the blastula forms
before the marula due to the open spaces they
think that the other cells are still in progress.
• Structure of the developing foetus in the
uterus, using a diagram
•
Functions of the:
✓ Chorion and chorionic villi
✓ Amnion, amniotic cavity, and amniotic
fluid
✓ Umbilical cord (including umbilical
artery and umbilical vein)
✓ Placenta (don’t get confused by the
functions of the placenta and amniotic
cavity)
106
B. MISCONCEPTIONS IN HUMAN REPRODUCTION
Misconceptions
Recommendations
candidates cannot distinguish between
describe the change in the follicle
diameter and explaining the changes.
learners should be clearly shown how an answer to
the question asking for a description of the changes in
the follicle diameter would be different from a
question requiring an explanation for the changes in
the follicle diameter as required. A description
requires a statement of the changes in the follicle size
over time whereas an explanation must include a
reason for the change in size. In this question, the
reason relates to the absence of fertilisation after the
ovum was released from the follicle during ovulation.
Teachers should also spend more time on teaching
the negative feedback mechanism that exists
between FSH and progesterone, as this information
was required to formulate an answer.
All these aspects must be taught by means of
diagrams, labels, and the functions. When they done
that they can write a short paragraph on how organs
or cells are suitable for their functions.
The structural suitability of sperm; The
process of fertilisation; and
The development of the zygote until
implantation. As a result of the above,
many candidates did not address one or
more of the aspects required by the
question. Candidates did not give
complete answers for the structural
suitability of the sperm cell. They often
named the part of the sperm cell without
indicating how it is suited for fertilisation.
Some candidates had an inaccurate
understanding of the events of
fertilisation. They spoke of the sperm cell
fusing with the ovum whereas it is only
the nucleus of the sperm cell that enters
the ovum and fuses with the nucleus of
the ovum.
Many candidates did not provide
information on the development of the
zygote in the correct sequence.
Learners have difficulty to distinguish
between the functions of the urethra
and the vagina.
Differentiation in the use of uterus and
uterine wall (endometrium).
Learners wrote the testis should be
kept at 20C/-20C instead of 20C lower
than body temperature. Learners
cannot express what optimum
temperature is.
Learners should be advised that since two marks are
generally allocated to each structural suitability, one
mark is allocated to the part/structure and the
second mark for the way it is suited to the function,
for example, for the structural suitability of the
sperm: • The front of the head of the sperm cell
contains an acrosome • which carries enzymes to
dissolve a path into the ovum • The nucleus of the
sperm • carries genetic material of the male into the
ovum during fertilisation 127 DIAGNOSTIC REPORT •
The middle piece of the sperm contains mitochondria
• which release energy so that sperms could swim •
The presence of a long tail • enables sperm cells to
swim towards the ovum
Diagrams should be used and explanations regarding
the development of the zygote.
Key words in the question should be underlined.
Learners must use diagrams to label and next to
the label the functions must be indicated.
Learners must use diagrams to label and next to
the label the functions must be indicated.
Emphasise normal body temperature and explain
to learners the difference between body
temperature and temperature of the testis.
107
Learners could not distinguish
between the development of an ovum
and a fertilized ovum. Learners
struggled to describe the development
of a zygote until the blastocyst is
implanted – they confuse morula and
blastocyst – and could not write it in
the correct sequence – they describe
the process taking place as meiosis
instead of mitosis.
Use diagrams of the ovary to explain step by step
the development of the graafian follicle and them
a diagram of the fallopian tube and all the steps
until the formation of the blastocyst. Learners
can use a table with descriptions and drawings.
In all the stages of development learners must
indicate the type of cell division.
Learners did not mention around the
time of ovulation.
Learners must be exposed to different graphs on
hormonal regulation of the menstrual cycle.
Previous questions papers can be used.
Teachers should expose learners to different
examples of diagrams and pictures, and not only
those in their textbooks.
Learners should draw annotated diagrams to
reinforce the structure with the function.
108
6.2 TERMINOLOGY
109
110
C. TEACHING TIPS – HUMAN REPRODUCTION
While teaching make sure that: (for active learning)
•
•
•
•
•
Learners have their own books
Highlighters (bear in mind the likes and dislikes of the either left-brained or right
brained learners in you class. Read about it because you as a teacher should know
how to treat the learner accordingly. Your left-brainers will not use highlighters)
Learners making notes
#1
#2
Interconnect notes of different topics
#3
Chunking
Learners must LISTEN
Type of teaching technique
Learners must READ
Learners must TALK or DO
Facts to highlight during teaching:
➢ Strictly stick to the ATP for the reproduction organs males and females
only the parts mentioned in the ATP
➢ Study the lesson plan: The purpose of the templates is for learners
to make summaries while the educator is teaching.
➢ When teaching the menstruation cycle use the diagram of the ovary
together with the table of menstruation
➢ Take time to teach gametogenesis stick to ATP
111
6.3 LEARNING TEMPLATES
TEMPLATE 1
112
TEMPLATE 2 Female reproductive system
119
TEMPLATE 3
OVARY
120
TEMPLATE 4
Spermatogenesis
Oogenesis
121
TEMPLATE 5
=
Ovarian Cycle and Uterine cycle
Ovarian Cycle
Menstrual Cycle
Uterine cycle
122
TEMPLATE 6
Development of the zygote
TEMPLATE 7
DEVELOPING FETUS
123
TEMPLATE 7
Development of the foetus
124
6.4
125
126
6.5 MARKING GUIDELINES ON QUESTIONS
MALE & FEMALE REPRODUCTIVE ORGANS (LABELS & FUNCTIONS)
OOGENESIS
- Under the influence of FSH
- Diploid (germinal epithelium) cells in the ovary
- Undergo mitosis to form numerous follicles
- One of these follicles enlarges and
- Undergoes meiosis
- Of the four cells produced, only one survives to form the haploid ovum
STRUCTURE AND FUNCTION OF OVUM
- Haploid nucleus which
- fuses with sperm's nucleus to form a diploid zygote
- jelly layer which protects the ovum and
- makes the ovum impenetrable once fertilisation has occurred
- the cytoplasm which provides nourishment
(Be able to draw the ovum with labels)
HORMONAL CONTROL OF THE MENSTRUAL CYCLE (OVARIAN AND UTERINE cycles)
- FSH is secreted
- By the pituitary gland
- FSH stimulates the development of a primary follicle
- into a Graafian follicle
- As the Graafian follicle develops, it secretes Oestrogen
- Which causes the lining of the uterus/ endometrium
- To become thicker/more vascular
- In preparation for a possible implantation
- The pituitary gland
- Secretes LH
- Which causes the Graafian follicle to rupture, releasing the ovum
- This is called ovulation
- The empty follicle changes and becomes the corpus luteum
- Which begins to secrete progesterone
- Which causes further thickening
- Of the endometrium
- High levels of progesterone
- Inhibit the secretion of FSH
- Which prevents the development of a new follicle in the ovary
- If there is no fertilisation, the corpus luteum degenerates
- Which leads to a drop in the progesterone levels
- The endometrium disintegrates and is shed during menstruation
- If fertilisation occurs, the corpus luteum remains intact
- Which leads to high levels of progesterone
- To maintain the pregnancy
- The secretion of progesterone is eventually taken over by the placenta
127
128
PROCESS OF SPERMATOGENESIS AND FORMATION OF SEMEN
- Spermatogenesis takes place under the influence of testosterone
- In the seminiferous tubules in the testes
- Diploid germinal epithelial cells undergo meiosis
- To form haploid sperm cells
Formation and transport of semen
- Sperm mature and are temporarily stored
- In the epididymis
- During ejaculation
- Sperm move into the vas deferens
- As it passes the seminal vesicles
- Prostate gland and
- Cowper’s glands
- Fluids are added that provide nutrition
- Promotes the movement of the sperm
- And neutralize the acids produced in the vagina and urethra
- The semen passes through the urethra
- Of the penis
- Into the vagina
- During copulation
- And swims up the Fallopian tube where it meets the ovum.
STRUCTURAL SUITABILITY OF THE SPERM FOR FERTILISATION
- The front of the head of the sperm cell has an acrosome
- which carries enzymes to dissolve a path into the ovum
- The nucleus of the sperm
- carries genetic material of the male
- The middle piece contains mitochondria
- which release energy so that the sperm can move
- The presence of a long tail
- enables sperm to "swim" towards the ovum
- The contents of the sperm cell such as the cytoplasm is reduced
- making the sperm light for efficient movement
PROCESS OF FERTILISATION
- In the fallopian tubes
- one sperm cell makes contact with the ovum’s membrane
- The nucleus of the sperm enters the ovum
- and the ovum becomes impenetrable to other sperm
- The nucleus of the sperm fuses with the nucleus of the ovum
- to form a diploid zygote
- This is called fertilisation
129
EVENTS AFTER FERTILISATION
- The zygote divides by mitosis many times
- to form an embryo
- which first consists of a ball of cells
- called the morula
- The morula then develops into a hollow ball of cells
- called the blastula
- which embeds itself into the uterine lining/endometrium
- using chorionic villi
- This structure is called the placenta
EVENTS AFTER IMPLANTATION
- Cells of the embryo continue to divide
- and differentiate
- to form the different organs and limbs
- It is now called a foetus
- The foetus is enclosed in a sac/membrane called the amnion
- filled with amniotic fluid
- which protects the foetus against temperature fluctuations,
- dehydration and
- mechanical injuries/acts as a shock absorber.
- The chorionic villi and the endometrium form the placenta
- where the blood of the foetus and the mother
- They run close to each other
- allowing nutrients to diffuse into the blood of the foetus
- The umbilical vein carries the absorbed nutrients from the mother to the
foetus
- The umbilical artery
- carries all the waste away from the foetus to the mother 
GASEOUS EXCHANGE AND NOURISHMENT OF THE FOETUS IN HUMANS
- In the placenta, the mother’s blood comes into close contact with the foetal
blood,
- Oxygen and nutrients diffuse from the mother’s blood into the foetal blood in
the umbilical veins
- This nutrient rich blood is carried to the foetus through the umbilical cord
- CO2 diffuses from the foetal blood in the umbilical artery into the maternal
blood
130
6.6 ACTIVITIES 17 - 25
HUMAN RERODUCTION: Human life cycle
Activity 17
1.
MEMO
The diagram represents the human life cycle.
HUMAN LIFE CYCLE
Ploidy of organisms A and B
Division D
Ploidy of
organism C
Organism A
Organism B
Division B
Division A
Ploidy of cells A and B
Division C
Cell B
Product Y
Cell A
Process X
1.1
Explain the term ploidy.
(4)
The number of sets of chromosomes in the nucleus of a cell. In normal
somatic (body) cells, the chromosomes exist in pairs. The condition is
called diploid. During meiosis the cell produces gametes each
containing half of the normal number of chromosomes called haploid.
131
1.2
Mention the type of ploidy at:
(a)
(b)
(c)
(d)
(e)
1.3
Organism A
Organism B
Organism C
Cell A
Cell Y
(5)
Diploid 2n
Diploid 2n
Diploid 2n
Haploid n
Diploid 2n
Name the type of cell division at both A and B. What is the purpose of
this type of cell division?
(3)
Meiosis.
It is a reduction division where the chromosome number in each cell
is halved from diploid to haploid. It results in the production of
gametes.
1.4
Process X leads to product Y. Name X and Y.
(2)
Process X = Fertilization
Product Y = Zygote
1.5
Name the ploidy of product Y and give a reason for your answer.
(3)
Diploid
Two haploid cells (sperm and ovum) fuses to become 2n
1.6
Use the diagram and describe the human life cycle in your own words.
Use the correct terminology.
(8)
In the reproductive organs of organisms, A and B meiosis occurs to
give rise to haploid gametes which are the sperm and ovum.
Fertilization takes place and the two gametes fuses to form a diploid
zygote. The zygote undergoes mitosis and the zygote forms after
weeks a foetus followed by a baby which will be diploid.
132
HUMAN RERODUCTION: Male reproductive system.
1.
The following diagram represent the male reproductive system.
Activity 18
MEMO
1.
Study the diagram below and answer the questions
1.1
Identify the parts 1 to 8.
1
2
3
4
5
6
7
8
1.2
1.3
-
Penis
Testis
Epididymis
Semen vesicle
Prostate gland
Vas deferens
Urethra
Scrotum
State the function of each of the following numbered parts.
1
2
3
4
-
5
-
6
7
8
-
(8)
(8)
Transfers semen into the vagina of the female
Produces sperm and testosterone
Stores sperm until they are matured
Produces seminal fluid with nutrients and enzymes for
sperm
Produces a fluid which increase mobility of sperm and
neutralize the urethra
Transport sperm to urethra
Tube through which urine or semen pass out of the body
A pouch found outside the body that protects the testis
and maintains a lower temperature for sperm production
Explain why the part numbered 2, must “hang outside” the male body.
(2)
It is because scrotum has a temperature 2-3oC lower than normal
body temperature, which is essential for the maximum production of
sperm.
133
1.4
State the name of the cells in part numbered 2 that secretes
testosterone.
(1)
Cells of Leydig
1.5
State ONE function of testosterone.
(1)
Stimulates the production of sperm and development of secondary
sexual characteristics.
1.6
In terms of n and 2n, give the chromosomal number of the part
numbered:
(a)
(b)
(c)
2.
1
4
6
(3)
2n
2n
2n
Study the micrograph of a cross section of the seminiferous tubules of the testes.
Draw a diagram of the micrograph in your workbook.
CRITERIA
Heading
Correct drawing
THREE correct labels
MARKS
1
1
3
(5)
TOTAL 36
sperm cell
cell of Sertoli
germinal epithelium cell
A cross section of the seminiferous tubule of the testes.
134
HUMAN RERODUCTION: Female reproductive system
Activity 19
1.
MEMO
The following diagram represent the female reproductive system.
1.1
Identify the parts labelled 1 to 7.
1
2
3
4
5
6
7
1.2
Cervix
Ovary
Fallopian tube
Uterus
Bladder
Urethra
Vagina
State the function of each of the following numbered parts.
1
2
3
4
5
6
7
(7)
(7)
Passage between the uterus and the vagina
Produces ova
Carries ova from ovary to uterus by means of peristaltic
movements and it serves as site of fertilization
Structure in which the foetus develops
Stores urine
Tube that carries urine out of the bladder
Canal where sperm is deposited and also acts as a birth canal
135
1.3
In terms of n and 2n, give the chromosomal number of the parts:
1
3
4
1.4
(3)
2n
2n
2n
The following is a diagram of an ovum. Write the numbers in your
workbook and add the labels.
(3)
1. Layer of jelly
2. Nucleus
3. Cytoplasm
1.5
1
A
B
C
5
A
B
C
Study the diagram below. Write down the numbers (1-16) of each block
and choose the correct letter, write it next to the number, e.g., 1A
Nr 4 is
pointing to…
Cervix
X Uterus
Vagina
Nr 7 is
pointing to…
Testis
X Ovary
Fimbriae
2
A
B
C
6
A
B
C
The endometrium is
indicated by…
3
X
8
6
The uterus is
indicated by nr…
X
3
8
4
3
A
B
C
7
A
B
C
Nr 2 indicates
to…
vagina
Uterus
X cervix
Nr 5 indicates
the…
Fimbriae
Ovary
X Fallopian tube
4
A
B
C
8
A
B
C
(16)
Which nr is pointing
to the Fallopian tube?
7
X
5
6
The cervix is indicated
by
1
X
2
4
136
9
What is nr 3
pointing to…
10
A
X
A
Which nr is pointing
to the ovary?
X
7
B
C
Myometrium
Endometrium
fimbriae
B
C
6
5
13
A
B
C
Nr 8 indicates
to the…
Myometrium
Fimbriae
X
14
A
B
C
Which nr is pointing
to the myometrium?
8
6
X
3
11
A
B
C
15
A
B
C
Nr 1 is pointing
to…
Uterus
X
Vagina
cervix
What is nr 6
pointing to?
X Fimbriae
Endometrium
myometrium
12
A
B
C
16
A
B
C
Where does
fertilisation occur?
X
5
4
1
Which nr is pointing
to the vagina?
X
1
2
4
endometrium
4.
Study the micrograph of an ovarium and draw a diagram in the workbook. (5)
137
HUMAN REPRODUCTION: Spermatogenesis
Activity 20
1.1
MEMO
List five changes in the male body during puberty.
(5)
Increased muscle mass, development of deeper voice, enlargement of
penis and testis, production of sperm, increase of facial and body hair
1.2
Give a definition of the following terms:
(4)
a) Gametogenese
The formation of gametes in the sex organs
b) Spermatogenese
Under the influence of testosterone
diploid cells in the seminiferous tubules of the testes undergo
meiosis to form haploid sperm cells
2.
Study the following diagrams representing different processes of gametogenesis.
Place where
formation of sperms
take place.
Cell A
Cell
division A
Cell B
Cell C
Cell division B
Cell D
Cell E
Cell F
138
2.1
Name Cell division A and B and their significant role during this
process.
(4)
Cell division A is mitosis.
Diploid germinal epithelial cells lining the
seminiferous tubules divide mitotically
and give rise to the diploid cells
Cell division B is Meiosis.
Cells undergo meiosis and after the first meiotic division, each gives
rise to haploid sperm cells.
2.2
Name and describe process A.
(5)
Spermatogenesis:
Under the influence of testosterone
diploid cells in the
seminiferous tubules of the testes
undergo meiosis to form
haploid sperm cells
2.3
Draw cell F with labels and their functions.
Label
Acrosome
Function
Produces enzymes to
dissolve the surface of the ovum
Head
Carries a haploid nucleus
Middle piece with
mitochondria
The mitochondria supply energy for
swimming
Tail
Use to swim to the fallopian tube
(6)
139
2.4
Describe the adaptions of Cell F to perform its function
(6)
The front of the head of the sperm cell has an acrosome
- which carries enzymes to dissolve a path into the ovum
- The nucleus of the sperm
- carries genetic material of the male
- The middle piece contains mitochondria
- which release energy so that the sperm can move
- The presence of a long tail
- enables sperm to "swim" towards the ovum
- The contents of the sperm cell such as the cytoplasm is reduced
- making the sperm light for efficient movement
140
HUMAN RERODUCTION: Oogenesis
Activity 21
1
MEMO
List five changes in the female body during puberty.
(5)
Increase in fat deposited below the skin, widening of the hips, development of
breasts, increase in height, development of ova in ovaries, start of
menstruation, growth of body hair, behavioural changes
2.
Study the diagram below and answer the questions.
Process
A
Germinal epithelium
Cell Division A
in the foetus
Oogonium
Growth
at birth
Primary oocyte
Cell Division B
puberty
Polar body
Cell Division C
from puberty
to
menopause
(Only if a sperm
penetrates
secondary oocyte)
three polar bodies (n)
2.1
fertilised ovum (2n)
Name Cell division A, B and C and discuss their roles during this process.
(6)
A Mitosis: The diploid germinal epithelial cells that form the outer layer of
the foetal ovary, divide by mitosis, and give rise to diploid oogonia.
B First meiotic division: The primary oocyte undergoes meiosis, and after
the first meiotic division each gives rise to a larger, haploid secondary
oocyte and a smaller, haploid polar body
141
C Second meiotic division: The second meiotic division, only occurs if a
sperm fertilises the secondary oocyte. It then divides into two daughter cells:
a larger haploid ovum and another polar body. Sometimes the first polar
body also divides to form two polar bodies.
2.2
Describe process A.
(7)
Diploid cells in the ovary undergo mitosis • to form numerous follicles.
• At the onset of puberty • and under the influence of FSH
• one cell inside a follicle enlarges and undergoes meiosis.
• Of the four cells that are produced, only one survives to form a mature,
haploid ovum.
• This occurs in a monthly cycle.
3.
Draw an ovum with labels.
4.
Describe the adaptions of an ovum to perform its function.
(8)
(10)
It has a haploid nucleus with 23 chromosomes. The cytoplasm of the ovum is
known as the yolk and provides reserve source of nutrients for the fertilized
ovum. The cytoplasm is enclosed by a plasma membrane. Surrounding the
plasma membrane is the vitelline or yolk membrane, which become
impermeable after fertilization. A jelly layer surrounds the yolk membrane and
remains for some time after fertilization. It provides protection to the early
development stages of the fertilized ovum. An outermost granular layer, called
the corona radiata, consists of follicle cells that surrounded the secondary
oocyte prior to ovulation. During fertilization it is dissolved by enzymes that are
released by the sperm.
TOTAL:
43
142
HUMAN RERODUCTION: Ovarian cycle and hormones
Activity 22
1
MEMO
Study the diagram below and answer the questions.
D
C
B
A
E
I
H
F
1.1
Name the structure above and mention if it is haploid or diploid.
Ovary
1.2
1
2
3
G
(2)
2n
Draw the table in your workbook and complete it accordingly.
(6)
Cyclical change in ovary
When does it happen?
Developing of primary follicles into
Graafian follicles
Rupturing of the follicle and release
of immature ovum
Formation of the Corpus luteum
Day 1-14
Which hormone is
responsible
FSH
Day 14
LH
From day 15
LH
1.3
Name cell F and indicate if it is a haploid and diploid product.
(2)
Ovum n
1.4
Discuss the process taking place from G to I.
(6)
After ovulation the remains of the Graafian follicle develop under the
influence of the hormone LH, into a mass of yellow cells known as the
corpus luteum.
If the ovum is not fertilised, the corpus luteum degenerates until only a
small scar remains.
143
HUMAN RERODUCTION: Menstruation
Activity 23
1.1
MEMO
Name the two cycles that forms part of the menstrual cycle.
(2)
Ovarian cycle
Uterine cycle
1.2
Use the diagram below, describe the process of the ovarian cycle.
(15)
Number 1 shows the ovaries wherein the ovarian cycle is taking place. 
The hypophysis secretes FSH which allow the formation of follicles
The germinal epithelial cells will divide by mitosis to form follicles which is
represented by number 13
These follicles develop into primary follicles which develops into bigger
follicles until a Graafian Follicle forms (7).
The Graafian follicle secrets oestrogen that are responsible for secondary
female sexual characteristics as the development of the endometrium.
At number 8 ovulation is taking place where a haploid ovum is released.
The hypophysis secretes LH on day 14 and stimulates ovulation
After ovulation the remains of the Graafian follicle develop under the
influence of LH into a corpus luteum number 9.
The corpus luteum secretes progesterone which maintains the
endometrium for implantation.
144
1.3
Use the diagram below and describe the uterine cycle.
(5)
The endometrium of the uterus is rich in glands
and blood vessels to prepare for implantation of a fertilized ovum.
Oestrogen and progesterone are responsible for thickening the
endometrium.
According to the chart the endometrium is thickening.
1.4
Explain the following terms:
(3)
(a) Menstruation
• The endometrium breaks down with an accompanying discharge
of blood, unfertilized ovum and mucus via the vagina if fertilization
is not taking place.
(b) Ovulation
Under the influence of LH, the Graafian follicle swells and
eventually burst to release an immature ovum
(c) Negative feedback
An increase in the level of one hormone will result in a
decrease or the complete inhibition of the secretion of another
hormone.
145
1.5
Study the diagram and describe the fluctuations of the four different
female reproductive hormones over a period of 28 days.
(16)
LH:
Around day 13 of the cycle oestrogen is sufficiently high and it
produces a sudden release of LH.
FSH: In the first half of the 28-day cycle FSH is released that
stimulates follicular growth in the ovary.
Oestrogen:
Oestrogen levels rise and fall twice during the menstrual
cycle. The levels rise during the mid-follicular phase and
then drops steeply after ovulation This is followed by a
secondary rise in oestrogen levels during the mid-luteal
phase with a decrease at the end menstruation cycle.
Progesterone: After ovulation progesterone is produced increasingly
from the corpus luteum and the progesterone levels
gradually rise, Levels continue to rise until it reaches a
peak 7 days after ovulation. When fertilization did not
take place the levels will drop.
146
2.
Study the diagram below, write the numbers of the table in your workbook and
write the correct answer.
(11)
147
•
•
•
OVARY
a follicle develops
secretes
3…………… the blood
•
lining of the uterus grows thick, spongy
•
•
When the follicle is fully developed
•
follicles rupture and release fully
developed ovum 4 ………………
•
•
•
•
empty follicle stops secreting 5 ……
becomes a 6…………………………
secretes 7 ……………………………
uterus lining thick, spongy, well
supplied with blood in case an ovum is
fertilised
If the ovum is NOT FERTILISED
• corpus luteum 8 ……………………..
• no more 10 ……………… secreted
• uterus lining breaks down
Menstruation
•
a new follicle develops
PITUITARY GLAND
secretes 1………. and 2…………
stimulates follicle to secrete oestrogen
LH
and FSH
•
•
•
•
LH and FSH
If the ovum IS FERTILISED
corpus luteum 9 …………………
secretes 11 ………………………. until
the embryo sinks into uterus wall and a
placenta develops
Placenta secretes progesterone through
pregnancy
• it maintains the uterus lining so that the
menstruation does not happen during
pregnancy
1 – LH
2 – FSH
3 – Oestrogen
4 – Ovulation
5 – Oestrogen
6 – corpus luteum
7 – Progesterone
8 – Gradually disappears
9 – Does not degenerate so quickly
10 – progesterone
11 – progesterone
148
3.
Describe the process of negative feedback between FSH and progesterone
controlling the production of ova by using the numbers and names of the
diagram below.
Function A
(17)
Function B
Gland A
Process B
Process A
Hormone A
Function C
Gland B
Hormone B
Function D
Increasing levels of oestrogen hormone A secreted by the developing
Graafian follice, 
inhibits release of FSH  process A by hypophysis.
This prevents the development of futher folliclles in the ovaries.
Increasing levels of progesteroe, hormone B secreted by the corpus
luteum, inhibits the releaese of FSH and LH 
process B from the hypophysis.
This prevents the development of any other follicles function A as well as
ovulation function B.
Once the corpus luteum degenerates, oestrogen and progesterone levels
in the blood will drop.
Therefore, the secretion of FSH ad LH is no longer inhibited, their
concentration rises, and the process starts all over again. 
Total 65
149
HUMAN RERODUCTION: Implantation
Activity 24
1.
MEMO
Study the diagram below.
I
(5)
H
G
F
E
D
C
B
J
K
A
L
1.1
Name gametes A and C
(2)
A - Ovum and
B - sperm
1.2
What process is taking place at B? Where does this process normally
take place?
(2)
Fertilization,
Fallopian tube, 
1.3
Name the product at D.
(1)
Zygote
1.4
What type of cell division is taking place at E. Give a reason for your
answer.
(2)
Mitosis, to allow growth
150
1.5
Draw the table in your workbook and complete the table regarding F
and G.
Name
Structure
F
Morula
A solid ball of cells
Where we find it
Fallopian tube
1.6
(6)
G
Blastocyst
A hollow sphere filled
with fluid
Fallopian tube
Uterus
Name the structures that assist in the movement of the embryo/morula
in the place where fertilization takes place?
(1)
Cilia
1.7
J, K and L forms part of the ….?
(1)
Uterus
1.8
What is the ploidy of the parts that are numbered A, D and K
respectively?
(3)
n, 2n and 2n
151
HUMAN RERODUCTION: Gestation
Activity 25
1.
MEMO
Study the diagram below.
1.1
Define the term gestation.
(2)
It is the period of development during the carrying of an embryo, and
later foetus, inside viviparous animals.
1.2
In this diagram there is a reference to a foetus. What is the difference
between a foetus and an embryo?
(2)
An embryo is formed by the repeated cell division of a zygote and is in
the uterus in the early stages of development (up to 8 weeks)
A foetus is formed by the growth and development of an embryo and is
the later stages in the uterus (from week 9). Growth and specialization
occur from the ninth week until birth.
152
2
2.1.
Draw the diagram in your workbook and complete the table.
(6)
Name
Structural
features
F
Amnion
It is a tough membrane lining the
chorion.
H
Chorion
It is the outermost extra-embryonic
membrane surrounding the embryo
Function
It encloses the amniotic cavity, which
is filled with amniotic fluid.
The chorion develops a rich supply of
blood vessels and forms an intimate
association with the endometrium.
The endometrium and the chorion
together form the placenta
2.2
2.3
Identify D and E. Give ONE function of each.
D
Umbilical artery: carries deoxygenated blood and waste products
from the foetus to the placenta.
E
Umbilical vein: Carries oxygenate blood, rich in nutrients, from
the placenta to the foetus.
B is the placenta. Name the TWO tissues with the numbers that forms
the placenta.
(4)
(4)
A Maternal uterine blood vessels
C Villus from the chorion
2.1.3 Name 5 functions of the placenta
(5)
Supply embryo with nutrients via umbilical cord
Excretion of metabolic waste via umbilical cord
Gaseous exchange
Acts as microfilter
Has also an endocrine function
2.1.4 The maternal blood and foetal blood are in close contact and never mix.
What is the reason for this? How does substances move from mother
to baby.
(2)
If the mother and the foetus have different blood groups and it mix both
can die.
Diffusion
TOTAL 25
153