5. Variation
• Variation with in a species can provide some
individuals with an increase chance of surviving
over others.
• Asexual reproduction – no variation as daughter
cells identical to parent (mitosis)
• Sexual reproduction – great variation as daughter
cells are not identical.
With 23 pairs of chromosomes in each sperm and
eggs there is 8 388 608 different possible ways to
divide to make the daughter cells ( Gametes)
(meiosis)
7. Two main types of Cells and their
production in our body
• 1. Gametes (sex cells – egg and sperm) = 23
chromosomes
• Produced by Meiosis
• 2. Somatic Cells
(normal body cells)
= 46 chromosomes
Produced by Mitosis
13. Meiosis
Gametes (Sex Cells)
Production
Sex cells:
1. Sperm
2. Eggs
Nuclei of sex cells contain
have the number of
chromosomes then normal
cells = 23 individual
chromosomes
Fertilization =
23 + 23 = 46
SPERM EGG
Sex cells made when a
normal body cell in the sex
organs divides into and the
Pairs separate (no
replication occurs)
14. Chromosomes
carried in the sperm
are called maternal
chromosomes
Chromosomes
carried in the
sperm are
called paternal
chromosomes
MUM DAD
15. Remember your Human Karyotype
• Below is from one cells nucleus and all 23 pairs of chromosomes have
been colour coded to make it easier to see partner chromosomes.
• We are going to use two chromosomes as an example in the next few
slides.
Chromosome number 1
From
Mum
From
Dad
Chromosome number 4
From
Mum
From
Dad
17. Student Activity – Play-Doh
chromosomes
Your will need per pair:
• Two coloured play-Doh pieces
• 1 m string that should be cut up into 4 pieces.
Instructions:
• In pairs collect your two coloured play-Doh (one colour for
mum and one for dad) as per teacher demo and make the
chromosomes below.
• Use one piece of string
to make the nucleus
envelope.
Chromosome number 1
Chromosome number 4
18. Activity Continued ….
Mitosis vs Meiosis Worksheet
• Read through Mitosis vs Meiosis worksheet.
• Colour code your chromosomes as per your
play-Doh.
• Practically do the mitosis and then the meiosis
division using your play-Doh and string
following the diagrams on the worksheet.
• Answer the questions on the bottom of the
sheet.
19.
20. So what have you learnt? Complete a postie on
LIFE to compare Meiosis and Mitosis and show
your understanding by answer the questions
below. Use your textbook page 66 to 67.
Why use it?
Where does
it occur?
Features of
cells
produced.
21. Girl or Boy
• Read page. 69
• Complete Investigation 2.2
What’s the chance?
1. Read instructions
2. Predict number of times your get tails and heads. Give a
reason for your prediction.
3. Complete the practical. Record class results in the table on
board.
4. Answers questions 2 to 6.
22. Exercises
• Workbook pg. 13 to 15
• Textbook Pg. 70
• Remember 2 to 4, 6, 7 (b, c, d, f, h, I, j)
