2.4 Dividing to Multiply

Two types of Reproduction

Use Mitosis Use Meiosis

Asexual reproduction

• http://www.youtube.com/watch?v=DY9DNWcqxI4

Sexual reproduction

• http://www.youtube.com/watch?v=6CBBzw6xUJE

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)

Humans

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 chromosomesProduced by Mitosis

Mitosis Somatic Cell Production

Body constantly making new cells.Process of making new cells

Normal Cell division:

Mitosis

Mitosis - When a normal body cells (autosomal) undergoes cell division.Mitosis is how cells grow.

Mitosis

Meiosis

• http://www.youtube.com/watch?v=D1_-mQS_FZ0

MeiosisGametes (Sex Cells) ProductionSex cells:1. Sperm 2. EggsNuclei of sex cells contain have the number of chromosomes then normal cells = 23 individual chromosomes

Fertilization = 23 + 23 = 46 SPERM EGGSex cells made when a normal body cell in the sex organs divides into and the Pairs separate (no replication occurs)

Chromosomes carried in the sperm are called maternal chromosomes

Chromosomes carried in the sperm are called paternal chromosomes

MUM DAD

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

Teacher Discussion and Demo with Play-Doh

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

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.

Comparing Mitosis and Meiosis

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.

Girl or Boy

• Read page. 69• Complete Investigation 2.2

What’s the chance?1. Read instructions2. 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.

Exercises

• Workbook pg. 13 to 15

• Textbook Pg. 70• Remember 2 to 4, 6, 7 (b, c, d, f, h, I, j)