1. Biology 12

2. Cell division Needed for: reproduction in unicellular organisms
growth in multicellular organisms
replacement of damaged or dying cells
repair of damaged organs or tissues

3. Mitosis Involves: replication of DNA
controlled division of the nuclear material so new each cell has the same DNA
division of cytoplasm and organelles so each new cell has similar contents

4. DNA replication Occurs in interphase – before mitosis starts
One set of enzymes split the strands
Another set of enzymes join new nucleotides to each strand
Nucleotides match up by the base pairing rule (C – G, A - T)
The end result is two identical strands, joined at a point called the centromere

5. DNA replication 2

6. Chromosomes Chromosomes are only visible during cell division
They consist of two strands (chromatids) of tightly coiled DNA joined at the centromere

7. Cell cycle

8. Stages of mitosis

9. Interphase Phase of growth and normal metabolism
Nucleus and nucleolus visible
DNA replication occurs just before cell division occurs

10. Prophase First stage of division Nucleus and nucleolus disappear
Spindle starts to form
DNA condenses and becomes visible as chromosomes
Centrioles move to opposite poles (animal cells)

11. Metaphase
Chromosomes line up on spindle at the equator of the cell

12. Anaphase Chromatids pull apart at the centromere
One chromatid from each chromosome moves to each end of the cell

13. Telophase Chromosomes uncondense and a new nucleus forms around them
The cytoplasm splits (cytokinesis) to form two new cells identical to the original except smaller

14. Interphase Phase of growth and normal metabolism
Nucleus and nucleolus visible

15. Identify the stages of mitosis
telophase
anaphase
interphase
metaphase
early prophase
early prophase
metaphase
early prophase

16. Identify the stages of mitosis 2
telophase
late anaphase/early telophase
anaphase
prophase
early prophase
late anaphase/early telophase
metaphase
interphase

17. Designing experiments
Pose a question
Suggest some answers
Define your hypothesis
eg using pesticides will increase yield

18. What shall I change? Select one thing to test
That is the independent variable
eg pesticides

19. How do I know if it has an effect?
eg yield
Measured by weight, height or volume
What will I measure?
How will I measure it?
That is the dependent variable
What will I compare it to?
That is the control
eg group without pesticides

20. How do I know my results are true?
Define your controlled variables
Define how you will increase reliability
eg same soil type, same type & number of seeds/plants, same water, sun,
temperature, humidity, weed control, fertiliser, etc

21. The language of experimental design
Hypothesis
Independent variable
Dependent variable
The control
Controlled variables
Reliability

22. Ways to increase reliability
Use accurate measurements
Increase number of measurements
Run experiment for longer
Repeat the experiment
Increase the sample size
Get someone else to replicate the experiment
Share the results and get a review