Transcript Key Area 3 Producing New Cells

Starter Activity:
Answer the following in full sentences in
your notebook:
1.
2.
3.
4.
Draw and label a basic animal cell.
State what is found in the nucleus.
Explain the function of the nucleus.
Describe what a chromosome is.
Key Area 3
Making new cells
Making New Cells
Learning Intention:
To understand how living organisms grow.
Success Criteria:
• State where genetic material is found in
living organisms.
• Understand the need for cell division.
• Explain the process of mitosis.
• Give uses of cell division.
Importance of Cell Division
• In animals, this cell is
formed when an egg
cell is fertilised by a
sperm cell.
• The fertilised egg
then divides into
many cells to form an
embryo.
• The embryo
continues to grow
into a new animal.
Making New Cells
• New cells are made
to allow living
organisms to grow.
• New cells are also
made to replace
dead cells, repair
tissues and heal
wounds.
• All new cells are
made from existing
cells by the
process of cell
division.
Cell division definition - Twig clip
Importance of Cell Division
• Every living organism
produced by sexual
reproduction starts life
as one cell.
• In plants, this cell is
formed when an egg cell
is fertilised by a pollen
grain.
• The fertilised egg cell
then divides into many
cells to form a seed.
• The seed can then grow
into a new plant.
pollen grain
pollen tube
pollen
nucleus
egg cell
Growth
• All living organisms
grow during their
lifetime.
• All of this growth
happens due to cells
dividing to form new
cells.
Repair to tissues
• When we get
injured, new cells
are made to repair
and replace the
damaged tissues.
• New skin cells
form to heal a cut
or graze, and new
bone cells grow to
repair a broken
bone.
Cell Division
• The process of cell division is called
mitosis.
• Mitosis is required for growth and
repair.
Importance of Cell Division
Your task..
Think: On a show me board list ideas why cell
division is important.
Pair: Decide with your partner two key
reasons why cell division is important.
Share: Show your ideas on one show me board
In your notebook: List the key reasons why
cell division is important.
Making New Cells
Learning Intention:
To understand how living organisms grow.
Success Criteria:
• State where genetic material is found in
living organisms.
• Understand the need for cell division.
• Explain the process of mitosis.
• Give uses of cell division.
Starter Activity:
On a show me board:
Why is cell division
important?
Cells and chromosomes
• Inside the nucleus
of a cell there are
chromosomes which
carry the genetic
information of the
organism.
• Each chromosome is
made up or two
chromatids.
• Human cells have 46
chromosomes in
their nucleus.
Matching sets of chromosomes
•Normal cells have 2 sets of matching chromosomes.
•These are known as diploid cells.
•In humans this is 2 sets of 23 chromosomes.
•This diagram shows the chromosomes of a human female
laid out in order of size.
Cell division
• Cells are able to
make new cells by
cell division.
• The parent cell
splits to form two
cells.
• Each new cell is
identical to the
original parent cell.
Embryonic cell division
Chromosomes and cell division
Spindle fibres pull the
chromatids apart.
• The chromosomes all make copies of themselves in a process
called DNA replication.
• The cell then divides into two diploid cells. This is called mitosis.
• Each new cell ends up with the same number of chromosomes as
the parent cell.
• This means each new cell has all the genetic information.
Twig Video Clip - Cell Division: Mitosis
Mitosis in detail
Equator (middle)
Each chromosome
duplicates to
make a double
chromosome
Spindle fibres
Chromosomes
line up on
the equator
of the cell
Chromosomes
split into two
and spindle
fibres pull
the
chromatids
apart
Cytoplasm
divides to
make two
cells
Looking at dividing cells – root tip
slides
Equipment : microscope, prepared slide
of onion root tip
Method :
1.
Set up the microscope at low
power.
2.
Look at the area just behind the
tip of the root at low power.
3.
Look for cells where chromosomes
can be seen.
4.
Increase to medium and then high
power.
5.
Look for cells where the
chromosomes are about to
separate, and where they have
already separated.
6.
Make enlarged drawings of three
different cells.
Mitosis in action
• You will use pipe cleaners and card to
make a model of a cell.
• You will then take the cell through the
process of mitosis.
• Your teacher will lead you through this
activity.
Making New Cells
Learning Intention:
To understand how living organisms grow.
Success Criteria:
• State where genetic material is found in
living organisms.
• Understand the need for cell division.
• Explain the process of mitosis.
• Give uses of cell division.
Starter Activity:
In pairs:
Describe the
process of mitosis
Starter
Starter
2
Modelling Mitosis
We must… Plan and prepare mitosis video clips.
We should… Swap and evaluate each other’s clips.
We could… Use feedback to improve the clips.
Modelling Mitosis
The mitosis video clip must:
 be at least one minute long
 be presented in a clear and concise way
 include a short description about what mitosis is
The mitosis video clip should:
 describe the different stages of mitosis
 show the presenter using a clear voice with varied
tone
The mitosis video clip could:
 explain the different stages of mitosis
 Explain the importance of mitosis
 be well structured with appropriate content
Self evaluation comment:
Cell division in bacteria
• Bacteria are single celled living
organisms.
• They are too small to see with
the naked eye.
• Bacterial cells can divide very
rapidly to form new cells.
• When they do this, they form
colonies of millions of cells
which can be seen with the
naked eye.
• Your teacher will show you how
to grow bacteria on an agar
plate like the one shown in the
bottom picture.
• This is called cell culturing:
• Cell culture is the complex
process by which cells are
grown under controlled
conditions in a laboratory.
Growing bacteria on an agar plate
Equipment : Sterile petri dish with agar
Broth culture of bacteria
Inoculating loop
Bunsen burner
Disinfectant
Sticky tape
Label
Method :
1.
Wash your hands and sterilise the bench with disinfectant.
2.
Label the petri dish with your initials.
3.
Heat the inoculating loop in a blue flame until it glows red hot. Allow
it to cool for 20 seconds. This will sterilise it.
4.
Dip the loop into the broth and remove. Replace the lid on the broth
quickly.
5.
Take the lid off the petri dish and gently spread the liquid onto the
surface of the agar.
6.
Replace the lid on the petri dish as quickly as possible.
7.
Put the loop back into the flame until it glows red hot again.
8.
Seal the dish with two pieces of sellotape at opposite sides.
9.
Sterilise the bench with disinfectant and wash your hands.
Growing bacteria on an agar plate
• Results :
Make a drawing of your petri dish after
it has been incubated in an oven for 2-3
days. (Do not open the dish!)
Aseptic (sterile) techniques
• It is very important to ensure that no
unwanted bacteria get onto the agar and
start to grow.
• It is also important to avoid contaminating
the lab or yourself with bacteria.
• Make a list of 5 precautions that you took
when preparing your agar plate which reduced
the chance of this happening.
Answers
• Wash hands before and after experiment.
• Sterilise the bench with disinfectant before
and after use.
• Sterilise the loop before and after use in a
bunsen flame.
• Replace the lid on the bottle quickly.
• Replace the lid on the petri dish quickly.
• Seal the dish with sticky tape.
• Work around the Bunsen flame to reduce risk
of contaminants in the air.
• Sterilise the neck of the bottle before and
after use in the Bunsen flame.
Making New Cells
Learning Intention:
To understand how living organisms grow.
Success Criteria:
• State where genetic material is found in
living organisms.
• Understand the need for cell division.
• Explain the process of mitosis.
• Give uses of cell division.
Starter Activity:
In pairs:
Explain the importance
of aseptic technique.
Hand Washing Investigation
Think… How could you plan an experiment about hand washing?
Pair… Discuss the factors you could investigate.
Share… Write down you ideas on a show me board.
Hand Washing Investigation
Aim: To investigate the effect of different hand wash on bacterial growth.
Method:
You will use one agar plate to culture the bacteria found on your
hands before and after washing with different hand wash substances.
You will split your plate into four and gently place the following finger
prints in each quarter:
1. Thumb:
unwashed
4. Third finger:
wiped with a
cotton bud dipped
in branded hand
wash.
2. First finger:
wiped with a cotton
bud dipped in water.
3. Second finger:
wiped with a cotton
bud dipped in school
soap.
Prediction: Which quarter will show the most bacterial growth and
which quarter will show the least bacterial growth?
Hand Washing Investigation
Equipment :Sterile Petri dish with agar
Disinfectant
3 cotton buds
Spotting tile
1 sample of school soap
1 sample of branded hand wash
Sticky tape
Label/fine tip marker pen
Method :
1.
Sterilise the bench with disinfectant. Make sure it is NOT the person who is having their hands
swabbed who does this!
2.
Label the Petri dish with your initials around the outside of the plate.
3.
Split your plate into four equal quarters. Use the fine tip marker on the bottom of the plate
containing the agar, number them 1, 2, 3, 4 around the edge.
4.
Put a sample of water, school soap and branded hand wash in separate dimples in a spotting tile.
5.
Very gently place a thumb print in quarter number 1.
6.
Replace the lid on the Petri dish as quickly as possible.
7.
Wipe your first finger with a cotton bud dipped in water and then very gently place your finger
print in quarter number 2.
8.
Replace the lid on the Petri dish as quickly as possible.
9.
Wipe your second finger with a cotton bud dipped in school soap and then very gently place your
finger print in quarter number 3.
10.
Replace the lid on the Petri dish as quickly as possible.
11.
Wipe your third finger with a cotton bud dipped in the branded hand wash and then very gently
place your finger print in quarter number 4.
12.
Replace the lid on the Petri dish as quickly as possible.
13.
Seal the dish with two pieces of sellotape at opposite sides.
14.
Sterilise the bench with disinfectant and wash your hands.
Hand Washing Investigation
Aim: To investigate the effect of different hand wash on bacterial
growth.
Prediction: Which quarter will show the most bacterial growth and which
quarter will show the least bacterial growth?
Independent variable: What did you change in this investigation?
Dependent variable: What did you measure in this investigation?
Control variables: How did you make this investigation a valid (fair) test?
Method: Write a brief method to explain how you set up the experiment.
Remember to include a diagram of the Petri dish and the
importance of aseptic technique.
Hand Washing Investigation
Results:
Hand wash substance
Bacterial Growth
(number of colonies)
1. None
2. Water
3. School soap
4. Branded hand wash
Number of colonies: the number of clearly separate circles of growth you can see.
Graph: Draw a suitable graph to show your results. Extension: collate class average
Conclusion: Describe the results you have seen and relate your conclusion back
to the aim of your investigation. What is the relationship between hand wash and
bacterial growth? Remember to quote data from your results.
Evaluation: What were the good points about method? How did you control your
experiment? What could you do to make your investigation more reliable?
Summary: Write a 50-100 word summary of your investigation.
Drawing a suitable graph
Dependent variable: What you measure
(Units)
Golden Rules for Drawing Graphs
1. Decide what type of graph is most appropriate:
Continuous scale of numbers = Line graph.
Distinct categories/words = Bar graph.
2. Copy the exact results table headings with UNITS
to label your axis.
3. The independent variable always goes on the X axis.
4. The dependent variable always goes on the Y axis.
5. Always use at least 50% of the graph paper.
6. Only plot the results you have NEVER draw a line
graph to zero unless your results show this.
7. Plot your points with a X and join them point to
point with a ruler.
Independent variable: What you change (units)
(number of colonies)
(Average) bacterial growth
Drawing a suitable graph
Hand wash substance
Hand Washing Investigation
Results:
Hand wash substance
Bacterial Growth
(number of colonies)
1. None
2. Water
3. School soap
4. Branded hand wash
Number of colonies: the number of clearly separate circles of growth you can see.
Graph: Draw a suitable graph to show your results. Extension: collate class average
Conclusion: Describe the results you have seen and relate your conclusion back
to the aim of your investigation. What is the relationship between hand wash and
bacterial growth? Remember to quote data from your results.
Evaluation: What were the good points about method? How did you control your
experiment? What could you do to make your investigation more reliable?
Summary: Write a 50-100 word summary of your investigation.
Optimum (best) conditions for
the growth of cells.
If they are to divide, cells need the following:
• A suitable growth medium containing sugars
– nutrient agar or nutrient broth.
• A suitable temperature – around 30°C for
bacterial cells.
• Suitable pH conditions – not too acidic or
alkaline
• A source of oxygen
Industrial fermenters
• Pure cultures of bacterial
or fungal cells can be
grown in large vessels
called fermenters.
• Fermenters can contain up
to 200,000 litres of
bacterial or yeast broth.
• In the fermenter, the
cells are given the perfect
conditions for growth
– Correct temperature
– Air (for oxygen)
– Sugar (for food)
– A suitable pH
Your task…
Write a short summary of the key
points about industrial fermenters.
A simple fermenter
• Your teacher will show you a model of a
simple fermenter.
Making New Cells
Learning Intention:
To understand how living organisms grow.
Success Criteria:
• State where genetic material is found in
living organisms.
• Understand the need for cell division.
• Explain the process of mitosis.
• Give uses of cell division.