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Experiments

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UNIT 1

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Enzyme Experiments

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To investigate the effect of pH on enzyme activity

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Name a factor other than pH, which effects enzyme activity

Temperature

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Explain the term optimum activity

The pH/temperature where the enzyme works best at

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Name an enzyme that you used in this investigation

Catalase

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State the source of the enzyme

Celery

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State the substrate of the enzyme

Hydrogen peroxide

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Explain why changing the pH would have an effect on enzyme activity

This would change the shape of the enzyme
It would no longer join with the substrate

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How did you measure the rate of enzyme activity

The amount of foam produced in 2 minutes

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Sketch a graph to show the effect of pH on enzyme activity

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What was the purpose of the washing up liquid

To allow foam to be produced

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To investigate the effect of temperature on enzyme activity

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What term is used for the result from the action of an enzyme on its substrate

Product

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Name an enzyme that you used in this investigation

Catalase

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State the source of the enzyme

Celery

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State the substrate of the enzyme

Hydrogen peroxide

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What is the chemical nature of enzymes

Proteins

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Comment on enzymes molecular shape

3D
Folded

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How was the pH kept constant throughout this investigation

Used the same buffers

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How was temperature varied

Use different beakers with different temperatures

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Sketch a graph to show the effect of temperature on enzyme activity

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Investigate the effect of heat denaturation on the activity of an enzyme

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Name the enzyme used

Catalase

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Name the substrate of the enzyme

Hydrogen peroxide

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How did you denature the enzyme

Boil celery in 100 degrees celsius for 10 minutes

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How did you know that the enzyme had been denatured

There was no foam produced after 2 minutes

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Why are buffers needed when carrying out the experiments

To keep the pH at an optimum rate so it wont affect the experiment

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What is a denatured enzyme

When an enzyme stops working

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What is meant by an enzyme

Biological catalyst that speeds up chemical reactions without being used up in the reaction

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What was the control during the experiment

Unboiled celery

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Prepare one enzyme immobilisation and examine its application

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What is enzyme immobilisation

When an enzyme is fixed in an inert substance

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What are the advantages of enzyme immobilisation

Enzyme can be reused
A purer product

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Name the gel substance you used to trap the enzyme

Sodium alginate gel

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Name the second substance you used to make the gel insoluble

Calcium chloride

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Name the enzyme immobilised

Sucrase

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Name the source of the enzyme

Yeast

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Name the substrate

Sucrose solution

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Describe how immobilisation is carried out

Mix sodium alginate with water in a beaker
Mix yeast and water in another beaker
Add yeast solution to sodium alginate and mix well
Prepare a calcium chloride solution in a beaker
Using syringe, add yeast + alginate mixture to calcium beaker
Leave to sit for 10 minutes
Remove beads and wash with distilled water

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Prepare and show alcohol production by yeast

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What is respiring in this experiment

Yeast is respiring

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Draw a labelled diagram of the apparatus to prepare alcohol using yeast

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How did you establish anaerobic conditions

Boiled glucose solution and let it cool to drive out any oxygen or other gases present
Used a fermentation lock

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What was placed in the fermentation lock

Half filled with limewater

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What colour did the test limewater turn

Milky due to CO2

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Give another function of fermentation lock

Prevent the entry of contaminants

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How did you know fermentation was taking place

Bubbles of CO2
Froth in the conical flask

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How did you know fermentation had ceased

No more CO2 bubbles produced

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How did you test for alcohol (ethanol)

Iodoform test

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Describe the iodoform test

Added potassium iodide solution and sodium hypochlorite solution to both test tubes
Then heated the test tubes for 4-5 minutes

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What indicated a positive result

Formation of yellow crystals

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Describe how you carried out the practical

Create anaerobic conditions

Create glucose solution, boil and let it cool
Add 250cm cubed of glucose solution to two different conical flasks
Into one flask add 5g of yeast
No yeast is added to the other (control)
Add fermentation lock
Add limewater to fermentation lock

2. Breakdown of glucose

Add both vessels into water bath set at 25-30 degrees celcius
Leave overnight for 24 hours

3. Test for alcohol (Ethanol)

After 24 hours remove the fermentation lock and filter the contents
Add some of the test filtrate into one test tube
Add some of the control filtrate into another test tube
Perform iodoform test (added potassium iodide solution and sodium hypochlorite solution to both test tubes)
Warm both in water bath for 4-5 minutes
Allow to cool and note results

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Be Familiar with the Light Microscope

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Draw a diagram of a light microscope

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What is the purpose of a coverslip

To protect the objective lens

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How do you calculate the magnifying power of a microscope

Eyepiece magnification X Objective lens magnification = total magnification

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How do you alter the amount of light shining on your specimens

Adjust the lamp

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The eye piece is marked 10X and the objective lens is marked 40X. A cell is viewed through both lenses and the image that appears is 0.8mm in diameter. What is the actual diameter of the cell?

The actual diameter will be smaller than the magnified diameter
The total magnification is 10 x 40 = 400
0.8/400 = 0.002mm diameter

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Describe how you used the microscope to view the cells

Look through the eyepiece lens
Use the coarse focus wheel to make the class visible
Use the fine focus wheel to sharpen the image

👨🏻‍🔬The Scientific Method

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UNIT 2

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Food Tests

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State a use for the biuret reagent

Test for the presence of protein

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What does the biuret reagent consist of

Sodium hydroxide
Copper sulfate

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State a use for the benedict’s solution

Test for the presence of reducing sugars

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Why is brown paper used to test for fats allowed to be dried out

Fats will leave a permanent/translucent stain on brown paper

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Which food test requires the application of heat

Test for reducing sugars / benedicts test

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Name a control used in the testing of a reducing sugar and state the colour change of the contents of the control tube at the end of the test

Control used - benedicts added to water
Colour - blue

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What is used to test for starch

Iodine

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State the colour change for both the test & the control for the following tests:

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Protein Test

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What colour did the test turn

Purple

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What colour was the control

Stayed blue

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Reducing Sugar Test

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What colour did the test turn

Brick red

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What colour did control turn

Stayed blue

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Starch

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What colour did test turn

Blue/black

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What colour did the control turn

Red/yellow

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Describe the results of the experiment to test for fats (& control)

Fat (butter) left a permanent/translucent stain on brown paper
Water did not

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Use bullet points to describe how to carry out the following food tests

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Protein

Add water to a test tube
Add milk to another test tube
Add biuret reagent to both test tubes
Swirl test tubes
Note colour change

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Reducing Sugar

Add water to test tube
Dissolve glucose in water, in another test tube
Add equal amounts of benedict's solution to both test tubes
Heat both test tubes in beaker of boiling water
Note colour change

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Starch

Add water to a test tube
Add starch solution to another test tube
Add iodine to both test tubes
Note colour change

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Fats

Rub butter on brown paper
Rub water on another piece of brown paper
Leave to dry
Note the stains left by both the water and fat

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To prepare and examine one animal cell and one plant cell using the light microscope

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How did you transfer the human cheek cells to the slides

Used cotton swab

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How did you improve the visibility of the cells on the slide

Used iodine to stain plant cell to see nucleus
Used methylene blue to stain animal cell to see nucleus

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Explain how the coverslip is applied

Applied at a 45 degree angle to prevent air bubbles

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What is the purpose of the coverslip

To protect the cell

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What is the purpose of water

Prevent the cell from drying out

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Draw a labelled diagram of animal cells using a microscope

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Draw a labelled diagram of plant cells using a microscope

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Describe the difference in colour or depth of colour, if any between the nucleus and cytoplasm when the stained cell was viewed under the microscope

The nucleus was more visible when stained
Darker in colour

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To Isolate DNA from plant tissue

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When extracting DNA from plant tissue, why do you use washing up liquid

Breaks down the lipids in the phospholipid bilayer

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When extracting DNA from plant tissue, why did you use freezer cold ethanol

TO ensure DNA is insoluble
If DNA was room temp it would be soluble

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Why is salt (NaCl) (sodium chloride) added to the chopped plant tissue

Clumps together the DNA

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Why is the mixture kept at 60 degrees Celsius for 15mins

To denature the enzymes that breakdown DNA

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State the function of the protease

Breakdown proteins that surround DNA

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What did you use as form of protease

Pineapple juice

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What plant did you use as a source of DNA

Kiwi

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What was the first procedure you carried out and why did you carry it out

Chop up kiwi
To breakdown cell wall and membrane

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What is a protease

An enzyme that breaks down proteins into amino acids

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How is the freezer cold ethanol applied

Slid down the side of test tube using a pipette

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Why is a blender use

To further breakdown cell walls and membrane

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Why is the blender only used for 3 seconds

If used for any longer it would destroy the DNA

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Why is it put into a water bath

Prevent the breakdown of DNA

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What does the filter paper remove

Large cellular debris

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What is in the filtrate

DNA and protein

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Draw a diagram to display the results

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Demonstrating Osmosis

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Why did you use visking tubing

To act as a semi-permeable membrane

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How did you know osmosis had taken place

The final mass of the visking tubing was heavier than the initial mass

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Describe the osmosis experiment

Cut 2 pieces of visking tubing
Tie one end of both
Fill one with sucrose solution (sugar) and water
Fill other with water
Use weighing scales to get initial mass
Place each in separate beakers
After 20 mins remove, dry and re-weigh for final mass

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Outline the conclusion of this experiment

Visking tubing with sucrose solution increased in size by osmosis
Final mass increased when compared to initial mass

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Effect of varying light intensity on photosynthesis

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Where in the cell does the dark stage take place

Chloroplast

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Why is stage called the dark stage

Because it doesn't require light

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Name a plant that you used for this investigation

Elodea

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Give a specific reason for using this plant

It can survive under water
Produces bubbles of oxygen gas

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How did you measure the rate of photosynthesis

The number of bubbles counted every minute

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Name an enzyme that you used in this investigation

Catalase

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State the source of this enzyme

Celery

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How did you vary light intensity

Move the lamp closer or further from the elodea

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Sketch a graph to show the rate of photosynthesis

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Explain the shape of your graph

As the light increases, the rate of photosynthesis increases
The rate levels off due to light saturation
The plant has reached its maximum rate of photosynthesis

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State the precise role of carbon dioxide in photosynthesis

Supply carbon to produce glucose

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State the precise role of water in photosynthesis

To supply protons and electrons

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State a factor that remained constant

Carbon dioxide levels

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How did you keep carbon dioxide constant

Saturate the water with sodium bicarbonate

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State another factor that you kept constant

Temperature

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How did you ensured it remained constant

Used a water bath

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Identify any five fauna and any five flora using simple keys. Identify a variety of habitats within the selected ecosystem

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Give one example of a possible error in ecological surveying

Miscounting

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Suggest how this error might be minimised

Recount
Double check answer with another person counting also

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Why is ecological surveying important

Monitors for biodiversity
Detects any potential problems such as pollution

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Distinguish between terms of habitat and ecosystem

Habitat - where an organism lives
Ecosystem - organisms interacting with their environment

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How were you able to identify the animals that you found in an ecosystem

A key

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Name 5 plants in the ecosystem that you studied (Grassland)

Dasies
Grass
Clover
Dock leaves
Nettles

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Name 5 animals in the ecosystem you studied (Grassland)

Ladybirds
Greenfly
Spider
Slug
Mice

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Name the different pieces of apparatus used to collect plants and animals in an ecosystem

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Pooter

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How is a pooter used

Used to suck organisms into a jar

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What is a pooter used to collect

Spiders
Insects

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Draw a diagram of a pooter trap

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Beating Tray

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How is a beating tray used

Placed under a bush/hedge/tree
Shake bush/hedge/tree
Note insects that fall onto the tray

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What is a beating tray used to collect

Spiders
Insects
Caterpillars

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Draw a diagram of a beating tray trap

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Pitfall Trap

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How is a pitfall trap used

Hole is made in the ground
Covered to stop rain entering

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What is a pitfall trap used to collect

Insects
Snails

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Draw a diagram of a pitfall trap

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Mammal Trap

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How is a mammal trap used

Bait is placed in a box
Has a trap door which allows animals in but not out

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What is a mammal trap used to collect

Shrews
Mice

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Draw a diagram of a mammal trap

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Cryptozoic Trap

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How is a cryptozoic trap used

A piece of wood / log is placed on the ground and left for some time
Collects animals that prefer dark or moist conditions

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What is a cryptozoic trap used to collect

Slugs
Snails
Worms

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Draw a diagram of a cryptozoic trap

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Conduct a quantitative study of the plants in an ecosystem

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Describe how you carried out a quantitative survey of a named plant species

Species - Daisies (or any flora)

Throw a pencil over your shoulder for random selection
Place a quadrant where the pencil lands and count the number of daisies
Repeat this process 9 more times to get an average
Put results into a table and graph the percentage cover of the daisies

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Name and describe another method for a quantitative study of plants in an ecosystem

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Describe how you carried out a qualitative study an ecosystem

Line Transect Experiment

A rope is marked at intervals
Each interval is known as a station
The type of plant touching each station along the rope is recorded

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Conduct a quantitative study of animals in an ecosystem

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Describe how you carried out a quantitative study of a named animal species

Capture-recapture Method
Species - Snail

Set up a pitfall trap
Leave for 24 hours (overnight)
Come back and count the snails present in the pitfall trap
Mark the snails with a non-toxic paint and release them
Return the following day and count the snails again
Count and record the amount of new snails and previously marked snails
Use the formula Count 1 x Count 2 to find the total population of snails

Already marked on count 2

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Draw a diagram of the pitfall trap

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Investigate 3 abiotic factors present in the selected ecosystem

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Name 3 abiotic factors

Any of the following :

Rainwater
Wind
Light
Water
pH

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How did you measure a named abiotic factor other than temperature or pH

Water

Used a rain gauge

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UNIT 3

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Investigate the growth of leaf yeast using agar plates

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Name the fungus, other than yeast, that you have studied

Rhizopus

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Give two ways in which this fungus differs from yeast

Rhizopus is multicellular, yeast is unicellular
Rhizopus has hyphea, yeast does not

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Name two aseptic techniques to ensure a pathogen free environment

Wash lab bench with disinfectant
Flame tweezers
Wear gloves

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What type of agar is most appropriate for the growth of yeast and other fungi

Malt agar

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Describe how the plates were stored from introduction of fungi until the fungi was visible

Stored the correct side up for 24 hours
Then upside down in an incubator at 25 degrees for 5 days

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How did you identify the leaf yeast on the agar

Pink colonies

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Name the type of leaf used

Sycamore leaf

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What is the control used

Unopened petri dish

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Suggest a reason why few or no yeast may have grown on the agar

The time of year

Leaf yeast is more plentiful in the summer months than in the winter
This is due to temperature conditions being warmer in the summer for optimum enzyme activity

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What is the principle nutrient added to the agar for the yeast

Malt

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How did you introduce the yeast into the petri dish

Flame tweezers to sterilise
Attach the leaf to lid using vaseline
Replace the lid

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Are fungi eukaryotic or prokaryotic

Eukaryotic

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What is the purpose of using agar plates when growing fungi or bacteria in a lab

A source of nutrients

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How did you safely dispose of the plates at the end of the investigation

Soaked in disinfectant

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Draw a graph to show how the number of leaf yeasts varied following their introduction into the plate

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Dissect, display and identify a sheep`s heart

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When dissecting a mammalian heart, where, precisely, did you locate the tricuspid valve

Between the right atrium and the right ventricle

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Briefly describe how you carried out the dissection to expose this valve

Cut through the right side of the heart using a scalpel

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Where did you find the semi-lunar valves during the dissection

At the base of the aorta and pulmonary artery

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Name the cavity in which the heart and lings are located

Thoracic cavity

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State one way in which the heart muscles differ from other muscles in the body

Heart muscle doesn't tire

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Describe the steps that you followed in order to identify and display the inner structures of the heart

Identify the front and the back
Wearing gloves - use a scalpel to cut the righthand side to view the right atrium and right ventricle
Cut the left hand side to view the left atrium and left ventricle

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Cardiac muscle is described as a contractile tissue, explain the meaning of contractile

It can shorten, or contract

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Which chamber of the heart has the greatest amount of muscle in its wall and state why

Left ventricle

Because this chamber pumps blood around the entire body (except the lungs)

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What is the function of the semi-lunar valve

Prevent the backflow of blood into the heart

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Where in your dissection did you find the origin of the coronary artery

At the aorta

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Investigate the affect of exercise on the breathing rate or pulse rate of a human

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What is a pulse

The expansion of an artery

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What makes the wrist or neck a suitable part of the body to detect a pulse

The arteries are near the surface

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What is the control in this investigation

The resting pulse rate

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What is the purpose of this control

For comparison

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How is recovery time measured

Immediately start counting the pulse after the exercise
Measure the length of time until resting rate is reached

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Prepare and examine the T.S of a dicot stem

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What is meant by the term dicotyledonous (dicot)

Two seed leaves present

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Name the plant you used to examine a dicot stem

Celery

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Why must a very thin section be examined

To allow light to pass through in order to view the cells clearly

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Describe two steps you undertook to cut the stem safely

Use a scalpel
Cut away from the body

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How did you transfer the section to the microscope slide

Use a paintbrush or tweezers

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Name the part of the microscope to bring the dicot into sharp focus

Fine focus wheel

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Draw a labelled diagram of the section you observed under the microscope

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How to monocot and dicot stems differ

Monocots vascular bundles are scattered, dicots are circular

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Why is a herbaceous stem used rather than a woody one

It is softer, making it easier to cut

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Investigate the affect of IAA growth regulator on plant tissue

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What was the purpose of the serial dilution of the IAA solution

To make different concentrations of IAA

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Why did you place the seeds on a grid in petri dishes

To measure the shoot and root growth more accurately

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Describe how you carried out the investigation into the affect of IAA on plant tissue

Expose seeds to different concentrations of IAA
Have one set of seeds with no IAA (control group)
Leave for 5 days
Measure the growth
Compare to control

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What were the results of your investigation

The higher the IAA concentration - the greater the shoot growth
The lower the IAA concentration - the greater the root growth

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Name the growth regulator used when investigating plant growth

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What is a tropism

A growth response to a stimulus

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What is a plant growth regulator

Controls the growth of a plant

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Name the plant tissue used for the investigation

Raddish seeds

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Name the control used in this investigation

Water or no IAA

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Give an example of a growth regulator that promotes growth

Auxin

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Give an example of a growth regulator that inhibits growth

Auxin

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Name a safety procedure carried out

Use gloves and goggles

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Investigate the effect of water, oxygen and temperature on germination

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How did you ensure an oxygen free environment

Put oil over the boiled and cooled water

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How did you determine germination had taken place

Roots and shoots were observed

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Describe the composition of a triglyceride molecule

Three fatty acids and a glycerol

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Explain what is meant by the term dormancy in seeds

A period of low metabolism in which little or no growth activity occurs

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Name a part of the seed in which food for germination is stored

Cotyledon or endosperm

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Name the three factors necessary for seeds to germinate

Water
Oxygen
Suitable temperature

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Why were the seeds sterillised

To kill any microorganisms

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How did you demonstrate oxygen is necessary for germination

Removed oxygen (using boiled water and oil) and compare to seeds with oxygen

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What is meant by germination

The growth of a seed

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Use starch agar or skimmed milk plates to show digestive activity during germination

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How does digestion contribute to successful seed germination

To make nutrients soluble for the embryo

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Name a type of enzyme in the seed that carries out this digestion

Amylase

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Why were the seeds soaked in water at the start of the investigation

To soften the testa and metabolic activity

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Why were the seeds sterillised

To kill all microorganisms

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Why was the split seeds placed open side down on the agar

To expose the enzyme to the substrate (starch)

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How did you know that digestive activity has not occurred

No clear areas
Blue/black present everywhere

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Give a reason why digestive activity had not occurred

The enzyme (amylase) had been denatured