All Prescribed Practicals

Question 1

Using a light microscope to examine and identify the structures of a typical plant and animal cell and record them in a drawing

(6)

Answer 1

• peel thin layer of onion epidermis;
• place (onion) epidermis on (microscope) slide
• stain with iodine
• lower coverslip onto the slide/lower coverslip using a mounted needle/
  forceps
• place slide onto stage of microscope
• focus/turn coarse focus knob/turn knob to focus

Question 2

Investigating the need for light and chlorophyll in photosynthesis

(In A)

Question 3

Investigating the energy content of food by burning food samples

(In A)

Question 4

Investigating the effect of temperature on the action of an enzyme

(on DA)

Question 5

Investigating factors affecting the respiration of yeast

(Temperature and type of sugar)

(8)

Answer 5

For temperature:

• mix yeast and glucose with 100cm³ of boiled and cooled water in a beaker
• leave at room temp for an hour
• fill a small test tube with the mixture
• place a boiling tube upside down over the small test tube containing the yeast mixture and quickly invert both tubes
• place the tubes in a water bath at 10ºC
• measure the height of the bubble at the top of the inner small tube
• measure the height again 30 minutes later
• repeat at different temperatures

For different sugars:

Repeat the experiment at a constant temperature but use different sugars

Question 6

Using quadrats to investigate the abundance of plants and animals in a habitat with:

1. A largely similar habitat
2. A changing habitat

(5)

Answer 6

1. Similar

Random sampling:

• place two measuring tapes at right angles to mark the area to be sampled
• use a random number generator to select 5 sets of coordinates to sample
• place a 1m² quadrat at each coordinate and count the number of each plant / estimate / calculate percentage cover
• using a key to identify them
• record results

2. Changing

Belt transect sampling:

Largely the same, but place quadrats at regular intervals along the line

Question 7

Investigate the process of osmosis by measuring the change in length or mass of plant tissue or model cells using Visking Tubing

(on DA)

Question 8

Use a potometer (bubble and weight potometer) to investigate the factors affecting the rate of water uptake by a plant

(on DA)

Question 9

Investigate the effect of different chemicals or antibiotic discs on the growth of bacteria

Question 10

Practical 1.1: how do you make structures in the cell more evident?

Answer 10

By staining with iodine solution

Question 11

What does an anemometer measure?

Answer 11

Wind speed

Question 12

Practical 2.2: why is the potometer set up underwater?

Answer 12

To prevent the formation of air bubbles

Question 13

What name is given to enzymes that work at a wide range of temperatures?

Answer 13

Thermostable enzymes

Question 14

Practical 1.1: what is the name of the glass applied to the slide?

Answer 14

Coverslip

Question 15

Practical 1.5: what apparatus is used to investigate the respiration of yeast? (5)

Answer 15

• a water bath
• containing a boiling tube
• containing an inverted test tube
• containing yeast and glucose solution
• a thermometer

Question 16

Practical 1.6: what are the two forms of sampling? When are they used?

What apparatus is used?

Answer 16

• belt transect sampling: in a habitat with a gradual change in each species
• random sampling: where the habitat is largely the same

• quadrats
• a measuring tape vertically and horizontally
• possibly a number generator (random sampling)

Question 17

Use the washing line method to investigate the factors affecting the rate of water loss from leaves

(6)

Answer 17

• take 6 leaves off a tree
• smear petroleum jelly over the cut stalks to make them waterproof
• measure the mass of each leaf
• hang the leaves using paper clips on a line of string between 2 retort stands
• suspend half of the leaves at a high temp and the other half at a lower temp
• after 24 hours, reweigh the leaves and calculate the average loss of mass for each condition

Question 18

Describe Benedict’s test and colour changes.

What does it test for?

(3)

Answer 18

• Add Benedict’s solution to the food and heat in a water bath.
• Changes from blue-black to brick red
• in the presence of small sugars

Question 19

Describe the Biuret test and colour changes

What does it test for?

Answer 19

• Sodium hydroxide and copper sulfate mixed together.
• Changes from blue to purple
• proteins

Question 20

Describe the test for lipids and colour changes.

(3)

Answer 20

• Mix the fat with ethanol to dissolve some of it,
• then add it to water.
• Changes from clear to cloudy white