paper 2 required practicals

Question 1

What is a quadrat used for?

Answer 1

-To study the distribution of small organisms or estimate population sizes in a specific area.

Question 2

What is meant by ‘abundance’ in ecology?

Answer 2

-The number of individuals of one species in a given area.

Question 3

What do you record in each quadrat?

Answer 3

-The number of organisms of the species you are studying (e.g. daisies), or percentage cover.

Question 4

What is the formula to calculate population size?

Answer 4

-Mean number of organisms per quadrat × total area ÷ area of one quadrat

Question 5

Why is it important to take multiple quadrat samples?

Answer 5

-To calculate a reliable mean and account for random variation.

Question 6

What are the control variables in the quadrat practical?

Answer 6

-Quadrat size, sampling method, and the environmental conditions (if comparing two areas).

Question 7

Describe how you would carry out the quadrat practical to estimate population size of a plant species. (6 marks)

Answer 7

-Place two tape measures at right angles to form a grid over the sample area.
-Use a random number generator to select coordinates on the grid.
-Place a quadrat at each set of random coordinates.
-Count the number of chosen plant species (e.g. daisies) in each quadrat.
-Repeat the process at least 10 times to calculate a mean number per quadrat.
-Multiply the mean by the total number of quadrats that would fit in the area to estimate population size.

Question 8

Independent Variable of the quadrat required practical

Answer 8

-The location where the quadrat is placed (e.g. sunlit vs. shaded area, or distance along a transect).

Question 9

Dependent Variable of the quadrat required practical

Answer 9

• The number of organisms (e.g. daisies) or the percentage cover of the species within each quadrat.

Question 10

What is a transect?

Answer 10

-A straight line across a habitat along which samples are taken to study how the distribution of a species changes.

Question 11

When do we use a transect instead of random sampling?

Answer 11

-When we want to see how a factor (like light, moisture, or shade) affects the distribution of organisms across a gradient.

Question 12

How do you set up a transect?

Answer 12

-Lay a tape measure (transect line) across the area you want to study — e.g. from a path into a field.

Question 13

How do you sample along a transect?

Answer 13

-Place quadrats at regular intervals (e.g. every 1 m) along the tape.

Question 14

What do you record in each quadrat along the transect?

Answer 14

-The number of a specific species (e.g. daisies) or percentage cover.

Question 15

What might you measure alongside the species distribution?

Answer 15

-An abiotic factor (e.g. light intensity, soil moisture) at each quadrat point.

Question 16

Why do you repeat the transect in other areas?

Answer 16

-To improve reliability and identify patterns across different parts of the habitat.

Question 17

Describe how you would use a transect to investigate the effect of a factor on plant distribution. (6 marks)

Answer 17

-Place a tape measure in a straight line across the habitat you want to investigate.
-Place a quadrat at regular intervals (e.g. every 1 metre) along the line.
-In each quadrat, count the number of the plant species being studied or estimate percentage cover.
-Measure the abiotic factor at each quadrat position (e.g. light intensity using a light meter).
-Repeat the transect in different areas to improve reliability.
-Analyse how the number of organisms changes in relation to the abiotic factor across the transect.

Question 18

Independent Variable for the transect practical

Answer 18

-The distance along the transect line or environmental gradient (e.g. distance from a path or hedge).

Question 19

Dependent Variable for the transect practical

Answer 19

-The number of organisms or percentage cover of a plant species in each quadrat.

Question 20

Control Variables for the transect practical

Answer 20

-Size of the quadrat

Question 21

What is the aim of the decay required practical?

Answer 21

• To investigate the effect of temperature on the rate of decay using milk, lipase, and phenolphthalein.

Question 22

What indicator is used and why?

Answer 22

-Phenolphthalein, which is pink in alkaline solutions and turns colourless when the pH decreases due to fatty acid release.

Question 23

What enzyme is used and what does it do?

Answer 23

• Lipase – it breaks down lipids (fats) into fatty acids and glycerol.

Question 24

What causes the colour change in the solution?

Answer 24

• The production of fatty acids from lipid breakdown lowers the pH, making the solution lose its pink colour.

Question 25

What is being measured to determine the rate of decay?

Answer 25

-The time it takes for the pink colour to disappear.

Question 26

Why is the solution placed in a water bath?

Answer 26

-To keep the reaction mixture at a specific temperature for each test.

Question 27

Why are temperatures repeated?

Answer 27

-To compare how the rate of decay changes with different temperatures and identify the optimum.

Question 28

Describe how to carry out the investigating decay practical. (6 marks)

Answer 28

-Label test tubes with different temperatures and set up water baths (e.g. 20°C, 30°C, 40°C, etc.). -Add 5 cm³ of lipase solution to one test tube and 5 cm³ of milk, 5 drops of phenolphthalein, and 7 cm³ of sodium carbonate to another. -Place both tubes in the same water bath and wait until they reach the target temperature. -Mix the contents of both tubes in one test tube and start the timer immediately. -Stop the timer when the solution loses its pink colour, indicating the pH has dropped. -Repeat at different temperatures and compare results to determine the effect of temperature on the rate of decay.

Question 29

Independent Variable of the decay practical

Answer 29

- Temperature of the water bath.

Question 30

Dependent Variable of the decay practical

Answer 30

- Time taken for the pink colour to disappear (i.e. rate of decay).

Question 31

Control Variables of the decay practical

Answer 31

-Volume of lipase solution and milk solution used. -Concentration of lipase and sodium carbonate. -Volume of phenolphthalein indicator.