B2- Organisms in the Environment

Question 1

How can leaves be tested for presence of starch?

Answer 1

Iodine test- The iodine will turn blue-black on a leaf where starch is present.

Question 2

Describe the 3 processes of photosynthesis.

Answer 2

1. CO₂ taken in by leaves, water taken up by roots.
2. Chlorophyll traps light energy needed for photosynthesis.
3. This energy is used to convert CO₂ + water to glucose.

Question 3

How are leaves well adapted for photosynthesis?

Answer 3

• Large surface area to absorb light and CO_2.
• Flat shape therefore short diffusion distance.
• Many chloroplasts in palisade layer to trap maximum amount of light.
• Lots of stomata to allow CO₂ to diffuse into cell for use in photosynthesis.

Question 4

What are the three limiting factors of photosynthesis?

Answer 4

• Light (Intensity).
• Temperature.
• CO₂ Concentration.

Question 5

The equation for photosynthesis is…

Answer 5

Carbon dioxide + water ➡️glucose + oxygen.

Question 6

How do plants use glucose?

Answer 6

• Respiration.
• Converted into insoluble starch/fats and oils for storage.
• Growth➡️Cellulose for cell wall.
• Growth➡️To produce proteins➡️Need nitrates from soil to make proteins.

Question 7

How can plant growers improve plant growth?

Answer 7

Artificially controlling the environment:

• Greenhouses with heaters and lamps.
• Adding CO₂ to the air.
• Adding nitrate ions to the soil.

Question 8

The distribution of organisms is affected by environmental factors such as…

Answer 8

• Temperature.
• Availability of nutrients.
• Amount of light.
• Availability of water.
• Availability of oxygen.
• Availability of CO_2.

Question 9

Define independent variable.

Answer 9

Variable being tested.

Question 10

Define dependent variable.

Answer 10

Variable being measured.

Question 11

Describe how one should sample a plant from two habitats to collect valid data. (2 marks)

Answer 11

Use of quadrant (1) randomly placed (1).

Question 12

“The difference in the modes is due to the plants receiving different amounts of sunlight.”

Suggest how students can test this hypothesis (2 marks).

Answer 12

Light meter (1).

Take measurements at same time of the day (1).

Question 13

How can quantitative data be obtained?

Answer 13

• Random quantitative sampling using a quadrat.
• Sampling along a transect.

Question 14

What is a quadrat?

Answer 14

A square frame made of metal or wood which may be subdivided into a grid. If several quadrants are placed randomly in a field the investigator can count the number of a particular type of plant or animal in each quadrat.

Question 15

What is a transect?

Answer 15

A transect is not random. A line is marked between two points. This method supplies a lot of information about the habitat and the organisms in it.

Question 16

Plants need energy to make glucose. How do plants get this energy? (2 marks)

Answer 16

Photosynthesis- plants use light energy trapped by the chlorophyll in chloroplasts to change carbon dioxide and water into glucose (and oxygen).