B2- Organisms in the Environment

Question 1

The equation for photosynthesis is…

Answer 1

Carbon dioxide + water ➡️glucose + oxygen.

Question 2

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

Answer 2

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

Question 3

Describe the 3 processes of photosynthesis.

Answer 3

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 4

How can plant growers improve plant growth?

Answer 4

Artificially controlling the environment:

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

Question 5

Define dependent variable.

Answer 5

Variable being measured.

Question 6

How can quantitative data be obtained?

Answer 6

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

Question 7

How are leaves well adapted for photosynthesis?

Answer 7

• 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 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

What is a transect?

Answer 9

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 10

How can leaves be tested for presence of starch?

Answer 10

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

Question 11

How do plants use glucose?

Answer 11

• 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 12

What are the three limiting factors of photosynthesis?

Answer 12

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

Question 13

Define independent variable.

Answer 13

Variable being tested.

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

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

Answer 15

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