Organisms in the Environment

Question 1

Which organisms can carry out photosynthesis?

Answer 1

Only green plants and algae

Question 2

What is the word equation of photosynthesis?

Answer 2

carbon dioxide + water (+ light energy) → glucose + oxygen

Question 3

What is the process of photosynthesis?

Answer 3

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

Question 4

What role do choloroplasts play in photosynthesis?

Answer 4

They contain cholorphyll which absorbs the Sun’s light energy

Question 5

What is released as a by-product of photosynthesis?

Answer 5

Oxygen

Question 6

What is some of the glucose produced by photosynthesis converted into?

Answer 6

Insoluble starch so it can be stored

Question 7

How can show that photosynthesis has occured in a leaf?

Answer 7

• Iodine can be used to test for starch.
• Variegated leaves have patches of green (with cholorphyll) and white (without cholorphyll)
• Only green patches will turn the iodine solution blue-black to show the presence of starch
• Starch shows that photosynthesis has taken place because it is made of some of the glucose created that has been stored by the plant

Question 8

What does variegated mean?

Answer 8

Having different colours

Question 9

What is a limiting factor?

Answer 9

Something that limits the rate of photosynthesis

Question 10

If you want to find out the effect of a certain limiting factor what must you also be aware of?

Answer 10

Other limiting factors that can effect the plant

You should make sure to control these factors in your experiment

Question 11

What is the independant variable?

Answer 11

The one being tested

Question 12

What is the dependant variable?

Answer 12

The one that you measure

It is the one that changes due to the independant variable changing (although not always…

Question 13

Give some examples of limiting factors for photosynthesis and why they limit it

Answer 13

• Light - slows down process as it provides the energy for it. May be limited to plants that are in the shade
• Cold - enzymes do not work effectively
• Too little CO₂ - needed for process to take place. Mya be due to plant being in an enclosed space

Question 14

Draw three graphs showing the effect of CO₂ concentration, light intensity, and temperature on the rate of photosynthesis

Answer 14

Question 15

What are the uses of soluble glucose?

Answer 15

• Can be converted into insoluble starch to be stored
• Used for respiration
• Converted into fats + oils to be stored
• Used to produce cellulose which strengthens cell walls
• Used to produce proteins

Question 16

Why do plant and algal cells also need a supply of mineral ions and nitrate ions?

Answer 16

In order to make proteins

Question 17

How do plants absorb nitrate ions?

Answer 17

From the soil (with their roots)

Question 18

How do algae absorb nitrate ions?

Answer 18

From the water they live in

Question 19

How do plant growers try to give their plants the best conditions for growth?

Answer 19

By controlling the environment and limiting factors of photosynthesis

Question 20

How can greenhouses and polytunnels be used by plant growers and what are the advantages + disadvantages of them?

Answer 20

• If the greenhouse has lamps or heaters the rate of growth may increase. However, this may stop is the light intensity/temperature is too high
• Carbon dioxide can be added to the air to increase the growth rate.
• Nitrate ions can be added to the soil to ensure plants can make the proteins they need for healthy growth

Question 21

How might a plant grower evaluate the effectiveness of using greenhouses or polytunnels?

Answer 21

By comparing the biomass of plants grown indoors and outdoors

Question 22

What physical factors may affect the distribution of organisms?

Answer 22

• Temperature - Arctic plants are small, limiting the number of plant eaters that can survive in that area
• Availability of nutrients - Most plants struggle to grow where there are few mineral ions. This also limits the number of animals
• Amount of light - Few plants live on the forest floor because light is blocked out by trees. Shaded plants have broader leaves or more cholorphyll
• Availability of water
• Availability of oxygen
• Availability of CO₂

Question 23

How can quantitative data be obtained?

Answer 23

• Random quantitive sampling using a quadrat
• Sampling along a transect

Question 24

What is quantitive sampling?

Answer 24

Sampling which records the numbers of organisms not just the types

Question 25

What is a quadrat?

Answer 25

An aparatus used for sampling

It is a square frame made of metal or wood which may be subdivided into a grid

Question 26

How can quadrats be used?

Answer 26

They can be placed randomly or along a transect

The number of organisms in the quadrats can then be counted and used to estimate the number of orgamisms in that particular area

(e.g. daisies in a field)

Question 27

Why is sample size important?

Answer 27

In a large field, enough random quadrats must be placed in otder to be sure the sample is representative of the whole field

Question 28

What is a transect?

Answer 28

A measured line along which ecological measurements are made

It is not random

Question 29

Aside from the number of organisms, what can also be measured at each point along a transect?

Answer 29

The physical factors

Question 30

Why is using a transect a good way of colelcting data and why might using one be better than random sampling?

Answer 30

Supplies a lot of information about the habitat and the organsisms in it

(e.g. can also be used to measure physical factors and compare how distribution changes along the transect)

Question 31

Why can investigations about the distribution of organisms in their environment be difficult?

Answer 31

They are often done over a long period of time

Not all variables can be controlled

Question 32

Complete the sentence:

In a valid investigation, all…

Answer 32

…possible variables must be controlled

Question 33

What does valid mean?

Answer 33

Suitablity of an investigative proceedure to test a hypothesis

Question 34

What does repeatable mean?

Answer 34

The origional experimenter repeats the experiment using the same method + equipment and gets the same results

Question 35

What does reproducable mean?

Answer 35

The experiment can be carried out by a different person or with different equipment and the same results can be produced

Question 36

Why is sample size an important factor in obtaining valib, repeatable, and reproducable data?

Answer 36

If it is too small it may not be representative

Question 37

What makes data/an investigation valib/reliable?

Answer 37

• Validity - controlling all possible variables
• Repeatability - the same person repeats it with the same equipment and gets the same results
• Reproducability - different people repeat the experiment or different equipment is used the the same results are obtained