Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Biology mark schemes, High school final essays of Biology

Biology

For questions in biology now for you

Typology: High school final essays

2024/2025

Uploaded on 04/19/2026

james-roberts-2
james-roberts-2 ๐Ÿ‡ฌ๐Ÿ‡ง

9 documents

1 / 6

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Q1.
(a)๎˜„๎˜„๎˜„๎˜„ Describe the mass flow hypothesis for the mechanism of translocation in plants.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
(4)
Scientists measured translocation in the phloem of trees. They used carbon dioxide
labelled with radioactive 14C.
They put a large, clear plastic bag over the leaves and branches of each tree and added
14CO2. The main trunk of the tree was not in the plastic bag.
At regular intervals after adding the 14CO2 to the bag, the scientists measured the amount
of 14CO2 released from the top and bottom of the main trunk of the tree. On the surface of
the trunk of these trees, there are pores for gas exchange.
The following figure shows the scientistsโ€™ results.
๎˜„
๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„๎˜„ Time after 14C labelled CO2 given / hours
(b)๎˜„๎˜„๎˜„๎˜„ Name the process that produced the 14CO2 released from the trunk.
___________________________________________________________________
(1)
Page 1 of 6
pf3
pf4
pf5

Partial preview of the text

Download Biology mark schemes and more High school final essays Biology in PDF only on Docsity!

Q1.

(a) Describe the mass flow hypothesis for the mechanism of translocation in plants.

(4) Scientists measured translocation in the phloem of trees. They used carbon dioxide labelled with radioactive 14 C. They put a large, clear plastic bag over the leaves and branches of each tree and added (^14) CO 2. The main trunk of the tree was not in the plastic bag. At regular intervals after adding the 14 CO 2 to the bag, the scientists measured the amount of 14 CO 2 released from the top and bottom of the main trunk of the tree. On the surface of the trunk of these trees, there are pores for gas exchange. The following figure shows the scientistsโ€™ results. Time after 14 C labelled CO 2 given / hours (b) Name the process that produced the 14 CO 2 released from the trunk.

(1)

(c) How long did it take the 14 C label to get from the top of the trunk to the bottom of the trunk? Explain how you reached your answer.

(2) (d) What other information is required in order to calculate the mean rate of movement of the 14 C down the trunk?

(1) (Total 8 marks)

Q2.

(a) Scientists measured the rate of water flow and the pressure in the xylem in a small branch. Their results are shown in the graph. (i) Use your knowledge of transpiration to explain the changes in the rate of flow in the xylem shown in the graph.

______________________________________________________________

______________________________________________________________

______________________________________________________________

(1) (c) Describe how tissue fluid is formed and how it is returned to the circulatory system.

(6) (Total 15 marks)

Mark schemes

Q1.

(a) 1. In source / leaf sugars actively transported into phloem;

  1. By companion cells;
  2. Lowers water potential of sieve cell / tube and water enters by osmosis;
  3. Increase in pressure causes mass movement (towards sink / root);
  4. Sugars used / converted in root for respiration for storage. Accept starch 4 max (b) Respiration. 1 (c) 1. (About) 30 hours;
  5. Time between peak 14 C at top of trunk and bottom. 2 (d) Length of trunk (between top and bottom). 1 [8]

Q2.

(a) (i) 1. Stomata open; Allow converse

  1. Transpiration highest around mid-day as middle of day warmer / lighter; 2. Allow โ€˜Sun is at its hottestโ€™
  2. (Increased) tension / water potential gradient; Ignore โ€˜pull, suckโ€™ 3 (ii) (Inside xylem) lower than atmospheric pressure / (water is under) tension; Accept cohesion tension. Ignore vacuum 1 (b) (i) High pressure / smoothes out blood flow / artery wall contains more collagen / muscle / elastic (fibres) / connective tissue; Accept converse for pulmonary vein Incorrect function of artery disqualifies mark 1 (ii) 1. (Aorta wall) stretches because ventricle / heart contracts / systole / pressure increases; 1. Allow expand
  3. (Aorta wall) recoils because ventricle relaxes / heart relaxes / diastole / pressure falls;