| Date | November 2018 | Marks available | 2 | Reference code | 18N.2.SL.TZ0.3 |
| Level | Standard level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
| Command term | Suggest | Question number | 3 | Adapted from | N/A |
Question
Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world’s forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.
Identify the dominant plant phylum in the boreal forest.
In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this.
An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.
The boreal forests are situated close to the north pole and even in summer the intensity of sunlight is lower than at the equator. Sketch a graph showing the effect of light on the rate of photosynthesis, labelling the axes.
Markscheme
coniferophyta/conifer/coniferous/gymnosperms/pinophyta ✔
a. waterlogged soil/poor drainage
OR
acidic soil
OR
anaerobic conditions/soil ✔
b. organic matter is not «fully» decomposed «leading to peat formation»
OR
decomposers/saprotrophs less active/fewer in cold «temperatures» ✔
a. higher temperatures so more transpiration/droughts/dehydration/water shortage ✔
b. more forest fires ✔
c. more/new pests/diseases because of the changed conditions ✔
d. competition from trees/plants «that colonize/spread to boreal forests» ✔
e. trees/«named» organisms «of boreal forests» not adapted to warmer conditions
OR
trees/«named» organisms migrate/extend range due to the warmer conditions ✔
f. trees die so there is loss of habitat for animals ✔
g. faster decomposition/nutrient cycling «so conditions in the ecosystem change» ✔
h. standing water/floods due to more snow/permafrost melting ✔
a. x-axis labelled as light intensity/amount of light AND y-axis labelled as rate of photosynthesis/rate of oxygen release/rate of carbon dioxide uptake ✔
b. curve starting at/slightly to the right of the x-axis origin and rising rapidly and then more slowly and plateauing but never dropping ✔
Examiners report
Syllabus sections
-
21M.2.HL.TZ2.3a:
On the diagram, label the testa and the radicle.
- 17M.2.HL.TZ2.1b: Identify the relationship between the concentration of auxin and the age of the different...
- 18N.2.HL.TZ0.8b: Describe the roles of the shoot apex in the growth of plants.
- 17M.3.HL.TZ2.1a: In order to form galls, the insects choose a location where cell division occurs at a high...
- 18N.2.HL.TZ0.4b: In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to...
- 17M.1.SL.TZ1.1: Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C....
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18M.1.HL.TZ2.30:
The image shows seedlings that have been exposed to unidirectional light.
[Source: The Micro Gardener (https://themicrogardener.com/prevent-fix-leggy-seedlings/)]
Which statement explains the growth towards the light source?
A. Light causes auxin to inhibit cell division in the shoot meristem.
B. Light causes auxin to promote cell division in the shoot meristem.
C. Auxin is concentrated in the side of the shoot with light and inhibits cell elongation.
D. Auxin is concentrated in the side of the shoot without light and promotes cell elongation.
- 17M.2.HL.TZ2.1e: Based on all the data presented and your knowledge of auxin, discuss the pattern of auxin...
- 17M.2.HL.TZ2.1d.i: Compare and contrast the changes in auxin concentration in the stem base over time for the...
- 17M.2.HL.TZ2.1c: Analyse the effect of NPA on the formation of roots.
-
22M.1.HL.TZ2.33:
The picture shows lentils sprouts growing towards a light source from the left.
[Source: Russell Neches, Lentil sprouts reaching for the sun [image online] Available at https://www.flickr.com/photos/rneches/2081938105/ This file is licensed under
the Creative Commons Attribution 2.0 Generic (CC BY 2.0)
https://creativecommons.org/licenses/by/2.0/.]How has this response been brought about?
A. A higher concentration of auxins on the light side caused faster photosynthesis.
B. A higher concentration of auxins on the shaded side caused faster meiosis.
C. A higher concentration of auxins on the shaded side caused faster cell elongation.
D. A higher concentration of chloroplasts on the light side allowed for more photosynthesis.
- 20N.1.HL.TZ0.33: How does auxin exert its effect on plant cells? A. Acts directly on the cell wall, causing...
- 17M.2.HL.TZ2.1d.ii: Deduce the effect of NPA on auxin transport between L6 and the stem base.
- 22M.1.HL.TZ1.34: What is an aspect of indeterminate growth in plants? A. The shoot apex retains...
- 21M.1.HL.TZ1.40: Expansin is a plant protein that loosens connections between cellulose fibres in plant cell...
-
21M.2.HL.TZ1.6b:
Outline how the hormone auxin controls phototropism in plant shoots.
- 17M.2.HL.TZ2.1f.iii: The scientists concluded that auxin activates the transcription of the GH3 gene. Using the...
-
16N.1.HL.TZ0.34:
What is/are the effect(s) of auxin in plants?
I. Increasing the rate of cell elongation in stems
II. Changing the pattern of gene expression in shoot cells
III. Detecting the direction of lightA. I only
B. I and II only
C. II and III only
D. I, II and III -
19M.1.HL.TZ2.39:
The photomicrograph shows a section through the top of a plant shoot.
[Source: Charles Good: The Ohio State University at Lima]
What are the structures labelled X and Y?
- 17M.2.HL.TZ2.1a: Calculate the difference in the concentration of auxin found in L1 and L6. . . . . . . . . ....
- 19N.2.HL.TZ0.8b: Outline the growth of plant shoot apex.
-
17M.2.HL.TZ2.1f.ii:
Compare the pattern of GH3 transcription with the pattern of auxin concentration in the stem base control cuttings. You may use the table provided to help you to record the patterns before you compare them. (Please note: a simple
comparison in the table will not gain marks)
- 21M.1.HL.TZ2.34: How does auxin contribute to phototropism? A. It increases production of light-sensitive...
-
21N.2.HL.TZ0.5c:
Outline the extension of the stem in plants.
-
21N.1.HL.TZ1.33:
The diagram shows a plant shoot and the direction of the light which the shoot received.
[Source: USDA-NRCS PLANTS Database. Available at: https://commons.wikimedia.org/wiki/File:Alnus_seedling_drawing.png
[Accessed 30 November 2021].]What are the direction of movement and the effect of auxin in the tip of a plant shoot when receiving light from one side?
