Survival and Response MS Flashcards
Q1.(a) Give one similarity and one difference between a taxis and a tropism.
(2)
- Similarity − directional response (to a stimulus) / movement
towards / away from a stimulus; - Difference − taxis (whole) organism moves and tropism a growth
(response).
Must be clear which one, taxis or tropism, they are referring
to
Taxis occurs in animals / motile organisms and tropism
occurs in plants
Scientists investigated tropisms in the roots of tomato plants. They grew tomato
plants from seeds on vertical agar plates, as shown in Figure 1. The top of each
plate was made of agar gel containing no salt. The bottom of each plate was made
of one of the following:
• agar gel containing no salt
• agar gel containing salt.
Typical results for growth of the roots are shown in Figure 1.
(b) What do these results show about the responses of the roots of tomato plants to
gravity and salt? (3)
- Grow in direction of / towards (pull of) gravity;
Accept: tropism for growth
Ignore: pulled by gravity
Accept: positively geotropic / gravitropic - Grow away from salt;
Accept: negatively chemotropic / halotropic
1 and 2. Ignore: references to bends / moves - Salt has more effect (than gravity).
Accept: converse statement for gravity
Note: all three points may appear in one sentence
Explain why this root tip would grow away from salt.
3
(c) 1. More carriers in (cell) L / lower in R;
Accept: left for L and right for R / side nearer salt for L
- (So) less IAA in (cell) L / more IAA in (cell) R;
Accept: more IAA moves out of L / less IAA moves out of R - (So) more (elongation) growth in L / less (elongation) growth in R.
Accept: less inhibition of growth in L / more inhibition of
growth in R;
(a) The biologist concluded that the worms’ behaviour demonstrated taxis.
How do these results support this conclusion?
M2.(a) 1. (Taxis is) movement towards / away from a stimulus / a directional response /
movement (to a stimulus);
- (Move towards) temperature they were used to / cultured in;
Movement towards temperature they were used to = 2 marks
(b) Using the information provided, suggest an explanation for the worms’ behaviour on
the glass surfaces in the absence of food (3)
- Hungry, so seeking food / in absence of food respond to temperature;
Ignore references to temperature and enzymes
Must be stated not inferred from other statements - Move towards temperature they were used to / cultured in;
- Associate (this temperature) with food;
Accept they think food is here
Stated not inferred - (Then) stay in this temperature;
c) In each experiment, the biologist exposed the surfaces to light that was dim and
even, so he could see where the worms went.
Apart from seeing where the worms went, suggest two reasons why it was
important that the light was dim and even. (2)
- (Dim) worms live in soil / dark / affected by bright light / dim light is like
normal environment / what they are used to; - (Even) because worms might move towards / away from bright light / to
avoid creating light gradient / prevent worms showing phototaxis / all
parts of surface exposed to same light;
Accept to avoid kinesis due to light - (Dim light) ensures heat from light not a variable / heat from lamp could
kill / dry out worms;
Not just to control variables / factors
(a) In the test plot of land, identify the push stimulus and the pull stimulus (1)
Push – legume
Pull – grass;
(b) When measuring the mean percentage damage to maize plants, 60 plants from
each test plot were selected at random and examined.
Describe how the maize plants could be selected at random. (3)
- Set up tape measures on two sides of the plot / make grid of plot;
Allow ‘Number each plant’. With this approach mp3 cannot
be awarded. - Use random number table / calculator / generator;
Allow ‘Select from a hat’ idea. - To generate coordinates;
(c) In the test plot, bare ground was left between the maize and the grass species.
Suggest an explanation why. (2)
- To prevent competition between the maize and the grass;
- For light / nutrients / water;
OR - Idea of limits movement of pest (between grass and maize);
- Only eating / damaging grass;
d) The legume plants have nodules containing nitrogen-fixing bacteria on their roots.
Explain how nitrogen-fixing bacteria could increase the growth of the maize (2)
- Nitrogen-fixing bacteria convert nitrogen (in the air) into ammonium
compounds (in the soil) which are converted into nitrates / nitrification
occurs;
Accept ‘ammonia’ for ‘ammonium compounds’. - Maize uses nitrates (in soil) for amino acid / protein / ATP / nucleotide
production; - Must be in the context of maize.
Ignore ionic formulae unless only these are given.
(e) A year after this investigation, the government of one country decided that their
farmers should use these push-pull stimuli.
How do these data support this decision? (3)
- Reduced % damage to maize plants / increased maize grain yield;
- Calculation to justify mp 1;
- Standard deviation shows no overlap but need stats to show significance
of this difference; - More profit / net income / greater income than additional cost (with
push-pull); - $322 extra / 408% more / $401 v $79 profit;
Accept ‘$350 extra income compared to $28 extra spend’.
Mp5 gains credit for both mp4 and 5
(a) Describe three changes in the root tip cells between stages A and D.
(3)
M4.(a) Three changes described;;;
Neutral nucleus shrinks, since it doesn’t
Eg
1. Formation / growth of vacuole;
2. Formation of starch grains / amyloplasts;
2. Accept starch grains get bigger
3. Movement of grains / amyloplasts towards bottom of cell;
Note − list rule applies
4. Cells get longer / wider / larger;
(b) The scientists’ hypothesis was that there was a relationship between the starch
grains in the root tip cells and the bending and direction of growth of lateral roots.
Does the information in the diagram support this hypothesis? Give reasons for your
answer. (3)
- Grows sideways before starch grains form;
Q - Bending starts when / as grains form;
- More bending as grains increase in number;
- Ignore starch grain growth references
- More elongation (of cells) / growth (of roots) downwards as starch
grains increase / move; - Bending starts before grains move down;
- Could be related to vacuole;
- Ignore references to nucleus
c) The diagram shows the distribution of indoleacetic acid (IAA) in the lateral root at Stage B (2)
Explain how this distribution of IAA causes the root to bend.
- (IAA) at bottom of root / where IAA concentration high inhibits expansion
/ elongation (of cells);
2 and 3 need reference to expansion / elongation, not just
growth - (IAA) at top of root / where IAA concentration low leads to expansion /
elongation (of cells); - Accept less inhibition
(a) The pea seedlings were kept in the dark after each treatment. Explain why this was
necessary (1)
(a) 1. (Seedlings) respond to light / are phototropic;
Reject: roots are positively phototropic / grow towards light
OR
Neutral: ‘to control a variable’
- (Only) measuring the effect of gravity / response to gravity;
Neutral: light affects growth / results
