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25 Cards in this Set

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Outline the potential harmful effects of increased carbon dioxide concentration on the ecosystem and state one measure that could be taken to reduce the amount of carbon dioxide in the atmosphere. (6)
effect: [5]

global warming/causing the earth to be warmer;
leads to range/altitude shifts of species;
increased competition;
rising of sea levels affects coastal ecosystems;
melting ice caps leads to changes in salinity/upwelling/currents;
increased frequency of coral bleaching;
changes in weather patterns / climate could affect biome distribution in long-run;
increased microbe activity in permafrost;
rapid ecological change favours emergent pathogens/pest species;

measure: [1]

carbon dioxide absorption by photosynthesis must be encouraged / avoid deforestation /
induce reforestation / nutrients in oceans to induce growth of algae / burning of fossils
fuels must be reduced / use of solar energy / insulating homes / any other suitable
measure;
Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack.
Suggest advantages that vascular tissue confers. (3)
a. would make it easier to stand upright (against gravity)/structural support / allows (angiospermophytes) to be bigger;
b. could put leaves higher in the air to get more sunlight;
c. transport of water supply/nutrients from roots to other tissues;
d. could (more efficiently) transport/translocate sugars/food from leaves for storage;
X - palisade mesophyll/layer
Y - guard cells
Z - vascular bundle/tissue / xylem (vessel)
Outline two adaptations of xerophytes that help to reduce transpiration from the leaves.
a. reduced/few leaves/needles to lower surface area;
b. rolled leaves to increase humidity around stomata;
c. spines to collect water;
d. waxy cuticle;
e. fewer stomata/closing of stomata;
f. stomata in pits to increase humidity;
g. CAM metabolism so stomata can remain closed during light;
h. C4 photosynthesis so stomata can remain closed during light;
Outline pollination, fertilization and seed dispersal. (4)
a. pollination is the transfer of pollen to the stigma/carpel/pistil of a flower;
b. pollen grains grow a pollen tube down the style to the ovule;
c. male and female gametes/nuclei join/fuse (in the ovule/ovary) during fertilization;
d. the ovary matures into a fruit;
e. dispersal of seeds depends on the fruit;
f. example of seed dispersal (e.g. pods split open to scatter seeds, animal eats fruit / ingests and egests seed)
Explain how water is moved from roots to leaves in terrestrial plants (8)
a. water enters roots through the root hairs by osmosis;
b. root hairs provide an extended surface area (for active transport and osmosis);
c. active transport of ions from soil into the roots (enhances osmotic pressure);
d. osmotic pressure moves water into the xylem;
e. water is carried (in a transpiration stream) in the xylem;
f. adhesion of water to the inside of the xylem helps move water up;
g. cohesion of water to itself enhances water movement up the xylem;
h. water diffuses into air spaces (in spongy mesophyll) of leaves;
i. it passes out through the stomata by evaporation/transpiration;
j. evaporation sets up a transpiration pull that keeps the water moving;
k. guard cells control the rate of transpiration pull/evaporation;
l. xylem vessels are tubes with helical rings to enhance water movement/resist low pressure;
Explain the light-independent reactions of photosynthesis. (9)
take place in the stroma of the chloroplast;
CO is fixed to form a carbohydrate;
ribulose bisphosphate/RuBP is a five carbon compound;
carbon dioxide fixed/added to RuBP / carboxylation;
by RuBP carboxylase (enzyme)/Rubisco;
forms unstable six carbon compound;
this splits into (two molecules of) glycerate-3-phosphate/GP;
ATP and NADPH produced in light-dependent reaction;
ATP provides the energy;
GP reduced to triose phosphate/TP;
NADPH provides hydrogen;
some three carbon sugars go to form hexose sugars;
some go to making more RuBP;
this requires ATP;
called the Calvin (Benson) cycle;
Describe the differences in the structures of dicotyledonous plants and monocotyledonous plants (5)
monocotyledon seeds contain one cotyledon/seed leaf;
dicotyledon seeds contain two cotyledons/seed leaves;
monocotyledons have parallel veins;
dicotyledons have net-like veins;
monocotyledon stems have scattered vascular bundles;
dicotyledon stems have vascular bundles around edge;
monocotyledon roots are adventitious/fibrous;
dicotyledon roots are from radicle/tap root/branched;
monocotyledon flower parts/petals are (usually) in threes;
dicotyledon flower parts/petals are (usually) in fours or fives;
Define the term transpiration and explain the factors that can affect transpiration in a typical terrestrial plant. (9)
(transpiration is) loss of water vapour from the leaves/stomata (and stems) of plants;

temperature, humidity, light (intensity) and wind all affect transpiration;

high temperatures increase evaporation rate of water/transpiration;

high humidity lowers the rate of water evaporation/transpiration;

air currents/wind increase water evaporation/transpiration;

high light (intensity)/sunlight (usually) increases photosynthesis/water evaporation through the stomata/transpiration;

stomata open to allow gaseous exchange/entry of CO2;
abscisic acid stimulates closing of stomata;
guard cells open/close the stomata;

adaptations of (xerophyte) plant structures reduce water loss/transpiration;
one example;
(thicker leaf cuticle / reduced surface area/rolled leaves/spines /sunken/reduced stomata / close stomata in day / low growth form / CAM / C4 physiology)
second example; (of above)
Explain the role of auxin in phototropism. (8)
auxin is a plant hormone;
produced by the tip of the stem/shoot tip;
causes transport of hydrogen ions from cytoplasm to cell wall;
decrease in pH / H+ pumping breaks bonds between cell wall fibres;
makes cell walls flexible/extensible/plastic/softens cell walls;
auxin makes cells enlarge/grow;
gene expression also altered by auxin to promote cell growth;
(positive) phototropism is growth towards light;
shoot tip senses direction of (brightest) light;
auxin moved to side of stem with least light/darker side causes cells on dark side to elongate/cells on dark side grow faster;
Outline the light-dependent reactions of photosynthesis. (6)
(chlorophyll/antenna) in photosystem II absorbs light;
absorbing light/photoactivation produces an excited/high energy/free electron;
electron passed along a series of carriers;
reduction of NADP / generates NADPH H ;
absorption of light in photosystem II provides electron for photosystem I;
photolysis of water produces 2 H+ /O ;
called non-cyclic photophosphorylation;
in cyclic photophosphorylation electron returns to chlorophyll;
generates ATP by H+ pumped across thylakoid membrane / by chemiosmosis /
through ATP synthetase/synthase;
Explain the effect of light intensity and temperature on the rate of photosynthesis. (8)
both light and temperature can be limiting factors;
other factors can be limiting;
graph showing increase and plateau with increasing light / description of this;
graph showing increase and decrease with increasing temperature / description of
this;

light:
affects the light-dependent stage;
at low intensities insufficient ATP;
and insufficient NADPH H produced;
this stops the Calvin cycle operating (at maximum rate);

temperature:
affects light-independent stage / Calvin cycle;
temperature affects enzyme activity;
less active at low temperatures / maximum rate at high temperatures;
but will then be denatured (as temperature rises further);
Outline the cellular locations of different named processes in both photosynthesis and cell respiration. (6)
photosynthesis: [3 max]
chloroplasts/photosystems: for light absorption/photosynthesis;
stroma: light-independent reactions / Calvin cycle;
thylakoid membranes of chloroplast: chemiosmosis / photophosphorylation/light dependent reactions;
thylakoid space: build up H+ concentration gradient;
inner membrane of thylakoid: electron transfer;
inner membrane: ATP synthesis;

cell respiration: [3 max]
mitochondria: for ATP production/aerobic respiration;
cytoplasm: glycolysis / matrix: Krebs cycle/oxidative phosphorylation/link reaction;
double / inner membranes of mitochondria: chemiosmosis / oxidative phosphorylation;
intermembrane space: build-up H+ concentration gradient;
inner membrane of mitochondria:
Explain the role of limiting factors in photosynthesis. (8)
a. factor nearest its minimum/furthest from its optimum is limiting;
b. increasing a limiting factor with other factors constant increases the rate;
c. increasing a non-limiting factor with other factors constant has no effect on
rate;
d. light intensity is limiting in dim/low intensity light / at night;
e. photosynthesis (directly) proportional to intensity up to plateau / graph to
show this;
f. light intensity affects the light-dependent reactions/production of ATP/NADPH;
g. temperature limiting at low and high temperatures;
h. optimum temperature with lower rates above and below plateau / graph to
show this;
i. low temperatures limit the rate of light-independent reactions/Calvin cycle;
j. RuBP carboxylase/rubisco does not fix carbon dioxide at high temperatures;
k. carbon dioxide concentration is limiting in bright light and warm temperatures;
l. photosynthesis is (directly) proportional to CO2 concentration up to plateau /graph to show this;
m. low CO2 concentration limits carbon
Explain the relationship between the distribution of tissues in a typical mesophytic leaf and the functions of these tissues. (8)
the function of most leaves is photosynthesis;
they are broad and flat to maximize surface area (to volume ratio);
palisade mesophyll is main photosynthetic tissue;
it is near the surface / densely packed where the light intensity is highest;
the cuticle prevents water loss;
it is thicker on the upper surface where sunlight is more intense;
the spongy mesophyll provides the main gas exchange surface;
the vascular bundle transports materials such as sugars/water/minerals;
it is centrally positioned near all tissues;
xylem conducts water and minerals and phloem conducts sugars/amino acids;
epidermal tissue covers the outside of the leaf and provides protection;
the stomata are sites of water loss;
they are on the lower surface/part of lower epidermis to prevent excessive water
loss;
Describe the process of water uptake and movement in roots. (6)
root hair/root branching/cortex cells add surface area;
plants actively transport minerals from soils;
creating a solute gradient within the root;
that draws water into the root through osmosis which requires no energy;
(most) water travels through the apoplastic pathway/through cell walls;
movement is by capillary action;
some water travels via the symplastic pathway/through cell cytoplasm (and
plasmodesmata);
apoplast water cannot bypass Casparian strip of endodermis;
enters xylem within vascular cylinder/stele;
Describe how plants carry out gas exchange in the leaves. (5)
a. gases/O2 and CO2 enter/exit the leaf through the stomata;
b. by diffusion / down the concentration gradient;
c. photosynthesis maintains concentration gradients/high O2 and low CO2 in
the leaf;
d. guard cells open the stomata during the day / close the stomata at night;
e. gases/O2/CO2 move through air spaces in the spongy (mesophyll);
f. CO2 dissolves in moisture in (mesophyll) cell walls;
Explain how triose phosphate is produced and used in the chloroplasts of a plant. (5)
ribulose bisphosphate/RuBP and carbon dioxide react together;
(this is) carbon fixation/part of light-independent reactions;
catalysed by RuBP carboxylase/Rubisco;
glycerate 3-phosphate/GP produced;
glycerate 3-phosphate/GP reduced/converted to triose phosphate/TP;
using NADPH/(NADPH+H+) and ATP;
from the light-dependent reactions;
some triose phosphate used to regenerate RuBP;
some triose phosphate used to synthesize glucose (phosphate)/starch;
Explain the conditions that are needed to allow a seed to germinate. (8)
water needed to rehydrate the seed;
gibberellin released / active after water absorbed;
gibberellin needed to produce amylase;
water needed to allow substances inside the seedling to be transported;
oxygen needed for (aerobic) cell respiration;
warmth needed to speed up metabolism/enzyme activity;
warmth indicates that it is a favourable season for germination/spring;
some seeds need a cold period to stimulate germination;
some seeds need fire to stimulate germination;
some seeds need to pass through an animal (gut) to stimulate germination;
Outline the adaptations of plant roots for absorption of mineral ions from the soil. (5)
mineral ions are absorbed by active transport;
large surface area;
branching (increases surface area);
root hairs;
root hair cells have carrier protein/ion pumps (in their plasma membrane);
(many) mitochondria in root (hair) cells;
to provide ATP for active transport;
connections with fungi in the soil/fungal hyphae;
Photosynthesis and transpiration occur in leaves. Explain how temperature affects these
processes. (8)
photosynthesis rate increases as temperature rises (up to an optimum temperature);
(due to) increase in the rate of enzyme catalysed reactions/light independent
reactions/the Calvin cycle;
(steep) drop in rate of photosynthesis above the optimum;
at high temperatures enzymes/Rubisco/RuBP carboxylase denature(s);
graph with correctly labelled axes showing relationship between temperature and rate
of photosynthesis;
transpiration rate increases as temperature rises;
(energy/heat leads to more) to more evaporation of water (in the leaf);
faster diffusion of water vapour at higher temperatures;
relative humidity falls as temperature rises / warmer air can hold more water vapour;
stomata may close at very high temperatures reducing the transpiration rate;
some plants open their stomata at very high temperatures to cool by transpiration;
Describe how water is carried by the transpiration stream. (7)
transpiration is water loss (from plant) by evaporation;
flow of water through xylem from roots to leaves is the transpiration stream;
evaporation from spongy mesophyll cells;
replaced by osmosis from the xylem;
(diffusion of water vapour) through stomata;
water lost replaced from xylem / clear diagram showing movement of water from xylem through cell(s) (walls) to air space;
water pulled out of xylem creates suction/low pressure/tension; transpiration pull results;
water molecules stick together/are cohesive;
due to hydrogen bonding/polarity of water molecules;
xylem vessels are thin (hollow) tubes;
adhesion between water and xylem due to polarity of water molecules;
creates continuous column/transpiration stream;
Explain how flowering is controlled in long-day and short-day plants. (7)
flowering affected by light;
phytochrome;
exists in two (interconvertible) forms/Pfr and Pr;
Pr (red absorbing/660 nm) converted to Pfr (far-red/730 nm absorbing) in red or day light;
sunlight contains more red than far red light so Pfr predominates during the day;
gradual reversion of Pfr to Pr occurs in darkness;
Pfr is active form / Pr is inactive form;
in long-day plants, flowering induced by dark periods shorter than a critical length / occurs when day is longer than a critical length;
enough Pfr remains in long-day plants at end of short nights to stimulate flowering;
Pfr acts as promoter of flowering in long-day plants;
short-day plants induced to flower by dark periods longer than a critical length/days shorter than a critical value;
at end of long nights enough Pfr has been converted to Pr to allow flowering to occur;
Pfr acts as inhibitor of flowering in short-day plants;
Using the theory of natural selection, explain how new species of dicotyledonous plants develop. (5)
plants produce huge amounts of pollen/ovules/seeds;
(overproduction) leads to struggle for survival;
variety caused by sexual reproduction;
fertilization is random;
variety caused during meiosis/recombination;
variety caused by mutations;
change in environmental conditions occurs;
plants with the most favourable variations/best suited survive/are selected;
reproduce and pass on (favourable) genes;
in different (environmental) conditions different plants have better/more suited
traits/characteristics so different plants survive;
reference to geographic isolation;
formation of reproductive barriers / isolation;
over time/over many generations new species develop;
Outline the conversion of light energy to chemical energy in photosynthesis. (6)
light energy absorbed by chlorophyll (photo) activates photosystems;
electron in chlorophyll/photosystem activated/excited / raised to higher energy
level;
photolysis of water replaces excited electrons;
energy passed through electron carriers/ETS;
hydrogen/high energy electrons reduce NADP+ ;
photophosphorylation by chemiosmosis;
(some) H+/protons pumped into thylakoid spaces;
proton gradient is created;
energy released as protons pass through ATP synthetase;
ATP produced;
correct reference to (non cyclic or cyclic) photophosphorylation;