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Assessment Schedule PLANT REPRODUCTION
AS 90463 Describe diversity in the structure and function of plants [Bio 2.7] 2007
Question
Achievement
1
Describes the adaptations of three
plant groups. Minimum of three
adaptations per group.
Descriptions –
 Can be sentences, notes, or
labelled diagrams
 Need to use correct biological
terms
As for Achieved linked to a
reason [relates to purpose,
habitat, niche].
Eg
Mosses
 Small plants dependent on moist
habitats. The green leafy plant is
the gametophyte.
 Gametophyte is the dominant
phase in the life cycle of the
moss plant.
 Gametophyte is n
 Separate sex organs form at tips
of leafy mature plant – antheridia
[male] and archegonia [female]
 Sperm has a flagellum and swims
in water.
 Zygote develops into sporophyte
2n
 Sporangia form and meiosis
produces spores inside
 Sporangia has peristome teeth to
release mature spores.
 Many light spores produced
 Spores grow into thread like
protonema which buds off male
and female moss plants.
Eg
Ferns
 Larger plants than mosses [have
vascular /support tissues] but still
dependent on moisture for
fertilization. Large leafy plant is
the sporophyte.
 Gametophyte [n] much reduced
[approx 1cm2] to a leaf like
prothallus amongst the rhizoids.
 On the underside of the
prothallus are the antheridia and
archegonia.
 Sperm has flagellum for
swimming.
Achievement with Merit
Achievement with
Excellence
Marking Key:
 = describes adaptation
Explanations need to be
sentences; could be annotated
diagrams. Accuracy is needed not
just broad generalisations.
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Gametes formed by mitosis –
sperm and egg /ovum
Sperm follows chemical trail
to fertilize egg [=
chemotaxis]; dependent on
moist environment for
fertilization.
Sporophyte develops and is
parasitic on the [female]
gametophyte
Meiosis reduces the
chromosome number to n in
spore formation
Teeth dry out and separate to
fling the spores into the air.
Spores are light for wind
dispersal. Many produced to
maximise chances of finding
moist habitat to germinate.
Germination of the spores
restores the gametophyte
generation.
The n gametophyte
generation is now reduced in
importance.
The archegonia and antheridia
produce gametes as for
mosses.
Fertilization occurs as for
mosses.
Sporophyte lives independent
of the gametophyte, unlike the
parasitic moss.
The sporophyte generation is
now the dominant one.
(structures and function)
R# = Reason how/why
plant carries out
process is linked to
adaptation
A# = meets Achievement
standard for one
plant group
2
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Zygote grows through the
prothallus into the sporophyte
[2n].
Sporophyte forms the large plant
with fronds, rhizome, rhizoids.
Sori form on the underside of the
fronds.
Thickened cell layer the annulus
acts to release the spores.
Spores germinate and form the
prothallus.
Angiosperms
 Most successful plant group,
completely adapted to terrestrial
habitat. Sophisticated vascular
system; also leaves. Reproduce
using flowers; seeds. Animals as
pollinators. Gametophyte now
only a few cells.
 Gametophyte [n] microscopic – a
few cells within the sporophyte
[2n].
 Flowers may have :
o Sepals
o Petals
o Nectaries
o Scent glands
o Stamen with anther and
filament [male]
o Carpels with stigma,
style, ovary [female]
 Male gametophyte within pollen
grain
 Pollen may be light or heavy
/sticky; produced in large or
small amounts
 Female gametophyte within the
ovary
 Fertilization occurs after
pollination with a pollen tube
growing down the style and
entering the ovary through the
micropyle [small opening]
 Seeds dispersed by varied means
 Seed dormancy may occur
 Germination occurs only in
favourable conditions
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Sori contain the spore forming
sporangia. Spores [n] form
through meiosis.
The annulus cells dry out and
abruptly tear open the capsule
throwing the spores out and
dispersing them.
The gametophyte generation
is restored.
Gametophyte is now protected
by the sporophyte which is
completely dominant.
Sepals protect the bud
Petals are large /showy to
attract animal pollinators
Nectaries sugary to attract
pollinators [eg bees]
Scent gland produces perfume
to attract pollinators
Anther produces the pollen;
filament holds anther up to
release pollen from flower.
Stigma is sticky to trap pollen;
style holds stigma up for
pollination; ovary contains the
ovule.
Male gametophyte is 3 nuclei
- 1 controls formation of the
pollen tube; 1 fuses with polar
nuclei to form endosperm;
other fertilises the egg
Lots of light pollen produced
if wind pollination to increase
success of blowing to suitable
flower; little amounts heavy
/sticky produced for animal
pollination as success rates
higher as carried stuck to
animal.
Female gametophyte is of 7
cells and 8 nuclei. The largest
cell has 2 nuclei [polar nuclei]
that will fuse with 1 male
nucleus to make the
endosperm – the food reserve.
Another cell with nucleus is
the egg which will be
fertilized to form the seed.
Fertilization forms the zygote
[2n] which grows into the
seed.
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Seeds may be dispersed by
wind, animals, water,
explosion – spread reduces
competition
May enter dormancy awaiting
favourable conditions for
germination
Germination needs warmth,
water, O2 to begin growth into
the new [sporophyte] plant.
Discussion has evidence of in depth explanations linking biological ideas into extended paragraphs
[bullet points are not a discussion]. The discussion could :
 Justify similarities
 Evaluate the differences
 Analyse reasons for adaptations related to habitat /niche
Possible areas to discuss :
• significance of the increasing dominance of the sporophyte generation,
• the significance of the mechanisms to increase genetic variability within the species,
• complexity of floral structures relevant to increasing specialisation of pollination,
• sperm / flagellated gametes suitable in a wet environment,
• wind pollination suitable in windy environment when large numbers of the species are present, etc.
Eg
Reproduction in plants characterized by ‘alternation of generations’ in which gametophyte (gamete
producing plant) and sporophyte (spore producing plant) alternate. In mosses the gametophyte is
dominant; in angiosperms it is the sporophyte – this reflects the transition from dependency on water [for
fertilization] to becoming a completely terrestrial living.
Eg
Flowering plants that rely on animals for pollination need to attract their pollinators. Bees see blue, yellow
and ultra-violet well, so bee pollinated flowers tend to have showy petals in these colours. They may even
have “honey guides” marked on white petals with UV pigment to lead the bee into the flower. Birds see
red colours best, so bird pollinated flowers have petals that are red, orange or yellow eg kowhai. As the
birds and bees tend to visit one flower after another, this is an efficient way of ensuring pollination and
good rates of seed set.
Unlike bird and bee pollinated flowers, wind pollinated flowers do not need to attract a pollinator they do
not need to have petals and can save energy and resources to produce more pollen or seeds to increase the
chance of successful reproduction and survival. This strategy works well in a barren, windswept
environment where insects find it hard to fly and where there is not enough food for birds. Bees and
insects would both work better than wind in an enclosed community like a forest, and birds would be
better than insects on a windy coastline.
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Sufficiency Statement
Achievement
Description for EACH plant
group that describes how the
plant carries out the process
through description of structures
and associated functions.
Achievement with Merit
Explanation gives REASONS
for how the plant carries out the
process, linked to structures and
function, in at least TWO named
plant groups.
Achievement with Excellence
A discussion of the REASONS
for DIVERSITY of structures
and functions that enable plant
groups to live in their
environment. Diversity in at
least TWO plant groups.
3 Descriptions for each plant
group (A1+ A2+ A3)
Achieved plus Merit for TWO
plants (A1+ A2+ A3+ 2xM)
As for Merit PLUS :
A candidate must demonstrate an
understanding of the general purpose
of the overall process.
A discussion of the reasons for
diversity/differences shown across at
least 2 plant groups. Eg a discussion of
the evolutionary significance of the
differences, the reduction in
competition due to occupation of
different niches/habitats/envts, the
significance of the changes in the
process related to the
niche/habitats/environment., etc
Compare and contrast at least 2 plant
groups.