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A2 BIOLOGY > 4.2 Plant reproduction > Flashcards

4.2 Plant reproduction Flashcards

1
Q

what is an angiosperm

A

plants that produce flowers

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2
Q

what is the reproductive organ of an angiosperm

A

flower

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3
Q

label an angiosperm

A
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4
Q

what is the stamen

A

male reproductive organs

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5
Q

what does the stamen contain

A

anther and filament

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6
Q

what is the carpel

A

female reproductive organ

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7
Q

what does the carpel consist of

A

stigma
style
ovary

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8
Q

function of sepal

A

protects the flower when in bud

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9
Q

function of receptacle

A

the thickened part of the cell, from which the flower grows

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10
Q

function of corolla

A

a ring of colourful petals inside the sepal

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11
Q

function of the nectary

A

found at the base of the flower, releases scented nectar to attract pollinators such as insects

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12
Q

function of petals

A

in insect pollinated plants they are colourful and have scent to attract insects

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13
Q

function of stamen

A

male parts
made of an anther and attached to a long filament

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14
Q

function of anther

A

pollen grains are produced inside 4 pollen sacs by meiosis

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15
Q

function of the filament

A

contains vascular tissue, which transports mineral ions and water to the developing pollen grains

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16
Q

function of the carpel

A

female parts
made of the stigma, style and ovary

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16
Q

function of ovules

A

made inside the ovary
contain an egg cell formed by meiosis

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16
Q

what is a calyx

A

a collection of sepals

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17
Q

are most adult flowers haploid or diploid

A

diploid

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18
Q

where does meiosis occur

A

within their reproductive tissues to make haploid spores

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19
Q

what are male spores also known as

A

pollen grains

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20
Q

what happens to pollen grains during pollination

A

each pollen grain produces 2 male gametes

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21
Q

what are female spores called

A

ovules

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22
Q

what do the ovule contain

A

the female gamete called the egg cell nucleus

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23
Q

definition:
pollination

A

the transfer of pollen grains from anther to the stigma of plant of the same species

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24
Q

insect pollinated vs wind pollinated
(6 comparisons)

A
  1. colourful petals, sometimes nectar guides vs usually no petals or small green and inconspicuous
  2. scent and nectar vs no scent or nectar
  3. anthers within the flowers vs anthers hanging outside flower
  4. stigma within the flower vs large, feathery stigmas hanging outside of flower
  5. small quantities of sticky, sculptured pollen produced vs large quantities of pollen produced
  6. produces larger pollen grains vs produces smaller pollen grains
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25
Q

what is the benefit of plants having anthers that hang outside the flower

A

pollen is caught easier

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26
Q

benefit of sticky sculptures pollen for pollination

A

will stick to insects

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27
Q

DEFINITION
self-pollination

A

pollen is transferred from the anthers of one flower to the stigmas of the same flower/another flower of the same plant

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28
Q

DEFINITION
cross-pollination

A

pollen transferred from the anthers of one flower to the stigmas of a different flower of the same species

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29
Q

consequences of self-pollination

A

-results in inbreeding
- reduces genetic variation in the population
-increases chances of infavourable double recessive alleles
-depends upon random assortment of chromosomes and crossing over during meiosis and mutations to bring about variations

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30
Q

advantages of self-pollination

A

preserves good genomes which are suited for a stable environment

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31
Q

advantages of cross-pollination

A
  • greater variation
    -reduces the chance of producing harmful allele combinations
    -greater evolutionary significance
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32
Q

what does having greater evolutionary significance mean

A

more different combinations of alleles means some members of a population are more likely to survive if the environment changes (natural selection)

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33
Q

3 ways plants reduce self-pollination

A

-stamen and stigma ripen at different times of the year
- the anthers are below the stigmas so the pollen cannot fall onto it
-separate male and female flowers on the same plant

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34
Q

what is protandry

A

where the stamens ripen first

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35
Q

what is protogyny

A

stigma ripens first

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36
Q

label cross section of male gamete (anther)

A
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37
Q

what is the tapetum

A

layer of cells surrounding the pollen sacs

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38
Q

function of tapetum

A

provides nutrients to the developing pollen grains
protects the pollen grains from chemicals, UV light and drying out

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39
Q

what does an anther contain

A

4 pollen sacs (in pairs) which is where the pollen grains develop

40
Q

what are found in the pollen grains

A

male gametes

41
Q

what do pollen sacs contain

A

diploid pollen mother cells

42
Q

what are large number of pollen mother cells produced by

A

mitosis

43
Q

what happens to each pollen mother cell

A

meiosis to form 4 pollen grains

44
Q

what happens to young pollen grains

A

exit in groups callled tetrads

45
Q

explain how male gametes end up as seperate pollen grains

A

pollen mother cell (d) undergo meiosis 1, then meiosis 2 until there’s a tetrad of 4 haploid pollen cells. then there’s a secretion of walls and separate pollen grains are left

46
Q

label a mature pollen grain

A
47
Q

what happens to the nucleus of a mature pollen grain

A

divides by mitosis to form 2 nuclei

48
Q

explain dehiscence

A

when pollen is mature, anthers outer layers dry out, this causes tension in lateral grooves and dehiscence occurs
pollen sacs burst exposing the pollen grains into the air

49
Q

explain ovule development
-within the ovary

A
  • one or more ovules develop, the main body of the ovule is called the nucellus
50
Q

explain ovule development
- within the nucellus

A

there is a diploid megaspore mother cell surrounded by an embryo sac (provides nutrients)
the megaspore mother cells undergoes meiosis to form 4 haploid cells

51
Q

ovule development
-after the 4 haploid cells are formed

A

of the 4, 3 of these disintegrate, the remaining megaspore cells undergoes 3 rounds of mitosis to produce 8 haploid nuclei (n)
2 of the haploid nuclei fuse to form one diploid nucleus called the polar nucleus (2n)

52
Q
A
53
Q

ovule development
- what happens at the micropyle end of the embryo sac

A
  • 3 of the haploid nuclei migrate towards the micropyle end of the embryo sac
  • the central nucleus is the female gamete (egg cell/ oosphere)
  • the 2 nuclei adjacent to the cell are called the synergids
54
Q

role of synergids

A

play a role in pollen tube guidance during fertilisation

55
Q

ovule development
-end furthest from the micropyle

A
  • the 3 nuclei furthest from the micropyle form antipodal cells
    -antipodal cells are thought to play a role in embryo nutrition as seeds germinate into seedlings
56
Q

what does double fertilisation invovle

A

2 male gametes in 2 separate fertilisation events

57
Q

what are the 2 fertilisation events

A

fertilisation of female gamete to form a diploid zygote and fertilisation of the polar nuclei to form a triploid endosperm nucelus

58
Q

explain the first step of double fertilisation

A
  • pollen grain lands on stigma and absorbs water. if pollen grain and stigma are compatible, the pollen grain will germinate
59
Q

what will the stigma contain

A
  • a sticky sugary solution, allows pollen grain to adhere and provides nutrition
60
Q

double fertilisation
what happens after the pollen grain germinates

A

pollen tube will be produced, at the tip of this is a male tube nucleus and behind it is the generative nucleus

61
Q

double fertilisation
role of the tube nucleus

A

controls the growth of the pollen tube

62
Q

double fertilisation
what is found behind the tube nucleus

A

generative nucleus

63
Q

double fertilisation
what happens as the the pollen tube grows and during germination

A

the generative nucleus undergoes mitosis to form 2 nuclei (male gametes)

64
Q

double fertilisation
what does the pollen tube nucleus code for

A

the synthesis of hydrolase enzymes (cellulase and protease)

65
Q

double fertilisation
describe the growth of pollen tube

A

grows out of the pollen grain through a gap in the cell wall called the pit. it grows against a gradient of chemo attractants (e.g GABA) from the ovules

66
Q

double fertilisation
what type of response is the growth of the pollen tube

A

positive chemotrophic response, the pollen tube grows towards chemicals secreted by the embryo sac

67
Q

double fertilisation
what does the pollen tube do after growing against the gradients

A

digests its way down the style,
pollen tube continues to grow through the micropyle and into the embryo sac

68
Q

double fertilisation
what are the products of digestion used for

A

used by the growing pollen tubes

69
Q

double fertilisation
after the pollen tube grows through the micropyle and into the embryo sac, what happens to the tube nucleus

A

it disintegrates as it is no longer needed

70
Q

double fertilisation
what happens to the tip of the pollen tube after the tube nucleus disintegrates

A

the tip of the pollen tube opens to release the two male gametes ( generative nuclei into the embryo sac)

71
Q

double fertilisation
what happens after the 2 male gametes are released

A

one of the male gametes fuse with the female gamete (egg cell) to form a diploid zygote (2n)
the other male gamete fuses with the diploid polar nuclei to form a triploid endosperm nucleus (3n)

72
Q

double fertilisation
what happens to synergids and antipodal cells

A

they play no further role

73
Q

summary of double fertilisation

A
  1. generative nucleus (n) + polar nucleus (2n) = endosperm nucleus (3n)
  2. generative nucleus (n) + egg cell nucleus (n) = zygote (2n)
74
Q

seed and fruit development
what does the fertilised ovule develop into

A

a seed

75
Q

what happens within a seed

A

the diploid zygote divides by mitosis to become the embryo

76
Q

what does the embryon consist of

A

the plumule
the radicle
one/two cotyledons

77
Q

what is the plumule
radicle
cotyledon

A

developing shoot
developing root
seed leaves

78
Q

what is the testa

A

the outer coat, the integument hardens

79
Q

monocot vs dicot

A

dicotyledon has 2 seed leaves (cotyledon) e.g broad bean. they are endospermic
monocotyledon has 1 cotyledon e.g. maize

80
Q

explain cereal grains

A

are a monocot
remain as food store because they’re endospermic. remain small as seeds become dormant when active growth is suspended. germination will only happen when specific conditions are met

81
Q

what would happen if seeds fell close to parent plant

A
  • parent plant would be more successful at obtaining water and minerals from soil.
  • parent plant would be taller and cast shade on seedling (lack of photosynthesis)
  • seedling would be out-competed
82
Q

explain how seeds have developed for dispersal of seeds

A

seeds have evolved as a survival strategy for a terrestrial mode of life
plants have developed different mechanisms to enable the dispersal of seeds which reduces competition following germination and increases the chances of growth into mature plants, also allows the colonisation of new habitats

83
Q

different methods of seed dispersal

A

rolling
wind
transport
carrying
bursting

84
Q

seeds and survival

A

seeds can remain dormant for very long times, dormant seeds have very low metabolic rates. the testa is chemically resistant (to allow seeds to survive adverse chemical conditions)
dormant seeds have a water content below 10%
the cotyledons of the endosperm provide nutrients to the seed until germination when the seedling photosynthesise

85
Q

definition
germination

A

is the biochemical and physiological process through which a seed becomes a photosynthesising plant

86
Q

what is needed for germination

A

suitable temp- enzymes to work best (synoptic)
water- mobilise enzymes (synoptic)
oxygen- aerobic respiration (links)
light/dark- some species germinate in the light, some in the dark

87
Q

germination in a non-endospermic seed
(broad bean/ dicotyledon)

A
  • cotyledons have absorbed the food reserves, the seed imbibes water through the micropyle
88
Q

what is imbibing

A

means to absorbs water through ultramicroscopic

89
Q

germination in a non-endospermic seed
(broad bean/ dicotyledon)
what happens after the seed imbibes water

A

the cotyledons swell, the testa splits to allow entry of more oxygen for hydrolysis.
food reserves from the cotyledons, starch and proteins are mobilised through hydrolysis into soluble products

90
Q

what happens to these soluble products after they are hydrolysed

A

transported to the embryo and carried in the phloem to the apical (lots of mitosis) meristem of the plumule and radicle

91
Q

germination in a non-endospermic seed
(broad bean/ dicotyledon)
what happens in the plumule and radicle

A

rapid cell division, some sugars are converted to cellulose for cell walls, aerobic respiration releases energy from sugars and amino acids to synthesise new proteins (CO2 produced)

92
Q

germination in endospermic seed (e,g, maize)

A

following imbibition of wate, giberellin is released by the embryo

93
Q

what is maize

A

a monocotyledon, its food reserves are stored within the endosperm

94
Q

what is giberellin

A

is a plant growth regulator

95
Q

germination in endospermic seed (e,g, maize)
what does gibberellin do

A

diffused to the aleurone layer which contains proteins. it switches on genes in the aleurone layer to synthesis amylase and protease

96
Q

germination in endospermic seed (e,g, maize)
what do the amino acids produces in the aleurone layer used for

A

used to synthesise amylase. amylase diffuses from the aleurone layer into the endosperm to hydrolyse starch.

97
Q

germination in endospermic seed (e,g, maize)
what is the job of the maltose and glucose that are produced

A

they diffuse into the radicle and plumule of the embryo. in the emrbyo they are used in aerobic respiration and growth i.e. brings the seed out of dormancy

98
Q

explain the growth of the radicle and plumule in a DICOT

A

radicle is positive geotrophic and negative phototrophic = grow downwards
plumule is positively phototrophic and negatively geotrophic =grows upwards

99
Q

graph

A

A2 BIOLOGY (6 decks)

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