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A LEVEL BIOLOGY > 8 - Sexual Reproduction in Plants (C2) > Flashcards

8 - Sexual Reproduction in Plants (C2) Flashcards

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1
Q

What do the haploid spores contain?

A

Gametes

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2
Q

What are the male spores and where are they produced?

A

Pollen grains, produced in the anther

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3
Q

What is the female spore and where is it produced?

A

The embryo sac, produced in the ovule in the ovary

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4
Q

What is the outermost structure of a plant called which contains the sepals?

A

The calyx

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5
Q

What is the male part of the flower called and what does it contain?

A

The stamen - contains the anther and filament

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6
Q

What is the female part of the flower called and what does it contain?

A

The carpel - contains the stigma, style and ovary

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7
Q

What does the filament contain?

A

Vascular tissue

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8
Q

What does the vascular tissue in the plant do?

A

Transports sucrose, mineral ions and water to the developing pollen grains

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9
Q

What is the main function of the sepals?

A

To protect the flower while they bud

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10
Q

What are the features of insect-pollinated flowers?

A
  • Colourful flowers
  • Scent and nectar
  • Anthers and stigma are within plant
  • Small quantities of sticky, sculptured pollen
  • Larger pollen grains
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11
Q

What are the features of wind-pollinated flowers?

A
  • Petals absent or small and green
  • No scent or nectar
  • Anthers and stigma hang outside plant
  • Large quantities of smooth pollen
  • Smaller pollen grains
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12
Q

Why do the anthers of wind-pollinated plants hang outside the flower?

A

So the wind can blow away the small, smooth and light pollen

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13
Q

Why do the stigmas of wind-pollinated plants hang outside the flower?

A

To provide a large SA for catching pollen grains that are blown into their path

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14
Q

What is the tapetum?

A

A layer of cells around the pollen sac

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15
Q

What is the function of the tapetum?

A

Provides nutrients and regulatory molecules to the developing pollen grains

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16
Q

What are features of the pollen cell wall?

A
  • Tough
  • Resistant to chemicals
  • Resistant to desiccation (drying out)
  • UV light can’t penetrate it
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17
Q

Why can’t UV light penetrate the pollen cell wall?

A

To protect the DNA in pollen from mutation

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18
Q

What does the haploid nucleus in the pollen grain undergo mitosis to produce?

A

Two nuclei:

  • Generative nucleus (which produces 2 male nuclei by mitosis)
  • Tube nucleus
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19
Q

What is dehiscence?

A

The opening of the anther, releasing pollen grains

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20
Q

What is the process of the development of the female gamete?

A
  • Megaspore mother cell undergoes meiosis, producing 4 haploid cells
  • 3 disintegrate
  • Remaining cell undergoes mitosis X3, producing 8 haploid nuclei, 1 of which is the female gamete
  • 2 of the haploid nuclei fuse to make a diploid nucleus called the polar nucleus
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21
Q

What is the nucellus?

A

A layer of cells surrounding the nuclei in embryo sac which provides nutrients

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22
Q

What is the name of the two layers of cells that surround the nucellus?

A

The integuments

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23
Q

What is the gap in the integuments called?

A

The micropyle

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24
Q

What does the embryo sac in a mature ovule contain?

A
  • 3 antipodals (haploid)
  • 2 synergids (haploid)
  • 1 oosphere (haploid)
  • 1 polar nucleus (diploid)
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25
Q

What is the definition of pollination?

A

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

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26
Q

What is self-pollination?

A

When pollen from the anthers of a flower is transferred to the mature stigma of the same flower or another flower on the same plant

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27
Q

What is cross-pollination?

A

When pollen from the anthers of a flower is transferred to the mature stigma of another flower on another plant of the same species

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28
Q

What are advantages and disadvantages of self-pollination?

A

+ Preserves successful genomes

  • Less genetic variation
  • Greater chance of 2 potentially harmful recessive alleles being brought together at fertilisation
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29
Q

What are advantages of cross-pollination?

A

+ Genetic variation
+ Allows species to adapt and survive environmental changes
+ Reduces the chances of harmful allele combinations

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30
Q

How is cross-pollination ensured?

A
  • Protandry
  • Anther is below stigma so pollen can’t fall onto it
  • Genetic incompatibility, so pollen can’t germinate on the stigma of the flower which produced it
  • Separate male and female flowers on the same plant
  • Separate male and female plants
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31
Q

What is the definition of fertilisation?

A

The fusion of a female and male gamete, producing a zygote

32
Q

How is the male gamete delivered to the female gamete in plants?

A

By a pollen tube

33
Q

What is the process of double fertilisation?

A
  • When a compatible pollen grain lands on the stigma, it germinates in the sucrose solution secreted by stigma and produces a pollen tube
  • Pollen tube grows out of the pollen grain through a gap in the cell wall, called a pit, down the style and digests its way through the tissues of the style
  • Pollen tube grows through the micropyle into the embryo sac
  • Pollen tube nucleus disintegrates
  • Tip of pollen tube opens, releasing the 2 male gametes into the embryo sac
  • 1 of the male gametes fuses with the female gamete (oosphere) forming a zygote
  • 1 of the male gametes fuses with the diploid polar nucleus forming a triploid nucleus (endosperm nucleus)
34
Q

What is the definition of a fruit?

A

A structure developing from the ovary wall, containing 1 or more seeds

35
Q

What is the definition of a seed?

A

Structure developed from a fertilised ovule containing an embryo and food store enclosed within a testa

36
Q

What is the plumule?

A

The developing shoot

37
Q

What is the radicle?

A

The developing root

38
Q

What are the cotyledons?

A

Seed leaves

39
Q

How do seeds and fruit develop?

A
  • Diploid zygote divides by mitosis, becoming an embryo that consists of a plumule, radicle and 1 or 2 cotyledons
  • Triploid endosperm nucleus develops into a food store
  • Outer integument dries out, hardens and becomes the seed coat / testa
  • Ovule becomes the seed
  • Funicle / stalk, of ovule becomes funicle of seed
  • Ovary becomes the fruit
40
Q

Why does the broad bean have a ‘non-endospermic’ seed?

A

Because the endosperm is absorbed into the cotyledons and is no longer the food store

41
Q

Why are maize seeds ‘endospermic’?

A

The endosperm remains as the food store

42
Q

Why does maize have a one-seeded fruit?

A

Because the testa fuses with the ovary wall

43
Q

What does it mean when seeds are dormant?

A

The active growth of seeds is suspended as germination will only occur under specific conditions

44
Q

What is seed dispersal?

A

The movement of seeds away from the parent plant

45
Q

Why do seeds disperse?

A
  • Ensures the parent plant doesn’t obtain most of the water and nutrients from the soil
  • Ensures seedling isn’t shaded by parent plant, as this would prevent it photosynthesising
46
Q

What is the dispersal method of bursting?

A

When legume pods split and scatter seeds

47
Q

What is the dispersal method of transport?

A

When seeds are passed through the digestive system of birds and dispersed in the faeces

48
Q

What is the dispersal method of water?

A

When seeds fall into water, float and are carried away

49
Q

What are the names of the dispersal methods?

A
  • Wind
  • Transport
  • Rolling
  • Bursting
  • Water
  • Carrying
50
Q

What is the definition of germination?

A

The biochemical and physiological processes through which a seed becomes a photosynthesising plant

51
Q

What are the 3 main requirements for germination?

A
  • Suitable temperature
  • Water (to mobilise enzymes for transport in xylem and phloem, and to vacuolate cells, making them turgid)
  • Oxygen (aerobic respiration releases energy which fuels metabolism and growth)
52
Q

During germination why is the plumule bent over in the shape of a hook?

A

To protect the tip from damage by soil abrasion

53
Q

What is the plant growth regulator secreted by the barley embryo?

A

Gibberellic acid

54
Q

What does gibberellic acid do?

A

Switches on genes in the cells of the aleurone layer, resulting in transcription and translation, producing protease and amylase

55
Q

What does the protease produced by gibberellic acid do?

A

Hydrolyses protein in the aleurone layer to amino acids, which are used to make amylase

56
Q

What does the amylase produced by the gibberellic acid do?

A

Diffuses out of the aleurone layer and hydrolyses the starch stored in the endosperm cells

57
Q

What does the maltose and glucose produced from gibberellin acid do?

A
  • They diffuse back through the endosperm to the plumule and radicle of the embryo
  • Are respired for energy, fuelling biosynthesis and cell division which brings the seeds out of dormancy
58
Q

What is protandry?

A

When the stamens of a flower ripen before the stigmas

59
Q

What are pollinators such as bees attracted to plants by?

A
  • Large, coloured petals

- Scent and nectar

60
Q

What are angiosperms?

A

Plants that have flowers and produce seeds enclosed within a carpel

61
Q

When the male gamete fuses with the diploid polar nucleus it forms a triploid nucleus (endosperm nucleus). What does this do?

A

Divides repeatedly by mitosis, generating the endosperm tissue, which takes over from the nucellus in providing nutrition for the developing embryo

62
Q

What is the definition of double fertilisation?

A
  • Fusion of male and female gamete, forming a zygote
  • Fusion of male gamete and polar nucleus, forming endosperm
  • Unique process to flowering plants
63
Q

What are features of monocots?

A
  • 1 cotyledon in seed
  • Leaf veins are parallel
  • Sepals, petals and stamens in multiples of 3
  • Vascular bundles scattered in stems and roots
64
Q

What are features of dicots?

A
  • 2 cotyledons in seed
  • Leaf veins form a network
  • Sepals, petals and stamens in multiples of 4 or 5
  • Vascular bundles in a ring in stems
  • Vascular bundle in centre of roots
65
Q

What is the dispersal method of wind?

A

When seeds are blown off and transported

66
Q

What is the dispersal method of rolling?

A

When the fruit breaks open and the seed falls to the ground and rolls away from the parent tree

67
Q

What is the dispersal method of carrying?

A

When hooked seeds attach to animals coats and are carried away

68
Q

How can dormant seeds survive very cold weather?

A

Due to their low metabolic rate

69
Q

How can seeds survive adverse chemical conditions?

A

Their testa is chemically resistant

70
Q

How can dormant seeds survive very dry conditions?

A

As the water content of a dormant seed is reduced below 10%

71
Q

Until what point does the endosperm or cotyledons provide nutrients to the seed?

A

Until it can photosynthesise adequately

72
Q

What may seed inhibitors do?

A

Only allow germination at a suitable time of year

73
Q

What is the germination sequence?

A
  • Seed imbibes water
  • Testa splits
  • Radicle emerges
  • Plumule emerges
  • Elongation pushes shoot above ground
74
Q

Why must food reserves in seeds be broken into soluble molecules?

A

As the food reserves are insoluble in water and can’t be transported to the embryo until they’re hydrolysed

75
Q

In what way does the plumule grow if it is positively phototrophic and negatively geotrophic?

A

Upwards

76
Q

What is the aleurone layer in the endosperm?

A

A layer of cells towards the outside of the seed, which has a high protein content

77
Q

What is the process of the effect of gibberellin?

A
  • Barley embryo secretes gibberellic acid, which diffuses through endosperm to aleurone layer
  • Gibberellic acid switches on genes in cells of aleurone layer, resulting in transcription and translation, producing enzymes
  • Proteases hydrolyse protein in aleurone layer to amino acids, which are used to make amylase
  • Amylase diffuses out of aleurone layer and hydrolyse starch stored in endosperm cells
  • Maltose and glucose produced diffuse back through endosperm to plumule and radicle of embryo
  • They’re respired for energy, which fuels biosynthesis and cell division, and brings the seed out of dormancy

A LEVEL BIOLOGY (13 decks)

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