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A-Level EDUQUAS Biology > Component 2: Plant Reproduction > Flashcards

Component 2: Plant Reproduction Flashcards

1
Q

What are all the parts of a dicotyledonous insect-pollinated flower?

A

receptacle, calyx, sepal, corolla, petal
stamen (male parts): anther and filament
carpel (female parts): stigma, style, ovary and ovule

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2
Q

What is the calyx?

A

Outermost ring of structures, collective term for all of the sepals

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3
Q

What is the function of a sepal?

A
  • they protect the flower when it is in a bud

- usually green

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4
Q

What is the corolla?

A

A ring of petals (collective name)

- may be a nectary at the base (releasing nectars to attract pollinators)

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5
Q

What is the function of a petal?

A
  • Colourful to attract insects

- the inner sterile whorl of a flower

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6
Q

What is the function of the anther?

A
  • where pollen is produced

- consists of 4 pollen sacs that split and release pollen

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7
Q

What is the function of the filament?

A
  • vascular tissue that supports the anther

- transports food materials needed for formation of pollen grains

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8
Q

What is the function of the stigma?

A

sticky part that receives pollen from the anther

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9
Q

What is the function of the style?

A

pollen grows a tube down the style to the ovule

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10
Q

What is the function of the ovary?

A

Fertile part of the carpel, meiosis occurs here to produce haploid ovules

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11
Q

What is the function of the ovule?

A

contains an egg that after fertilisation forms the seed

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12
Q

What is the function of the stamen?

A

male part of the flower, consisting of the anther and the filament

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13
Q

What is the function of the carpel?

A

female part of the flower, consisting of the stigma, style, ovary and ovule

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14
Q

Insect-pollinated flower vs wind-pollinated: pollen

A

insect: produces small quantities of sticky, sculptured pollen, larger pollen grains (less wastage of pollen)
wind: produces large quantities of smooth, small pollen (most pollen doesn’t reach another flower)

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15
Q

Insect-pollinated flower vs wind-pollinated: anther and stigma

A

insect: both within the flower, anther positioned to rub pollen onto the back of insects (e.g. bees)
wind: hang outside the flower so they can be exposed to wind (wind carry pollen away), feathery to increase SA for catching pollen

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16
Q

Insect-pollinated flower vs wind-pollinated: petals

A

insect: colourful petals to attract insects
wind: absent

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17
Q

Insect-pollinated flower vs wind-pollinated: nectar

A

insect: usually contain nectar (sucrose)
wind: no nectar

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18
Q

Insect-pollinated flower vs wind-pollinated: scent

A

insect: produce a scent
wind: no scent

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19
Q

Insect-pollinated flower vs wind-pollinated: attracting insects

A

insect: attracts
wind: no need to attract insects

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20
Q

What are the 2 distinct phases of the life cycle in flowering plants?

A
  • the diploid sporophyte

- the haploid gametophyte

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21
Q

What is the diploid sporophyte phase?

A

Produces haploid spores by meiosis

- spores develop into haploid gametophyte, which produces haploid gametes by meiosis

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22
Q

What is self-pollination?

A

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

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23
Q

What is cross-pollination?

A

Pollen is transferred from the anthers of one flower to the mature stigma of another flower on another plant of the same species

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24
Q

What are the advantages of self-pollination?

A
  • diversity only arises from independent assortment and crossing over
  • suited to stable environments
  • preserves genes well suited to that environment
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25
Q

What are the advantages to cross-pollination?

A
  • prevents inbreeding (form of outbreeding)
  • harmful recessive alleles less likely to be expressed
  • allows species to survive in a changing environment (can withstand environmental change)
  • increases genetic variation
  • not all wiped out by disease
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26
Q

How do flowers prevent self-pollination?

A
  • stigma is above the stamen (pollen can’t fall onto it)
  • stigma and anther mature at different times (protandry or protogyny)
  • separate male and female plants (dioecious)
  • separate male and female flowers on the same plant
  • genetic (or self) incompatibility - pollen cannot germinate on the stigma of a flower that produced it
  • insects pick up pollen on different parts of the body
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27
Q

What is pollination?

A

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

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28
Q

What are the labels of the cross section of an anther?

A 
Pollen sac
filament (contains vascular bundle)
epidermis
fibrous layer
tapetum
pollen
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29
Q

Describe the cross section of the anther?

A
  • cross section of anther shows 4 chambers called pollen sacs
  • each pollen sac is enclosed by a protective epidermis and fibrous layer
  • inside the fibrous layer is the tapetum (food store providing energy for cell divisions)
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30
Q

What happens when the pollen has matured?

A

The anther dries out, splits open at the weakest part/stomium, this exposes the pollen grains
This process is called dehiscence

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31
Q

What is dehiscence?

A

The opening of the anther, releasing pollen grains

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32
Q

Draw a simple flow chart of pollen formation

A

Diploid cell -meiosis I and II-> tetrad of microspores (n) -mitosis and development of exine and intine layer-> 4 pollen grains (n)

33
Q

Describe the process of pollen formation in the anther?

A
  • each pollen sac is filled with diploid cells containing large nuclei
  • the anther grows and each cell goes through meiosis forming a tetrad of microspores (young pollen grains)
  • the nucleus of each pollen grain undergoes mitosis to produce 2 nuclei: a generative nucleus (n) and a tube nucleus (n)
  • when pollen grains are mature, outer layers of anther dry out and split open at the weakest point (in dehiscence) and releases pollen for pollination to occur
  • the generative nucleus (n) will later divide by mitosis to form 2 male gametes
34
Q

Describe the development of the female gamete?

A
  • in each ovule a megaspore mother cell (2n), surrounded by cells of the nucellus, divides by meiosis forming 4 haploid cells (megaspores)
  • three of these cells disintegrate
  • the remaining nucleus of the megaspore undergoes 3 meiotic divisions producing 8 haploid nuclei one of which is the female gamete (oopshere)
  • the entire structure is called the embryo sac
35
Q

How many ovules does an ovary contain?

A

one or more

36
Q

Draw and label an embryo sac

A

(at the top) 3 antipodals nuclei (n)
(in the middle) 2 polar nuclei (n)
(at the bottom) 2 synergids nuclei (n) on either side of the oopshere (n)

37
Q

What are all the labels of the female structure?

A 
stigma
style
ovary wall
funicle
2 integuments 
micropyle
ovule
embryo sac
nucellus
38
Q

What does the ovule consist of?

A

The outer integuments surrounding the nucellus and an embryo sac containing seven nuclei

39
Q

What is the nucellus?

A

Cells that surround the embryo sac and provide nutrition for growth of the ovule

40
Q

What is the small opening in the integuments called and what does it do?

A

called the micropyle

where water enters

41
Q

What is fertilisation?

A

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

42
Q

What happens when the pollen reaches another flower in double fertilisation?

A
  • compatible pollen grain lands on the stigma, it germinates in sucrose solution secreted by the stigma
  • produces a pollen tube
  • pollen tube nucleus at the tip secretes enzymes to digest cells of the style as it grows
  • 2 male nuclei behind it control growth of the tube (these nuclei originate from the generative nucleus)
43
Q

What happens when the pollen tube reaches the ovule in double fertilisation?

A
  • pollen tube grows through the gap in the integuments (micropyle), passing into the embryo sac
  • pollen tube nucleus disintegrates, top of the pollen tube opens, releasing the 2 male gametes into the embryo sac
44
Q

What happens in the double fertilisation phase?

A
  • one of the two male gametes fuses with the oopshere (female gamete) to form a diploid zygote
  • the other male gamete fuses with both polar nuclei to form the triploid endosperm nucleus
  • a double fertilisation has occured (2 fusions)
  • a zygote eventually develops into an embryo and grows into a new plant
45
Q

What type of fertilisation occurs in flowering plants only?

A

double fertilisation

46
Q

What are the labels of a fruit and seed?

A 
Ovary (fruit)
Embryo plant (plumule and radicle)
Funicle
Micropyle
Testa
Cotyledon
47
Q

What is the plumule?

A

Embryo plant shoot

48
Q

What is the radicle?

A

Embryo plant root

49
Q

What is the testa?

A

The tough/protective outer covering of the seed

  • often has outgrowths which keep in dispersal of the seed
  • also called the seed coat
50
Q

What is the cotyledon?

A

Food store

51
Q

What happens after fertilisation?

A
  • the fruit and the seed develop
  • stamen and the sepals fall off
  • ovule turns into a seed
  • fertilised egg inside develops into an embryo plant
52
Q

What does the zygote turn into?

A
  • divides by mitosis into the embryo consisting of the plumule and radicle
  • as well as one of two cotyledons
53
Q

What does the triploid endosperm nucleus develop into?

A

into a food store providing food for the developing embryo

54
Q

What happens to the micropyle?

A

remains as a pore in the seed

55
Q

What happens to the outer integuments?

A
  • dries out, hardens and becomes waterproof

- becomes the seed coat (testa)

56
Q

What does the funicle of the ovule develop into?

A

Funicle of the seed

57
Q

What does the ovary develop into?

A

becomes the fruit

58
Q

What does the ovule develop into?

A

becomes the seed

59
Q

What is the fruit?

A

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

60
Q

What is the seed?

A

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

61
Q

What is meant by dormant?

A

describes a seed when its active growth is suspended, germination will only occur when specific conditions are met

62
Q

What does a seed do to become dormant?

A
  • Dehydrates itself, water content falls below 10%

- this reduces metabolic rate

63
Q

What 3 things provide nutrition to the developing embryo?

A
  1. the nucellus
  2. the endosperm
  3. one or two cotyledons
64
Q

What 2 groups are flowering plants divided into?

A
  1. monocotyledons, have on cotyledon only (includes cereals)

2. dicotyledons, they have 2 seed leaves or 2 cotyledons (broad beans)

65
Q

What is the eternal structure of a seed?

A
  • testa
  • endosperm
  • coleophile (plumule sheath)
  • hypocotyl -> plumule and radicle
  • cotyledon
  • funicle
66
Q

What is the embryo of a seed?

A
  • consisting of a radicle (gives rise to the root) and a plumule (growing part of a shoot)
  • part containing both of these is the hypocotyl
  • one or two seed leaves (cotyledons) grow from the hypocotyl
67
Q

What is the food-store of the seed?

A

the reserve of food which supplies the embryo and growing plant until it can make its own food through photosynthesis

  • may be in the cotyledon or in the endosperm
  • these add nutritional value to seeds for animals and humans
68
Q

What is the endosperm?

A

Tissue produced inside the seeds of the most flowering plants

  • surrounds the embryo
  • act as a food store for the seed
  • found in monocots
  • not photosynthetic
69
Q

What is the cotyledon?

A
  • provides nutrition to developing embryo within seed of the plant
  • found in dicots
  • are photosynthetic
70
Q

Why is the dormancy of seeds important?

A
  • allows the seed to survive in unfavourable conditions
  • ensures that it ensures it germinates in favourable conditions
  • allows seed to avoid competition with its parent
  • provides time for seed to be dispersed
71
Q

What are the adaptations of seeds for dormancy?

A
  • low metabolic rate
  • testa physically protects by providing a hard outer coating
  • testa is chemically resistant (survive adverse chemical reactions)
  • low water content allows it to be resistant to desiccation
    endosperms/cotyledon provide a source of nutrients
72
Q

Describe the sequence of events that take place during fertilisation [4 marks]

A
  • pollen tube grows through the style controlled by the pollen tube nucleus
  • enzymes digest a path through the style to the micropyle
  • one male nucleus fuses with female gamete to form the zygote
  • second male nucleus fuses with female gamete to form the zygote
73
Q

What are the different ways of transportation/seed dispersal?

A
  • rolling
  • carrying
  • bursting
  • wind
  • water
  • animals (either disperse them in faeces or require scarification)
74
Q

What is scarification?

A

the digestive system of an animal weakens the testa by physical attack

75
Q

What are the 3 optimum temperatures needed for seed germination?

A

Water, Oxygen and Temperature

76
Q

Why is the optimum amount of water required for seed germination?

A

nutrients in the dry tissue need to be rehydrated
mobilises enzymes for transport in xylem and phloem
cracks testa so that roots can grow out

77
Q

Why is an optimum amount of oxygen required for seed germination?

A

aerobic respiration releases energy which fuels metabolism and growth

78
Q

Why is an optimum temperature needed for seed germination?

A

optimum temperature for enzymes involved in the process (enzyme action)
however this temperature varies between species as they may grow best at different times of year (seasonal variation)

A-Level EDUQUAS Biology (24 decks)

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