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A level Biology > Unit 4.2 - Sexual reproduction in plants > Flashcards

Unit 4.2 - Sexual reproduction in plants Flashcards

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1
Q

What make up the carpel in an insect pollinated flower?

A

Stigma
Style
Ovary

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2
Q

What do the stigma, style and ovary make up in an insect pollinated flower?

A

The carpel

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3
Q

Carpel

A

Inner structure of flower

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4
Q

What make up the stamen of an insect pollinated flower?

A

Anther
Filament

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5
Q

What do the anther and filament make up in an insect pollinated flower?

A

The stamen

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6
Q

What does pollen do?

A

Carries male gametes

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7
Q

Pollination

A

The transfer of pollen from one flower to another (or within the same flower)

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8
Q

Describe the petals of insect pollinated flowers

A

Are large and colourful in order to attract insects

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9
Q

Describe the sepal of insect pollinated flowers

A

Forms the bud within the early stages of development and protects the flower within whilst its developing

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10
Q

What form the bud during the early stages of development of a flower?

A

The sepal

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11
Q

Describe the receptacle of insect pollinated flowers

A

Where the whole flower structure is attached

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12
Q

Describe the pedicel of insect pollinated flowers

A

Holds the flower up

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13
Q

Describe the ovary of insect pollinated flowers

A

Has several ovules, which is where female gametes develop

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14
Q

Where do female gametes develop in flowers?

A

In ovules in the ovaries

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15
Q

Describe the nectary of insect pollinated flowers

A

Where nectar is produced - a sweet, sugary fluid that insects feed on

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16
Q

Explain the mutualistic relationship between plants and insects?

A

When insects go to collet nectar from the nectary, they brush past the anther when collecting this
They transfer pollen to the stigma, which is sticky = pollination

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17
Q

What do insects carry from flower to flower?

A

Pollen

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18
Q

How does the stigma get the pollen from insects?

A

It’s sticky

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19
Q

How do pollinating insects benefit from the process of pollination?

A

The flowers provide nectar as a reward

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20
Q

What features can wind pollinated flowers have?

A

Fast growing
High productivity

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21
Q

What are the things to label on a wind-pollinated flower?

A

Bract
Stigma
Anther
Ovary

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22
Q

What does the anther in wind pollinated flowers do?

A

Releases pollen into the air

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23
Q

What does the bract in wind pollinated flowers do?

A

Is protective

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24
Q

Which part of a wind pollinated flower is adapted for its function? Describe this

A

Stigma
Is feathery to increase its surface area so that it’s more likely to catch pollen grains

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25
Q

What does the ovary in wind pollinated flowers do?

A

Contains the ovules

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26
Q

Why do wind pollinated flowers not have petals?

A

No need to attract insects

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27
Q

What adaptation do wind pollinated flowers have to obtain pollen blown in the wind? Explain this

A

High up off he ground on a stalk to catch the wind current and catch the pollen blown in the wind

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28
Q

Summarise the things we can compare between wind and insect-pollinated flowers

A

Petals
Stigma
Anthers
Pollen grains

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29
Q

Compare the petals of a wind-pollinated flower to an insect-pollinated flower

A

Petals small and green or no petals at all. The flowers are located above the leaves or produced in early spring to give maximum advantage from wind currents without interference from leaves.
V.s
Large and brightly coloured petals, often with guidelines to the nectaries to attract the insect pollinators

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30
Q

Compare the stigma of a wind-pollinated flower to an insect-pollinated flower

A

The stigmas are large and feathery and hang outside the flower to catch airborne pollen in wind currents
V.s
The stigma is sticky to trap pollen grains and is inside the flower, where insects rub against it thus causing pollen to be deposited

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31
Q

Compare the anther of a wind-pollinated flower to an insect-pollinated flower

A

Large anthers suspended outside the flower to release pollen grains into wind currents
V.s
Anthers on rigid filaments inside the flower: where insects must rub against them. This increases the change of pollen being deposited on insects’ bodies

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32
Q

Compare the pollen grains of wind-pollinated flowers to an insect-pollinated flowers

A

Vast numbers of small, light, smooth-walled pollen grains are produced which are easily carried by the wind
V.s
The pollen grains are large with spiky and sculptured walls which stick to insect bodies

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33
Q

Describe and explain the guidelines on the petals of insect-pollinated flowers

A

These lines show up brightly in UV light
Insects have good vision and can see clearly in the UV region of the e.m spectrum

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34
Q

Which part of a plant is where pollen is produced?

A

The anther

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35
Q

What do pollen grains contain?

A

The male gametes

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36
Q

Where are pollen grains formed?

A

Within the pollen sacs

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37
Q

Describe the pollen sacs in an anther

A

Their ranged in two parts, side by side

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38
Q

Where specifically in an aether are pollen grains produced?

A

In the pollen sacs

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39
Q

Describe the development of pollen in the anther

A

Pollen mother cell (diploid, 2n)
Undergoes mitosis to produce many of them
1st and 2nd meiotic division occur to form a tetrad of 4 haploid (n) pollen grains
Mitosis of these nuclei occur and they mature - DNA is replicated and separated into 2 haploid nuclei in each pollen grain
This forms 4 mature pollen grains

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40
Q

Features of a mature pollen grain

A

Tube nucleus (n)
Generative nucleus (n)
Thick sculptured wall - intine and exine

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41
Q

What does the cell wall of a pollen grain prevent from happening?

A

Prevents desiccation (drying out)

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42
Q

Why does the cell wall of a pollen grain prevent dessiction?

A

It’s waterproof and can survive in a dry environment

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43
Q

What is the cell wall of a pollen grain an adaptation to?

A

A terrestrial environment

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44
Q

What have pollen grains adapted to which animals haven’t? Explain

A

A terrestrial environment
Sperm cells have to stay in a fluid environment

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45
Q

Generative nucleus

A

Will fertilise the female gamete to form the zygote
During pollination, will divide by mitosis to form 2 male nuclei

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46
Q

Which nucleus in a pollen grain will fertilise the female gamete to form the zygote?

A

The generative nucleus

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47
Q

What will the tube nucleus do in a pollen grain?

A

Will form the pollen tube, which is part of fertilisation

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48
Q

Explain the purpose of the tube nucleus of a pollen grain and how it works

A

When the pollen grain lands on the stigma, the gamete has to be transported from the pollen grain to the female gamete
Therefore, the tube grows towards the ovary in the ovule to transfer the male gamete to the female gamete
This is why, in the pollen grain, there is a nucleus to start the growth of the pollen tube towards the female gamete

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49
Q

Explain dehiscence

A

When the pollen grains are mature and ready to be released, the outer layers of the anther dry out.
This causes tension on the stromium and the walls of the anther pull apart, releasing the pollen
This is known s dehiscence

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50
Q

What is it called when the outer layers of the anther dry out, causing tension on the stromium and the walls of the anther pulling apart, releasing the pollen?

A

Dehiscence

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51
Q

Tapetum

A

Tissue around the pollen sac involved in providing nourishment and nutrients for the developing grains

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52
Q

What have plants evolved to do over time?

A

Live on dry land

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53
Q

How have plants evolved to live on dry land?

A
  • water proof cell wall
    -seeds
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54
Q

Where exactly does the female gamete develop in flowering plants?

A

In the ovule in the ovary in the carpel

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55
Q

In which part of the ovule do female gametes develop in flowering plants?

A

In the embryo sack

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56
Q

What is the embryo sack of the ovule surrounded by?

A

The nucellus

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57
Q

Nucellus

A

A mass of cells that gives nutrients to the cells in the embryo sack

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58
Q

What surrounds the nucellus in the ovule?

A

Two protective integuments

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59
Q

Via what does the pollen go into the ovule when fertilisation occurs?

A

Via the micropyle

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60
Q

What is the whole ovule attached to the plant to and carried on?

A

A short stalk called the funiculus

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61
Q

What does the funiculus do?

A

Carried nutrients when developing from the plant to the ovule

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62
Q

What does one cell in the nucellus of the ovule develop into?

A

The megaspore mother cell (2n)

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63
Q

Explain the stages of the development of the embryo sac

A
  1. Start with the megaspore mother cell (diploid)
  2. This undergoes meiosis to form 4 haploid cells. 3 of the 4 cells degenerate. Only 1 forms the embryo sac
  3. The inner cell grows to form the megaspore or embryo sac (haploid)
  4. When grown, the cell undergoes 3 mitotic divisions. The DNA has been replicated and it’s the megaspore nucleus that undergoes the divisions in order to form 8 haploid (n) nuclei.
  5. 2 nuclei move to the centre of the embryo sac to form polar nuclei (n). The remaining nuclei develop cytoplasm around them and become separated by cell walls.
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64
Q

Things to label on an embryo sac

A

Antipodal cells
Polar nuclei
Egg cell (ovum)
Synergies
Micropylar end

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65
Q

Things to label on an ovule

A

Chalaza
Nucellus
Funiculus
Embryo sac
Integuments
Micropyle

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66
Q

Which cells in the embryo sac play no further role after development and have no part in fertilisation?

A

The thee antipodal cells

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67
Q

Which cell in the embryo sac develops into the female gamete?

A

One cell nearest micropyle (the centre cell)

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68
Q

What do the other two cells nearest the micropylar end in an embryo sac form?

A

Synergids that degenerate after fertilisation

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69
Q

When do the synergids in an embryo sac degenerate?

A

After fertilisation

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70
Q

Pollination

A

The transfer of pollen from the anther to the stigma

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71
Q

Self pollination

A

The transfer of pollen from the anther to the stigma of the same flower

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72
Q

Cross pollination

A

Transfer of pollen from the anther of one flower to the stigma of a different flower

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73
Q

Stamen

A

Pollen producing part of a flower

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74
Q

How is an anther different to a stamen?

A

The anther is the specific part of the stamen where pollen is produced

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75
Q

Pistil

A

Contains several carpels

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76
Q

Explain briefly how cross pollination can occur

A

1.) pollen from stamens stick to a bee as it visits a flower to collect food
2. The bee travels to another plant of the same type
3. Pollen on the bee sticks to a pistil of a flower on the other plant

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77
Q

What type of pollination is the most advantageous in terms of genetic diversity?

A

Cross pollination

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78
Q

What is cross pollination the most advantageous in terms of?

A

Genetic diversity

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79
Q

What have plants done due to cross pollination being the most advantageous method of pollination in terms of genetic diversity?

A

Have evolved methods to make it more likely to cross pollinate than to self pollinate

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80
Q

Why are the things we can mention when comparing self-pollination and cross-pollination?

A

Transfer of pollen
Fertilisation
Genetic variation
Harmful alleles
Genome preservation

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81
Q

Compare self-pollination and cross-pollination in terms of transfer of pollen

A

Transfer of pollen from the anther of a flower to the mature stigma of the same flower, or another flower on the same plant of the same species (it’s the same plant so it’s self-pollination)
Vs
Transfer of Poland, from the answer of a flower to the mature, stigma of another flower on another plant of the same species

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82
Q

Compare self-pollination and cross-pollination in terms of fertilisation and what they lead to

A

Self-pollination leads to self-fertilisation which leads to inbreeding
Cross-pollination leads to cross-fertilisation which leads to outbreeding

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83
Q

Compare self-pollination and cross-pollination in terms of genetic variation

A

Both:
Genetic variation dependent on
-crossing over during prophase I or meiosis
-independent assortment during metaphase I of meiosis
-mutation

Cross-pollination also has the additional:
-combining genotypes of gametes from two different individuals

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84
Q

Compare self-pollination and cross-pollination in terms of genetic variation

A

Less, more

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85
Q

Compare self-pollination and cross-pollination in terms of the risk of harmful combinations of alleles

A

Self-pollination: greater chance of two potentially harmful recessive alleles combining
Cross-pollination: reduced chance of producing harmful combinations of alleles

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86
Q

Compare self-pollination and cross-pollination in terms of genome preservation

A

Successful genomes are preserved, which is an advantage in a stable environment but a disadvantage if the environment changes suddenly

Advantageous in terms of evolution because if the environment changes suddenly, it is likely that there are individuals within the population with a combination of alleles that will allow the species to survive

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87
Q

What do gardeners often do in order to preserve characteristics?

A

Self-pollinate

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88
Q

List the adaptations of flowers to promote cross-pollination

A
  1. Chemical self-incompatibility
  2. Irregular flower structure
  3. Dichogamy
  4. Monoecious plants
  5. Dioecious plants
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89
Q

Chemical self-incompatibility

A

Gametes from the same parent plant are unable to fuse and form a zygote or, if the zygote forms, then it fails to develop = prevents self-fertilisation

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90
Q

Dichogamy

A

Anthers and stigmas mature at different times on the same plant so self-pollination can’t occur

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91
Q

Example of flowers with irregular flower structures

A

Primroses

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92
Q

Monoecious plants

A

Have separate female and male flowers on the same plant

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93
Q

Example of a monoecious plant

A

Hazel

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94
Q

Dioecious plants

A

Have separate male and female plants

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95
Q

Example of a dioecious plant

A

Willow

96
Q

Where are primroses found?

A

Found in hedgerows and sides of paths

97
Q

Why are there 2 versions of primroses?

A

An adaptation to ensure that cross-pollination occurs

98
Q

2 varieties of primroses

A

Pin eyed primula
Thrum eyed primula

99
Q

What’s the difference between the pin eyed and thrum eyed primulas?

A

The length of the stigma and anther are different in both

100
Q

Length of style and anthers in pin eyed primula

A

Long style, short anthers

101
Q

Length of style and anthers in thrum eyed primula

A

Long anthers, short styles

102
Q

Where are the anthers in thrum-eyed primulas?

A

Close to the opening as they’re long

103
Q

What is the difference between style and stigma?

A

Stigma is the end bit of the style

104
Q

What variety of primroses will pollen grains not fall into and why?

A

Pin-eyed since the stigma is above the anthers

105
Q

At what level do insects tend to pollinate a sigma?

A

On the same level as anthers that they collected the pollen from

106
Q

Where do pollen grains tend to be transferred in primroses?

A

From pin eyed to thrum eyed and vice versa

107
Q

Explain how pollen would be transferred to thrum eyed primroses

A

Bees tongue extends to the base to obtain nectar
Brushed against the anther, picking up pollen
The bee flies to the next flower, a pin-eyed one and sticks its head in
Pollen grains rub off onto the stigma and start fertilisation

108
Q

What would happen if pollination was attempted to occur between 2 pin-eyed flowers?

A

Pollen grains won’t fall onto it so self-pollination is less likely

109
Q

Explain the mutual relationship between Darwin’s Hawk mother and an orchid

A

The orchid has a long tube protruding from it which has the nectary at the very bottom
Darwin predicted that there must be an insect with a tongue long enough to be able to reach this, which there was
His prediction was correct. He knew that the plant wouldn’t exist following evolution if an insect hadn’t developed to get its pollen and pollinate it

110
Q

What is fertilisation?

A

The process in which a male gamete fuses with a female gamete to form a zygote

111
Q

Where is the female game in flowering plants?

A

In the ovule, protected within the ovary

112
Q

What undergoes mitosis during double fertilisation and what does this form?

A

The generative nucleus
Produced two haploid male gametes in the pollen grain

113
Q

How are the two haploid male gametes formed by the mitosis of the generative nucleus during double fertilisation delivered?

A

By the pollen tube

114
Q

How many cells does the pollen tube initially contain?

A

Two haploid cells - the generative cell and the tube cell

115
Q

What is the location of double fertilisation?

A

The embryo sac

116
Q

What is within the embryo sac for double fertilisation?

A

2 haploid polar nuclei
Also the haploid female gamete

117
Q

What will the 2 male nuclei fuse with during double fertilisation?

A

The haploid polar nulei
The haploid female gamete

118
Q

Explain double fertilisation

A
  1. When a compatible pollen grain lands on the stigma, it germinates in the sucrose solution secreted by the stigma and produces a pollen tube
  2. The pollen tube nucleus is at the tip of the tube, with the two male nuclei behind
  3. The pollen tube grows out of the pollen grain through a gap in the cell wall, called a pit, and down the style up a gradient of chemoattractants e.g - GABA from the ovule.
    The pollen tube nucleus codes for the production of hydrolyses including cellulases and proteases, and it digests its way through the tissues of the style. The products of digestion are used by the growing pollen tube.
  4. The pollen tube grows through the gap in the integuments, the micropyle, and passes into the embryo sac
  5. The pollen tube nucleus disintegrates, presumably having completed its function of controlling the growth of the pollen tube
  6. The tip of the pollen tube opens, releasing the 2 male gametes into the embryo sac
  7. The male gametes enter the cytoplasm of the synergid
  8. The synergid breaks down
  9. The male and female gametes are haploid. One of the male gametes fuses with the female gamete, the oosphere, to form a zygote which is diploid
  10. The other male gamete fuses with the diploid polar nucleus to form a triploid nucleus. This triploid nucleus is the endosperm nucleus. When is subsequently divides repeatedly by mitosis, it generated the endosperm tissue, which takes over from the nucellus in providing nutrition for the developing embryo
119
Q

Triploid nucleus formed during double fertilisation

A

Endosperm nucleus

120
Q

When does the pollen tube nucleus disintegrate during double fertilisation?

A

Presumably having completed its function of controlling the growth of the pollen tube

121
Q

Name for the female gamete involved in double fertilisation

A

Oosphere

122
Q

What does the ovule do at the end of double fertilisation?

A

Develops into a seed

123
Q

Why is double fertilisation called this?

A

Two fusions have occurred - one to form the zygote and one to form the endosperm.

124
Q

What is double fertilisation unique to?

A

Seed plants

125
Q

How many pollen grains germinate successfully during double fertilisation and what happens to the others?

A

Only one, the others disintegrate

126
Q

Roles of the tube nucleus in double fertilisation

A

Controls and directs the growth of the tube nucleus
DNA codes for enzymes that digest their way through the tissues of the style. This creates a path for the growing pollen tube and the products of digestion are used by the growing pollen tube.

127
Q

What happens to the diploid zygote following double fertilisation?

A

Develops into the embryo plant

128
Q

What happens to the triploid endosperm cell following double fertilisation?

A

Develops into the food reserve in the seed

129
Q

How does the triploid endosperm cell develop into the food reserve in the seed following double fertilisation?

A

When the seed generate, the embryo can absorb the food and grow

130
Q

What happens to the integuments following double fertilisation?

A

Develop into the seed-coat (testa) - outer layer of seed

131
Q

Name for the seed-coat formed by integuments after double fertilisation

A

Testa

132
Q

What happens to the ovary wall following double fertilisation?

A

Can grow and sweet in order to develop into a fruit

133
Q

Where is the ovary wall?

A

Outside the ovules

134
Q

Testa

A

Seed-coat that forms from the integuments following double fertilisation

135
Q

Why is fertilisation in plants referred to as double fertilisation?

A

1 male nucleus fuses with the female gamete to form a diploid zygote
1 male nucleus joins with the 2 polar nuclei to form the triploid endosperm nucleus

136
Q

What do we need to remember to always refer to when describing stages of fertilisation?

A

Refer to the number of sets of chromosomes

137
Q

Stigma

A

The receptive surface for pollen

138
Q

Things to label on an ovary

A

Epidermis
Ovary wall
Ovule
Funicle
Nucellus
Embryo sac

139
Q

What forms in plants after fertilisation?

A

Seeds

140
Q

What are seeds unique to?

A

Plants

141
Q

What are the 2 purposes of seeds?

A

They’re part of the plat’s reproductive system but also act as a survival capsule of the plant

142
Q

Why are seeds described as “survival capsules” for plants?

A

There aren’t always favourable conditions for the growth of plants, for example during long, dry seasons in some countries that involve very little rain, leaving not much water in the soil. Also during the winter in temperate countries

143
Q

When are seeds the most useful as survival capsules?

A

During long, dry seasons in some countries that involve very little rain
During the winter in temperate countries

144
Q

Dormant seeds

A

Alive but not growing

145
Q

Describe seeds when they are dormant

A

Remain lime this in the soil for long periods of time where their metabolism is almost at zero

146
Q

“Long periods of time” that seeds can remain dormant for

A

Years in some cases

147
Q

When will dormant seeds germinate and grow?

A

When the conditions are right

148
Q

2 main types of seeds

A

Dicotyledon seeds
Monocotyledon seeds

149
Q

Name for dicotyledon seeds

A

Vicia faba

150
Q

Monocoyledon seeds name

A

Zea mays

151
Q

Example of a dicotyledon seed

A

Broad beans

152
Q

Example of a monocotyledon seed

A

Maize

153
Q

What are the things we label on seeds (dicotyledon and monocotyledon)?

A

Testa
Hypocotyl
Plumule
Hilum (scar of the funicle) (dicotyledon only)
Micropyle
Radicle
Cotyledon
Funicle (monocotyledon only)
Endosperm (monocotyledon only)
Testa and pericarp fused (monocotyledon only)

154
Q

How come the micropyle is still in the seed and where?

A

The pollen tube grew into the ovule through the micropyle and it’s still in the testa

155
Q

Micropyle function in seeds

A

Allows the seed to draw in water during germination

156
Q

Plumule in seeds function

A

When the seed germinates, it develops into the stem and leaves of the plant - embryonic shoot with first leaves

157
Q

Radicle of seeds function

A

When the seed germinates, it develops into the roots - embryonic root

158
Q

What takes up most of the inside of a monocotyledon seed?

A

The endosperm

159
Q

What does the endosperm in a seed do?

A

It stores starch which provides a food source for the growing embryo

160
Q

When was the endosperm of a seed generated?

A

During double fertilisation

161
Q

Difference between the cotyledon in a dicotyledon and a monocotyledon seed

A

Monocotyledon —> only 1 and is smaller

162
Q

Cotyledon in a seed function

A

The seed food reserve. When the embryo plant generates, it draws its nutrients from the cotyledon.

163
Q

What is the testa in a seed?

A

The seed coat

164
Q

Testa in seeds description

A

The seed coat. Developed from the integuments that were around the ovule.

165
Q

What did the testa of seeds develop from?

A

The integuments that were round the ovule

166
Q

What are the 2 halves of a peanut seed?

A

The cotyledons

167
Q

What are peanuts in reality and why?

A

Beans,not nuts
They’re related to the same family as legumes (have root nodules etc.)

168
Q

Which part is the fruit when bean seeds grow in a pod and why?

A

The pod since it formed from the ovary wall

169
Q

Which part are the seeds when beans grow in a pod?

A

The beans

170
Q

What makes something a fruit?

A

Formed from the ovary wall

171
Q

Why would bean seeds turn black and under which conditions would this be?

A

If we were to open a bean seed, remove their testa and separate the cotyledon before putting iodine on them, they would turn black since they’re full of starch

172
Q

Why do dicotyledon seeds not have an endosperm?

A

The cotyledons are small to begin with but then absorb the nutrients form the endosperm as they develop before taking over and filling the whole seed

173
Q

How do cotyledons end up taking over the whole of dicotyledon seeds?

A

They’re small to begin with but then absorb the nutrients from the endosperm as they develop before taking over and filling the whole seed

174
Q

What form the embryo in monocotyledon seeds?

A

The plumule and the radicle

175
Q

Pericarp of a monocotyledon seed description

A

Forms the outer coat of the monocotyledon. It is the fruit of the plant.

176
Q

Fruit of the monocotyledan

A

Pericarp

177
Q

Why is the pericarp the fruit of monocotyledon seeds?

A

It’s formed from the ovary wall

178
Q

What colour is the endosperm of monocotyledon seeds and what is the significance of this?

A

White
Is used to form cornflour and is nutritious

179
Q

What are the inner parts of monocotyledon seeds formed from?

A

The ovule

180
Q

What is the name of the layer that’s only in monocotyledon seeds?

A

Aleurone layer

181
Q

What does the aleurone layer contain?

A

Proteins and enzymes

182
Q

Describe the enzymes of the aleurone layer when a seed is dormant

A

Inactive

183
Q

When are the enzymes of the aleurone layer in monocotyledon seeds active and what does this lead to?

A

As soon as germination starts
They break down the food reserve (starch in the endosperm). This allows the embryo of the plant to absorb the nutrients and grow.

184
Q

Purpose of the active enzymes of the aleurone layer during germination of a monocotyledon seed

A

They break down the food reserve (starch in the endosperm) and this allows the embryo of the plant to absorb the nutrients and grow

185
Q

Food reserve in a monocotyledon seed

A

Starch in the endosperm

186
Q

How does the embryo of a monocotyledon seed start absorbing nutrients and grow?

A

When the enzymes in the aleurone layer activate during germination and break down the food reserve (starch in the endosperm)

187
Q

Why is seed dispersal important?

A

Since seeds are part of a plants reproductive cycle

188
Q

What needs to happen for seeds to play a part in a plants reproductive cycle?

A

They need to be dispersed

189
Q

Why is it important that seeds disperse?

A

The seeds need to move away from the parent plant so that you don’t get lots of seeds in the same area competing against each other

190
Q

How do seeds ensure that you don’t get lots of seeds in the same area competing against each other?

A

Have evolved strategies to disperse

191
Q

What are the different ways in which plants disperse seeds?

A

Wind
Animals
Water
Explosion

192
Q

Two examples of seeds that are dispersed by wind

A

Dandelion seeds
Sycamore seeds

193
Q

How are dandelion seeds dispersed by the wind?

A

Have a feathery stalk

194
Q

How have sycamore seeds adapted to be better dispersed?

A

They spin as they fall as they have veins that rotate them when they catch the air. This slows down the rate of fall so that they can be carried further by the wind.

195
Q

Main way seeds are dispersed using animals

A

Have spoken structures so that they can latch onto animal fur

196
Q

Explain why some seeds are colourful in terms of dispersal

A

Attract animals to eat them. These will have a tough outer coat so as to survive the animals digestive system. They will then be excreted in the faeces and the seeds will be distributed from the parent plant (assuming that the bird has flown away)

197
Q

Explain the relationship between jays and oak trees

A

Jays cause seed dispersal
They like acorns however all of the acorns become available at the same time of year (October). Therefore, the birds stored acorns for feeding all over the winter. They do this by burying them so that squirrels etc don’t eat them. The jays find approximately 60% of these buried acorns so the other 40% of them stay in the soil and grow into new oak trees in the spring

198
Q

Explain how coconut seeds are dispersed by water

A

Have a buoyant husk on the outside (fibres which catch air). We usually see coconuts growing on beaches since when the coconut falls, it rolls into the sea and is carried by the tides to grow somewhere else

199
Q

Give an example and explain a plant that disperses its seeds via explosion

A

Himalayan Balsam
When touched, the seeds explode open. These plants are often found by rivers therefore the seeds are then transported into the river and are carried away by the water.

200
Q

Compare the roots of the plant of a monocotyledon and a dicotyledon

A

Fibrous, tap root

201
Q

Compare the veins of the plants of monocotyledon and dicotyledon

A

Parallel, netlike

202
Q

Extra things to label on a fully grown monocotyledon plant

A

Leaf sheath

203
Q

Extra things to label on a fully grown dicotyledon plant

A

Withering cotyledons

204
Q

What is the major factor that prevents germination?

A

The water content of seeds being very low

205
Q

What does the water content of seeds being very low prevent?

A

Germination

206
Q

Describe the soil during dry seasons and what this prevents

A

Very dry, prevents germination

207
Q

How will seeds remain until suitable conditions are present?

A

Dormant

208
Q

All of the conditions required for seeds to no longer remain dormant and for germination to occur

A

Water to mobilise enzymes, for transport of dissolved substances, and to vacuolate cells to make them turgid and swell cotyledons
Oxygen for aerobic respiration and ATP for metabolism
Suitable temperature for enzymes to operate + speeds up rate of diffusion

209
Q

Explain what germination involves

A

The rapid onset of biochemical activity and growth of a seedling until the plant can carry out photosynthesis and become independent of the food stores contained in the cotyledons or endosperm

210
Q

What can’t a seed do when it’s first germinated and what must it do instead?

A

Can’t photosynthesise until it’s grown leaves so it’s dependent on the cotyledons

211
Q

Explain germination in a non-endospermic seed (dicotyledon seed)

A

When there’s enough water and the temperature is right, the seed starts to germinate…
1. Water is imbibed (taken in) through the micropyle (a hole in the testa)
2. The cotyledons swell and the testa splits, allowing entry of more water and oxygen for aerobic respiration
3. Starch and protein reserves in the cotyledons are hydrolysed
4. Products of hydrolysis are used as:
- a source of energy for respiration - glucose
- growth of the plumule and radicle - amino acids

212
Q

What does the plumule of a plant develop into?

A

Shoots

213
Q

What does the radicle of a plant develop into?

A

Roots

214
Q

Example of a non- endospermic seed

A

Viscia faba

215
Q

Explain the germination of a monocotyledon seed

A
  1. Following the imbibing of water gibberellin (gibberellic acid) - a type of hormone - is released by the embryo
  2. The gibberellin diffuses to the aleurone layer (the outer layer of the endosperm) which contains protein. Gibberellin induces the production of hydrolytic enzymes e.g amylase
  3. The hydrolytic enzymes diffuse into the inner layer if the endosperm and catalyse the breakdown/hydrolysis of stored nutrients here (e.g - starch)
  4. Glucose and other breakdown products of the stored nutrients diffuse into the embryo
  5. They are used for aerobic respiration and growth of the radicle and plumule
216
Q

Method for the experiment involving germinating seeds in starch agar

A
  1. Germinating seeds cut in half (use boiled seeds)
  2. As the seeds germinate, they produce amylase that digests the starch agar
  3. By flooding the plate with iodine, we will see clear zones where the enzymes have digested the starch/starch has been hydrolysed
217
Q

What are the clear zones in the germinating seeds on starch agar experiment?

A

This is where the enzymes (amylase produced when germinating) have digested the starch and the starch has been hydrolysed

218
Q

What can we see in the areas where the enzymes have digested the starch with germinating seeds on starch agar?

A

Clear zones

219
Q

How can we measure how different factors affect the germination of plants using the germinating seeds in starch agar experiment?

A

By measuring the diameter of the clear zones around the germinating seeds

220
Q

Which factors can we compare to see their effects on germination in plants using the germinating seeds on starch agar experiment?

A

Use different varieties of seed (keep other variables the same)
Use different temperatures
Use different oxygen partial pressures
Initially soak the seeds for different times
Use different light intensities (some seeds need light to germinate)

221
Q

Why do only fertilised ovules develop into fruit?

A

No zygote/no fertilisation of the egg cell means no stored food. This saves the plant resources and energy for other processes.

222
Q

Will flowers on the same plant be genetically identical? Explain

A

Yes since they’re produced by mitosis and are clones

223
Q

What do we need to ensure that we do when comparing different varieties of seed in the germination of seeds on starch agar practical?

A

Keep other variables the same

224
Q

Why could we use different light intensities as a factor to compare the germination of plants in the germinating seeds on starch agar practical?

A

Some seeds need light to germinate

225
Q

What does amylase digest starch in cotyledons into (dicotyledon seeds)?

A

Amylase digest starch in cotyledons to maltose

226
Q

What are proteins/fats in dicotyledon seeds broken down into?

A

Amino acids

227
Q

What does Gibberellic acid to do to protein?

A

Break down into amino acids

228
Q

What are amino acids used for (when broken down by Gibberellic acid in monocotyledon seeds)?

A

To synthesise enzymes such as amylase

229
Q

What does amylase do to starch in the endosperm of monocotyledon seeds?

A

Breaks it down into maltose

230
Q

Which enzyme digests starch?

A

Amylase

231
Q

What is starch digested into by amylase?

A

Maltose

232
Q

What are amylase enzymes synthesised from?

A

Amino acids

233
Q

What breaks down starch in the endosperm of monocotyledon seeds into maltose?

A

Amylase

234
Q

What is one of the remaining nuclei formed from the 3 mitotic divisions of the one cell from the meiosis of the megaspore mother cell?

A

The egg cell

235
Q

Why can seeds still germinate?

A

Because of food stores

236
Q

Difference between fruit and seed

A

Fruit = ovary wall and testa fuses
Seed = only testa

A level Biology (26 decks)

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