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Component 2 Biology > Plant Reproduction > Flashcards

Plant Reproduction Flashcards

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1
Q

What are the reproductive organs of the plant?

A

The flowers and these vary depending on the method of pollination, each flower consist of four sets of modified leaves.

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2
Q

What are attached to the receptacle?

A

The sepals, petals, stamens and carpels.

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3
Q

What is the petal?

A

The inner whorl of the flower often colourful to attract insects.

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4
Q

What is the collective term for petals?

A

Corulla

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5
Q

What are the sepals?

A

It is the outermost ring of a flower which is usually green with its main function to protect the flower when it is in bud.

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6
Q

What is the collective term for the sepals?

A

calyx

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7
Q

What is the receptacle?

A

The basal portion of the flower to which all floor parts are attached.

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8
Q

What part of the flower are connected with the male reproduction?

A

The stamen

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9
Q

What does the stamen consist of?

A

The anther and the filament

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10
Q

What is the anther?

A

It’s where pollen is produced which usually consist of four pollen sacs, the sacs eventually split to release the pollen.

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11
Q

What is the filament?

A

Vascular tissue which supports the anther. It also transports amino acids (mineral ions) and sucrose to developing pollen grains.

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12
Q

What is the female reproductive organ known as?

A

The carpel

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13
Q

What does the carpel consist of?

A

The stigma, style and ovary

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14
Q

What does the stigma do?

A

Receive the pollen from the anther

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15
Q

What does the style do?

A

It holds the stigma to receive the pollen, the pollen produces a tube which grows down the style to the ovule.

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16
Q

What is the ovary?

A

It contains the ovules and develops into the fruit. Meiosis occurs in the ovary to produce haploid ovules.

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17
Q

What is an ovule?

A

It is made inside the ovary and contains an excel formed by reproduction which involves meiosis after fertilisation the ovules form seeds.

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18
Q

What type of sexual reproduction do plants undergo?

A

They undergo sexual reproduction as the flower has both male and female gametes.

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19
Q

What contains the male gamete?

A

The pollen grain

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20
Q

Where does the development of the pollen grain occur?

A

Within the pollen sac of another anther

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21
Q

Describe the structure of a developing anther?

A
  • It displays four chambers which are called pollen sacs.
  • Each sac is enclosed by a protective epidermis and a fibrous layer.
  • Inside the fibrous layer is the tapetum which is the food store which provides energy for future cell divisions.
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22
Q

What is each pollen sac filled with?

A

Large number of diploid mother cells, which are produced in mitosis.

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23
Q

Describe pollen formation?

A
  • Each mother cell (2n) goes through meiosis I and II forming a tetrad, which are called microspores and are haploid.
  • Microspores divide via mitosis and differentiate to form a pollen grain.
  • Inside the pollen grain the haploid nucleus undergoes mitosis to produce two nuclei: a generative and tube nucleus. The generative nuclei later develops into 2 male nuclei
  • The pollen grain is surrounded by an inner wall (intine) and a sculptured outer wall (extine)
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24
Q

What happens when the anther matures?

A

The outer layer of the anther dries out. Tension is set up in the lateral grooves and the anther splits open along its length and and opens out - DEHISCENCEwhich releases the pollen grain so pollination can occur.

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25
Q

What is dehiscence?

A

It is the splitting of the anther which releases the pollen grain.

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26
Q

What is the nucellus ?

A

It contains cells which provide nutrition for the growth of the ovule

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27
Q

What is the micropyle?

A

It is a small opening in the integuments which allows the pollen tube to enter.

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28
Q

Describe ovule production?

A
  • In the ovule a mother diploid cell divides by meiosis to form 4 haploid cells (megaspores).
  • 3/4 cells degenerate and 1/4 cell survives.
  • The surviving megaspore undergoes three meiotic divisions.
  • 8 haploid nucleus now represent the ‘megaspore’ cell.
  • The structure is called the embryo sac.
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29
Q

Describe the distribution of the eight haploid nucleus in the embryo sac?

A
  • 3 antipodal at the top
  • 2 polar nuclei in the centre which fuse to produce a diploid nucleus (polar)
  • 2 synergies either side of the haploid female gamete (egg cell) next to the micropyle.
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30
Q

What is pollination?

A

It is the transfer of pollen grains from the anther to the stigma.

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31
Q

Why does pollination occur?

A

It is so that pollen grains containing male gametes are brought close to female gametes for fertilisation.

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32
Q

What is self pollination?

A

It’s when pollen grains fall on the stigma of the same flower or different flowers of the same plant.

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33
Q

What is cross pollination?

A

It’s when pollen grains from one plant fall on the stigma of a different plant via wind, insects or another agent.

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34
Q

Why is cross pollination desirable?

A

As it promotes variation.

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35
Q

What fertilisation occurs in self pollination and cross pollination?

A

SELF POLLINATION: self fertilisation

CROSS POLLINATION: cross fertilisation

36
Q

What breeding occurs in self pollination and cross pollination?

A

SELF POLLINATION: inbreeding

CROSS POLLINATION: outbreeding

37
Q

How does variation differ in self pollination to cross pollination?

A

SELF POLLINATION: there is a reduce in genetic and phenotypic variation. Variation is dependent on mutation, random assortment and crossing over in meiosis

CROSS POLLINATION: there is an increase in genetic and phenotypic variation. Variation is dependent on mutation, random assortment and crossing over in meiosis and random assortment of gametes during fertilisation.

38
Q

What are the chances of two recessive undesirable alleles in self pollination and cross pollination?

A

SELF POLLINATION: the chances of these undesirable recessive alleles being brought together are increased during fertilisation.

CROSS POLLINATION: the chances of two recessive undesirable alleles being brought together at fertilisation is reduced.

39
Q

Why is self pollination good for preservation?

A

As they can preserve good genomes suited to a stable environment.

40
Q

How does the evolutionary significance of self pollination differ to cross pollination?

A

SELF POLLINATION: less evolutionary significance is reduced variation of individuals within the species as it is not desirable.

CROSS POLLINATION: there is a greater evolutionary significance due to an increase in variation of individuals within the species.

41
Q

How are insect pollinated flowers adapted to attract insects which enables the transfer of pollen?

A
  • nectar and a scent is present.
  • sticky stigma to collect pollen (disgrace and within the flower).
  • small quantities of sticky pollen
  • brightly coloured petals
  • barbs for hooking onto insect fur
  • anther is positioned to rub pulling onto insects within the flower.
42
Q

How are flowers adapted for wind pollination?

A
  • need to be exposed to wind
  • petals are small and green
  • no scent or nectary
  • stigma is large and feathery to catch pollen exposed by the wind
  • anthers hang outside the leaf so are exposed to the wind so it’s easily blown away
  • large quantities of small, smooth, light pollen.
43
Q

What is it called when the stamen ripens first?

A

PROTANDRY

44
Q

What is it called when the stigma ripens first?

A

PROTOGYNY

45
Q

What are the other ways to encourage cross pollination?

A
  • Separate male and female flowers on the same plants e.g. maize.
  • Separate male and female plants e.g. Holly.
  • Genetic incompatibility – pollen can’t germinate on the stigma which produces it (same plant) e.g. chemical self incompatibility in red clover.
46
Q

How does the male gamete in the nucleus (of the pollen grain) reach the female nucleus in the ovule?

A

By means of a pollen tube

47
Q

What does the pollen nucleus do?

A

It controls the growth of the pollen tube through the style. The pollen tube nucleus codes for the production of these hydrolases.

48
Q

How does double fertilisation occur?

A
  • pollen tube secretes hydrolytic enzymes ie celluloses and proteases which digest the style tissues, gaining nutrients from the digested products.
  • germination is stimulated by sugar on the stigma, enzymes and WP differences (producing a pollen tube).
  • the pollen tube protrudes through the outer wall of the pollen grain which penetrated the surface of the stigma and grows down the style.
  • It travels down the style following a gradient of chemoattractants secreted by the ovule (GABA)
  • Generative nucleus divides via mitosis to produce 2 haploid male nuclei (at the tip there are now 3 nuclei)
  • pollen tube penetrates the embryo sac through the micropyle
  • Pollen tube bursts releasing the two male nuclei, one near the egg cell and the other near the pollen nuclei in the embryo sac
49
Q

What aerotrophic is the pollen tube?

A

Negative as it grows away from oxygen

50
Q

What is the role of the tube nucleus?

A

Control the growth of the pollen tube. The pollen tube disintegrates after fertilisation

51
Q

1 male nuclei + egg cell

A

diploid zygote

later develops into an embryo

52
Q

1 male nuclei + polar nuclei

A

triploid endosperm (food store)

53
Q

What happens after double fertilisation?

A

The development of the fruit and seed.

54
Q

What does the seed develop from?

A

It develops from a fertilised ovule and contains an embryonic plant and a food store.

55
Q

What happens to the diploid zygote?

A

It divides via mitosis and becomes an embryo.

56
Q

What are the parts in which the embryo differentiates into?

A
  • Radicle: young root
  • Plumule: young shoot
  • Cotyledons: seed leaves (one or two)
57
Q

What is the suspensor?

A

It’s when the embryo is attached to the wall of the embryo sac via cells in which you have change nutrients.

58
Q

What happens to the triploid endosperm nucleus?

A

It divides by mitosis to form endosperm tissue which is an important food storage tissue which surrounds the embryo.

59
Q

What happens to the outer integument?

A

It develops into the testa: the micropyle remains as a pore in the testa (integument dries out, hardens and becomes waterproof with ligin deposits)

60
Q

What does the ovary wall become?

A

It becomes a fruit wall, enclosing the seeds.

61
Q

What does the ovule become?

A

The seed which comprises of the embryo, endosperm and testa

62
Q

What happens to the sepals, petals, style and stigma?

A

They all wither away

63
Q

What happens to the receptacle?

A

It develops into the fleshy part of the fruit

64
Q

Why is there a food store?

A

It is what supplies the embryo and the growing plant with food until it’s able to make its own. The food store could be in the cotyledons or in the endosperm. It’s the store food which is the nutritional value to humans and other animals.

65
Q

What happens when water leads to seed?

A

They dehydrate and become dormant because metabolic reactions stop.

66
Q

What are monocotyledons?

A

One seed leaf, the endosperm is the main food source for the embryo e.g maize.

67
Q

What are dicotyledons?

A

They have two leaves, the endosperm is absorbed within the cotyledons which provides a food source i.e. legumes, beans and peas.

68
Q

Describe the maize grain?

A
  • seed and fruit monocotyledon
  • one cotyledon (in the zygote)
  • endosperm is the food source
  • fruit wall very thin and fused with the seed coat so almost all of the edible grain is a seed
69
Q

Why do you say it’s need to be dispersed away from the parent plant?

A

To reduce competition for space, light, nutrients and water. They have developed different mechanisms to enable this so reduces competition following germination and increases the chances of growth into mature plants.

70
Q

How can seeds be dispersed?

A

wind
water
mechanical
animals

71
Q

What survival strategies have seeds evolved?

A

That they can remain dormant until suitable conditions are present.

72
Q

What are the three main conditions needed for germination?

A

water
suitable temp
oxygen

light can also be a factor

73
Q

Why is a suitable temperature needed for germination?

A

The optimum temperature for germination depends on the optimum temperature of the enzymes in the seed.

74
Q

Why is water needed for germination?

A

The nutrients in the dry tissue need to be re-hydrated before they can be used. Water softens the tester so that the roots can grow: fill vacuoles of cells, mobilise and activate enzymes and transport ions and nutrients to grow in plants,

75
Q

Why is oxygen needed for germination?

A

Aerobic respiration can occur to produce ATP for metabolism and growth.

76
Q

How can light affect germination?

A

Because some need darkness and some need light.

77
Q

What does germination involve?

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 in the cotyledons.

78
Q

Are the food reserves in the seed insoluble?

A

The food reserves are insoluble in water (starch, protein, lipids) they need to be hydrolysed into small soluble molecules which can be transported to the radical and plumule.

79
Q

Describe the mobilisation of food reserves?

A
  • Rapid uptake of water through the micropyle.
  • Tissue swell and the seed coat ruptures.
  • Water uptake stimulates the release of gibberellin a hormone.
  • This diffuses to the aleurone layer which contains proteins.
  • This activates the genes which code for amylase and protease (codes for hydrolytic enzymes production).
    Enzymes are mobilised and in solution.
  • Amylase hydrolyses starch —> maltose.
  • Protease hydrolyses proteins —> amino acids.
  • Soluble products are transported to growing plants.
  • Rapid mobilisation of food reserves leads to successful germination.
80
Q

What stimulates the release of the hormone gibberellin?

A

Water uptake

81
Q

What does mobilising enzymes lead to?

A

High rate of aerobic respiration as glucose and other nutrients diffuse to the embryo where they are used in aerobic respiration and growth.

82
Q

How does the plumule grow?

A

It pushes through the seed coat and grows upward

83
Q

How does the radicle grow?

A

Pushes through the seed coat and grows downward

84
Q

What happens to starch?

A

It gets broken down by enzymes into maltose and then glucose. Glucose is then used in respiration to provide ATP for growth.

85
Q

Describe germination of a broad bean?

A
  • The testa ruptures as the radical pushes out first which grows downward where as the plumule grows upward. - The dicotyledons of the broadband grow/remain below ground.
  • The plumule is bent over in a hook shape as it pushes to the soil preventing the tip from being damaged by soil abrasion.
  • When the plumule emerges it unfurls and begins to make food for itself by photosynthesis.
  • Food reserves in the cotyledons are depleted
86
Q

What happens when water enters the micropyle and the cotyledon swell?

A

The testa splits allowing more oxygen to enter for aerobic respiration.The food reserves from cotyledons: starch and proteins are mobilised through hydrolysis.
Providing sources of energy for respiration and growth of the radicle and plumule

Component 2 Biology (9 decks)

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