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biology - component 2 > plant reproduction > Flashcards

plant reproduction Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are flowering plants known as?

A

angiosperms

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2
Q

what is the collective name for the sepals?

A

calyx

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3
Q

what is the corolla?

A

all the petals on a flower

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4
Q

describe an insect pollinated flower

A
  • colourful petals
  • scented
  • has nectar
  • anthers located within flowers
  • stigma located within flowers
  • small quantities of larger stick sculpted pollen
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5
Q

describe a wind pollinated flower

A
  • petals usually absent
  • small, green inconspicuous petals
  • no scent or nectar
  • anthers hanging outside flower
  • large feathery stigmas hang outside flowers
  • large quantities of smaller pollen
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6
Q

outline the process of the formation of a pollen grain

A

pollen grains are formed in the anther by mitosis and meiosis
- mitosis occurs to produce large numbers of diploid pollen mother cells
- the mother cells undergo meiosis to produce a tetrad (four) haploid cells
- these cells form pollen grains that contain the male gamete

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7
Q

what is the tapetum?
what is its function?

A
  • a layer of cells around the pollen sac
  • it provides nutrients to the developing pollen grains and produces a waterproof coat for the pollen grain
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8
Q

what is the role of the vascular bundle in the anther?

A

supplies water and sucrose to the anther

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9
Q

outline the process of forming the male nuclei

A
  • inside each pollen grain the haploid nucleus undergoes mitosis to produce two nuclei: a generative nucleus and a pollen tube nucleus
  • the generative nucleus will later undergo mitosis to give rise to two male nuclei
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10
Q

describe the pollen cell wall

A

called the exine
- tough and resistant to chemicals
- resists desiccation

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11
Q

what is pollen resistant to and what does this mean?

A

resistant to UV radiation
- pollen can be carried at high altitudes without DNA mutation occuring

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12
Q

what is dehiscence?

A

release of pollen

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13
Q

outline the process of dehiscence

A
  • the outer layers of the anther dry out, causing tension
  • dehiscence occurs, tension pulls the walls of the anther apart and the edges of the pollen sacs curl away
  • an opening called the stomium exposes the pollen grains and they are carried away by insects or the wind
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14
Q

describe the development of the ovule

A

the ovule contains the female gamete and is formed in the ovary by mitosis and meiosis
- the megaspore mother cell in the nucellus undergoes meiosis to produce four haploid megaspores
- three of the megaspores cells degenerate and only one grows and develops
- this one megaspore undergoes three mitotic divisions to produce eight haploid nuclei within the embryo sac of the ovule

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15
Q

what does the haploid nuclei include?

A

one female gamete, two polar nuclei, two synergids and three antipodal cells

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16
Q

define micropyle

A

a gap in the integuments for the male nuclei to enter the embryo sac

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17
Q

define integuments

A

protects the embryo sac

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18
Q

define funicle

A

attaches the ovule to the ovary wall

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19
Q

define polar nuclei

A

fuses with a male nucleus to form a zygote

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20
Q

define female gamete

A

fuse with a male nucleus in double fertilisation to form a triploid endosperm

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21
Q

define pollination

A

the transfer of pollen grains from the anther to the stigma

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22
Q

why is pollination necessary?

A

so that the pollen grains, containing the male gametes, are brought into contact with the female part of the flower so that the fertilisation can be achieved

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23
Q

what are the 2 types of pollination?

A
  1. self pollination
  2. cross pollination
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24
Q

define self pollination

A

transfer of pollen grains from an anther to a stigma of the same plant

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25
Q

define cross pollination

A

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

26
Q

source of variation for self pollination?

A
  • crossing over
  • independent assortment
27
Q

source of variation for cross pollination?

A
  • crossing over
  • independent assortment
  • mixing of parental genotypes when haploid gametes fuse
28
Q

what are the advantages of self pollination?

A
  • faster, easier (as only one parent is needed)
  • can help maintain genotypes which are well adapted to the current environment
29
Q

what are the disadvantages of self-pollination?

A
  • less genetic variation, offspring may be less likely to survive changes in the environment
  • increases the chance of offspring being homozygous for recessive alleles which could lead to genetic diseases
30
Q

why is cross pollination of greater evolutionary significance than self pollination?

A

increases genetic variation so a species can adapt to environmental change - natural selection

31
Q

how could cross pollination be prevented during plant reproduction experiments?

A

prevent the transfer of pollen from one flower to another by enclosing or isolating the flower in a bag

32
Q

where do insect pollinated flowers have their nectaries located? why is this an advantage?

A
  • below the antha/stigma
  • this promotes insects transferring pollen grains as they will brush past the anther/stigma when going down to the nectaries
33
Q

explain how the stamen and stigma ripening at different times causes cross pollination to occur?

A
  • even if pollen produced by the anther lands on the stigma, it will not germinate or form a pollen tube
    OR
  • no pollen will fall onto the ripe stigma as it is not being produced by the anther
34
Q

explain how the anther being below the stigma causes cross pollination to occur

A

pollen cannot fall from the anther onto the stigma

35
Q

explain how genetic/chemical incompatibility ensures cross pollination to occur

A

pollen is unable to germinate on the stigma of the flower which produced it

36
Q

explain how separate male and female plants ensures cross pollination to occur

A

plant does not have both male and female sex organs so can not self pollinate

37
Q

outline the process of fertilisation

A
  • when a compatible pollen grain lands on a stigma, the stigma secretes a sugary solution
  • the pollen grain then germinates and the pollen tube nucleus controls the growth of a pollen tube
  • the pollen tube nucleus codes for hydrolytic enzymes that digest through the tissues of the style. the products of digestion are used by the pollen tube.
  • the pollen tube nucleus is at the tip of the pollen tube with the two male nuclei behind
  • the pollen tube enters the embryo sac through the micropyle
  • the pollen tube nucleus now disintegrates and the tip of the pollen tube opens, releasing the two male nuclei into the embryo sac
38
Q

describe double fertilisation

A

both male gametes are involved in separate fertilisation events:
- one male gamete fuses with the female gamete to produce a diploid zygote
- the second male gamete fuses with the two polar nuclei to form a triploid primary endosperm nucleus

39
Q

what are the similarities and differences between fertilisation in humans and fertilisation in flowering plants?

A

SIMILARITIES:
- both involve the fusion of haploid gametes to form a zygote
- both involve internal fertilisation in females
- both involve the secretion of digestion enzymes
DIFFERENCES:
- double fertilisation in plants
- pollen tube formation in plants/acrosome reaction in humans
- male gametes is able to swim in humans

40
Q

what does the zygote become in the formation of the seed and fruit?

A

by mitosis
- diploid embryo, consisting of plumule, radicle and one or two cotyledons

41
Q

define plumule

A

developing shoot

42
Q

define radicle

A

developing root

43
Q

what does the triploid endosperm nucleus become in the formation of the seed and fruit?

A

by mitosis
endosperm tissue, an important food storage tissue in cereal grains

44
Q

what does the ovule become in the formation of the seed and fruit?

A

seed

45
Q

what does the ovary wall become in the formation of the seed and fruit?

A

develops into a fruit wall enclosing the seeds

46
Q

what does the integument become in the formation of the seed and fruit?

A

develop into the testa (seed coat)

47
Q

what does the micropyle become in the formation of the seed and fruit?

A

remains as a pore in the testa

48
Q

what is a cotyledon?

A

a seed leaf

49
Q

define monocotyledones and give an example

A

seeds with one cotyledon
e.g maize and wheat

50
Q

define dicotyledones, give an example

A

seeds with two cotyledons
e.g broad beans

51
Q

describe maize

A
  • monocotyledons so only has one cotyledon
  • the endosperm acts as a food store therefore maize is endospermic
52
Q

describe broad bean

A
  • dicotyledons, they have two cotyledons, with the embryo lying between them
  • broad bean seeds use the cotyledons as food storage tissue
  • this means they do not have an endosperm so are non-endospermic
53
Q

how are seeds adapted for life on land?

A
  • the testa is chemically resistant so seeds survive adverse chemical conditions
  • also provides physical protection
  • endosperm provides a supply of nutrients until photosynthesis can occur
54
Q

why is seed dispersal important for plants?

A
  • reduces competition with parent plant and other offspring plants
  • allows for colonisation of new trees
55
Q

why are fruit important in seed dispersal?

A

fruit are eaten by animals, the seeds pass through the animal’s digestive system and then egests, disperses seeds

56
Q

what types of seed dispersal are there?

A
  • water dispersal
  • wind dispersal
  • animal fur
57
Q

what are the main requirements for successful germination?

A
  • oxygen: aerobic respiration to produce ATP for metabolism
  • suitable temperature: optimum temperature speeds up the rate of diffusion and increases enzyme activity
  • water: transport medium for enzymes and softens of the testes
58
Q

what do the first steps of germination involve?

A
  • water is imbibed (taken in) through the micropyle
  • the tissues then swell, splitting or softening of the testa, allowing entry of more oxygen
  • oxygen can then be used in aerobic respiration to produce ATP energy for metabolism
59
Q

outline germination in non-endospermic seeds

A
  • mobilised enzymes hydrolyse large, insoluble food stores
  • amylase hydrolyses starch into maltose
  • lipase hydrolyses lipids into fatty acids & glycerol
  • protease hydrolyses protein into amino acids
  • these soluble products are transported to the plumule and the radicle for use in respiration
  • aerobic respiration can then produce ATP energy for mitosis and growth
  • the plumule grows upwards. the radicle grows downwards
  • the plumule emerges from the soil, the leaves unfurl and begin to photosynthesise
  • the plant is now independent of food stores in the seed
60
Q

outline germination in endospermic seeds

A

endosperm contains starch, proteins, fats
- following inhibition of water, gibberellin is released by the embryo and diffuses to the aleurone layer
- gibberellins cause transcription and translation to then occur, producing hydrolytic enzymes
- protease digests the proteins in the aleurone layer to form amino acids, these can be used in further enzyme synthesis e.g amylase
- amylase diffuses into the endosperm and hydrolyses the starch stored there into maltose
- proteins and fats in the endosperm are also hydrolysed into amino acids and fatty acids & glycerol
- maltose, glucose and other nutrients diffuse to the embryo where they are used in aerobic respiration to provide ATP for the growth of the plumule and radicle

biology - component 2 (7 decks)

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