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WJEC Biology A-Level > Unit 4.2 - Sexual reproduction in plants (physicsandmathstutorflashcards) > Flashcards

Unit 4.2 - Sexual reproduction in plants (physicsandmathstutorflashcards)

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1
Q

what is a dicotyledon

A

a plant that produces seeds containing 2 cotyledons
2 primary leaves

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2
Q

what is an insect-pollinated flower

A

a type of flower that relies on insects to transfer pollen grains between flowers

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2
Q

what is the calyx

A

-first part of a flower which is formed
-consists of leafy structures that protect the flower during development

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3
Q

what is the corolla

A

all of the petals of a flower

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4
Q

what is the carpel

A

the female part of the plant

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5
Q

what does the carpel consist of

A
  • stigma
  • style
  • ovary
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6
Q

what is the stamen

A

the male part of the plant involved in the production of male gametes

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7
Q

what form do male gametes take

A

pollen grains

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8
Q

what are the parts of the stamen

A
  • anther
  • filament
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9
Q

what are the 5 adaptations of insect-pollinated plants

A
  • internal anthers + small stigma (directly touch insects)
  • large, bright petals and nectar from glands (attract insects)
  • produce chemicals (to mimic scent of female insects)
  • grow individually
  • large pollen grains with projections (attach to insect)
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10
Q

what is a wind-pollinated plant

A

a type of flower that relies on wind to transfer pollen grains between flowers

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10
Q

describe the 6 adaptations of wind-pollinated plants

A
  • external anthers (optimise pollen dispersal)
  • excess pollen (compensates for wind wastage)
  • feathery stigma (catches pollen from air)
  • small dull petals
  • grow densely
  • light pollen grains
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11
Q

how does a pollen grain form in the anther

A
  • large number of pollen (2n) mother cells produced by mitosis
  • meiosis of mother cells in anther = four (1n) haploid microspores
  • (1n) microspores mature into pollen grains via mitosis
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11
Q

describe the role of the tapetum in pollen grain development

A
  • specialised layers of cells in the anther
  • provides nutrients to developing pollen grains
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12
Q

describe the structure of mature pollen grains

A
  • generative cell (haploid nucleus) produces two male gametes via mitosis
  • pollen tube cell (has own nucleus) elongates to penetrate ovule
  • outer protective coating
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13
Q

define dehiscence

A

splitting of the anther resulting in the release of pollen grains.

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14
Q

how does the ovule form in the ovary

A
  • meiosis of megaspore cell = four (1n) megaspores
  • growth + development (3 mitotic divisions of a megaspore)
  • embryo sac forms (contains eight 1n nuclei)
15
Q

Describe the structure of the embryo sac

A
  • 2 polar nuclei (form endosperm)
  • ovum (forms zygote)
  • two synergids (help generative nucleus of pollen grain to reach ovum)
  • three antipodal cells
  • outer protective coating
16
Q

define pollination

A

the deposition of pollen into a stigma from an anther

17
Q

what are the 2 types of pollination

A
  • cross pollination
  • self pollination
18
Q

what is cross pollination

A

when pollen is transferred from an anther of one plant to a stigma of a DIFFERENT plant

19
Q

what is self-pollination

A

when pollen is transferred from an anther of one plant to a stigma of the SAME plant

20
Q

where does double fertilisation occur

A

embryo sac of ovule

21
Q

how do the male nuclei reach the embryo sac

A
  • pollen grain from one plant lands on the stigma of another
  • mitosis of pollen grain to form a pollen tube nucleus and two male gametes
  • pollen tube grows from the grain down to the ovule via the digestion of the style
  • pollen tube delivers two male gametes
22
Q

how does the pollen tube enter into the embryo sac

A

via the micropyle

23
Q

what is the micropyle

A
  • pore in the ovule where the pollen tube enters the embryo sac
  • remains as a pore in the testa (seed coat)
24
Q

what happens during double fertilisation

A

in the embryo sac of ovule:
- 1st male gamete fuses with female gamete = (2n) zygote
- 2nd male gamete fuses with 2 polar nuclei = (3n) primary endosperm

25
Q

what happens to the ovule during double fertilisation

A

develops into the seed

26
Q

how is the (2n) embryo formed following double fertilization

A

diploid zygote undergoes mitosis = 2n embryo

27
Q

how is endosperm formed

A

nucleus of triploid endosperm divides by mitosis = endosperm

28
Q

what is the function of the endosperm

A

acts as a nutrient source for the embryo

29
Q

what structure forms the testa

A

integuments develop into the testa

30
Q

what happens to the ovary following double fertilization

A

it develops into a fruit wall surrounding the seed

31
Q

what is the plumule

A

the part of a plant embryo that develops into the primary shoot

32
Q

what is the radicle

A

the part of a plant embryo that develps into the root

33
Q

what is the hilum

A

a scar on the testa as a result of separation from its funicle

34
Q

define germination

A

the process by which a plant grows from a seed

34
Q

give an example of a non-endospermic seed

A

broad bean

35
Q

describe the stages of germination in a non-endospermic seed

A
  • seed absorbs water (through micropyle) causing cotyledon swelling = enzyme activation + rupture of seed coat
  • food reserves from cotyledon are hydrolysed
  • provides energy for growth of plumule+radicle (and respiration)
36
Q

describe the stages of germination in an endospermic seed

A
  1. seed absorbs water (activating embryo to secrete gibberellin)
  2. gibberellins induce the synthesis of amylase
  3. amylase diffuses to the endosperm layer and causes the hydrolysis of starch into glucose
37
Q

state the factors affecting seed germination

A
  • water availability
  • temperature
  • availability of O₂ (for respiration)
  • use of fertilisers provide extra nutrients for growth
38
Q
A

WJEC Biology A-Level (14 decks)

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