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YEAR 2 BIO > sexual reproduction in plants > Flashcards

sexual reproduction in plants Flashcards

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Biology 101 flashcards
1
Q

what are sepals

A

cover the flower structure while flower is developing. in some species these are modified to petals

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2
Q

what are petals

A

surround the male and female flower parts. attract animal pollinators - usually brightly coloured and have a scent. may also produce nectar

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3
Q

what is the carpel

A

THE FEMALE PART
- stigma
- style
- ovary
stigma = surface on which pollen lands and the pollen tube grows down to the ovary
style = connects the stigma to the ovary
ovary = contains the ovules (single egg nuclei)

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4
Q

what is the stamen

A

THE MALE PART
- anther
- filament
filament = supports the anthers that produce the pollen grains also contain vascular tissue which transports the food materials required for the formation of pollen grains
anther = made up of 4 pollen sacs arranged in 2 pairs

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5
Q

methods of pollination

A

pollination = transfer of pollen from anther to stigma

  • if the transfer occurs between two plants of the same species it is cross pollination ( 2 plants of different genetic make up)
  • transfer takes place between flowers of identical genetic constitution, the process is self-pollination
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6
Q

what is self pollination

A

1) within the same flower. pollen from the anther is transferred to stigma of the same flower
2) occurs between two flowers. pollen from the anther of one transfers to the stigma of the anther

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7
Q

characteristics of insect pollinated flowers

A
  • bright
  • smell nice
  • petals large
  • marking (nectar guides)
  • far away from each other
  • anthers within flower
  • stigma within flower
  • small amounts of sticky, sculptured pollen
  • larger pollen grains
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8
Q

characteristics of wind pollinated flowers

A
  • little or no petals
  • light seeds
  • no scent or nectar
  • anthers hang outside flowers
  • closer together
  • large feathery stigmas hand outside flower
  • large amounts of smooth pollen
  • produces smaller pollen grains
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9
Q

what is male gamete development

A
  • anther typically consists of 4 pollen sacs in which the pollen develops
  • vascular tissue supplies water and nutrients to the anther
  • the pollen sac is lined with a layer of cells known as the tapetum which regulates pollen development and supplies nutrients to the developing pollen grains
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10
Q

formation of male gamete

A

pollen mother cell –> 4 pollen grains –> generative nucleus + tube nucleus (pollen tube) –> male nucleus (2)

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11
Q

steps of formation of male gamete

A

1) meiosis
2) mitosis
3) mitosis

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12
Q

formation of female gamete

A

megaspore mother cell –> 4 megaspore (3 disintegrate) –> 2 nuclei –> 4 nuclei –> 8 nuclei –> 2 synergids + 3 antipodals + 2 polar nuclei + 1 oosphere

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13
Q

steps of formation of female gamete

A

1) meiosis
2) mitosis
3) mitosis
4) mitosis
5) cell wall formation

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14
Q

genetic consequences of self and cross pollination

A
  • self pollination is an advantage to a plant if there are no similar plants nearby, it results in in-breeding. this leads to a reduction in the gene pool and reduces variation in the population
  • self pollinated species depend on random assortment and crossing over during meiosis and on mutation to bring about variation in the genomes of male and female gametes. therefore self-fertilised species display less genetic variation than cross fertilised species
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15
Q

mechanisms favouring cross-pollination include –>

A

1) DIOECIOUS
2) MONOECIOUS
3) anthers and stigmas maturing at different times e.g. bluebell
4) structural adaptations which make self-pollination unlikely e.g anthers and stigmas arranged at different levels so that cross pollination between pin-eyed and thrum-eyed flowers is favourable
5) genetic incompatibility which prevent germination of the pollen grain on a genetically similar plant

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16
Q

what is dioecious

A

having separate male and female plants

17
Q

what is monoecious

A

having separate male and female flowers on one plants

18
Q

what is in-breeding

A

while out breeding is of greater evolutionary significance due to the fact that some genomes are more successful than others in the struggle for survival - there are advantages to inbreeding e.g. it preserves good genomes which may be suited to a relatively stable environment

19
Q

describe the process of double fertilisation

A

1) pollen hydrates and absorbs sucrose produced by the stigma
2) tube grows from the pollen grain
3) grows towards the egg cell up a chemical gradient
4) produces enzymes to digest the cells in the style using the products for nutrition
5) it nether the micropyle and into the embryo sac. the pollen tub nucleus disintegrates
6) one sperm nucleus fuses within the egg cell nucleus to from the diploid zygote
7) the other haploid sperm cell nucleus fuses with the other two polar nuclei to from the triploid endosperm

20
Q

what does the diploid zygote become

A

divides by mitosis

becomes the plumule (shoot) ,radicle (root) and cotyledons (leaves)

21
Q

what does the triploid endosperm become

A

food store

22
Q

what does the outer integument become

A

seed coat (testa)

23
Q

what does the ovule become

A

seed

24
Q

what does the funicle of the ovule become

A

funicle of seed

attaches at the hilum

25
Q

what does the ovary become

A

fruit

26
Q

characteristics of monocotyledons

A
  • one cotyledon in seed
  • leaf veins are parallel
  • sepals, petals and stamens in multiples of 3
  • vascular bundles scattered in stems
  • vascular bundles scattered in roots
    eg maize
  • cotyledon remains small and does not develop
    testa of a maize seed fuses with ovary wall so maize has a one seeded fruit
27
Q

characteristics of dicotyledons

A
  • two cotyledons in seed
  • leaf veins form a network
  • sepals, petals and stamens in multiples of 4 or 5
  • vascular bundles in a ring in stems
  • vascular bundles in centre of roots
    e. g. broad bean
  • plumule becomes the shoot and radicle becomes the root. endosperm is absorbed by cotyledons
28
Q

types of dispersal

A
  • wind
  • transport
  • rolling
  • bursting
  • water
  • carrying
29
Q

examples of wind dispersal

A

ash and sycamore fruit has said that allow wind dispersal

dandelions had parachutes

30
Q

examples of transport dispersal

A

birds eat seeds the pass through their digestive system

SCARIFICATION digestive systems weaken the testa by physical attack, by acid and enzymes

31
Q

examples of rolling dispersal

A

fruit of a horse chestnut tree breaks open and the conker rolls away

32
Q

examples of bursting dispersal

A

legume pops dry, split and seeds scatter

33
Q

examples of water dispersal

A

coconut palms float and carried away

34
Q

examples of carrying dispersal

A

hooked seeds attach to animals coats and are carried away.

35
Q

steps in germination

A

1) bean seed absorbs water through pore
2) starch in the seed is hydrolysed into maltose by the enzyme amylase
3) proteins are hydrolysed by protease to amino acids
4) these break down products are absorbed by the embryo plant and the plumule and radicle cell start to divide and differentiate
5) the swollen cotyledons rupture the testa and oxygen enters allowing increased aerobic respiration and rapid growth
6) the radicle emerges and grows downwards due to + geotropism and - phototropism
7) the plumule emerges and grows upwards due to - geotropism and + phototropism
8) once the leaves develop the food reserves in the cotyledons will have been used up

36
Q

positives of seed germination

A
  • spread far = modified for dispersal
  • protects the embryo
  • dormant until fertilised
  • self contained = have an energy store
  • less than 10% moisture so don’t rot
37
Q

what conditions are needed for germination to occur

A
  • need water
  • need correct temp
  • require oxygen for aerobic respiration
38
Q

germination in endospermic seeds

A
  • embryo secretes a gibberellic acid which affects a layer of seeds towards the outside of the seed
  • the gibberelic acid switches on genes in the cells of the aleurone layer, resulting in transcription and translation, producing enzymes including protease and amylase
  • the proteases hydrolyse protein in the aleurone layer to make amino acids used to make amylase
  • amylase diffuses out of the aleurone layer and hydrolyses the starch stored in the endosperm cells
  • maltose and glucose produced diffuse back through the endosperm to the plumule and radicle of the embryo
  • they are respired for energy which fuels biosynthesis and cell division which brings the seed out of dormancy
39
Q

functions of gibberelinns

A
  • stimulates cell elongation
  • help in breaking seed dormancy
  • promote flowering in some plants even under unfavourable conditions
  • help in seed germination
  • promote production of male flower

YEAR 2 BIO (11 decks)

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