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A Level Biology Flashcards - BB > 22 Plant reproduction > Flashcards

22 Plant reproduction Flashcards

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1
Q

what is the definition of pollination?

A

the transfer of pollen grains from male reproductive structures to female reproductive structures of another plant prior to fertilisation

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2
Q

what is self-pollination?

A

pollen is transferred to a stigma of the same flower/another flower on the same plant

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3
Q

what is the advantage of self-pollination?

A

more reliable than cross-pollination

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4
Q

what is the disadvantage of self-pollination?

A

less genetic variation –> inbreeding –> disadvantageous recessive characteristics more likely to be passed on

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5
Q

how is self-pollination avoided?

A

male and female parts mature at different times (protandry and protogyny)

physical separation of male and female parts

some flowers are monoecious (i.e. only male/female)

chemicals on stigma prevent pollen grains from same plant producing pollen tube (self-incompatibility)

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6
Q

what is cross-pollination?

A

pollen is transferred from one plant’s anther to another plant’s stigma

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7
Q

what are the features of plants that are pollinated by insects?

A

colourful, scented petals (can mimic female insects)

nectar produced

short stamen with firmly attached anthers

small, sticky pollen grains

small, sticky stigma

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8
Q

what are the features of plants that are pollinated by the wind?

A

small and inconspicuous petals

long stamen with loosely attached anthers

large, smooth, light pollen

large, feathery stigma

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9
Q

what are the advantages of cross-pollination?

A

increases variation and widens gene pool

more heterozygous plants ∴ allele frequency of advantageous genes increases ∴ less susceptible to disease

better chance of adaptation to environment

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10
Q

what are the disadvantages of cross-pollination?

A

requires a pollinating agent

waste of energy

transmission of disease more likely

takes longer

fewer offspring produced

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11
Q

outline the first stage of fertilisation in angiosperms

A

pollen grain lands on stigma, completes development and matures

pollen tube grows a cytoplasmic extension down the style (chemotropism), controlled by tube nucleus

pollen tube enters the ovary through the micropyle

tube tip bursts to release male gametes

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12
Q

outline the second stage of fertilisation in angiosperms

A

double fertilisation:

  • one sperm nucleus fuses with ovum –> zygote
  • one sperm nucleus fuses with 2 polar nuclei within embryo sac –> 3n endosperm tissue –> embryo food supply

ovules develop into seeds (containing embryo and endosperm)

ovary develops into fruit

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13
Q

what is the genetic advantage of fertilisation in angiosperms?

A

restores chromosome number to diploid

increases genetic variation

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14
Q

what are the features of a seed’s embryo?

A

plumule = shoot

hypocotyl = simple stem

radicle = root

1 or 2 cotyledons

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15
Q

what are the three main features of an endospermic seed?

A

embryo

endosperm

testa

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16
Q

why might a seed lack an endosperm?

A

to prevent it from germinating in the autumn/winter by reducing its metabolic rate

17
Q

what would a seed have instead of an endosperm?

A

seed leaves - absorb nutrient reserves from the endosperm

18
Q

what is the function of the micropyle?

A

to allow the entry of water and nutrients to the seed

19
Q

what is the definition of germination?

A

plant growth from a seed, including the growth of an embryo root and shoot

20
Q

what are gibberellins?

A

plant ‘hormones’ required for germination as growth regulators and cell signalling molecules

21
Q

outline the process of germination

A

exposure to water causes rehydration of the seed

water washes out enzyme that was inhibiting growth

metabolic rate reactivated

insoluble starch in endosperm hydrolysed to maltose by a-amylase and then to G/S by maltase

gibberellins induce synthesis of amylase –> initiates break down of starch

22
Q

how does water affect germination?

A

enters by osmosis and softens testa to allow it to rupture

mobilises food reserves in the endosperm

activates enzymes

required for hydrolysis and as a solvent

washes out germination/growth inhibitors

23
Q

how does temperature affect germination?

A

increased metabolic rate

optimum for enzymes

digests food reserves

moderates respiration and growth

24
Q

how does oxygen affect germination?

A

required for aerobic respiration

required for oxidation of glucose and lipids as respiratory substrates

25
Q

what are the three vegetative structures?

A

root

stem

leaves

26
Q

what are triggers for development to the reproductive phase?

A

temperature

duration of dark period

27
Q

what is unique in each flowering plant that causes it to flower?

A

the proportions of Pr and Pfr

28
Q

what are the two isomers of phytochrome?

A

Pr - 660nm

Pfr - 730nm

29
Q

what is photoperiodism?

A

the reactions of Pr Pfr that occur in daylight and darkness

30
Q

which phytochrome accumulates in darkness?

A

Pr

31
Q

how is day length measured by the plant?

A

the conversion rate of Pr –> Pfr

32
Q

how is the apical meristem triggered to its development phase?

A

active form of phytochrome

causes transcription of flowering time gene

FT mRNA transported in phloem to shoot apical meristem

translated to FT protein

protein binds to transcription factor

activation of flowering gene –> reproductive meristems

33
Q

give an example of a cereal

A

rice

maize

wheat

34
Q

why are cereals used as a source of food by humans?

A

rich in starch

35
Q

what is the definition of global supply?

A

the annual production of a specific crop, plus stockpiles of it carried over from previous years

36
Q

what is the effect of the increasing human population on cereal production?

A

increasing use

demand exceeding supply

37
Q

why is sustainability of food increasingly more difficult?

A

population increasing

BUT available land and water decreasing

+ increasing costs

A Level Biology Flashcards - BB (35 decks)

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