plant reproduction Flashcards
1
Q
how is cross pollination promoted
A
- male and femal parts of most flowers develop at different times
2
Q
what do flowering plants or angiosperms use for their reproductive structures
A
flowers
3
Q
where are the gametes found within flowering plants / angiosperms
A
- male gametes are contained within polled which is produced within the anthers
- the ovule contains an embruo sac with one female gamete inside
4
Q
what are the sepals and it function
A
- usually green
- protect the flower in the bud
5
Q
what are the colour of the petals
A
- petals range from being absent to small and green to large and brightly coloured
6
Q
what are the male parts of the flower and it’s function
A
- stamens
- consist of a filament supporting the anther which contains four pollen sacss
7
Q
what are the female parts of the flowers
A
- the carpels
- found at the centre of the flower
- contain the ovary where the ovules develop
8
Q
what is the function of the stigma
A
receptive surface which collects pollen during pollination
9
Q
pollination
A
transfer of pollen from the anther of one flower to the mature stigma of another flower of the same species
10
Q
what are the features and it functions of insect pollinated flower
A
- large colourful petals, scent and nectar to attract pollinators such as insects
- anthers within hte flower which transfer pollen to insects when they feed on nectar
- stigma within the flower to collect pollen from insect when it feeds on nectar
- small quantities of sticky sculptured pollen to stick to insect
11
Q
what are the structures and it function of wind pollinated flower
A
- small green and incospicous , no scent , petals usually absent
- anthers hanging outside the flower so wing can blow pollen away
- large feathery stigmas providing a large surface area to catch pollen grains
- large quantities of small smooth, light pollen to be carried by wing
12
Q
dehiscence
A
opening of the anther releasing pollen grains
13
Q
what is the function of the tapetum
A
- surrounding nutritive layer of the pollen sac provide nutrients to developing pollen grains
14
Q
what does the pollen sac contain
A
- many pollen mother cells
15
Q
describe male gamete development
A
- pollen mother cells each divide by meiosis to produce a tetrad
- haploid nucleus within the pollen grain undergoes mitosis to produce a generative nucleus and a pollen tube nucleus
- generative nucleus then undergoes further mitotic division producing two male nuclei
16
Q
what is the pollen cell wall made out of and it properties
A
- made of exine and intine
- tought and resistant to desiccation
17
Q
what is the process of dhiscence
A
- outer layers of the anther mature and dry out and outer wall curls away exposing the pollen grains
18
Q
describe the process of female gamete development
A
- ovules contain a megaspore mother cell which undergoes meiosis producing four haploid cells only one of which develops further
- produces eight haploid cells following three mitotic divisions
- two of these cells fuse to prodce a diploid polar nucleus leaving six haploid cells : 3 antipodals, 2 synergids and 1 oospher
- all contained within the embryo sac which is surrounded by the integuments
19
Q
protandry
A
stamens ripen before stigmas
20
Q
feritlisation
A
fusion of the male gamete with the female gamete producing a diploid zygote
21
Q
what is pollination
A
transfer of pollen from the anther of one flower to the mature stima of another flower of the same species
22
Q
what is self pollintation
A
When pollination occurs
between the anther and stigma in the same flower, or different ower on the same plant
23
Q
what is cross pollination
A
When pollen is transferred to
another flower on a different plant of the same species,
24
Q
what does self pollination lead to and why is it a risk of variation
A
- Self-pollination leads to self-fertilisation which results in inbreeding and so
genetic variation is greatly reduced, as it only occurs as a result of mutation, independent assortment and crossing over. - There is an increased risk of
harmful recessive alleles coming together, but inbreeding does preserve successful genomes.
25
what does cross polllination lead to and why is it an advantage to the species
* Cross-pollination combines the genetic material from
two different individuals so results in greater variation, and is referred to as outbreeding.
* Here the chance of harmful recessive alleles coming together
is reduced, and allows for greater genetic variation potentially leading to evolution of species over time.
26
how have plant species evolved to ensure cross pollination occurs
■ Stamen and stigma ripen at different times. When the stamens ripen rst it
is referred to as protandry.
■ The anther is located below the stigma, reducing the risk of displaced
pollen falling onto it.
■ Some plants have separate male and female owers, e.g. maize, or separate
male and female plants, e.g. holly.
■ Some plants show genetic incompatibility, e.g. red clover, where pollen
cannot germinate on the stigma of the same plant.
27
describe double fertilisation in a plant
* When a pollen grain lands on the mature stigma of another plant of the same species, (or same plant in the case of self-pollination) it germinates producing a pollen tube.
* The growth of the tube is
controlled by the pollen tube nucleus, which also produces hydrolases, e.g. cellulases and proteases which digest a path through the style towards the
micropyle and into the embryo sac guided by chemical attractants, e.g. GABA.
* The tube nucleus then disintegrates and the two male gametes enter the
ovule.
* One male nucleus fuses with the haploid female nucleus, the oosphere, to form the zygote.
* The second male nucleus fuses with the diploid polar
nucleus to form a triploid nucleus which develops into the endosperm which
will provide nutrition for the developing embryo plant.
28
describe the events that occur after fertilisation
* ovary wall becomes the fruit
* ovule becomes the seed
29
what type of plant is a broad bean
dicotyledonous plants
30
what are the structure of dicotyledenous plants ater fertilisation
* two seed leaves of cotyledones which absorb the food store or the endoperm
* radicle forms the root
* plumule forms the shoot
31
what happens in monoctyledonous plants after fertilisation
* eg maize
* one cotyledon
* testa and ovary wall fuse
* one seeded fruit
32
what is one property of seeds
remain dormant for many years
33
why is seed dispersal important
allows seedlings to germinate away from the parent plant and so reduces comeptition for resources
34
what are methods of seed dispersal and give examples for each
■ Wind, e.g. dandelion seeds.
■ Water, e.g. coconuts.
■ Animals, attached to their fur, e.g. burdock.
■ Animals, eat the fruits and egest the seeds away from the parent plant, e.g.
cherries. The digestive system weakens the testa allowing germination to
occur, and supplies its own fertiliser – faeces.
35
germination
the biochemical and physiological process through which a seed becomes a photosynthesising plant
36
describe the requirements for broad bean
■ Optimum temperature for enzyme action.
■ Water for the mobilisation of enzymes and transport of products to
growing points.
■ Oxygen for aerobic respiration
37
describe the process of germination within a broad bean
■ Water is absorbed by the seed, causing the tissues to swell and mobilises
the enzymes.
■ The testa (seed coat) ruptures, the radicle pushes through rst downwards,
followed by the plumule upwards.
■ Amylase enzyme hydrolyses starch into maltose which is transported to the
growing points of the plant to be used in respiration.
■ During germination the cotyledons remain below ground.
■ The plumule is bent over in the shape of a hook to prevent damage to the
tip by soil abrasion.
■ When the plumule emerges from the soil it unfurls and begins to produce
glucose by photosynthesising as the food reserves in the cotyledons have
been now been depleted.
38
what happpens to the mass of the seed as it germinates
* As a seed germinates the dry mass of the cotyledons decreases as food reserves are used up fuelling growth of the embryo.
* The overall mass of the
seed decreases initially until the plumule can begin photosynthesising.
39
what are the effect and function of giberllin
* Gibberellic acid (GA) is a plant growth regulator which diffuses into the aleurone layer surrounding the endosperm switching on genes involved in transcription and translation, resulting in the production of amylases and
proteases.
* The amino acids produced by the hydrolysis of proteins are used to synthesise
amylases which in turn hydrolyse stored starch into maltose and glucose for respiration by cells in the radicle and plumule.
