Past Questions Flashcards
State any two functions of the sepals.
2/3
Protects the flower while it is in the bud
Photosynthesis
Attracts the insects
Name the part of the carpel on which the pollen grain lands.
Stigma
Describe the process by which a megaspore mother cell develops into a mature embryo sac.
(9)
Megaspore mother cell divides by meiosis
To form four haploid nuclei
Three of these degenerate
The remaining cell is the embryo sac
The haploid embryo sac divides by mitosis three times to form eight haploid nuclei
Five of these degenerate
The remaining three are the female gametes
Two form the polar nuclei in the embryo sac
One forms a thin cell wall and becomes the egg cell
Egg cell is at one end and polar nuclei are in the centre
Describe the role played by the generative nucleus nucleus in the process of fertilisation.
(3)
Divides by mitosis to form two haploid nuclei (sperm nuclei)
One sperm nucleus joins with the egg nucleus to form a diploid zygote
The other sperm nucleus joins with the two polar nuclei forming the triploid endosperm nucleus
Explain why self-pollination could prove to be a disadvantage for plants.
(5)
Resulting seeds are less sturdy and vigorous
There is less genetic variation so all plants could be wiped out by a disease
There is a lack of diversity - less able to adapt in new environments
Vigour of species decreases over time
No new useful characteristics introduced
State one advantage of self-pollination to horticulturists.
3
There is no genetic variation
They know what plants will result - know what they are getting
They know the plants will retain desirable characteristics
Describe the role of meiosis in the production of the male gametes.
Diploid microspore mother cell divides by meiosis to produce four haploid microspores
Name the structure from which the male gametes are eventually formed
Generative nucleus
Explain the process of double fertilisation.
3
The generative nucleus divides by mitosis to form two haploid nuclei (sperm nuclei)
One sperm nucleus joins with the egg nucleus to form a diploid zygote
The other sperm nucleus joins with the two polar nuclei forming the triploid endosperm nucleus
Where does double fertilisation take place?
Embryo sac
How does the stigma hanging outside the plant in wind-pollinated plants aid in pollination?
By hanging outside the flower the stigma can catch pollen floating in the air
How does the feathery stigma in wind-pollinated plants aid in pollination?
The feathery structure of the stigma increases the surface area for pollen to land on
State one reason cross-pollination is more beneficial to plants than self-pollination.
(2)
Seeds are more vigorous
Seeds show variation
Explain the link between hay fever and pollen,
Hay fever is an allergic reaction to pollen
In the flowering plant, at what stage during the development of the male gametes does meiosis occur?
During the division of the diploid microspore mother cell by meiosis to produce four haploid microspores
What is the function of the generative nucleus?
To divide by mitosis to form the male gametes
(forms two sperm cells which are used during double fertilisation, one fuses with the egg to form the diploid nucleus and the other fuses with the polar nuclei to form the triploid endosperm nucleus)
What is the function of the growth regulators produced by seeds?
Stimulates the growth of fruit
Suggest any one reason reproduction by means of seeds may be advantageous to a plant in nature.
(1/2)
Seeds can be widely dispersed which reduces competition
Seed can survive adverse conditions
Describe the formation of an egg cell from the a megaspore mother cell in a flowering plant.
(9)
Megaspore mother cell divides by meiosis
To form four haploid nuclei
Three of these degenerate
The remaining cell is the embryo sac
The haploid embryo sac divides by mitosis three times to form eight haploid nuclei
Five of these degenerate
The remaining three are the female gametes
Two form the polar nuclei in the embryo sac
One forms a thin cell wall and becomes the egg cell
State any two reasons why seedless fruit might be produced by a plant.
Due to genetics - natural or special breeding programmes
Spraying plants with growth regulators
Suggest any one way seedless fruit may be favoured by consumers.
(2)
They don’t have to pick out the seeds
There is more fruit, e.g. seedless oranges
Explain why the dispersal of seeds increases their chances of survival.
(2)
It minimises competition
It avoids overcrowding
State any two reasons why dormancy can be beneficial.
2/5
Allows the plant to avoid the harsh conditions of winter
It gives the embryo time to develop fully
It provides times for the seed to be dispersed
It maximises the growing season for young seedlings
It helps the survival of the species - duration of dormancy varies - dormant seeds can replace matured plants that die off
Explain why oxygen is necessary for germination.
It is needed in aerobic respiration
