f5 chap 6: sexual reproduction in flowers

Question 1

what are the flower’s structures?

Answer 1

peduncles, sepals, petals

Question 2

whats stamen?

Answer 2

male reproductive organ

Question 3

whats carpel?

Answer 3

female reproductive organ

Question 3

what are the similarities of male & female flower parts

Answer 3

both produces gametes, both are located at flower’s organs

Question 3

what are the differences between male & female flower parts

Answer 3

male flower part: consists of stamen, has filament and anther, produces pollen grains, projecting out from base of ovary

female flower part: consists of carpel, has stigma, style and ovary, produces embryo sac, located in the middle part of flower

Question 4

what does stamen consist of?

Answer 4

anther, filament

Question 4

what does carpel consist of?

Answer 4

stigma, style, ovary

Question 5

explain formation of pollen grains in anther

Answer 5

1. 4 pollen sacs is formed in each lobe during development of anther. each pollen sacs has 100s of microspore mother (diploid: 2n)
2. microspore mother cell divides by meiosis to produce 4 haploid microspore cells (tetrad)
3. each cell in tetrad develops into pollen grain
4. nucleus in pollen grain divides by mitosis & produces 2 nuclei: generative & tube
5. pollen grains are released when wall of pollen sacs break

Question 5

explain formation of embryo sac in ovule

Answer 5

1. megaspore mother cell divides by meiosis to produce 4 haploid megaspore cells
2. 3 of megaspore cells degenerate & only 1 megaspore cell develops
3. nucles of cell that has developed, divides mitotically 3 times to produce a cell with 8 nuclei
4. 3 nuclei move to one end of embryo sac to form 3 antipodal cells, 3 nuclei move to opposite end of embryo to form 2 synergid cells & 1 egg cell
5. 2 nuclei in centre of embryo sac form polar nuclei

Question 6

pollinating agents that assist in pollination

Answer 6

insects, mammals, birds

Question 7

formation of pollen tube & male gamete

Answer 7

1. wall of anther from mature pollen will
   dry, shrink dan split. Pollen grains in the
   pollen sac are released.
2. released pollen grains are transferred
   to the stigma of the same flower or different
   flowers by pollinating agent.
3. pollen grains that have been transferred
   to the stigma will germinate and form a pollen
   tube. The pollen tube grows down towards the
   ovule through the style.
4. generative nucleus will move along the
   pollen tube towards the ovule. At the same
   time, the generative nucleus will divide by
   mitosis to form two male gametes (n).
5. The end of the pollen tube will secrete an
   enzyme to digest the tissues of the style.

Question 8

function of the 2 male gametes in double fertilisation?

Answer 8

first male gamete: fertilises the egg cell to form a diploid zygote
second male gamete: fuses with polar nuclei to form
triploid endosperm tissue.

Question 8

what does double fertilisation involve?

Answer 8

2 male gametes

Question 9

explain double fertilisation in the formation of diploid zygote and triploid nucleus

Answer 9

1. When both the male gametes reaches the embryo
   sac, the pollen tube will penetrate the ovule through the micropyle. The tube nucleus will degenerate and both male gametes enter the embryo sac.
2. One of the male gametes fertilises the egg cell and
   produces a diploid zygote. The second male gamete fuses with the two polar nuclei to form a triploid endosperm nucleus.

Question 10

importance of Double Fertilisation for the Survival of
Flowering Plants?

Answer 10

Genetic information is passed down from one generation to the next when fusion of one of the male gametes with the egg cell produces a zygote.

Question 10

endosperm tissue function?

Answer 10

food storing tissue which surrounds and supplies nutrients to the embryo.

Question 11

what happens after double fertilisation?

Answer 11

the triploid endosperm nucleus divides by mitosis and form the endosperm tissue.

Question 11

what are the 2 cells zygote formed by dividing through mitosis

Answer 11

terminal cell, basal cell

Question 12

zygote divides into larger cell & smaller cell through mitosis during embryo formation. the smaller cell will later become an embryo that consist of?

Answer 12

plumule, radicle and cotyledon

Question 13

explain development of embryo (flower)

Answer 13

double fertilisation occurs, the triploid endosperm nucleus
divides by mitosis and form the endosperm tissue. zygote divides by mitosis to form two cells, a larger cell and a
smaller cell. The larger cell develops into a suspensor that anchors the embryo to the wall of the embryo sac. The smaller cell will become an embryo that consists of plumule, radicle and cotyledon

Question 14

explain development of ovary into fruit after fertilisation

Answer 14

The ovule develops to become the seed in the fruit. The integument becomes two layers of seed coat that serves to protect the embryo. During the development of ovule and seed, the ovary develops into a fruit. Other flower parts such as the stigma and style degenerate and leave a scar on the ovary wall
The ovary wall becomes the pericarp of the fruit which consists of the exocarp, mesocarp and endocarp.

Question 15

what does ovary wall consist of?

Answer 15

exocarp, mesocarp and endocarp.

Question 16

state 3 importance of seeds for survival

Answer 16

1. Seeds contain embryo that germinate to form seedlings.
2. Seeds can form a dormant structure which enables the seeds to be stored for a long time.
3. Seeds are enclosed by the testa which is strong and water
   impermeable to prevent the seeds from spoiling.

Question 17

what are the special features of seeds?

Answer 17

light, have spongy tissue, strong, doesnt spoil easily