Topic 2- sexual repro. in plants

Question 1

Female structure- carpel

Answer 1

• stigma: where pollen grain lands
• style: supports stigma
• ovary: contain ovule with female gametes

Question 2

Male structures- Stamen

Answer 2

• anther: produces pollen grains containing male gametes
• filament: supports anther

Question 3

Formation of female gametes (1)

Answer 3

megaspore mother divides by meiosis to produces 4 haploid cells

Question 4

Formation of female gametes (2)

Answer 4

3 of 4 megaspores disintegrate, leaving surviving one to grow until it almost fills nucells

Question 5

Formation of female gametes (3)

Answer 5

nucleus of surviving megaspore divides 3x by mitosis to form cell containing 8 haploid nuclei (immature embryo sac)

Question 6

Formation of female gametes (4)

Answer 6

cytoplasm of embryo sac divides to form 7 cells

Question 7

Formation of female gametes (5)

Answer 7

• 3 of 7 cells near micropyle are ovum.
• 3 furthest are antipodal cells
• 2 remaining remain in centre of embryo sac (polar nuclei)

Question 8

Formation of male gametes (1)

Answer 8

• each anther has 2-4 lobes
• each lobe contains diploid micropore mother cells

Question 9

Formation of male gametes (2)

Answer 9

each diploid micropore mother divides once by meiosis to form 4 haploid microspores

Question 10

Formation of male gametes (3)

Answer 10

each haploid microspore divides by mitosis to produce 2 haploid nuclei:
- tube nucleus
- regenerative nucleus (male gamete)

Question 11

Pollination

Answer 11

occurs when a pollen grain lands on the stigma of a plant of the same cell

Question 12

Self-pollination

Answer 12

pollen is transferred from the anther of one plant to the stigma of the same plant

Question 13

Cross pollination

Answer 13

pollen is transferred from the anther of one plant by insects, other animals or the wind the the stigma of another plant

Question 14

Fertilisation

Answer 14

occurs when the male gamete in the pollen grain fuses with the female gamete in the embryo sac

Question 15

Fertilisation stages (1)

Answer 15

mature pollen grain lands on the stigma, absorbs water, swells and splits open

Question 16

Fertilisation stages (2)

Answer 16

once open, forms pollen tube that grows down towards the embryo sac- controlled by pollen tube nucleus

Question 17

Fertilisation stages (3)

Answer 17

pollen tube grows through tissues of stigma, style and ovary towards the embryo sac by digestion enzymes

Question 18

Fertilisation stages (4)

Question 19

Double fertilisation

Answer 19

• one male nucleus fuses with the female gamete forming a diploid zygote
• the other male nucleus fuses with two polar nuclei to form a triploid primary endosperm cell

Question 20

Double fertilisation products

Answer 20

• zygote: embryo plant
• primary endosperm cell: mass of food tissue
• embryo sac: develops into a seed
• wall of ovary: fruit