Ch. 39 - Sexual Reproduction In Flowering Plants

Question 1

What is asexual reproduction?

Answer 1

Asexual reproduction involves only one parent.

Question 2

What is sexual reproduction?

Answer 2

Sexual reproduction is the union of 2 gametes to produce a diploid zygote.

Question 3

What are gametes?

Answer 3

Gametes are haploid cells capable of fusion.

Question 4

What is a stamen?

Answer 4

A stamen is the male parts of the flower.

Question 5

What is a carpel?

Answer 5

A carpel is the female parts of the flower.

Question 6

Draw a flower.

Answer 6

Pg. 439
Carpel - stigma, style, ovary.
Stamen - anther, filament.
Sepal, receptacle.

Question 7

State the function of the receptacle.

Answer 7

The receptacle supports the flower.

Question 8

State the function of the sepal.

Answer 8

The sepal protects the flower when it is a bud.

Question 9

State the function of the petal.

Answer 9

The petal is brightly coloured to attract animals.

Question 10

State the function of the filament.

Answer 10

The filament supports the anther.

Question 11

State the function of the anther.

Answer 11

The anther produces pollen grains by meiosis and stores them.

Question 12

State the function of the stigma.

Answer 12

The stigma is where the pollen lands.

Question 13

State the function of the style.

Answer 13

The style is where the pollen tube grows.

Question 14

State the function of the ovary.

Answer 14

The ovary contains ovules for reproduction.

Question 15

Describe male gamete formation in the anther.

Answer 15

The diploid microspore mother cell divides by meiosis to form 4 haploid cells(tetrad). These divide by mitosis so that each pollen grain has 2 nuclei, the tube nucleus and the generative nucleus. Then mitosis occurs in the generative nucleus to form 2 sperm nuclei for a total of 3 nuclei in the cell.

Question 16

Describe female gamete formation in the ovary.

Answer 16

The diploid megaspore mother cell divides by meiosis. 4 haploid cells are formed. 3 die, 1 survives. This cell becomes the embryo sac, the embryo sac’s nucleus divides by mitosis 3 times, giving 8 haploid nuclei. 2 of these nuclei become polar nuclei. 1 of the haploid nuclei becomes the egg. 5 die.

Question 17

Draw a diagram of the ovary.

Answer 17

Pg. 442.
Contains stigma, style, ovule, integument, micropyle, 2 polar nuclei and an egg cell.

Question 18

What is pollination?

Answer 18

Pollination is the transfer of pollen from an anther to a stigma of a flower from the same species.

Question 19

Differentiate between self and cross pollination.

Answer 19

Self-pollination involves the transfer of pollen from an anther to a stigma on the same plant. While cross pollination requires that the anther and stigma be from different plants.

Question 20

What are methods of pollination.

Answer 20

Wind and animal.

Question 21

How do petals, pollen, anthers and stigmas adapt to wind pollination?

Answer 21

Petals are small, not brightly coloured, no scent and have no nectary. Large amounts of pollen are produced, they are small, dry and smooth. Anthers are large, outside petals and loosely attached to the filament. Stigmas are large and feathery, they are outside the petal.

Question 22

How do petals, pollen, anthers and stigmas adapt to animal pollination?

Answer 22

Petals are brightly coloured, scented and contain a nectary. Small amounts of pollen are produced, they are large and sticky. Anthers are small, inside the petal and firmly attached to the filament. Stigmas are small, sticky and inside the petal.

Question 23

What is fertilisation?

Answer 23

Fertilisation is the union of the male and female gamete to form a diploid zygote.

Question 24

Describe the pollination of a stigma.

Answer 24

A pollen grain lands on the stigma. The pollen grain germinates and produces a pollen tube. The tube nucleus digests through the style until it reaches the ovary. The generative nucleus divides by mitosis to form 2 haploid nuclei which enter the embryo sac. One haploid nucleus fuses with the egg to form a diploid zygote. The other fuses with the 2 polar nuclei to form a triploid endosperm.

Question 25

What is the radicle?

Answer 25

The radicle is the part of the plant embryo that develops into a root.

Question 26

What is the plumule?

Answer 26

The plumule is the part of the plant embryo that develops into the shoot.

Question 27

Differentiate between an endospermic and a non-endospermic seed by drawing diagrams.

Answer 27

Pg. 445.

Question 28

What are the changes in the flower after fertilisation?

Answer 28

The ovule turns into the seed. The integuments turn into the testa. The nucellus turns into the endosperm which in turn becomes the cotyledon. The egg becomes a zygote and in turn becomes an embryo. The ovary becomes a fruit. The ovary wall becomes a pericarp (fruit coat).

Question 29

What is dispersal?

Answer 29

Dispersal is the transfer of a seed or fruit away from the parent plant.

Question 30

What is dormancy?

Answer 30

Dormancy is a resting period when seeds undergo no growth and have a reduced metabolism.

Question 31

What is germination?

Answer 31

Germination is the regrowth of the embryo, after a period of dormancy, if the environmental conditions are suitable.

Question 32

What are advantages of dispersal to the plant?

Answer 32

Dispersal is necessary to find new habitats for growth and to increase the number of the species.

Question 33

How do seeds contribute to the formation of fruit?

Answer 33

Seeds produce growth regulators(auxin).

Question 34

What are advantages of dormancy?

Answer 34

Dormancy allows the plant to avoid the harsh conditions of winter. It gives the embryo time to develop fully. And it provides time for the seed to be dispersed.

Question 35

Mandatory experiment: To use starch agar or skimmed milk plates to show digestive activity during germination.
-Why were the seeds soaked in water prior to the investigation?
-What was the control?
-How were the seeds prepared and added to the agar plates?
-How were the plates containing the seeds stored.
-How was digestion shown?

Answer 35

-The 4 broad bean seeds were soaked in a beaker of distilled water overnight. This softens the testa, allows water to enter and breaks dormancy. Hence, digestive enzymes were activated in the seed.
-The control was 2 seeds that were boiled to eliminate enzyme activity.
-The 4 seeds were cut in half and placed into a beaker with disinfectant, this killed any micro-organsims. Bench was also disinfected. Starch agar was placed in 2 sterile petri dishes. Aseptic technique was used for the forceps(they were flamed). Lid is not fully removed and never for more than a few seconds. One petri dish contains live seeds, the other with dead seeds.
-The agar plates were stored in an incubator set for 25C for 2 days.
-The seeds were removed, then both petri dishes were flooded with iodine solution. The plate which had the live seeds showed 4 light patches where the seeds had been placed. Hence, no starch present, amylase had acted on starch. In the dish that contained the dead seeds, the whole plate turned blue-black, no enzymes activity.