Reproduction in Plants

Question 1

A flower consists of

Answer 1

an expanded stem tip, the receptacle, which usually bears four whorls (rings) of modified leaves, sepals, petals, stamens,andone or more carpels in the centre.

Question 2

female parts

Answer 2

carpels; produce one or more ovules which contain the female gametes

Question 3

male parts

Answer 3

stamens; these produce the pollen grains which contain the male gametes

Question 4

honey guides

Answer 4

markings or
patterns on petals to guide
insects to the nectar

Question 5

anther

Answer 5

produces pollen grains containing
male gametes

Question 6

filament

Answer 6

– holds the
anther where it can best deliver pollen

Question 7

stamen –

Answer 7

male part of the flower
composed of the anther and the filament

Question 8

sepal

Answer 8

usually green. Protects the flower when in bud

Question 9

pedicel

Answer 9

pedicel – the flower stalk

Question 10

petal

Answer 10

– provides colourand scent to attract insects and birds for pollination

Question 11

stigma

Answer 11

sticky end of the style. Catches pollen grains

Question 12

style

Answer 12

– holds the stigma where it can best catch pollen

Question 13

ovary

Answer 13

contains ovules

Question 14

ovule

Answer 14

conatins an ovum, the female gamete

Question 15

nectary

Answer 15

– at the base of the petal.
Contains nectar to attract insects and birds for pollination

Question 16

receptacle

Answer 16

bears the flower parts

Question 17

carpel

Answer 17

the female part of the flower
consists of the stigma, style and ovary and ovules

Question 18

flower- wind pollinated vs insect polinated

Answer 18

• Usually small and inconspicuous.

*Usually large and conspicuous

Question 19

petals- wind pollinated vs insect pollinated

Answer 19

• Often absent. If present they are small, green or dull coloured and have noscent, nectar or honey guides. There are no pollinating agents to attract.

*Usually relatively large, brightly coloured and scented, and have nectaries and honey guides to attract insects.

Question 20

pollen grains- wind pollinated vs insect pollinated

Answer 20

• Small, smooth and light so they areeasily carried by the wind.
• Large quantities are produced as many are lost

*Relatively large, sticky or spiky to stickonto the body of insects.
* Smaller quantities are produced asfewer are lost

Question 21

stigmas(anthers) wind pollinated vs insect pollinated

Answer 21

• Long, branched and feathery and hang outside the flower to provide a large area to catch the pollen grains.
• Flat or lobed and sticky, and are usually situated inside the flower sothe insect brushes against them as itgoes to get nectar and deposits pollen onto them.

Question 22

wind pollinated plants

Answer 22

Guinea grass, maize, sugar cane.

Question 23

insect pollinated plants

Answer 23

Pride of Barbados, flamboyant, allamanda.

Question 24

mechanism of fertilisation in flowerings plants after pollination occurs
STEP 1

Answer 24

A pollen grain lands on the stigma.It absorbs nutrients present, swells and develops a pollen tube.

Question 25

STAGE 2

Answer 25

The pollentube, withtwomale nuclei and a tube nucleus in its tip, grows down Through the style by secreting digestive enzymes that digest a pathway.

Question 26

STAGE 3

Answer 26

The pollen tube grows through the ovary wall and through the micropyle of the ovule and bursts.The tube nucleus degenerates, and one male nucleus fuses with the female gamete to form the zygote. The other male nucleus and the two polar nuclei fuse to form the endosperm.

Question 27

Seed development

Answer 27

After fertilisation, each ovule develops into a seed:
* The zygote divides by mitosis forming the embryo which develops into three parts
:the plumule or embryonic shoot
the radicle or embryonic root
one cotyledon/seed leaf in monocotyledonous seeds
or two cotyledons in dicotyledons

Question 28

seed development continued

Answer 28

• The endosperm remains in endospermic seeds, e.g. maize and castor oil, but is absorbed by thecotyledons in non-endospermic seeds, e.g. green bean and pigeon pea. In endospermic seeds, theendosperm stores food; in non-endospermic seeds, the cotyledons store food.
• The integuments become dry and develop into thetesta, and the micropyle remains in the testa.
• Water is withdrawn from the seed and it becomes dormant

Question 29

fruit development

Answer 29

After fertilisation, the ovary wall develops into the fruit. A fruit contains one or more seeds; thenumber depends on the number of ovules in the original ovary that were fertilised. The shape and structure of many fruits is very similar to the original ovary.

The stigma, style, stamens and petals wither and drop off. The sepals may drop off or they may remain, e.g. in eggplant.

Question 30

male reproductive system- humans

Answer 30

The male gametes are called sperm or spermatozoa and they are produced in the testes which form part of the male reproductive system. Unlike the ovaries which are inside the female body, the testesare located outside the body in a sac called the scrotum. This keeps the sperm at a slightly lower temperature than body temperature which is essential for their proper development.

Question 31

production of ova

Answer 31

ovary- secretes hormones and produces female gametes

At birth, each female ovary contains many thousand immature ova. Each is surrounded by a fluid filled space which forms a primary follicle. Each month between puberty at about 11 to 13 years old, and menopause at about 45 to 50 years old, one immature ovum will develop into a mature ovum. About 450 immature ova will ever mature. To produce a mature ovum, the immature ovum undergoes meiosis (see page 147). One of the four cells produced develops into a mature ovum which is released during ovulation.

Question 32

Production of sperm

Answer 32

Sperm cells are produced continuously from puberty in the seminiferous tubules of the testes. Cells inthe tubule walls undergo meiosis andall the cells produced develop into mature sperm. These are stored in the epididymis until ejaculation