Chapter 17: Reproduction In Plants

Front 1

What is asexual reproduction?

Back 1

Asexual reproduction is a process resulting in the production ofgenetically identical offspring from one parent,without the fusion of gametes

Front 2

What is sexual reproduction?

Back 2

Sexual reproduction is a process involving the fusion of 2 gametes to form a zygote, producing genetically dissimilar offspring

Front 3

What are the advantages of asexual reproduction?

Back 3

- Only one parent required as fusion of gametes is not required. - All beneficial qualities are passed onto the offspring. - Faster method of producing offspring as compared with sexual reproduction. - Since organisms are already in a suitable habitat, they can colonise the area rapidly.

Front 4

What are the disadvantages of asexual reproduction?

Back 4

- No genetic variation in the offspring. Hence, species are may be wiped out if not well adapted to changes in the environment.

Front 5

What are the advantages of sexual reproduction?

Back 5

- Offspring may inherit beneficial qualities from both parents. - There is greater genetic variation in the offspring, thus species can be better adapted to changes in the environment.

Front 6

What are the disadvantages of sexual reproduction?

Back 6

- Two parents are required (except in plants with bisexual flowers) as fusion of gametes is required

- Slower method of producing offspring as compared to asexual reproduction

Front 7

What is the stamen?

Back 7

The stamen is the male part of the flower consisting of an anther and a filament

Front 8

What is the carpel?

Back 8

The carpel is the female part of the flower that consists of the ovule, ovary, style and stigma

Front 9

What is the sepal?

Back 9

They are modified leaves which are found on the outermost ring of floral leaves which enclose and protect the flower when it is in bud stage.

Front 10

What are the petals for?

Back 10

They are modified leaves which form the most obvious part of the flower. They are large and brightly coloured in insect-pollinated plants and they form a platform for insects to land on

Front 11

What are the anthers for?

Back 11

• The anther consists of two lobes and a vascular bundle • Each lobe contains two pollen sacs, which contain pollen grains (male gametes)

Front 12

What is the filament for?

Back 12

It is stalk that holds the anther in a suitable position to disperse pollen

Front 13

What is the stigma?

Back 13

Stigma is a receptor of pollen grains that secretes a sugary fluid that stimulates germination of pollen grains.

Front 14

What is the style?

Back 14

It holds the stigma in position to trap pollen grains.

Front 15

What is the ovary?

Back 15

The ovary contains ovules

Front 16

What are ovules?

Back 16

The ovules contain female gametes

Front 17

What is pollination?

Back 17

Pollination is the transfer of pollen grains from the anther to the stigma

Front 18

What is self-pollination?

Back 18

Self-pollination is the transfer of pollen grains from the anther to the stigma of the same flower or of a different flower on the same plant

Front 19

What features favours self-pollination?

Back 19

1) Flowers are bisexual with anthers and stigmas maturing at the same time

2) The stigma is situated directly below the anthers

3) In certain plants with bisexual flowers, some flowers never open and only self-pollination can occur in these flowers

Front 20

What is cross pollination?

Back 20

Cross pollination is the transfer of pollen grains from 1 plant to the stigma of a flower in another plant of the same species

Front 21

What features favour cross pollination?

Back 21

• Plants bear only male or female flowers, thus self pollination is not possible • In plants with bisexual flowers, the anthers and the stigmas mature at different times. • The stigma and anthers are located very far away.

Front 22

What are the differences between insect-pollinated and wind-pollinated flowers?

Back 22

1) Petals of insect-pollinated flowers are large and brightly-coloured while petals of wind-pollinated flowers are small and dull-coloured

2) Nectar is present in insect-pollinated flowers while nectar is absent in wind-pollinated flowers

3) Insect-pollinated flowers are fragrant and swee-smelling while wind-pollinated flowers have no scent

4) The stigmas of insect-pollianted flowers are small, compact and they don't protrude out of the flower while stigams of wind-pollianted flowers are large, feathery and they protrude out of the flower

5) Stamens of insect-pollianted flowers don't have pendulous filaments and the anthers do notprotrude out of flowers while stamens of wind-pollinated flowers have long and pendulous filamentswith protruding anthers.

6) Insect-pollinated flowers have fairly abundant pollen grains that are larger with roughsurfaces while wind-pollinated flowers have more abundant pollen grains that are tiny with smooth surfaces.

7) Insect-pollinated flowers have nectra guides while wind-pollinated don't.

Front 23

How does fertilisation take place in plants?

Back 23

1. After pollination, the pollen grains germinate in response to the sugary fluid secreted by stigma.

2. A pollen tube grows out from each pollen grain. The cytoplasm and the two nuclei of the pollen grain, namely generative nucleus and pollen tube nucleus, pass into the pollen tube

3. Pollen tube secretes enzymes to digest the surrounding tissue of the stigma and style.

4. The generative nucleus divides to form two male gametes.

5. The pollen tube enters the ovule in the ovary through the micropyle.

6. Within the ovule, the tip of the pollen tubes absorbs sap and bursts, releasing the two male gametes.

7. One male gamete fuses with the nucleus of the ovum to form the zygote, while the other male gamete fuses with the definitive nucleus to form the endosperm nucleus

8. The ovule will develop into a seed and the ovary will develop into a fruit.

Front 24

what happens to the ovule after fertilisation?

Back 24

It develops into a seed

Front 25

what happens to the ovary after fertilisation?

Back 25

It develops into a fruit

Front 26

Why does the size of the ovule increase 7 days after pollination?

Back 26

It increases because the male sex gametes have reached the ovule 7 days after to fertilise the ovum, causing the ovum to enlarge