Reproduction in plants

Question 1

Petals

Answer 1

• In insect-pollinated flowers:
• they are brightly coloured to attract insects for pollination
• they provide a landing platform for insects

Question 2

Sepal

Answer 2

• Encloses and protects the other parts of the flower during the bud stage

Question 3

Anther

Answer 3

• Produced pollen grains

Question 4

Filament

Answer 4

• holds the anthers in a suitable position to disperse pollen

Question 5

Stigma

Answer 5

• Receives pollen grains
• The mature stigma secretes a sugary fluid that stimulates pollen grains to germinate

Question 6

Style

Answer 6

• Connects the stigma to the ovary
• Holds the stigma in a suitable position to receive pollen grains

Question 7

Ovary

Answer 7

• Contains one or more ovules

Question 8

Pollination

Answer 8

• The transfer of pollen grains from the anthers to the stigma
• Two types of pollination:
  1. Self-pollination
  2. Cross-pollination

Question 9

Self-pollination

Answer 9

The transfer of pollen grain from the anther to the stigma of the same flower or a different flower in the same plant

Question 10

Features that favour self-pollination

Answer 10

• Flowers are bisexual with anthers and stigmas maturing at different times
• Stigma situated below anthers
• Some flowers never open and can only be self-pollinated

Question 11

Advantages of self-pollination

Answer 11

• Only one parent required
• Offspring will inherit beneficial traits of the parent
• Does not depend on external factors
• Increased probability of pollination

Question 12

Disadvantages of self-pollination

Answer 12

• Less genetic variation in offsprings compared to cross-pollination, making them less well-adapted to changes in the environment
• Offspring become weaker, smaller and less resistant to diseases

Question 13

Cross-pollination

Answer 13

• The transfer of pollen grains from the anther to the stigma of a flower in a different plant

Question 14

Features that favour cross-pollination

Answer 14

• Some plants are only male or female
• In bisexual flowers, anthers and stigma may mature at different times
• Stigma situated far away from the anthers

Question 15

Advantages of cross-pollination

Answer 15

• More genetic variation in offspring compared to self-pollination, making them well-adpated to changes in the environment

Question 16

Disadvantages of cross-pollination

Answer 16

• Two parent plants are required
• Depends on external factors such as wind or insects
• Lower probability of pollination

Question 17

Features of insect-pollinated plants

Answer 17

• Petals are large and brightly coloured
• Anthers and filaments are non-pendulous and do not protrude out of the flower
• Stigma is small and compact and do not protrude out of the flower

Question 18

Features of wind-pollinated plants

Answer 18

• No petals or are dull-coloured
• Filament is long and pendulous, anthers are protruding out of the flower
• Stigma is large and feathery and protruding out of the flower

Question 19

Growth of pollen tube and entry into ovule

Answer 19

1. Pollen grains land on the stigma, the pollen grain is stimulated to germinate by the sugary fluid secreted by the stigma
2. A pollen tube grows out of the pollen grain. The male gamete enters the pollen tube and enzymes in the pollen tube digest the tissue in the stigma and style to allow the tube to grow towards the ovary
3. The pollen tube enters the ovule through an opening in the ovule wall called the micropyle
4. In the ovule, the tip of the pollen tube absorbs sap and burst, releasing the male gamete, the nucleus of the male gamete fuses with the female gamete in the ovum to form a zygote
5. After fertilization, the ovary develops into a fruit while the ovules develop into seeds