Ch 12 Reproduction in flowering plants

Question 1

Binary fission in bacteria

Answer 1

1. Binary fission starts with a parent cell
2. The chromosome replicates and the cell grows
3. The cell membrane grows inwards and a new cell wall is formed to divide the cell into two parts
4. Two daughter cells are formed. They are genetically identical and similar in size

Question 2

Vegetative propagation in flowering plants

Answer 2

1. In winter, the aerial part of the plant dies. The underground storage organ remains dormant.
2. When conditions become favourable, new aerial shoots develop from the buds. The storage organ provides food for the growth of the shoots
3. Adventitious roots are formed. They absorb water and minerals from the soil. Green leaves start to develop
4. The shoots develop into new plants. The storage organ dries up as food is used up
5. The plants carry out photosynthesis to make food. Some food is transported to and stored in the new storage organs

Question 3

Adaptations of insect-pollinated flowers

Answer 3

1. Large and brightly coloured petals. often have nectar guides and are scented to attract insects
2. Anthers located inside the flower and firmly attached to the filaments
3. Stigmas located inside the flower, broad and sticky to pick up pollen grains from insects
4. A small number of pollen grains is produced, larger and heavier, rough and sticky to help attach to insects
5. Nectaries are present to secrete nectar to attract insects

Question 4

Adaptations of wind-pollinated flower

Answer 4

1. Reduced, green or dull-coloured petals, scent is often absent
2. Anthers hanging outside the flower and loosely attached to the filaments to release pollen grains into the air
3. Stigmas hanging outside the flower, long and feathery to catch pollen grains in the air
4. A larger number of pollen grains is produced, small and lighter, smooth and dry so that they can be released to the air more easily
5. Nectaries are often absent

Question 5

Germination of pollen grains and fertilization

Answer 5

1. Pollen grains land on the stigma of the same species.
2. Sugary solution on the stigma stimulates germination of the pollen grain. A pollen tube develops from the pollen grain
3. The pollen tube secretes enzymes to digest the tissues of the style. This allows the pollen tube to grow down the style and then into the ovary. The pollen tube carries the male gamete towards the ovule in the ovary
4. The pollen tube grows through the micropyle. The tip of the pollen tube bursts to release the male gamete into the ovule
5. The male gamete fuses with the female gamete. Fertilization takes place and a zygote is formed

Question 6

Fate of various floral parts after fertilization

Answer 6

ovum -> embryo
ovule -> seed
ovary wall -> fruit wall
integuments -> seed coat

Question 7

Dispersal of seeds and fruits
(by wind / water / animal / ‘explosion’)

Answer 7

1. allowing the species to colonize new areas
2. reducing overcrowding and competition for resources among the daughter and parent plants
3. allowing the daughter plants to escape from pests and diseases associated with the daughter plants