Reproduction in plants

Question 1

Mitosis

Answer 1

parent cell divides once to produce two genetically identical daughter cells

Question 2

Importance of mitosis

Answer 2

• basis of growth in an organism
• means by which new cells replace damaged, worn-out cells
• asexual reproduction

Question 3

Stem cells

Answer 3

provide new cells for the body as it grows & replace specialised cells that are damaged / lost

Question 4

Special properties of stem cells

Answer 4

• have ability to divide repeatedly by mitosis to produce new cells
• can change & develop into the other types of cells that make up the body ; become specialised cells

Question 5

Meiosis

Answer 5

cell divides twice to give four cells with half the number of chromosomes as the parent cell
- genetically different from parent cell
- also called reduction division ; number of chromosomes reduces

Question 6

Importance of meiosis

Answer 6

• gametes are genetically different so that when they fuse during fertilisation, the new organisms produced will show genetic variation

Question 7

Cancer

Answer 7

if genes undergo mutation, the mechanism that controls cell division stops working
- cells start dividing in an uncontrolled manner ; formation of cancer
- extra cells form a mass of tissue ; tumour that can spread to other tissues

Question 8

Causes of cancer

Answer 8

• X-rays
• UV light
• chemicals from cigarette smoke

Question 9

Asexual reproduction

Answer 9

• genetically identical offspring ; clone
• one parent involved ; no fusion of gametes

Question 10

Asexual reproduction in plants as a commercial process

Answer 10

• produces large number of offspring
• rapid process
• maintains beneficial & desirable features in the offspring

Question 11

Disadvantages of asexual reproduction

Answer 11

• no genetic variation ; no adaptation to a changing environment
• any disease in the parent cell will also be transmitted to the offspring
• over-crowding & competition for light, space & nutrients between parent & offspring

Question 12

Sexual reproduction

Answer 12

fusion of male & female gametes to form a zygote
- genetically different offspring

Question 13

Advantages of sexual reproduction

Answer 13

• provides genetic variation
• survival advantage due to variation
• disease less likely to affect all individuals of a population

Question 14

Disadvantages of sexual reproduction

Answer 14

• fusion is difficult if two individuals are isolated
• takes a longer time for offspring to develop & mature enough to be born
• takes more time & energy for both male and female to find and compete for a chance to mate

Question 15

Changes in flower after fertilisation

Answer 15

• ovary -> fruit
• ovary wall -> pericarp ( fruit wall )
• ovules -> seeds
• intergument -> seed coat / testa
• sepals, style, petals, stamen, stigma wither and fall off
• zygote develops into the embryo that consists of a plumule, radicle & cotyledons

Question 16

Seed structure

Answer 16

• embryo -> new plant
• plumule -> shoot
• radicle -> root
• cotyledon -> store food for developing embryo

Question 17

Importance of water in germination

Answer 17

• causes testa to burtst , allowing plumule & radicle to grow out
• activates enzymes in cotyledons to digest stored food into soluble forms
• medium to carry soluble food products to growing regions
• hydrolysis process, to break down large food molecules into smaller ones

Question 18

Suitable temperature for germination

Answer 18

25 - 30 °C ; enables enzymes to work at optimum rate

Question 19

Presence of oxygen in germination

Answer 19

allows aerobic respiration to occur to produce sufficient energy for growth