9) Reproduction in plants

Question 1

Importance of variation

Answer 1

Allow adaptation, for more evolution and selection, reducing competition, increasing genetic diversity, increasing biodiversity, reducing risk of extinction

Question 2

Compare between two types of reproduction

Answer 2

Sexual reproduction:
- 2 parents
- Involves gametes from both parents that fuse together
- Meiosis is needed for production of gametes
- Produces genetically different offspring, showing more variation, adapt more, reproduce more, evolute.
- Slower
- Produces fewer number of offsprings

Asexual reproduction:
- 1 parent
- No gametes, no meiosis
- only mitosis
- produces genetically identical offsprings, no variation, less adaptation, survive less, reproduce less, no evolution.
- Faster
- Produces large number of offsprings

Question 3

Advantages of Sexual reproduction

Answer 3

1. Variation
2. More adaptations
3. More evolution and selection
4. Reduces competition increasing survival chance
5. Increase in gene pool and biodiversity
6. reduces risk of extinction
7. Less chance for genetic diseases to be inherited

Question 4

Disadvantages of sexual reproduction

Answer 4

1. slower
2. Produces fewer number of offsprings
3. Needs 2 parents
4. Wastage of gametes
5. Favourable characteristics have a lesser chance to be inherited

Question 5

Advantages of Asexual reproduction

Answer 5

1. Faster
2. Produces more offspring
3. Needs only one parent
4. Less energy wasted
5. More chance of favourable characteristics to be inherited

Question 6

Disadvantages of asexual reproduction

Answer 6

1. No variation
2. Less adaptation
3. Less selection and evolution
4. Increase in competition decreasing survival chance
5. decrease gene pool and biodiversity
6. increase risk of extinction
7. More chance for genetic diseases to be inherited

Question 7

Examples of asexual reproduction and explain how they reproduce

Answer 7

1. bacteria:
   - Bacteria divides asexually by binary fission
   - DNA replicate
   - Cell size increase, then divide, producing two genetically identical daughter cells
2. Potato
   - Potato has buds, buds by mitosis
   - Grows a shoot, aerial shoot and under ground shoot
   - Aerial shoot develop leaves, to carry photosynthesis producing glucose, which is condensed into sucrose to be translocated through phloem to the tips of the underground shoot
   - to swell and be stored as starch
   - forming a new potato tuber
3. Multicellular Fungi
   *Explain how fungi feed
   - Spore falls on food source and grows a feeding hyphae
   - fungi releases extra cellular enzymes to break large food substances into small simple soluble ones
   - Food is absorbed by hyphea to be used as a source of energy from respiration
   * Explain how they reproduce
   - Reproduce asexually
   - it will grow an aerial hyphae which will carry sporangium in which cells divide by mitosis
   - producing more spores
   - sporangium will rupture so spores released will be carried by air falling on another food source

Question 8

Carpel

Answer 8

Made of stigma, style , ovary

Question 9

Stigma

Answer 9

receives the pollen grain, produces substances to help pollen grain develop into pollen tube

Question 10

Style

Answer 10

Holds the stigma and allow the passage of pollen tube

Question 11

Ovary

Answer 11

contains ovules that contains female nucleus

Question 12

Micropyle

Answer 12

Small opening in the ovule allowing the male nucleus to enter the ovule for fertilisation

Question 13

Stamen

Answer 13

Consists of anther and filament

Question 14

Filament

Answer 14

holds the anther to release pollen grain for pollination

Question 15

Anther

Answer 15

produces pollen grains that contain male nucleus

Question 16

Petals

Answer 16

Large, scented, and coloured
To attract pollinators
Have nectary guide lines
Protects the reproductive organs

Question 17

Nectary glands

Answer 17

found at the base below the ovary
secretes sugary fluid to attract pollinators

Question 18

Sepals

Answer 18

Protect the flower when its a bud

Question 19

Types of pollination

Answer 19

1. Self pollination
   - Occurs in bisexual flower
   - Transfer of the protein grain from anther of one flower to the stigma of the same flower
2. Cross pollination
   - Occurs in bisexual or unisexual flower
   - transfer of the pollen grain from anther of one flower to the stigma of another flower of different plant but same species

Question 20

Implications of self pollination

Answer 20

1. Doesn’t rely on pollinators
2. Less wastage of pollen gains
3. offspring will be well adapted to conditions near parents
4. has an advantage for farmers in maintaining the selected varieties
5. Less variation
   - increase in homozygosity
   - Variation due to mutation , has less chance to be expressed
6. Less adaptation to new environments
7. More competition, decreasing survival chance
8. decrease in gene pool and biodiversity increasing risk of extinction
9. more chance for genetic diseases to be inherited

Question 21

Implications of cross pollination

Answer 21

1. Rely on pollinators
2. More wastage of pollen grains
3. Less chance for the offspring to inherit the favourable characteristic from the parents
4. More variation
   - more heterozygosity
   - variation due to mutation has more chance to be expressed
5. more adaptation, more selection and evolution
6. reduce competition increasing survival chance
7. increase in gene pool decreasing risk of extinction
8. less chance for genetic diseases to be inherited

Question 22

Methods of pollination

Answer 22

1. Wind pollination
2. Insect pollination

Question 23

Wind pollination features

Answer 23

1.small petals , with dull colours and no guide lines
2. No nectary gland
3. Feathery stigma: for large surface area to trap pollen grains
from air
4. Hanging/ Dangling anthers outside the petals for wind to easily carry pollen grains
5. Pollen grains are smaller in size, lighter, dry and larger in number

Question 24

Insect pollination features

Answer 24

1. Petals are large, coloured, with guide lines and scented
2. Have nectary glands
3. Stamen and Stigma are enclosed inside the petals
4. Stigma is sticky
5. Pollen grains are larger in size, sticky and less in number

Question 25

Steps of pollination, fertilization and seed formation

Answer 25

Pollination: Transfer of pollen grain from anther to stigma Fertilization: 1.Pollen grain land on the stigma 2.Pollen grain starts to develop the pollen tube 3. it grows down through the style 4. Pollen tube releases extra cellular enzymes 5. Male nucleus travels down the pollen tube 6. And it enters the ovules through micropyle 7. Where male and female haploid nuclei will fuse to form diploid zygote Seed formation: 1. Male nucleus enters the ovule through the micropyle where male and female haploid nuclei fuse forming diploid zygote (by fertilization) 2. Zygote divides by mitosis forming embryo 3. Embryo develops into plumule and radicle 4. Cytoplasm with food storage form cotyledon 5. Wall of the ovule forms the testa of the seed

Question 26

Seed germination

Answer 26

1. Water enters through micropyle in presence of optimum temperature, enzymes are activated and starts the breakdown of food storage. Protease breaks down proteins into amino acids for growth and development. Lipase breaks down lipids into fatty acids and glycerol 2. More water will enter so testa will split, allowing oxygen to diffuse into the seed, used in aerobic respiration for energy release for cell division and forming new molecules. 3. plumule will grow into shoot and radicle into root

Question 27

Factors needed for seed germinatio

Answer 27

W.O.W 1. Warm temperature: for optimum enzyme activity 2. Oxygen: for aerobic respiration and energy release for cell division 3. Water: to activate enzymes, solvent and for turgor pressure