Type of reproduction
1. Sexual
- Two parents
- Fusion of gametes
- Meiotic and mitotic divisions
- Offspring has different genetic makeup
2. Asexual
- One parent
- No fusion of gametes
- Only mititic cell division
- Genetic makeup identical to parent
Asexual reproduction
Binary fission
Bacteria: 1 --> 2
Vegetative propagation
- In winter the aerial part of the plant dies. The underground storage organ is dormant
- Favourable conditions: aerial shoots dev from buds. Storage organ provides food for growth
- Advantitious roots formed. abs water and minerals from soil. Green leaves dev
- Shoots dev into new plants. Storage organ dries as food used
- Plant carries photosynthesis to make food stored in new storage organs
Storage organs
1. Stem tuber
- Swollen end of underground stem
- eye= bud + scar of scale leaf
2. Bulb
- Vertical underground stem
- fleshy leaves
3. Corm
- Vertical underground stem
- no fleshy leaves
4. Rhizome
- Horizontal underground stem
Artificial vegetative propagation
cutting leaf put in water
When roots dev
cutting put in soil
Sexual reproduction
Sepals: form calyx protects inner parts of flower in budding
Petals: make corolla, Brightly coloured/ scented, nectar guides lead insects to nectaries at base
Male organs (Stamens)
- Long filament to support anther
- Anther with pollen sacs with pollen grains (contain male gametes)
Females organs (Carpels)
- Stigma receives pollen grains
- Style supports stigma
- Ovary with ovules with ova (contain female gametes)
- Ovule attached to ovary wall by funicle, 2 protective layers of integuments, a small hole of micropyle
Pollination
Transfer of pollen grains from anthers to stigmas
- Self-/cross-pollination
- Self: same flower
- Cross: different flower
- Insect/wind pollination
|
Insect |
Wind |
| Petals |
Large and brightly coloured, often hae nectar guides |
Reduced, green and dull-coloured |
| Scent |
Present |
Absent |
| Nectaries |
Present |
Absent |
| Anthers |
Located inside flower, firmly attached to filaments |
Hang outside flower, loosely attached to filaments |
| Pollen grains |
larger, heavier, rough spiky sticky, less |
Smaller, lighter, smooth, dry, more |
| Stigmas |
Inside flower, sticky surface |
Outsie flower, long and feathery |
Process
- Pollen grains land of stigma
- Suagry solution of stigma stimulates germination of pollen grain. Pollen tube develops from pollen grain
- Pollen tube grows down the style and into ovary by secreting enzymes to digest style tissue, carrying male gamete to ovule.
- Pollen tube grows through micropyle. Tip bursts to release male gamete to ovule
- Male and female gamete fuses to form zygote
Before and after
| Floral part |
After fertilization |
| Ovary |
Fruit |
| Ovary wall |
Fruit wall |
| Ovule |
Seed |
| Ovum |
Embryo |
| Integuments |
Seed coat |
| Sepals,petal, stamen |
Wither and fall off |
| Remains of stimga and style |
Scar |
Fruit: protect seeds and help dispersal
Seed dispersal
Methods:
- Wind dispersal
- Water currents
- faeces of animals
- hairs of animals
Significances:
- Reduce overcrowding and competition for resouces among daughter and parent plants
- Allows species to colonise new areas
- Escape from pests and diseases associated with parent plants
Showdown
| Asexual |
Sexual |
| Desirable characteriscs retained in offspring |
Desirable characteriscs not retained |
| No external agents required |
External agents required |
| Fast rate |
Slow rate |
| No genetic variations in offspring, species less adapted to environmental changes |
Genetic variations in offspring help species adapt to environmental changes |
| Overcrowding and competition of resources among offspring and parents |
Overcrowding and competition is reduced |
| More likely to tramsit diseases to offspring |
Less likely to transmit diseases to offspring |