1. Section 4 – Reproduction
National 4 & 5 - Multicellular Organisms

2. Learning Outcomes By the end of this lesson I will be able to:
- identify the difference between asexual & sexual reproduction
- identify the sites of gamete production in plants
- identify the key structures of these sites
- explain what happens during fertilisation
- compare the methods of fertilisation in different plants

3. Reproduction The production of new members of a species Can be sexual:
Requires sex cells (gametes)
These contain half the information needed to make a new organism
When they combine, a full set of information is formed
or asexual:
- does not require sex cells

4. Gametes and reproduction
All body cells have two sets of chromosomes
- 1 set from each parent
These cells are said to be diploid
Gametes are formed by meiosis
- a type of cell division
Gametes contain one set of chromosomes
- half of the original cells
They are said to be haploid
When two haploid cells join together = fertilisation
A new diploid cell is formed
- this is a zygote

5. Site of gamete production - plants
The reproductive parts of a plant are found in the flower
The male sex cells are found in pollen grains
These are found inside an anther
Female egg cells are called ovules
- found within the ovary

6. Reproduction in plants - pollination
The transfer of pollen from an anther to a stigma
The stigma is the top of the female part of the flower
Pollen can be transferred in two ways
- by the wind
- by insects

7. Insect Pollination vs. Wind Pollination
What are the differences in appearance/structure between insect and wind pollinated flowers?
WIND
INSECT

8. Insect Pollination vs. Wind Pollination
Complete the following table
WIND POLLINATED FLOWERS
INSECT POLLINATED FLOWERS
Structural Feature
Reason
Small, dull flowers with no scent or nectar
Large, colourful flowers with nectar and scent
Anthers hanging out of flower
Anthers firmly attached inside flower
Stigmas hanging out of flower
Stigmas inside the flower, with sticky surface
Light and smooth pollen
Sticky and rough pollen
Large quantity of pollen
Small quantity of pollen

9. Insect Pollination vs. Wind Pollination
Complete the following table
WIND POLLINATED FLOWERS
INSECT POLLINATED FLOWERS
Structural Feature
Reason
Small, dull flowers with no scent or nectar
Insects not needed
Large, colourful flowers with nectar and scent
To attract insects
Anthers hanging out of flower
So pollen is easily blown away by the wind
Anthers firmly attached inside flower
To brush against insects, so pollen is picked up
Stigmas hanging out of flower
So pollen can be caught and trapped
Stigmas inside the flower, with sticky surface
To ensure pollen attached to stigma
Light and smooth pollen
Easy to be lifted and carried by the wind
Sticky and rough pollen
Easy for pollen to stick to insects
Large quantity of pollen
Low chance of pollen landing on another plant
Small quantity of pollen
More likely to be transferred by insect

10. Reproduction in plants - fertilisation
Once transferred, the pollen then needs to travel down the stigma
It uses sugar on the stigma as an energy source
It uses this to form a pollen tube
The male gametes then travel down to the ovule
Once inside, the male and female sex cells join together
This is fertilisation
Plant sexual reproduction video

11. Asexual Reproduction
When a new organism is produced from a single parent
Doesn’t involve sex cells or fertilisation
All offspring are identical to their parent
Plants
- also known as vegetative propagation
Plants can form offspring from their stems
E.g. runners from strawberry/spider plant
Others can form offspring from their roots
E.g. onion , potato
Plants asexual-reproduction video

12. Asexual vs Sexual Reproduction
Both types of reproduction have advantages
Asexual
Sexual
Young plant has food source from parent or food store
New plant has a mixture of characteristics from different parents - variation
Young plant grows in a suitable environment
Plants well distributed
No need to depend on pollination