1. Section 4 – Reproduction
National 5 - Multicellular Organisms

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

3. Re-Cap 1) What are the two types of reproduction called?
2) What are gametes?
3) What do the terms haploid and diploid mean?

4. Site of gamete production - humans
In animals, the gametes are the sperm and the egg
The sperm are produced in the male testes
- sperm travel through the sperm duct into the penis
Egg cells are produced in the female ovaries
- process known as ovulation
The penis of the male deposits sperm
- inside the vagina of the female
The sperm them swim to the fallopian tube/oviduct to meet the egg
Here fertilisation occurs
Penis
Testes
Oviduct

5. Fertilisation When the sperm and egg cell nuclei fuse together
These haploid cells join to form a diploid cell
- this is called a zygote
This will then divide to form a ball of cells
- a blastocyst
This will then implant itself inside the wall of the uterus
It will then grow and develop – gestation period

6. Development of human embryo
Uterus wall
Placenta
Amniotic sac
Umbilical cord
Embryo/Foetus
Amniotic fluid

7. The Placenta
The placenta is where the blood of the mother and foetus are brought close together.
A thin barrier separates the bloodstream of mother and baby.
Oxygen and dissolved food diffuse into the baby’s bloodstream from the mother.
Carbon dioxide and waste diffuse from the baby into the mother’s blood.

8. OXYGEN WASTE FOOD CARBON DIOXIDE PLACENTA
Mother’s blood going to placenta
Mother’s blood leaving to placenta
Blood to the embryo
Blood From the embryo

9. Twins Account for around 3% of all births 2 possible types:
IDENTICAL (MONOZYGOTIC):
- after fertilisation, a zygote will sometimes split into two
- these will then develop separately into two different embryos
- these share a placenta and amniotic sac
- genetically identical
NON-IDENTICAL (DIZYGOTIC):
- when two eggs are released and fertilised by two sperm
- different placenta and amniotic sac
- genetically different

10. Asexual Reproduction Doesn’t involve sex cells or fertilisation
All offspring are identical to their parent
Animals
Usually only occurs in micro-organisms
- yeast reproduce by budding
- bacteria/fungi can reproduce by fission