Section 4 – Reproduction

1. Section 4– Reproduction National 4 & 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 diploidcell • - 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 Amniotic fluid http://www.on101.co.uk/foetal.html

7. ThePlacenta The placenta is where the blood of the mother and foetus are brought close together. Athin 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. PLACENTA OXYGEN WASTE FOOD CARBON DIOXIDE 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. Reproduction in other animals • Many animals reproduce externally • - e.g. fish/amphibians • - fertilisation occurs in water outside the body of the female • The chances of success are low • Therefore thousands of eggs are produced • Other animals reproduce internally • - e.g. reptiles/birds • - fertilisation is within the body of the female • Chances of success are higher • Fewer eggs are produced

11. Parental Care • Young fish receive little, or no, care and protection from their parents • They feed initially from their yolk sac • Once this is used up, they learn to catch food for themselves • Young mammals obtain food from their mother (suckling milk) • They are dependent on their parents for care and protection

12. Comparison 3000 12 1 12 In the water in the oviduct yolk in the egg from mothers blood Yolk in egg sac then finds its own from its mother mothers body soft covering none parents look after

13. 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