1. Fertilization and Embryology
People, Chickens, Opossums

2. The Ovary and a Follicle

3. Fertilization
Fusion of haploid (monoploid) sperm and haploid egg. They form a diploid Zygote
If the sperm and egg meet outside of the body, it’s called External Fertilization.
Fish, frogs, most aquatic animals do this
Many eggs are eaten and sperm and eggs can drift apart, so many are produced

4. Ovulation
The egg

5. The Sperm

6. Sperm on an egg

7. External Fertilization: The male fertilizes the eggs as they emerge

8. Internal Fertilization
If the sperm and egg meet inside the body, it’s called Internal Fertilization.
Sperm and eggs are confined, and no predators are inside to eat the eggs
Few eggs are produced because fertilization per egg is more likely

9. Stages of Development
Early development consists mainly of cell and tissue growth and differentiation

10. The ENDODERM gives rise to:
The lining of the digestive tract
The lining of the Respiratory Tract
Liver
Pancreas

11. The MESODERM gives rise to:
The Muscles
The circulatory system
The skeleton
The excretory system
The reproductive systems

12. The ECTODERM gives rise to:
The Nervous System
The skin

13. External Development Occurs outside of mom’s body
In water: many organisms have both external development as well as external fertilization.
The yolk stored in the egg is the embryo’s food source
On land: Birds, many reptiles and a few mammals develop externally after internal fertilization
The yolk is the embryo’s food source

14. Adaptations for external development on land
A Shell provides protection
Membranes help provide a good environment for embryo development. These include:
The amnion: contains amniotic fluid, protects from shock, keeps embryo from sticking to shell
Yolk sac surrounds yolk, blood vessels carry nutrients to embryo

15. More adaptations: Membranes
The Allantois works as a respiratory membrane and storage place for uric acid: the nitrogenous waste of the chick
The chorion surrounds everything, it lies just inside the shell and helps in gas exchange

16. The Egg
Amniotic Fluid
Reptile eggs have leathery shells

17. Internal Development
Growth of the embryo within the body of the female
Placental mammals: The embryo develops within the uterus
There is little yolk in eggs, so they’re small
The Placenta in the uterus forms from embryonic and maternal tissues
All transfer of materials from mom to baby and vice versa occurs through the placenta
These include nutrients, wastes, and respiratory gases

18. Placenta
There is no direct connection between the bloodstream of mom and fetus
Transport is done by diffusion and active transport through the placenta
When stretched out, and all wrinkles laid flat, it has the surface area of half of a tennis court!!!!!
Most mammals are placental

19. The placenta and its circulation

20. The Umbilical Cord It attaches the embryo to the placenta
It is full of blood vessels
At birth, it contains a wealth of embryonic stem cells, most of which are pumped into the baby during and in the few minutes after birth

21. Human Development
20 weeks
5 weeks
14 weeks

22. Ultrasound

23. Marsupials Mammals without placentas
Internal fertilization, and partial internal development without nourishment from mom. The yolk is stored in the egg, and the embryo is born in early development and completes development externally in a pouch with mammary glands found inside
The tiny baby has to crawl from the birth canal and find the pouch

24. Marsupials