1. AIM: What is the difference between internal and external fertilization and development?
Do Now: Using the following diagram, answer the following questions:
Name each structure
What is the chromosome number in each structure?
Identify process A
Identify process B
What process forms structures A and B?

2. Internal Fertilization
External Fertilization
Where does fertilization take place?
Sperm and egg unite inside the females body
Sperm and egg unite outside the females body
Type of environment
Land- why?
No water for the sperm to swim to the egg
Water- why?
There is water for the sperm to swim to the egg
Number of eggs produced
Few- why
Protected inside the females body
Parental care
Eggs are not eaten
Constant environment inside the body
Most of the eggs are fertilized
Many- why?
Egg and sperm may not meet
Some may get eaten
Environmental conditions may change
No parental care
Examples
Mammals
birds
fish

3. Embryonic Development
The zygote grows and develops into an entire body.
Development can be either INTERNAL or EXTERNAL, depending on the organism
fertilization

4. Internal Development
External Development
Embryo develops inside the females body
Humans
Most mammals
Embryo develops outside the females body

5. Stages of Embryonic Development:
The egg cell is fertilized by the sperm cell, forming the zygote
The zygote undergoes cleavage (mitotic cell division)
Morula  Blastula (implantation)  Gastrula

6. Gastrulation Cells start to differentiate Form specialized cells
Ex: blood cells, nerve cells, muscle cells
Every cell still contains the same genetic information

7. Differentiation Ectoderm Outer layer Skin, nerve Mesoderm Inner layer
Muscle, bone
Endoderm
organs

8. Where does fertilization usually occur?
In the fallopian tube (oviduct)

9. How are twins formed? Identical Fraternal Number of eggs released 1 2
Number of sperm
Zygote formation
One zygote splits during early cleavage
Two zygotes are formed
Genetic information
Not identical

10. What happens after fertilization?
The developing embryo travels to the uterus and implants itself in the uterine lining

11. Label each structure in the diagram
In which structure are the egg cells produced?
In which structure is estrogen produced?
I which structure does fertilization take place?
In which structure does embryonic development take place?