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?

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

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

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

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

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

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

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

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

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

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?