Aim: What happens after fertilization?
Do Now: Describe the process of fertilization.
A sperm enters an ovum, and the nuclei combine to form one with 46 chromosomes.
Fertilization: Four Major Steps
Sperm contacts the egg
Sperm or its nucleus enters the egg
Egg becomes activated and developmental changes begin
Sperm and egg nuclei fuse
Words to know…
Fuse- to physically join together
Ovum – egg cell (female gamete)
Cleavage – process of cell division during development
Differentiation – the process of forming different kinds of cells from similar cells of the early embryo
Embryo – an organism in an early stage of development
Morula – solid ball of cells formed from cleavage
Blastula – hollow ball of cells formed from cleavage
Gastrula – a hollow ball of cells with an “in pushing” and 3 layers (germ layers)
The Nuclei Fuse Together
Development of the zygote, the study of which is known as embryology or developmental biology.
The zygote undergoes a series of mitotic cell divisions called cleavage.
The stages of development are: Fertilized ovum (zygote) 2-cell stage 4-cell stage 8-cell stage Morula Blastula Early Gastrula Late Gastrula
Cleavage (divide via mitosis) forms the 2 cell stage
They split again to form the 4 cell stage
And again to form the 8 cell stage…
And eventually form a Morula
Next it becomes a blastula
And next, a gastrula
The Regents Diagram…
Sperm and ovum
Zygote (fertilized ovum)