Development

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Slide 1

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.

Slide 2

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

Slide 3

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)

Slide 4

Fertilization

Slide 5

The Nuclei Fuse Together

Slide 6

What happens now?

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

Slide 7

Cleavage (divide via mitosis) forms the 2 cell stage

Slide 8

They split again to form the 4 cell stage

Slide 9

And again to form the 8 cell stage…

Slide 10

And eventually form a Morula

Slide 11

Next it becomes a blastula

Slide 12

And next, a gastrula

Slide 13

The Regents Diagram…

Sperm and ovum

Zygote (fertilized ovum)

2-cell stage

4-cell stage