Warm up What kind of cells are created by meiosis Warm up What kind of cells are created by meiosis? Why is this process important?

Warm up Compare and contrast embryonic stem cells and adult stem cells.

Warm up As you finish, practice your presentations of y0ur cell Warm up As you finish, practice your presentations of y0ur cell. Presentations will start today.

Warm up work on your “cell growth and development” research project.

Cell Growth and development

Sexual Reproduction Gametes, sperm and eggs, are formed in a process called meiosis. Meiosis cuts the amount of DNA in half.

From this picture, let the student know a primardial germ cell can form 4 sperms. Don’t talk too much about the whole stages. The terminology will confuse them.

A fertilized egg is called a zygote.

diploid cells haploid diploid again iws.collin.edu

This occurs in plants and animals.

This occurs in plants and animals.

When an egg and sperm combine DNA, the fertilized egg has a complete set of DNA.

Early Development Then through cell division (mitosis), the zygote becomes a blastula. worms.zoology.wisc.edu blastula www.geol.umd.edu

Early Development The cells of the blastula are embryonic stem cells. Embryonic Stem Cells are unspecialized cells. This means they have not yet differentiated to build different tissues that make the body of the organism.

When the blastula starts to fold, the stem cells begin the journey that will lead to over 250 different kinds of cells.

Even though every cell has the same DNA as the original zygote, switches in the DNA turn genes off and on to make each type of cell different for the job it does.

Stem Cells Zygote Chemicals, like enzymes and hormones are passed from cell to cell controlling DNA switches. This will control the structure of the different types of cells that will eventually be produced in different parts of the body to do different jobs.

The cells differentiate by turning different genes off and on The cells differentiate by turning different genes off and on. This process is called gene expression. Once a cell becomes part of a tissue, it cannot change back to a stem cell.

The embryonic stem cells become differentiated tissues.

Adult stem cells are cells that still are undifferentiated but exist among differentiated cells in tissues

Under laboratory conditions, adult stem cells can become any other tissue.

At this step, each species tissues start to differentiate depending on evolutionary development. https://bealbio.wikispaces.com

In plants, the sperm is contained in pollen grains and the eggs are called ovules

At that moment of fertilization, all the characteristics of the plant have been determined.