Sexual Reproduction Part 3: Development Science 9 Ms. Jhaj

Human

Embryonic Development After fertilization, zygote undergoes repeated mitosis -One Cell (zygote) -2 Cells -4 Cells -8 Cells -Morula: ball of cells by end of 1st week

Embryonic Development By the 2nd week, a hallow ball of cells form, called the blastula.

Embryonic Development Blastula Stage: embryonic stem cells Next stage: Gastrula which is made out of three layers…

Layers of the Gastrula 1) Ectoderm: Outer Layer forms skin and nervous system 2) Mesoderm: Middle layer forms kidneys, muscles, blood vessels, reproductive organs and bones 3) Endoderm: Inner layer forms lungs, liver, and the lining of the digestive system

Fetal Development Differentiation: cell layers form organs and tissues Occurs for 38 weeks Divide this time into 3 trimesters, each 3 months long

Fetal Development Trimester 1: Developing Organ Systems 4 weeks: brain and spinal cord 8 weeks: bone cells and now called Fetus 12 weeks: organ systems formed

Fetal Development Trimester 2: Growth Weeks 12-16 rapid growth Week 20 mother can feel fetus move Weeks 20-24 slow growth

Fetal Development Trimester 3: Continued Growth Growth in preparation for birth Brain grows significantly Week 32: fat deposited under skin

Animation period of zygote http://www.youtube.com/watch?v=qhrZj2RuNgQ&feature=related How you were created - 3D animation video of new baby formation http://www.youtube.com/watch?v=plryH-USwNk http://www.youtube.com/watch?v=fKyljukBE70

Check Your Understanding BC Science 9 Workbook Pgs 88, 90-91 BC Science 9 Textbook Page 223, Q’s 10-12, & 20