1. Do Now 1) A cell with a solute concentration of.5 g/mL is placed in a beaker of DISTILLED water. What will happen? What is this solution called? 2) An ion must be pumped through a channel protein from low concentration to high. What type of TRANSPORT is this?

2. FERTILIZATION AND DEVELOPMENT From One Cell to Many

3. Fertilization and Early Development Fertilization: Fusion of Sperm and Egg

4. The Egg Surrounded by protective layer with binding sites for sperm attachment. Sperm release enzymes that break down protective layer. Once one sperm fertilizes egg, it is called a ZYGOTE.

5. Multiple Embryos What if two eggs are released during the same menstrual cycle? What if a single zygote splits apart and each cell begins dividing?

6. Days 1-6 Still in fallopian tube. Zygote begins mitosis. As embryo grows, a cavity forms in the center, until embryo becomes hollow ball of cells: Blastocyst.

7. Implantation 6-7 days after fertilization, blastocyst attaches to wall of uterus and begins to grow into tissues of mother.

8. Differentiation Blastocyst begins to specialize. Differentiation: results in development of the various types of body tissue. Inner Cell Mass: Cluster of cells that develops within the inner cavity of the blastocyst. (body of the embryo will develop from these cells, while other cells will differentiate into protective tissue)

9. Gastrulation Formation of three cell layers called the ectoderm, mesoderm, and endoderm. Ectoderm and Endoderm form first. Cells that migrate from each of these layers form the mesoderm.

10. Ectoderm Develops into skin and nervous system.

11. Mesoderm Differentiate and form many of the body’s internal structures, including bones, muscle, blood cells, and gonads.

12. Endoderm Forms linings of organs in the digestive system, such as the stomach, intestines, as well as in the respiratory and excretory systems.

13. Neurulation First step in development of the nervous system. Shortly after gastrulation is complete, a block of mesodermal tissue begins to differentiate into the notochord.

14. Neurulation (cont’d_ As notochord develops, the ectoderm near the notochord thickens and forms the neural plate. Raised edges of the neural plate form neural folds and the neural crest. Neural folds move together and form the neural tube.

15. Neurulation

16. Neurulation (cont’d) Spinal cord and brain will develop from the neural tube. Cells of the neural crest migrate to other locations and become types of nerve cells, skin pigment cells, and other structures, such as the lower jaw.

17. Neurulation (cont’d) If neural tube does not close completely, spina bifida can result. Folic acid can prevent most cases of spina bifida.

18. The Placenta Specialized membranes form to protect and nourish embryo. Amnion: sac filled with amniotic fluid that cushions the embryo. Chorion: outside amnion; makes direct contact with uterine tissues. Chorionic Villi: finger-like projections that devlop from chorion and extend into uterine lining.

19. The Placenta (cont’d) Placenta:  formed from chorionic villi and uterine lining  Connection between mother and embryo  Embryo’s organ of respiration, nourishment, and excretion  Materials diffuse from mother’s blood to baby’s without blood mixing.

21. The Placenta (cont’d) Umbilical Cord:  contains two arteries and one vein for exchange of gases  Connects embryo to placenta

22. Fetus After 8 weeks of development, the embryo is called a FETUS. After 3 months, most of the major organs and tissues of the fetus are fully formed. Fetus may begin to move and show signs of reflexes. (8 cm long, 28 grams) (.25 c)

23. Later Development Although most tissues and organs have been formed after 3 months, they are not yet ready to go to work on their own.

24. Months 4-6 Tissues become more complex, specialized, and begin to function.  Heart can be heard with stethoscope  Bone replaces cartilage to form skeleton  Lanugo: soft hair grows over fetus

25. Months 7-9 During the last three months before birth, the organ systems of the fetus mature, and the fetus grows in size and mass.  Doubles in mass  Lungs and other organs undergo changes  Fetus can regulate its body temperature  CNS and lung development complete

26. Childbirth About nine months after fertilization, factors trigger labor. Oxytocin released from mother’s pituitary gland, triggering involuntary muscles in uterine wall to contract. After baby is born, umbilical cord is clamped and cut. Piece of umbilical cord eventually falls of baby leaving scar: belly button.