1. Animal Growth & Development

2. Beginnings of the Embryo  Fertilization- union of the gametes Sperm- very small, mobile, ½ of chromosome set Egg- very large, contains yolk, other half of chromosome set  YOLK: energy-rich, contains lipids, proteins, RNA, many ribosomes, mitochondria

3. Fertilization process Sperm head hits surface of egg Enzymes break through egg’s surface Egg puts up barrier to other sperm once activated Sperm nucleus fuses with egg nucleus and forms zygote (earliest stage of the embryo

4. Egg Activation Fertilization turns on egg’s metabolism  Causes an increase in cell respiration  Synthesis of new proteins occurs using RNA molecules already present in cytoplasm  Plasma membrane blocks a second fertilization by another sperm  Zygote cytoplasm is rearranged by movements in cytoskeleton (produces differences among cells when they begin to divide)

5. 10.2 GROWTH, DIFFERENTION AND FORM Zygote to complex multicellular individual Cell division of embryo  Increasing number of cells make individual grow Differentiation  As cells divide some become specific cell types (Example: muscle, skin) Morphogenesis  As cells differentiate they organize into specific tissues to later form organs *each cell type has a specialized structure and function

7. How does differentiation occur ? All cells have same DNA Proteins make each cell different  Each cell type expresses certain genes making specific proteins by protein synthesis  Example: muscle cells make actin and myosin while red blood cells make hemoglobin

8. 10.3 One cell to many Cleavage  Immediately after fertilization the cell divides into two cells.  Cells continue to divide simultaneously increasing cell # 2x for each division: 2→4→8→16, etc.  At 16 cells to 64 cells the embryo is called and Morula  At the end of cleavage: mass of many cells called a Blastula All cells are same in size and appearance Usually hollow (hollow part called blastocoel) Shape depends on structure and arrangement of egg and yolk http://www.youtube.com/watch?v=UgT5rUQ9EmQ

9. Gastrulation Through differentiation and morphogenesis Blastula becomes Gastrula Forms primary germ layers (3):  Ectoderm- outer layer, will form skin, nervous system and related structures  Mesoderm- middle layer, will form bone, muscles, heart, blood, etc.  Endoderm- inner layer, “tube-like”, will form lining of digestive system

12. Summary Fertilization Morula (16-64 cells) ↓ Blastula (can have various shapes) ↓ Gastrula (3 layers- ectoderm, mesoderm, endoderm) (Pictures show sea urchin development)

14. Gastrulation continued... Body Plan  In vertebrates, appears during gastrulation  General shape of developing organism  Notochord Forms from first mesoderm Stiff rod that will become backbone Runs through middle of embryo just below dorsal ectoderm Establishes anterior-posterior axis (head to tail)  Neural tube Forms from dorsal ectoderm directly above notochord Will form brain, spinal cord and nerves

16. Some differences among animals... Some develop directly into young that are like the adult (birds and mammals) Other animals form larva (frogs, sea stars, insects  Does not resemble adult form  Later goes through metamorphosis Examples: maggot→ fly caterpillar→ butterfly tadpole → frog

17. 10.5 Human Development Embryo develops inside mother  Mother provides warm, protected environment  Blood circulation provides nutrition and oxygen, removes waste and CO 2 Zygote goes through cleavage while moving down oviduct After 5 days- blastocyst (like blastula in other animals) implants in uterine wall

18. Early changes in Embryo

20. Human development continued... Amnion- surrounds the embryo Chorion-encloses other membranes, forms outer wall of blastocyst Placenta  Forms in gastrulation  Chorion forms villi into uterine lining→ placenta  Exchanges nutrients, wastes, O 2, CO 2 between mother and embryo through umbilical cord (arteries and veins)

22. Eggs versus Embryo Chorion: lies just beneath the shell & functions in gas exchange. Allantois: collects & stores nitrogenous wastes. Yolk sac stores food. Amnion cushions & provides watery environment.

23. gestation 40 weeks to develop Called “fetus” after start of 8th week Divided into trimesters  1 st : organs and skeleton begin to form  2 nd :  3 rd : rapid growth and maturation http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter3/animation__fetal_developme nt_and_risk.html