Human Development

27.9 Relate the structure of sperm to its role in fertilization.

Describe the mechanisms that prevent more than one sperm from fertilizing an egg and that prevent hybridization between different species.

Describe this picture…

27.10 Describe the process and results of cleavage. Explain how identical and nonidentical twins form.

Describe this picture…

27.11 Describe the process of gastrulation and the resulting arrangement of the embryo.

Establish 3 cell layers ectoderm

outer body tissues skin, nails, teeth nerves, eyes, lining of mouth

mesoderm middle tissues

blood & lymph, bone & notochord, muscle

excretory & reproductive systems endoderm

inner lining digestive system lining of respiratory, excretory &

reproductive systems

Gastrulation

ectoderm

mesoderm

endoderm

protostome vs. deuterostome

gastrulation inprimitive chordates

27.12 Explain how organs form after the development of a gastrula.

Explain how changes in cell shape, induction, cell migration, and

apoptosis contribute to development

Pattern formation during embryonic development is controlled by ancient genes

27.15 Describe the initial embryonic stages and the formation and functions of the extraembryonic membranes in humans.

Human fetal development5 weeks4 weeks

Human fetal development10 weeks

Human fetal development

14 weeks 20 weeks

The fetus just spends much of the 2nd & 3rd trimesters just growing

…and doing various flip-turns & kicks inside amniotic fluid

Human fetal development

Week 20

24 weeks (6 months; 2nd trimester)Human fetal development

fetus is covered with fine, downy hair called lanugo. Its skin is protected by a waxy material called vernix

30 weeks (7.5 months)Human fetal development

umbilical cord

32 weeks (8 months)Getting crowded in there!!

The fetus sleeps 90-95% of the day & sometimes experiences REM sleep, an indication of dreaming