Download Activating Strategy AP Lesson #90

Activating Strategy
• Describe what is occurring in the following
animation.
AP Lesson #90
EQ: How do animals develop from a
single cell into multicellular organisms?
What are the stages for the development of
an organism?
1.
2.
3.
4.
5.
Fertilization
Cleavage
Gastrulation
Neurulation
Organogenesis
1
Step 1: How does fertilization occur?
• Protein receptors on egg surface recognize sperm
– Acrosomal enzymes digest vitellin layer
– sperm nucleus enters and fuses with egg nucleus
– cortical reaction occurs = only 1 sperm enters
• Occurs in the Fallopian Tube
Fig. 47-4
EXPERIMENT
10 sec after
fertilization
25 sec
35 sec
1 min
10 sec after
fertilization
20 sec
30 sec
500 µm
RESULTS
1 sec before
fertilization
500 µm
CONCLUSION
Point of
sperm
nucleus
entry
Spreading
wave of Ca2+
Fertilization
envelope
Step 2: What is Cleavage?
• Repeated mitotic divisions of zygote
– unequal divisions establishes body plan
• different cells receive different portions of egg cytoplasm &
therefore different regulatory signals
• Once complete, embryo implants into the lining
of the uterus
2
What changes occur to the cells during cleavage?
• zygote = single diploid cell→
• morula = solid ball of cells (blastomeres)→
• blastula = ball of cells with a fluid-filled cavity called a
blastocoel
– establishes future development
morula
zygote
gastrulation
archenteron
blastula
blastopore
How does cleavage effect cell signaling?
• Regulating the expression of genes that affect
the developmental fate of the cell
Step 3: What is Gastrulation?
• Rearranges the cells of a
blastula into a gastrula
• Establish 3 cell germ layers
Gastrula
– ectoderm
• outer body tissues
– skin, nails, teeth
– nerves, eyes, lining of mouth
ectoderm
– mesoderm
• middle tissues
mesoderm
– blood & lymph, bone & notochord,
muscle
– excretory & reproductive systems
– endoderm
endoderm
• inner lining
– digestive system
– lining of respiratory, excretory &
reproductive systems
3
Step 4: What is Neurulation?
• Formation of notochord & neural tube
– Notochord = stiff rod that provides support
– Neural tube = develops into the CNS
develops into CNS
Neural tube (brain & spinal cord)
Notochord
develops into
vertebral column
Step 5: What is Organogenesis?
• Various regions of the germ layers develop into
rudimentary organs
• Cells undergo cell differentiation
What are extraembryonic membranes?
• Membranes that develop outside the embryo
Mammalian embryo
Umbilical blood vessels
Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
Maternal blood vessels
4
What are the stages of human fetal development?
4 weeks
7 weeks
10 weeks
12 weeks
20 weeks
5
• The fetus just spends much of the 2nd & 3rd
trimesters just growing
…and doing various flip-turns & kicks inside amniotic
fluid
Week 20
• 24 weeks (6 months; 2nd trimester)
• fetus is covered with fine, downy hair called lanugo
• Its skin is protected by a waxy material called vernix
Getting crowded in there!!
• 32 weeks (8 months)
The fetus sleeps 9095% of the day &
sometimes
experiences REM
sleep, an indication of
dreaming
6
positive feedback
Birth
Birth (36 weeks)
Intestine
Placenta
Umbilical
cord
Wall of
uterus
Bladder
Cervix
Vagina
The end of the journey!
7
Summarizing Strategy
All of the following correctly describe the fate of the
embryonic layers of a vertebrate EXCEPT
A. neural tube and epidermis develop from ectoderm
B. linings of digestive organs and lungs develop from endoderm
C. notochord and kidneys develop from endoderm
D. skeletal muscles and heart develop from mesoderm
E. reproductive organs and blood vessels develop from mesoderm
Assessment
• HW: Reproduction MC ?’s
Mammalian embryo
Bird embryo
8
Mammalian embryo
Bird embryo
9