Lecture AP Biology Chapter 47 Animal development

Ch. 46/47 Warm-Up
1. (Ch. 46) How do oogenesis and spermatogenesis
differ?
2. (Ch. 46) How do these hormones affect the menstrual
cycle?
a) LH
b) FSH
c) Estrogen
d) Progesterone
3. (Ch. 47) Describe the process of fertilization.


Chapter 47
Animal Development


What you must know:
• The events that occur when a sperm contacts
an egg
• What occurs in cleavage, gastrulation, and
organogenesis
• Two structures derived from each germ layer


Mammalian Fertilization
1. Sperm binds to receptors in zona pellucida (extracellular
matrix of egg)
2. Acrosomal reaction: sperm releases hydrolytic enzymes to
digest z.p.
(Sea Urchins) Depolarization of membrane: prevent other
sperm from binding = fast block to polyspermy

3. Sperm + Egg Fuse
4. Cortical reaction: sperm + egg fusion triggers release of Ca2+
1. cortical granules fuse with z.p.  z.p. hardens to form
fertilization envelope = slow block to polyspermy
5. Ca2+ release also triggers activation of the egg


Fertilization in mammals


Cleavage: rapid mitotic cell division
• Zygote cytoplasm partitioned into smaller cells (blastomeres)
• Solid ball of cells = morula
• Blastula (hollow ball of cells) filled with fluid (blastocoel)
 Blastocyst (human)


Gastrulation: rearrange cells to form 3-layered
embryo w/primitive gut

Three Embryonic Germ Layers*

Ectoderm

Mesoderm

Endoderm

• Skin, nails, teeth
• Lens of eye

• Nervous system
(brain, spinal cord)

• Skeletal, muscular
• Epithelial linings of
systems
digestive, respiratory,
excretory tracts
• Notochord
• Liver, pancreas
• Excretory,
circulatory
• Reproductive system
• Blood, bone, muscle

* For AP Test, you should know at least 2 derivatives of each germ layer.



Organogenesis: development of 3 germ layers
into organs
• Notochord – stiff dorsal skeletal rod, forms
from mesoderm
• Neural plate  neural tube brain and spinal
cord
• Neurulation – forms hollow dorsal nerve
chord
• Somites – blocks of mesoderm arranged along
notochord; sign of segmentation

Early human
embryonic
development


Amniotic embryos (reptiles, birds, mammals)
• Develop in fluid-filled sac w/in a shell or uterus
• Amnion: fluid protects embryo – prevent
dehydration, cushions mechanical shock
• Yolk : nutrients in egg
• Mammalian eggs: little stored food
Amnion

Allantois

Embryo
Amniotic
cavity
with
amniotic
fluid

Albumen

Shell
Yolk
(nutrients)
Chorion

Yolk sac


Patterns of development
• Cytoplasmic determinants: chemical signals such
as mRNAs and transcription factors, influence
pattern of cleavage
• Induction: interaction among cells that
influences their fate, cause changes in gene
expression
• Totipotent cells: capable of developing into all
the different cell types
 all cells of mammalian embryos are totipotent until
the 16-cell stage