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 Hand in Meiosis Pictures Lab
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Something to think about as your
open up your notes
 Humans have approx. 50-75 trillion cells
and these cells are all different types (hair,
skin, liver, stomach cells, etc.).

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How can you explain all these types of
cells if humans only start as a single
cell?
Animal Reproduction
&
Development
AP Biology
2007-
Embryology
 The study of the
 Embryo

An organism in the
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IMPORTANT! RECOMBINATION
 Sperm = DNA (haploid) : one version of



each type of chromosome.
Egg =
DNA (haploid): same as above
The combination of one sperm with one egg
will unite and make
.
If another sperm or another egg unite, a
human would result.
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Recombination: SO MANY OPTIONS!
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3 stages of embryo development
1.
2.
3.
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Oogenesis
What is the
advantage of
this development
system?
 Unequal meiotic divisions



unequal distribution
of cytoplasm
egg
polar bodies
Meiosis 1 completed
during egg maturation
ovulation
Meiosis 2 completed
triggered by fertilization
Put all your egg
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in one basket!
Fertilization




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fertilization
cleavage
Gastrulation
Differentiation
Fertilization
 Joining of

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(nucleus) enters
1) Cleavage
 Repeated
of zygote
1st step to becoming
cellular
 unequal divisions establishes body plan

 different cells receive different portions of egg
cytoplasm & therefore different regulatory signals
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Cleavage
 zygote  m

 b
establishes future development
zygote
gastrulation
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Biology
morula
blastula
2) Gastrulation
gastrulation in
primitive chordates
 Establish 3 cell layers

E
 outer body tissues
 skin, nails, teeth
 nerves, eyes, lining of mouth

M
ectoderm
 middle tissues
 blood & lymph, bone & notochord,
mesoderm
muscle
 excretory & reproductive systems

E
 inner lining
 digestive system
 lining of respiratory, excretory &
reproductive systems
Honors Biologyvs. deuterostome
protostome
endoderm
Testing…
In a study of the development of frogs, groups of cells in the
germ layers of several embryos in the early gastrula stage
were stained with five different dyes that do not harm living
tissue. After organogenesis (organ formation), the location of
the dyes was noted, as shown in the table below.
Tissue
Brain
Notochord
Liver
Lens of the eye
Lining of the digestive tract
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Stain
Red
Yellow
Green
Blue
Purple
Neurulation
 Formation of notochord & neural tube

develop into
system
Neural tube
Notochord
develops into
vertebral column
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develops into CNS
(brain & spinal cord)
Growth and Differentiation
Mammalian embryo
Umbilical blood vessels
Chorion
Bird embryo
Amnion
Yolk
sac
Allantois
Fetal blood vessels
Placenta
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Maternal blood vessels
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AP Biology
Testing…
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
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A
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B
C
D
E
F
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3. Growth and Differentiation
 As embryo develops, the # of cells continues
to
 Differentiation
 cells become

Different sections of DNA are
turned
.
, some are
 Certain cells act as organizers
 These cells influence other cells to become
certain cells, tissues
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STEM CELLS
 Omnipotent = have the potential to be
type of cell.
 If mitosis is done, all cells are
identical.
 FACT: all of your cells contain the
(because of mitosis)
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HOW DO WE GET
DIFFERENT CELLS?
 Differentiation:
some DNA is
turned off and
only some
directions are
read, for
example:

Skin cells: all
DNA directions
are turned off,
except for how to
make skin.
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Internal Development
 Development of the embryo
of the body
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, in the
1. Placental Mammals

Placenta - part of the wall of the uterus


Site of
!!!!!!!!!!!!!!!!!!!!!!!!
Embryo’s and mother’s circulatory system are
touching BUT NOT
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
Umbilical cord
 Contains
that the embryo will get
nourishment and oxygen from the mother’s
blood to the
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Human fetal development
4 weeks
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7 weeks
Human fetal development
10 weeks
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Human fetal development
12
weeks
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Biology
20 weeks
Human fetal development
 The fetus just spends much of the 2nd &
3rd trimesters just growing
…and doing various flip-turns & kicks
inside amniotic fluid
Week 20
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Human fetal development
 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
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Human fetal development
 30 weeks (7.5 months)
umbilical cord
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positive feedback
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Birth
Getting crowded in there!!
 32 weeks (8 months)
The fetus
sleeps 90-95%
of the day &
sometimes
experiences
REM sleep, an
indication of
dreaming
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Birth (36 weeks)
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The end of the journey!
And you think
9 months of
BioH is hard!
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2. Nonplacental Mammals
mammals



Duckbilled platypus
Anteaters
mammals


Embryo begins to
develop in uterus
 Crawls into mother’s pouch
 Finishes developing in pouch
 Kangaroo, opossum
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1) Albumen –
S
A
A
E
A
Y
2) Allantois –
3) Amnion –
4) Yolk –
5) Shell – Calcium carbonate,
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August 08’
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June 08’
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August 07’
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