Do Now: Label each stage in the
development of the embryo below:
Aim: How does bird
development differ from
mammal development?
Where do birds develop?
Birds develop externally. Their eggs must:
Be protected
Be warm (Birds are warm blooded)
Allow gas exchange (oxygen in and carbon
dioxide out)
Keep moisture in
Store waste safely
Contain food to nourish the embryo
Amnion
Embryo
Chorion
Yolk sac
Shell
Allantois
Extraembryonic membranes
Extraembryonic
4
membranes:
1) chorion –
1
controls the
passage of O2 and
CO2 into/out of the
egg
2) yolk sac –
2
provides the
embryo with food
6
5
3
Extraembryonic membranes
4
6
5
1
2
3
3) shell with its
lining keeps
moisture inside the
egg, yet allows
gases in/out.
4) amnion – a fluidfilled sac that
protects the
embryo and keeps
it moist
Extraembryonic membranes
5) allantois – a sac
where the embryo
stores waste. It
also aids in gas
exchange.
6) bird or reptile
embryo
4
6
5
1
2
3
Comparison of Bird and Mammal Development
In placental mammals, the chorion, allantois, and yolk
sac become part of the placenta and umbilical cord.
How do placental mammals
develop?
In mammals, the
amnion continues to
protect the embryo
(fetus).
The placenta is an
organ made up of
maternal and fetal
blood vessels. The
blood does not mix.
How do placental mammals
develop?
Oxygen, nutrients,
water, drugs and
sometimes viruses
diffuse from mother’s
blood to the fetus.
Waste diffuses from
the fetus to the
mother.
An umbilical cord
connects the fetus to
the placenta.