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ANIMAL
FERTILIZED EGGS
= ZYGOTE
WHEN THEY GROW THEY BECOME EMBRYOS AND CAN
DEVELOP IN A NUMBER OF WAYS
Once the sperm and egg have fused to form a
zygote, it divides and becomes an embryo
EGGS CAN BE FERTILIZED:
Externally
Like frogs
Internally
Like sharks & humans
The embryo is the developing organism in
humans
ADVANTAGES OF INTERNAL
FERTILIZATION
Higher
survival
Fewer gametes are needed
Young are nourished and protected
especially if in an egg or placental
animal which carries it inside the body
EGGS
DEVELOPMENT OF THE ZYGOTE
The
embryo can be protected inside of:
Seeds
(seed plants)
Eggs (reptiles, fish, birds)
The Mother (most mammals, sharks)
FROG TADPOLE
SALMON ALEVIN
A
zygote in an egg usually has a food
source
Fish and amphibian eggs depend on water
or they will die
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4/26/2015
EGGS OF REPTILES AND BIRDS
AMNIOTIC
The
The
zygote in an egg
usually has a food source
called the yolk and is
protected by the amnion
and shell
Eggs can be laid (reptiles,
birds) to develop
externally
AMNIOTIC
evolution of the amniotic egg
was very important to reptiles and
birds living on land!
EGG
IN SOME MAMMALS THE
EMBRYO
DEVELOPS IN A POUCH
Marsupials
EGGS PROTECT THE EMBRYO
- like this kangaroo joey
MAMMALS THAT LAY EGGS ARE CALLED
MONOTREMES
IN MOST MAMMALS THE EMBRYO
DEVELOPS INSIDE THE MOTHER
For
a much longer time
– placental mammals like humans,
dogs, bears
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MOST MAMMALS THE EMBRYO DEVELOPS
INSIDE THE MOTHER
The
placenta is the
organ that connects
fetus to mother by
the umbilical cord
Removes waste
Brings in nutrients
ADVANTAGES OF PLACENTAL
DEVELOPMENT
Protection
by mother
Nourishment
Infant
is born well
developed
EMBRYOLOGY
Studying
embryos can tell
us how organisms are
related
Similar embryos = similar
ancestry
VOCABULARY TEXT PG. 90 - 91
Umbilical
cord
Marsupial
Monotreme
Chorion
Allantois
Amniotic
egg
Placenta
Embryo
Zygote
Internal
fertilization
DON’T BREAK THE EGG – LAB STATIONS
Check
out the eggs and embryos at the
lab stations & complete the lab
worksheet
Can you recognize the differences?
Can you suggest advantages and
disadvantages for each type of egg?
Where do you think fertilization takes
place? Inside or outside the female?
Why?
Where do the young develop?
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