Bio1152
Chapter
46
Animal Reproduction
Sexual
reproduction
is the creation of
offspring
by the fusion of male and female
to form a
.
Some animals
are
, but most must find a
mate
to reproduce.
Some animals can reproduce by
, where an egg develops into an adult without being
fertilized.
In humans, the gametes are produced in
.
In
females,
the gonads are the
where maturation of the
eggs,
or
, occurs.
Starting at puberty, oocytes are released in a
cycle
Review:
Reproductive System of the Human Female
In
males,
the gonads are the
where maturation of the
sperm,
or
, occurs.
Review:
Reproductive System of the Human Male
A fertilized
zygote
undergoes
to produce a
which is implanted in the
.
As the blastocyst develops into an
, its blood exchanges nutrients and waste with the
placenta
through the
cord.
Bio1152
Chapter
47
Animal Development
Fertilization occurs when the haploid nuclei of
and
fuse
to form a diploid
.
Contact of the sperm with the egg initiates an
reaction
followed by a
reaction
the blocks the entry of other sperm into the egg, or
.
Fertilization is followed by
, a period of rapid cell division without
growth,
producing many smaller cells called
that form a hollow ball of cells called a
.
The cells of a blastula start to differentiate in a process called
, forming a three-layered
(gastrula)
that has a primitive gut.
The three
embryonic
layers are the
, which forms the outer layer of the gastrula, the
, which lines the embryonic digestive tract, and the
in between.
Early in
vertebrate
organogenesis,
the
tube forms from infolding of the
, while the
and the
form from mesoderm.
The embryos of
(reptiles and mammals) develop within a fluid-filled sac with four
extraembryonic
.
Humans are
mammals with small eggs that store few nutrients; the
gives rise to the three germ
layers.
Summary:
Sea Urchin Development.