Biology
Slide
1 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Slide
2 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
(When an egg is fertilized, human development
begins.
In this process, a single cell undergoes a series of
cell divisions that results in the formation of a new
human being.)
Slide
3 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
(Fertilization
During sexual intercourse, sperm are released
when semen is ejaculated through the penis into
the vagina.
Sperm swim through the uterus into the Fallopian
tubes.
If an egg is present in one of the Fallopian tubes,
its chances of being fertilized are good.)
Slide
4 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Fertilization
(The egg is surrounded by a protective layer that
contains binding sites to which sperm can attach.
When a sperm attaches to a binding site, its head
releases enzymes that break down the protective
layer of the egg.
The sperm nucleus enters the egg, and
chromosomes from the sperm and egg are brought
together.)
Slide
5 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Fertilization
1. Fertilization:
*process of a sperm joining an
a. zygote: is the fertilized egg
Slide
6 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Fertilization
(After the two haploid (N) nuclei fuse, a single diploid
(2N) nucleus is formed.
A diploid cell has a set of chromosomes from each
parent cell. )
Slide
7 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
2. Early Development
a. in the FT, the zygote begins mitosis.
b. 4 days after fertilization, the embryo is a ,
morula- solid ball of about 64 cells
Slide
8 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
3. 3 stages of early development:
a. implantation
b. gastrulation
c. neurulation.
Slide
9 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
4. Implantation
a. morula grows into a blastocyst - hollow
structure with inner cavity
b. 6–7 days after fertilization, the blastocyst
attaches to uterine wall.
(The embryo secretes enzymes that digest a path
into it. )
Slide
10 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Fertilization
Fertilization and Implantation
Slide
11 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
4. differentiation:
a. Blastocyst cells specialize
(due to the activation of genes.)
b. development of the various types of
tissue in the body.
Slide
12 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
5. Gastrulation:
*formation of 3 cell layers
a. Ectoderm:
develops into skin and nervous system.
b. Endoderm:
forms the digestive lining and organs.
c. Mesoderm:
cells differentiate into internal tissues and
organs.
Slide
13 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(gastrulation is the formation of three cell layers—the
ectoderm, the mesoderm, and the endoderm.)
Amniotic cavity
Primitive
streak
Mesoderm
Ectoderm
Endoderm
Slide
14 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
6. Neurulation:
*development of the nervous system.
Slide
15 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(Shortly after gastrulation is complete, a block of
mesodermal tissue begins to differentiate into the
notochord. )
Slide
16 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(As the notochord develops, the neural groove
changes shape, producing neural folds.)
Neural crest
Neural fold
Notochord
Copyright Pearson Prentice Hall
Slide
17 of 47
39–4 Fertilization and
Development
Early Development
(Gradually, these folds move together to create a
neural tube from which the spinal cord and the
nervous system develop.)
Neural crest
Neural tube
Ectoderm
Notochord
Copyright Pearson Prentice Hall
Slide
18 of 47
39–4 Fertilization and
Development
Early Development
6. Extraembryonic Membranes
a. As the embryo develops, membranes form to
protect and nourish the embryo.
b. these membranes are the amnion and the
chorion.
Slide
19 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
Amniotic sac
(The amnion
develops into a
fluid-filled
amniotic sac,
which cushions
and protects the
developing
embryo. )
Placenta
Umbilical cord
Uterus
Amnion
Fetus
Slide
20 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(Fingerlike projections called chorionic villi form on
the outer surface of the chorion and extend into the
Maternal portion
uterine lining.)
Fetal portion
of placenta
of placenta
Chorionic villus
Amnion
Umbilical cord
Maternal
artery
Umbilical
arteries
Umbilical
vein
Maternal
vein
Copyright Pearson Prentice Hall
Slide
21 of 47
39–4 Fertilization and
Development
Early Development
7. Placenta:
a. connects mother to embryo
b. embryo's organ of respiration,
nourishment, and excretion.
Slide
22 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(The placenta acts as a barrier to some harmful or
disease-causing agents.
Some disease causing agents, such as German
measles and HIV can cross the placenta.
Some drugs, including alcohol and medications also
can penetrate the placenta and affect development.)
Slide
23 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Development
(After eight weeks, the embryo is called a
fetus.
After three months, most major organs and
tissues are formed. During this time, the
umbilical cord also forms.
The umbilical cord connects the fetus to the
placenta.)
Slide
24 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Control of Development
(Control of Development
The fates of many cells in the early embryo are not
fixed.
The inner cell mass contains embryonic stem cells,
unspecialized cells that can differentiate into nearly
any specialized cell type.
Researchers are still learning the mechanisms that
control stem cell differentiation.)
Slide
25 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Later Development
(Later Development
4–6 months after fertilization:
• The heart can be heard with a stethoscope.
• Bone replaces cartilage that forms the early
skeleton.
• A layer of soft hair grows over the fetus’s skin.
• The fetus grows and the mother can feel it
moving. )
Slide
26 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Later Development
(During the last three months, the organ systems
mature.
• The fetus doubles in mass.
• It can now regulate its body temperature.
• The central nervous system and lungs
completely develop.)
Slide
27 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Childbirth
(Childbirth
About nine months after fertilization, the fetus is
ready for birth.
A complex set of factors affects the onset of
childbirth.)
Slide
28 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Childbirth
(The mother’s posterior pituitary gland releases the
hormone oxytocin, which affects involuntary muscles
in the uterine wall.
These muscles begin rhythmic contractions known as
labor.
The contractions become more frequent and more
powerful.)
Slide
29 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Childbirth
(The opening of the cervix expands until it is large
enough for the head of the baby to pass through it.
At some point, the amniotic sac breaks, and the fluid
it contains rushes out of the vagina.
Contractions force the baby out through the vagina.)
Slide
30 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Childbirth
(The baby now begins an independent existence.
Its systems quickly adapt to life outside the uterus,
supplying its own oxygen, excreting waste on its own,
and maintaining its own body temperature.)
Slide
31 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Multiple Births
8. Multiple Births
a. If 2 eggs are released during the same cycle
and fertilized by 2 different sperm, fraternal twins
b. 1 zygote may split apart to produce 2 embryos,
are called identical twins.
Slide
32 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Early Years
(Early Years
The first two years of life are called infancy. It is a
period of rapid growth and development.
Childhood lasts from infancy until puberty.
Adolescence begins with puberty and ends with
adulthood.
Puberty produces a growth spurt that will conclude
in mid-adolescence.)
Slide
33 of 47
Copyright Pearson Prentice Hall
39–4 Fertilization and
Development
Adulthood
(Adulthood
Development continues during adulthood.
Adults reach their highest levels of physical
strength and development between the ages of 25
and 35.
Most people begin to show signs of aging in their
30s.
Around age 65, most body systems become less
efficient, making homeostasis more difficult to
maintain.)
Slide
34 of 47
Copyright Pearson Prentice Hall
39–4
Click to Launch:
Continue to:
- or -
Slide
35 of 47
Copyright Pearson Prentice Hall
39–4
Fertilization takes place in the
a. ovary.
b. Fallopian tube.
c. cavity of the uterus.
d. cervix.
Slide
36 of 47
Copyright Pearson Prentice Hall
39–4
The process in which a blastocyst attaches to
the wall of the uterus is called
a. fertilization.
b. implantation.
c. gastrulation.
d. neurulation.
Slide
37 of 47
Copyright Pearson Prentice Hall
39–4
The central nervous system develops during
which phase of early development?
a. gastrulation
b. neurulation
c. implantation
d. fertilization
Slide
38 of 47
Copyright Pearson Prentice Hall
39–4
The placenta is a structure that
a. belongs entirely to the mother.
b. belongs entirely to the fetus.
c. brings blood from the mother and fetus close
together.
d. provides an impermeable barrier between
the mother and the fetus.
Slide
39 of 47
Copyright Pearson Prentice Hall
39–4
Which of the following is NOT a primary germ
layer?
a. neural tube
b. endoderm
c. ectoderm
d. mesoderm
Slide
40 of 47
Copyright Pearson Prentice Hall
END OF SECTION