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Biology in Focus - Chapter 36
- 1. CAMPBELL BIOLOGY IN FOCUS
© 2014 Pearson Education, Inc.
Urry • Cain • Wasserman • Minorsky • Jackson • Reece
Lecture Presentations by
Kathleen Fitzpatrick and Nicole Tunbridge
36
Reproduction
and Development
- 2. © 2014 Pearson Education, Inc.
Overview: Pairing Up for Sexual Reproduction
Each sea slug produces sperm and eggs and thus
acts as both mother and father to the next generation
Animal reproduction takes many forms
A population outlives its members only by
reproduction, the generation of new individuals
from existing ones
- 4. © 2014 Pearson Education, Inc.
Concept 36.1: Both asexual and sexual
reproduction occur in the animal kingdom
Sexual reproduction is the creation of an offspring
by fusion of a male gamete (sperm) and female
gamete (egg) to form a zygote
Asexual reproduction is the creation of offspring
without the fusion of egg and sperm
- 5. © 2014 Pearson Education, Inc.
Mechanisms of Asexual Reproduction
Many invertebrates reproduce asexually by budding,
in which new individuals arise from outgrowths of
existing ones
Also common among invertebrates is fission, the
separation of a parent organism into two individuals
of approximately equal size
Video: Hydra Budding
- 7. © 2014 Pearson Education, Inc.
Fragmentation is breaking of the body into pieces,
some or all of which develop into adults
Fragmentation must be accompanied by
regeneration, regrowth of lost body parts
Parthenogenesis is the development of a new
individual from an unfertilized egg
- 8. © 2014 Pearson Education, Inc.
Sexual Reproduction: An Evolutionary Enigma
Sexual females have half as many daughters as
asexual females; this is the “twofold cost” of sexual
reproduction
Despite this, almost all eukaryotic species reproduce
sexually
- 9. © 2014 Pearson Education, Inc.
Figure 36.3-1
Asexual reproduction
Female
Female
Male
Sexual reproduction
Generation 1
Generation 2
- 10. © 2014 Pearson Education, Inc.
Figure 36.3-2
Asexual reproduction
Female
Female
Male
Sexual reproduction
Generation 1
Generation 2
Generation 3
- 11. © 2014 Pearson Education, Inc.
Figure 36.3-3
Asexual reproduction
Female
Female
Male
Sexual reproduction
Generation 1
Generation 2
Generation 3
Generation 4
- 12. © 2014 Pearson Education, Inc.
Sexual reproduction results in genetic recombination
The resulting increased variation among offspring
may enhance the reproductive success of parents in
changing environments
- 13. © 2014 Pearson Education, Inc.
Reproductive Cycles
Most animals exhibit reproductive cycles related to
changing seasons
Reproductive cycles are controlled by hormones and
environmental cues
Because seasonal temperature is often an important
cue in reproduction, climate change can decrease
reproductive success
- 15. © 2014 Pearson Education, Inc.
In some species of whiptail lizards, the members of
breeding pairs alternate roles
Reproduction is exclusively asexual, and there are
no males
However, courtship and mating behavior still take
place, with one female of each pair mimicking male
mating behavior
The two alternate roles two or three times during
the breeding season
- 16. © 2014 Pearson Education, Inc.
Figure 36.5
(a) A. uniparens females
Male-
like
Ovulation
Female Male-
like
Female
Time
(b) The sexual behavior of A. uniparens is
correlated with the cycle of ovulation.Behavior
Hormone
level
Ovary
size
Ovulation
Progesterone
Estradiol
- 17. © 2014 Pearson Education, Inc.
Figure 36.5a
(a) A. uniparens females
- 18. © 2014 Pearson Education, Inc.
Figure 36.5b
Male-
like
Ovulation
Female Male-
like
Female
Time
(b) The sexual behavior of A. uniparens is
correlated with the cycle of ovulation.
Behavior
Hormone
level
Ovary
size Ovulation
Progesterone
Estradiol
- 19. © 2014 Pearson Education, Inc.
For many animals, finding a partner for sexual
reproduction may be challenging
One solution is hermaphroditism, in which each
individual has male and female reproductive systems
Any two hermaphrodites can mate, and some
hermaphrodites can self-fertilize
Variation in Patterns of Sexual Reproduction
- 20. © 2014 Pearson Education, Inc.
Individuals of some species undergo sex reversals
For example, in a coral reef fish, the bluehead
wrasse, a lone male defends a group of females
If the male dies, the largest female in the group
transforms into a male
Within a few weeks, this individual can begin to
produce sperm instead of eggs
- 21. © 2014 Pearson Education, Inc.
External and Internal Fertilization
Sexual reproduction requires fertilization, the
union of sperm and eggs
In external fertilization, eggs shed by the female
are fertilized by sperm in the external environment
In internal fertilization, sperm are deposited in or
near the female reproductive tract, and fertilization
occurs within the tract
- 22. © 2014 Pearson Education, Inc.
A moist habitat is almost always required for external
fertilization to prevent gametes from drying out and to
allow sperm to swim to eggs
Many aquatic invertebrates simply shed gametes into
the surrounding water
In this case, timing of release of gametes is crucial to
ensure that sperm and egg encounter one another
If external fertilization is not synchronous across a
population, courtship behaviors might lead to
fertilization
- 24. © 2014 Pearson Education, Inc.
However fertilization occurs, the mating animals
may use pheromones, chemicals released by one
organism that can influence physiology and
behavior of another individual of the same species
- 25. © 2014 Pearson Education, Inc.
Ensuring the Survival of Offspring
Internal fertilization is typically associated with
production of fewer gametes but the survival of a
higher fraction of zygotes
Internal fertilization is also often associated with
mechanisms to provide protection of embryos and
parental care of young
- 26. © 2014 Pearson Education, Inc.
The embryos of some terrestrial animals develop in
eggs with calcium- and protein-containing shells and
several internal membranes
Some other animals retain the embryo, which
develops inside the female
In many animals, parental care helps ensure survival
of offspring
- 28. © 2014 Pearson Education, Inc.
Concept 36.2: Reproductive organs produce and
transport gametes
Sexual reproduction in animals relies on sets of
cells that are precursors for eggs and sperm
- 29. © 2014 Pearson Education, Inc.
Variation in Reproductive Systems
Many (but not all) animals have gonads, organs that
produce gametes
Some simple systems do not have gonads, but
gametes form from undifferentiated tissue
More elaborate systems include sets of accessory
tubes and glands that carry, nourish, and protect
gametes and sometimes developing embryos
- 30. © 2014 Pearson Education, Inc.
Most insects have separate sexes with complex
reproductive systems
In many insects, the female has a spermatheca in
which sperm is stored during copulation
- 31. © 2014 Pearson Education, Inc.
A cloaca is a common opening between the external
environment and the digestive, excretory, and
reproductive systems
A cloaca is common in nonmammalian vertebrates;
mammals usually have a separate opening to the
digestive tract
- 32. © 2014 Pearson Education, Inc.
Human Male Reproductive Anatomy
The male’s external reproductive organs are the
scrotum and penis
The internal organs are gonads that produce sperm
and reproductive hormones, accessory glands that
secrete products essential to sperm movement, and
ducts that carry sperm and glandular secretions
Animation: Male Reproductive Anatomy
- 33. © 2014 Pearson Education, Inc.
Figure 36.8
Seminal
vesicle
(Rectum)
Ejaculatory
duct
Bulbourethral
gland
Erectile
tissue
Vas deferens
Prostate gland
Epididymis
Scrotum
Vas deferens
Testis Prepuce
Penis
Glans
Urethra
(Pubic bone)
(Urinary duct)
(Urinary bladder)
- 34. © 2014 Pearson Education, Inc.
Testes
The male gonads, or testes, produce sperm in
highly coiled tubes called seminiferous tubules
Production of normal sperm cannot occur at the
body temperatures of most mammals
The scrotum, a fold of the body wall, maintains testis
temperature at about 2o
C below the core body
temperature
- 35. © 2014 Pearson Education, Inc.
Ducts
From the seminiferous tubules of a testis, sperm
pass into the coiled duct of the epididymis
During ejaculation, sperm are propelled through
the muscular vas deferens and the ejaculatory
duct and then exit the penis through the urethra
- 36. © 2014 Pearson Education, Inc.
Accessory Glands
Semen is composed of sperm plus secretions from
three sets of accessory glands
The two seminal vesicles contribute about 60% of
the total volume of semen
The prostate gland secretes its products directly
into the urethra through several small ducts
The bulbourethral glands secrete a clear mucus
before ejaculation that neutralizes acidic urine
remaining in the urethra
- 37. © 2014 Pearson Education, Inc.
Penis
The human penis is composed of three cylinders of
spongy erectile tissue
During sexual arousal, erectile tissue fills with blood
from the arteries, causing an erection
The head of the penis, or glans, has a thinner skin
covering than the shaft
The prepuce, or foreskin, is a fold of skin covering
the glans; it is removed when a male is circumcised
- 38. © 2014 Pearson Education, Inc.
Human Female Reproductive Anatomy
The female external reproductive structures include
the clitoris and two sets of labia
The internal organs are a pair of gonads and a
system of ducts and chambers that carry gametes
and house the embryo and fetus
Animation: Female Reproductive Anatomy
- 39. © 2014 Pearson Education, Inc.
Figure 36.9
Oviduct
(Rectum)
Cervix
Major vestibular
gland
Vagina
Vaginal opening
Ovary
Uterus
(Urinary
bladder)
(Pubic bone)
(Urethra)
Body
ClitorisGlans
Prepuce
Labia minora
Labia majora
- 40. © 2014 Pearson Education, Inc.
Ovaries
The female gonads, a pair of ovaries, lie in the
abdominal cavity
Each ovary contains many follicles, which consist
of a partially developed egg, called an oocyte,
surrounded by support cells
- 41. © 2014 Pearson Education, Inc.
Oviducts and Uterus
Upon ovulation, a mature egg cell is released
It travels from the ovary to the uterus via an oviduct
Cilia in the oviduct convey the egg to the uterus,
also called the womb
The uterus lining, the endometrium, has many
blood vessels
The neck of the uterus is the cervix, which opens
into the vagina
- 42. © 2014 Pearson Education, Inc.
Vagina and Vulva
The vagina is a muscular but elastic chamber that
is the repository for sperm during copulation and
serves as the birth canal
The vagina opens to the outside at the vulva, which
consists of the labia majora, labia minora, hymen,
and clitoris
- 43. © 2014 Pearson Education, Inc.
Mammary Glands
The mammary glands are not part of the
reproductive system but are important to mammalian
reproduction
Within the glands, small sacs of epithelial tissue
secrete milk
- 44. © 2014 Pearson Education, Inc.
Gametogenesis
Gametogenesis is the production of gametes
There is a close relationship between the structure
and function of the gonads
Video: Flagella in Sperm
Video: Sperm Flagellum
- 45. © 2014 Pearson Education, Inc.
Figure 36.10a
Epididymis
Seminiferous tubule
Testis
Cross section of
seminiferous tubule
Sertoli cell
nucleus
Plasma
membrane
Lumen of
seminiferous
tubule
Mitochondria
Nucleus
Acrosome
Midpiece
Tail
Head
Neck
Primordial germ cell in embryo
Spermatogonial
stem cell
Mitotic divisions
Spermatogonium
Mitotic divisions
Mitotic divisions
Primary spermatocyte
Secondary spermatocyte
Spermatids
(two stages)
Early
spermatid
Differentiation
(Sertoli cells
provide nutrients)
Meiosis I
Meiosis II
n n
2n
2n
2n
n n n n
n n n nSperm cell
- 46. © 2014 Pearson Education, Inc.
Figure 36.10aa
Epididymis
Seminiferous tubule
Testis
Cross section of
seminiferous tubule
Sertoli cell
nucleus
Spermatogonium
Primary
spermatocyte
Secondary
spermatocyte
Spermatids
(two stages)
Lumen of
seminiferous tubule
Sperm cell
- 47. © 2014 Pearson Education, Inc.
Figure 36.10ab
Primordial germ cell in embryo
Spermatogonial
stem cell
Mitotic divisions
Spermatogonium
Mitotic divisions
Mitotic divisions
Primary spermatocyte
Secondary spermatocyte
Early
spermatid
Differentiation
(Sertoli cells
provide nutrients)
Meiosis I
Meiosis II
n n
2n
2n
2n
n n n n
n n n nSperm cell
- 48. © 2014 Pearson Education, Inc.
Figure 36.10ac
Plasma
membrane
Mitochondria
Nucleus
Acrosome
Midpiece
Tail
Head
Neck
- 49. © 2014 Pearson Education, Inc.
Figure 36.10b
Primordial germ cell
Completion of meiosis I
and onset of meiosis II
Mitotic divisions
In embryo
Mitotic divisions
Mature follicle
Primary oocyte
(present at birth), arrested
in prophase of meiosis I
Ovulation, sperm entry
First
polar
body
Degenerating
corpus luteum
Ruptured
follicle
Ovulated
secondary oocyte
Fertilized egg
Ovary
Secondary oocyte,
arrested at metaphase of
meiosis II
Oogonium2n
n
Second
polar
body
Completion of meiosis II
2n
n
n
n
Primary oocyte
within follicle
Growing
follicle
Corpus luteum
- 50. © 2014 Pearson Education, Inc.
Figure 36.10ba
Mature
follicle
Degenerating
corpus
luteum
Ruptured
follicle
Ovulated
secondary
oocyte
Ovary
Primary
oocyte
within
follicle
Growing
follicle
Corpus
luteum
- 51. © 2014 Pearson Education, Inc.
Figure 36.10bb
Primordial germ cell
Mitotic divisions
In embryo
Mitotic divisions
Primary oocyte
(present at birth), arrested
in prophase of meiosis I
Oogonium2n
2n
- 52. © 2014 Pearson Education, Inc.
Figure 36.10bc
Completion of meiosis I
and onset of meiosis II
Ovulation, sperm entry
First
polar
body
Fertilized egg
Secondary oocyte,
arrested at metaphase of
meiosis II
n
Second
polar
body
Completion of meiosis II
n
n
n
- 53. © 2014 Pearson Education, Inc.
Spermatogenesis, the development of sperm, is
continuous and prolific (millions of sperm are
produced per day); each sperm takes about 7 weeks
to develop
Oogenesis, the development of a mature egg, is a
prolonged process
Immature eggs form in the female embryo but do not
complete their development until years or decades
later
- 54. © 2014 Pearson Education, Inc.
Spermatogenesis differs from oogenesis in three
ways
All four products of meiosis develop into sperm, while
only one of the four becomes an egg
Spermatogenesis occurs throughout adolescence and
adulthood
Sperm are produced continuously without the
prolonged interruptions in oogenesis
- 55. © 2014 Pearson Education, Inc.
Concept 36.3: The interplay of tropic and sex
hormones regulates reproduction in mammals
Human reproduction is coordinated by hormones
from the hypothalamus, anterior pituitary, and
gonads
Gonadotropin-releasing hormone (GnRH) is secreted
by the hypothalamus and directs the release of FSH
(follicle-stimulating hormone) and LH (luteinizing
hormone) from the anterior pituitary
- 56. © 2014 Pearson Education, Inc.
FSH and LH regulate processes in the gonads and
the production of sex hormones
The major androgen is testosterone and major
estrogens are estradiol and progesterone
Both males and females produce androgens and
estrogens but differ in their blood concentrations of
particular hormones
For example, males have testosterone levels about
10 times higher than females
- 57. © 2014 Pearson Education, Inc.
Sex hormones regulate gamete production both
directly and indirectly
They serve many additional functions including
sexual behavior and the development of primary and
secondary sex characteristics
Androgens are responsible for male vocalizations
and courtship displays
- 59. © 2014 Pearson Education, Inc.
FSH and LH act on different cells in the testes to
direct spermatogenesis
Sertoli cells, found in the seminiferous tubules,
respond to FSH by nourishing developing sperm
Leydig cells, connective tissue between the tubules,
respond to LH by secreting testosterone and other
androgens, which promote spermatogenesis
Hormonal Control of the Male Reproductive
System
Animation: Male Hormones
- 60. © 2014 Pearson Education, Inc.
Figure 36.12
Hypothalamus
Anterior pituitary
GnRH
Sertoli cells Leydig cells
Inhibin
Testis
Spermatogenesis Testosterone
FSH LH
Negativefeedback
Negativefeedback
- 61. © 2014 Pearson Education, Inc.
Two negative feedback mechanisms control sex
hormone production in males
Testosterone regulates the production of GnRH,
FSH, and LH through negative feedback
mechanisms
Sertoli cells secrete the hormone inhibin, which
reduces FSH secretion from the anterior pituitary
- 62. © 2014 Pearson Education, Inc.
Hormonal Control of Female Reproductive Cycles
Females produce eggs in cycles
Prior to ovulation, the endometrium thickens with
blood vessels in preparation for embryo implantation
If an embryo does not implant in the endometrium,
the endometrium is shed in a process called
menstruation
- 63. © 2014 Pearson Education, Inc.
Hormones closely link the two cycles of female
reproduction
Changes in the uterus define the menstrual cycle
(also called the uterine cycle)
Changes in the ovaries define the ovarian cycle
Animation: Ovulation
Animation: Post-Ovulation
- 64. © 2014 Pearson Education, Inc.
Figure 36.13
Anterior pituitary
Hypothalamus
GnRH
FSH LH
Control by hypothalamus(a)
FSH and LH stimulate
follicle to grow
Inhibited by low levels of
estradiol
FSH
LH
Pituitary gonadotropins
in blood
(b)
Growing follicle
Follicular phase Ovulation
Estradiol secreted
by growing follicle in
increasing amounts
Ovarian cycle(c)
Stimulated by high levels
of estradiol
Inhibited by combination of
estradiol and progesterone
LH surge triggers
ovulation
Maturing
follicle
Corpus
luteum
Degenerating
corpus luteum
Luteal phase
Progesterone and
estradiol secreted
by corpus luteum
Ovarian hormones
in blood
(d)
Uterine (menstrual) cycle(e)
Estradiol
Estradiol level
very low
Peak causes
LH surge
(see )
Progesterone
Progesterone and estra-
diol promote thickening
of endometrium
Endometrium
Menstrual flow phase Proliferative phase Secretory phase
0
Days
1
2
3
4
8
6
7
5
6
9
10
105 14 15 20 25 28
- 65. © 2014 Pearson Education, Inc.
Figure 36.13a
Anterior pituitary
Hypothalamus
GnRH
FSH LH
Control by hypothalamus(a)
FSH and LH stimulate
follicle to grow
Inhibited by low levels of
estradiol
FSH
LH
Pituitary gonadotropins
in blood
(b)
Stimulated by high levels
of estradiol
Inhibited by combination of
estradiol and progesterone
LH surge triggers
ovulation
1
2
3
6
Days
0 105 14 15 20 25 28
- 66. © 2014 Pearson Education, Inc.
4
Figure 36.13b
FSH and LH stimulate
follicle to grow
FSH
LH
Pituitary gonadotropins
in blood
(b)
Growing follicle
Follicular phase Ovulation
Estradiol secreted
by growing follicle in
increasing amounts
Ovarian cycle(c)
LH surge triggers
ovulation
Maturing
follicle
Corpus
luteum
Degenerating
corpus luteum
Luteal phase
Progesterone and
estradiol secreted
by corpus luteum
3
8
6
7
Days
0 105 14 15 20 25 28
- 67. © 2014 Pearson Education, Inc.
5
9
10
Figure 36.13c
Growing follicle
Follicular phase Ovulation
Estradiol secreted
by growing follicle in
increasing amounts
Ovarian cycle(c)
Maturing
follicle
Corpus
luteum
Degenerating
corpus luteum
Luteal phase
Progesterone and
estradiol secreted
by corpus luteum
Ovarian hormones
in blood
(d)
Estradiol
Estradiol level
very low
Peak causes
LH surge
(see )
Progesterone
Progesterone and estra-
diol promote thickening
of endometrium
4
87
6
Days
0 105 14 15 20 25 28
- 68. © 2014 Pearson Education, Inc.
Figure 36.13d
Uterine (menstrual) cycle(e)
Endometrium
Menstrual flow phase Proliferative phase Secretory phase
Days
5
9
10
Ovarian hormones
in blood
(d)
Estradiol
Estradiol level
very low
Peak causes
LH surge
(see )
Progesterone
Progesterone and estra-
diol promote thickening
of endometrium
6
0 105 14 15 20 25 28
- 69. © 2014 Pearson Education, Inc.
The Ovarian Cycle
The sequential release of GnRH then FSH and LH
stimulates follicle growth
Follicle and oocyte growth and an increase in the
hormone estradiol characterize the follicular phase
of the ovarian cycle
Estradiol causes GnRH, FSH, and LH levels to rise
through positive feedback
The final result is the maturation of the follicle
- 70. © 2014 Pearson Education, Inc.
At the end of the follicular phase, the follicle
releases the secondary oocyte
The follicular tissue left behind transforms into the
corpus luteum in response to LH; this is the luteal
phase
The corpus luteum disintegrates, and ovarian steroid
hormones decrease by negative feedback
mechanisms
- 71. © 2014 Pearson Education, Inc.
The Uterine (Menstrual) Cycle
Hormones coordinate the uterine cycle with the
ovarian cycle
Thickening of the endometrium during the
proliferative phase coordinates with the follicular
phase
Secretion of nutrients during the secretory phase
coordinates with the luteal phase
Shedding of the endometrium during the menstrual
flow phase coordinates with the growth of new
ovarian follicles
- 72. © 2014 Pearson Education, Inc.
Menopause
After about 500 cycles, human females undergo
menopause, the cessation of ovulation and
menstruation
Menopause is very unusual among animals
Menopause might have evolved to allow a mother to
provide better care for her children and grandchildren
- 73. © 2014 Pearson Education, Inc.
Menstrual Versus Estrous Cycles
Menstrual cycles are characteristic only of humans
and some other primates
The endometrium is shed from the uterus in a
bleeding called menstruation
Sexual receptivity is not limited to a time frame
- 74. © 2014 Pearson Education, Inc.
Estrous cycles are characteristic of most mammals
The endometrium is reabsorbed by the uterus
Sexual receptivity is limited to a “heat” period
The length and frequency of estrus cycles vary from
species to species
- 75. © 2014 Pearson Education, Inc.
Two reactions predominate in both sexes
Vasocongestion, the filling of tissue with blood
Myotonia, increased muscle tension
The sexual response cycle has four phases:
excitement, plateau, orgasm, and resolution
Excitement prepares the penis and vagina for coitus
(sexual intercourse)
Human Sexual Response
- 76. © 2014 Pearson Education, Inc.
Direct stimulation of genitalia maintains the plateau
phase and prepares the vagina for receipt of sperm
Orgasm is characterized by rhythmic contractions of
reproductive structures
In males, semen is first released into the urethra and
then ejaculated from the urethra
In females, the uterus and outer vagina contract
- 77. © 2014 Pearson Education, Inc.
During the resolution phase, organs return to their
normal state and muscles relax
- 78. © 2014 Pearson Education, Inc.
Concept 36.4: Fertilization, cleavage, and
gastrulation initiate embryonic development
Across animal species, embryonic development
involves common stages occurring in a set order
First is fertilization, which forms a zygote
During the cleavage stage, a series of mitoses
divide the zygote into a many-celled embryo
The resulting blastula then undergoes
rearrangements into a three-layered embryo called
a gastrula
- 79. © 2014 Pearson Education, Inc.
Figure 36.14
EMBRYONIC DEVELOPMENT
FERTILIZATION
GASTRULATION
CLEAVAGE
ORGANO-
GENESIS
Metamorphosis
Zygote
Blastula
Gastrula
Tail-bud
embryo
Larval
stages
Adult
frog
Sperm
Egg
- 80. © 2014 Pearson Education, Inc.
Fertilization
Molecules and events at the egg surface play a
crucial role in each step of fertilization
Sperm penetrate the protective layer around the egg
Receptors on the egg surface bind to molecules on
the sperm surface
Changes at the egg surface prevent polyspermy, the
entry of multiple sperm nuclei into the egg
- 81. © 2014 Pearson Education, Inc.
Video: Cortical Granule
Video: Calcium Release of Egg
Video: Calcium Wave of Egg
- 82. © 2014 Pearson Education, Inc.
Figure 35.15-1
Basal body
(centriole)
Sperm
head
Sperm-
binding
receptors
Acrosome
Jelly coat
Egg plasma membrane
Vitelline layer
- 83. © 2014 Pearson Education, Inc.
Figure 35.15-2
Basal body
(centriole)
Sperm
head
Sperm-
binding
receptors
Acrosome
Jelly coat
Egg plasma membrane
Hydrolytic enzymes
Vitelline layer
- 84. © 2014 Pearson Education, Inc.
Figure 35.15-3
Sperm
nucleus
Basal body
(centriole)
Sperm
head
Acrosomal
process
Actin
filament
Sperm-
binding
receptors
Acrosome
Jelly coat
Egg plasma membrane
Hydrolytic enzymes
Vitelline layer
- 85. © 2014 Pearson Education, Inc.
Figure 35.15-4
Sperm plasma
membrane
Sperm
nucleus
Basal body
(centriole)
Sperm
head
Acrosomal
process
Actin
filament
Sperm-
binding
receptors
Acrosome
Jelly coat
Fused
plasma
membranes
Egg plasma membrane
Hydrolytic enzymes
Vitelline layer
- 86. © 2014 Pearson Education, Inc.
Figure 35.15-5
Sperm plasma
membrane
Sperm
nucleus
Basal body
(centriole)
Sperm
head
Acrosomal
process
Actin
filament
Sperm-
binding
receptors
Acrosome
Jelly coat Fertilization
envelope
Perivitelline
space
Cortical
granuleFused
plasma
membranes
Egg plasma membrane
Hydrolytic enzymes
Vitelline layer
- 87. © 2014 Pearson Education, Inc.
The events of fertilization also initiate metabolic
reactions that trigger the onset of embryonic
development, thus “activating” the egg
Activation leads to events such as increased protein
synthesis that precede the formation of a diploid
nucleus
Sperm entry triggers a release of Ca2+
, which
activates the egg and triggers the cortical reaction,
the slow block to polyspermy
- 88. © 2014 Pearson Education, Inc.
Figure 36.16
First cell division
Onset of DNA synthesis
Fusion of egg and sperm nuclei complete
Increased protein synthesis
Formation of fertilization envelope complete
Binding of sperm to egg
Cortical reaction (slow block to polyspermy)
Increased intracellular calcium level
Acrosomal reaction: plasma membrane
depolarization (fast block to polyspermy)
MinutesSeconds
1
2
3
4
6
8
10
20
30
40
50
1
2
3
4
5
10
20
30
40
60
90
- 89. © 2014 Pearson Education, Inc.
Cleavage and Gastrulation
Fertilization is followed by cleavage, a period of
rapid cell division without growth
Cleavage partitions the cytoplasm of one large cell
into many smaller cells
The blastula is a ball of cells with a fluid-filled cavity
called a blastocoel
The blastula is produced after about five to seven
cleavage divisions
Video: Cleavage of Egg
- 90. © 2014 Pearson Education, Inc.
Figure 36.17
(a) Fertilized egg (b) Four-cell stage (c) Early blastula (d) Later blastula
50 µm
- 91. © 2014 Pearson Education, Inc.
Figure 36.17a
(a) Fertilized egg
50 µm
- 92. © 2014 Pearson Education, Inc.
Figure 36.17b
50 µm
(b) Four-cell stage
- 93. © 2014 Pearson Education, Inc.
Figure 36.17c
50 µm
(c) Early blastula
- 94. © 2014 Pearson Education, Inc.
Figure 36.17d
50 µm
(d) Later blastula
- 95. © 2014 Pearson Education, Inc.
After cleavage, the rate of cell division slows
The remaining stages of embryonic development
are responsible for morphogenesis, the cellular and
tissue-based processes by which the animal body
takes shape
- 96. © 2014 Pearson Education, Inc.
During gastrulation, a set of cells at or near the
surface of the blastula moves to an interior location,
cell layers are established, and a primitive digestive
tube forms
The hollow blastula is reorganized into a two- or
three-layered embryo called a gastrula
- 97. © 2014 Pearson Education, Inc.
The cell layers produced by gastrulation are called
germ layers
The ectoderm forms the outer layer and the
endoderm the inner layer
In vertebrates and other animals with bilateral
symmetry, a third germ layer, the mesoderm,
forms between the endoderm and ectoderm
- 98. © 2014 Pearson Education, Inc.
Figure 36.18
Mesenchyme cells
Vegetal plate
Blastocoel
Blastocoel
Blastocoel
Blastopore
Blastopore
Mesenchyme cells
Vegetal
pole
Animal
pole
Filopodia
Archenteron
ArchenteronEctoderm
Mouth
50 µm
Digestive tube (endoderm)
Anus (from blastopore)
Future ectoderm
Future endoderm
Future mesoderm
Key
Mesenchyme
(mesoderm forms
future skeleton)
- 99. © 2014 Pearson Education, Inc.
Figure 36.18a-1
Mesenchyme
cells
Vegetal plate
Blastocoel
Vegetal
pole
Animal
pole
Future ectoderm
Future endoderm
Future mesoderm
- 100. © 2014 Pearson Education, Inc.
Figure 36.18a-2
Mesenchyme
cells
Vegetal plate
Blastocoel
Vegetal
pole
Animal
pole
Filopodia
Archenteron
Future ectoderm
Future endoderm
Future mesoderm
- 101. © 2014 Pearson Education, Inc.
Figure 36.18a-3
Mesenchyme
cells
Vegetal plate
Blastocoel
Blastocoel
Blastopore
Vegetal
pole
Animal
pole
Filopodia
Archenteron
Archenteron
Future ectoderm
Future endoderm
Future mesoderm
- 102. © 2014 Pearson Education, Inc.
Figure 36.18a-4
Mesenchyme
cells
Vegetal plate
Blastocoel
Blastocoel
Blastopore
Vegetal
pole
Animal
pole
Filopodia
Archenteron
ArchenteronEctoderm
Mouth
Digestive tube (endoderm)
Anus (from blastopore)
Future ectoderm
Future endoderm
Future mesoderm
Mesenchyme
(mesoderm forms
future skeleton)
- 103. © 2014 Pearson Education, Inc.
Figure 36.18b
Blastocoel
Blastopore
Mesenchyme
cells
Filopodia
Archenteron
50 µm
- 104. © 2014 Pearson Education, Inc.
Cell movements and interactions that form the germ
layers vary among species
One distinction is whether the mouth develops at the
first opening that forms in the embryo (protostomes)
or the second (deuterostomes)
Sea urchins and other echinoderms are
deuterostomes, as are chordates
- 105. © 2014 Pearson Education, Inc.
Each germ layer contributes to a distinct set of
structures in the adult animal
Some organs and many organ systems derive from
more than one germ layer
- 106. © 2014 Pearson Education, Inc.
Figure 36.19
ECTODERM (outer layer of embryo)
ENDODERM (inner layer of embryo)
MESODERM (middle layer of embryo)
• Epithelial lining of digestive tract and associated organs
(liver, pancreas)
• Epithelial lining of respiratory, excretory, and reproductive tracts
and ducts
• Thymus, thyroid, and parathyroid glands
• Skeletal and muscular systems
• Circulatory and lymphatic systems
• Excretory and reproductive systems (except germ cells)
• Dermis of skin
• Adrenal cortex
• Epidermis of skin and its derivatives (including sweat glands,
hair follicles)
• Nervous and sensory systems
• Pituitary gland, adrenal medulla
• Jaws and teeth
• Germ cells
- 107. © 2014 Pearson Education, Inc.
Human Conception, Embryonic Development,
and Birth
Conception, fertilization of an egg by a sperm,
occurs in the oviduct
The resulting zygote begins cleavage about 24 hours
after fertilization and produces a blastocyst after
4 more days
A few days later, the embryo implants into the
endometrium of the uterus
- 108. © 2014 Pearson Education, Inc.
The condition of carrying one or more embryos in
the uterus is called gestation, or pregnancy
Human pregnancy averages 38 weeks from
fertilization
Gestation varies among mammals, from 21 days in
many rodents to more than 600 days in elephants
Human gestation is divided into three trimesters of
about three months each
- 109. © 2014 Pearson Education, Inc.
Figure 36.20
Cleavage
Fertilization
Ovulation
Ovary
Uterus
Endometrium
Implantation
Cleavage
continues.
TrophoblastBlastocyst
Endometrium Inner
cell
mass
(a) From ovulation to implantation
(b) Implantation of blastocyst
1
2
3
4
5
Cavity
- 110. © 2014 Pearson Education, Inc.
During the first trimester, the embryo secretes
hormones that signal its presence and regulate the
mother’s reproductive system
Human chorionic gonadotropin (hCG) acts to
maintain secretion of progesterone and estrogens by
the corpus luteum through the first few months of
pregnancy
- 111. © 2014 Pearson Education, Inc.
Occasionally an embryo splits during the first month
of development, resulting in identical or monozygotic
twins
Fraternal, or dizygotic, twins arise when two eggs
are fertilized and implant as two genetically distinct
embryos
Some embryos cannot complete development due to
chromosomal or other abnormalities
These spontaneously abort, often before a woman is
aware of her pregnancy
- 112. © 2014 Pearson Education, Inc.
During its first 2 to 4 weeks, the embryo obtains
nutrients directly from the endometrium
Meanwhile, the outer layer of the blastocyst, called
the trophoblast, mingles with the endometrium and
eventually forms the placenta
Materials diffuse between maternal and embryonic
circulation to supply the embryo with nutrients,
immune protection, and metabolic waste disposal
- 113. © 2014 Pearson Education, Inc.
The first trimester is the main period of
organogenesis, development of the body organs
All the major structures are present by 8 weeks, and
the embryo is called a fetus
Video: Ultrasound of Fetus
- 114. © 2014 Pearson Education, Inc.
Figure 36.21
(a) 5 weeks (c) 20 weeks(b) 14 weeks
- 118. © 2014 Pearson Education, Inc.
During the second trimester the fetus grows and is
very active
The mother may feel fetal movements as early as
one month into the second trimester
- 119. © 2014 Pearson Education, Inc.
During the third trimester, the fetus grows and fills
the space within the embryonic membranes
- 120. © 2014 Pearson Education, Inc.
Childbirth begins with labor, a series of strong,
rhythmic contractions that push the fetus and
placenta out of the body
Once labor begins, local regulators, prostaglandins
and hormones, induce and regulate further
contractions of the uterus
- 121. © 2014 Pearson Education, Inc.
Lactation, the production of milk, is an aspect of
maternal care unique to mammals
Suckling stimulates the release of prolactin, which in
turn stimulates mammary glands to produce milk,
and the secretion of oxytocin, which triggers milk
release from the glands
- 122. © 2014 Pearson Education, Inc.
Contraception
Contraception, the deliberate prevention of
pregnancy, can be achieved in a number of ways
Contraceptive methods fall into three categories
Preventing development or release of eggs and sperm
Keeping sperm and egg apart
Preventing implantation of an embryo
- 123. © 2014 Pearson Education, Inc.
A health-care provider should be consulted for
complete information on the choice and risks of
contraception methods
- 124. © 2014 Pearson Education, Inc.
Figure 36.22
Male Female
Method Event MethodEvent
Vasectomy
Abstinence
Condom
Coitus
interruptus
(very high
failure rate)
Tubal ligation
Abstinence
Female condom
Combination
birth control
pill (or injection,
patch, or
vaginal ring)
Spermicides;
diaphragm;
progestin alone
(as minipill
or injection)
Morning-after
pill; intrauterine
device (IUD)
Production of
sperm
Production of
primary oocytes
Sperm transport
down male
duct system
Oocyte
development
and ovulation
Sperm
deposited
in vagina
Capture of the
oocyte by the
oviduct
Sperm
movement
through female
reproductive
tract
Transport
of oocyte in
oviduct
Meeting of sperm and oocyte
in oviduct
Implantation of blastocyst
in endometrium
Union of sperm and egg
- 125. © 2014 Pearson Education, Inc.
Figure 36.22a
Male Female
Method Event MethodEvent
Vasectomy
Abstinence
Condom
Coitus
interruptus
(very high
failure rate)
Tubal ligation
Abstinence
Female condom
Combination
birth control
pill (or injection,
patch, or
vaginal ring)
Spermicides;
diaphragm;
progestin alone
(as minipill
or injection)
Production of
sperm
Production of
primary oocytes
Sperm transport
down male
duct system
Oocyte
development
and ovulation
Sperm
deposited
in vagina
Capture of the
oocyte by the
oviduct
- 126. © 2014 Pearson Education, Inc.
Figure 36.22b
Morning-after
pill; intrauterine
device (IUD)
Sperm
movement
through female
reproductive
tract
Transport
of oocyte in
oviduct
Meeting of sperm and oocyte
in oviduct
Implantation of blastocyst
in endometrium
Union of sperm and egg
Male Female
Method Event MethodEvent
- 127. © 2014 Pearson Education, Inc.
The rhythm method, or natural family planning, is
temporary abstinence when conception is most
likely; it has a pregnancy rate of 10–20%
Coitus interruptus, the withdrawal of the penis before
ejaculation, is unreliable
Barrier methods block fertilization with a pregnancy
rate of less than 10%
A condom fits over the penis
A diaphragm is inserted into the vagina before
intercourse
- 128. © 2014 Pearson Education, Inc.
Intrauterine devices (IUDs) are inserted into the
uterus and interfere with fertilization and implantation;
the pregnancy rate is less than 1%
Female birth control pills are hormonal
contraceptives with a pregnancy rate of less than 1%
- 129. © 2014 Pearson Education, Inc.
Infertility and In Vitro Fertilization
Infertility, the inability to conceive offspring, affects
about one in ten couples in the United States and
worldwide
The causes are varied and equally likely to affect
men and women
Sexually transmitted diseases (STDs) are the most
significant preventable causes of infertility
- 130. © 2014 Pearson Education, Inc.
Some forms of infertility are treatable
Hormone therapy can sometimes increase sperm or
egg production
In vitro fertilization (IVF) mixes oocytes with sperm
in culture dishes and returns the embryo to the uterus
at the eight-cell stage
Sperm may be injected directly into an oocyte as well
- 132. © 2014 Pearson Education, Inc.
Figure 36.UN02
Fertilized
egg
Polar body
Secondary
oocyte
Secondary
spermatocytes
Primary
oocyte
Primary
spermatocyte
Polar
body
Sperm
Spermatids
Spermatogenesis Oogenesis
Human gametogenesis
2n 2n
n
n
n
n
n n
n n n n
n n n n
Notes de l'éditeur
- Figure 36.1 How can each of these sea slugs be both male and female?
- Figure 36.2 Asexual reproduction of a sea anemone (Anthopleura elegantissima)
- Figure 36.3-1 The “reproductive handicap” of sex (step 1)
- Figure 36.3-2 The “reproductive handicap” of sex (step 2)
- Figure 36.3-3 The “reproductive handicap” of sex (step 3)
- Figure 36.4 Caribou (Rangifer tarandus) mother and calf
- Figure 36.5 Sexual behavior in parthenogenetic lizards
- Figure 36.5a Sexual behavior in parthenogenetic lizards (part 1: photo)
- Figure 36.5b Sexual behavior in parthenogenetic lizards (part 2: graph)
- Figure 36.6 External fertilization
- Figure 36.7 Parental care in an invertebrate
- Figure 36.8 Reproductive anatomy of the human male
- Figure 36.9 Reproductive anatomy of the human female
- Figure 36.10a Exploring human gametogenesis (part 1: spermatogenesis)
- Figure 36.10aa Exploring human gametogenesis (part 1a: spermatogenesis, location)
- Figure 36.10ab Exploring human gametogenesis (part 1b: spermatogenesis, cell divisions)
- Figure 36.10ac Exploring human gametogenesis (part 1c: anatomy of sperm)
- Figure 36.10b Exploring human gametogenesis (part 2: oogenesis)
- Figure 36.10ba Exploring human gametogenesis (part 2a: oogenesis, ovulation)
- Figure 36.10bb Exploring human gametogenesis (part 2b: oogenesis, meiosis I)
- Figure 36.10bc Exploring human gametogenesis (part 2c: oogenesis, meiosis II)
- Figure 36.11 Androgen-dependent male anatomy and behavior in a lizard
- Figure 36.12 Hormonal control of the testes
- Figure 36.13 The reproductive cycles of the human female
- Figure 36.13a The reproductive cycles of the human female (part 1: FSH and LH levels)
- Figure 36.13b The reproductive cycles of the human female (part 2: ovarian cycle)
- Figure 36.13c The reproductive cycles of the human female (part 3: ovarian hormone levels)
- Figure 36.13d The reproductive cycles of the human female (part 4: menstrual cycle)
- Figure 36.14 Developmental events in the life cycle of a frog
- Figure 36.15-1 The acrosomal and cortical reactions during sea urchin fertilization (step 1)
- Figure 36.15-2 The acrosomal and cortical reactions during sea urchin fertilization (step 2)
- Figure 36.15-3 The acrosomal and cortical reactions during sea urchin fertilization (step 3)
- Figure 36.15-4 The acrosomal and cortical reactions during sea urchin fertilization (step 4)
- Figure 36.15-5 The acrosomal and cortical reactions during sea urchin fertilization (step 5)
- Figure 36.16 Timeline for the fertilization of sea urchin eggs
- Figure 36.17 Cleavage in an echinoderm embryo
- Figure 36.17a Cleavage in an echinoderm embryo (part 1: fertilized egg)
- Figure 36.17b Cleavage in an echinoderm embryo (part 2: four-cell stage)
- Figure 36.17c Cleavage in an echinoderm embryo (part 3: early blastula)
- Figure 36.17d Cleavage in an echinoderm embryo (part 4: later blastula)
- Figure 36.18 Gastrulation in a sea urchin embryo
- Figure 36.18a-1 Gastrulation in a sea urchin embryo (part 1, step 1)
- Figure 36.18a-2 Gastrulation in a sea urchin embryo (part 1, step 2)
- Figure 36.18a-3 Gastrulation in a sea urchin embryo (part 1, step 3)
- Figure 36.18a-4 Gastrulation in a sea urchin embryo (part 1, step 4)
- Figure 36.18b Gastrulation in a sea urchin embryo (part 2: LM)
- Figure 36.19 Major derivatives of the three embryonic germ layers in vertebrates
- Figure 36.20 Formation of a human zygote and early postfertilization events
- Figure 36.21 Human fetal development
- Figure 36.21a Human fetal development (part 1: 5 weeks)
- Figure 36.21b Human fetal development (part 2: 14 weeks)
- Figure 36.21c Human fetal development (part 3: 20 weeks)
- Figure 36.22 Mechanisms of several contraceptive methods
- Figure 36.22a Mechanisms of several contraceptive methods (part 1)
- Figure 36.22b Mechanisms of several contraceptive methods (part 2)
- Figure 36.UN01 Skills exercise: making inferences and designing an experiment
- Figure 36.UN02 Summary of key concepts: human gametogenesis