Transcript Slide 1

SEXUAL REPRODUCTION
SEXUAL REPRODUCTION AND
DEVELOPMENT
SEXUAL REPRODUCTION
Sexual reproduction requires two different parent
cells from two separate organisms or from two
sexually different parts of a single organism.
Sexual reproduction produces off springs that are
genetically different from either parent.
In simple organisms, sexual reproduction
involves transport of genetic material from one
organism to another.
In more complex organisms, two special sex
cells, called gametes are needed. (pg: 417)
TYPES OF GAMETES
l) ISOGAMY
It is a condition in which the
sexual cells (gametes) are of
the same form and size. Many
algae and some fungi have
isogamous gametes. Ex: Ulotrix
TYPES OF GAMETES
ll) HETEROGAMY
It is a condition of having differently sized male
and female gametes.
A) ANISOGAMY
The union of morphologically unlike
motile gametes.
Oedogonium sp. (green algae)
TYPES OF GAMETES
B) OOGAMY
The union of unlike
gametes, usually a
large non-motile
female gamete and
a small motile male
gamete.
EXCEPTIONAL CASES IN SEXUAL
REPRODUCTION
A) Conjugation
The type of sexual process
most commonly found
among simple organisms
is called conjugation. In
conjugation, a cytoplasmic
bridge forms between two
cells, and an exchange or
transfer of nuclear material
takes place through the
bridge.
Ex: Paramecium, bacteria
EXCEPTIONAL CASES IN SEXUAL
REPRODUCTION
B) Hermaphroditism
B) Hermaphroditism
In some animals sexes are not
separate. Instead, each individual
has both testes and ovaries.
These organisms are called
hermaphrodite.
Hermaphroditism is usually found
among animals that move slowly
or those that are attached to
surface. Ex: earthworms,
flatworms, snails, hydras, sponges
and some flowering plants.
B) Hermaphroditism
Even though hermaphroditic organisms can produce both
eggs and sperm, self-fertilization is rare. Instead, these
organisms exchange sperm with another individual of the
same species.
B) Hermaphroditism
!
Self fertilization is seen in flatworms
but not in earth worms.
!
Reproductive organs of sponges
are not found at a particular site of
the organism. Some cells found in
different places of the organism
produce eggs and sperms.
C) Parthenogenesis
worker (2n)
mitosis
honey
Male bee(n)
Sperm cells
(n)
fertilization
(2n)
female
meiosis
Sterile female
royal jelly
Queen (2n)
Egg cells (n)
Queen (2n)
meiosis
No fertilization
parthenogenesis
Drone (n)
C) Parthenogenesis
The development of an unfertilized egg into adult
animal without fusion with sperm is called
parthenogenesis.
In nature it takes place in many insects, including
bees, wasps and certain ants.
For example, in bees, the queen bee mates only
once. She can then produce either unfertilized
eggs or fertilized eggs. The unfertilized eggs
become male drones while the fertilized eggs
become female workers or queen.
SEXUAL REPRODUCTION IN
ANIMALS
External Fertilization
The gametes fuse
outside of the body
Internal Fertilization
The gametes fuse
inside the body of
female
EXTERNAL FERTILIZATION
EXTERNAL FERTILIZATION
In external fertilization, the eggs are in the
environment outside the body of the
female.
Takes place in animals that live in water.
Ex: Fish (but not sharks), many
amphibians
To overcome the hazards of external
fertilization, large numbers of eggs and
sperm are released.
Embryo inside the fertilized egg develops
in aquatic environment.
EXTERNAL FERTILIZATION
INTERNAL FERTILIZATION
INTERNAL FERTILIZATION
Fertilization within the body of the female is called
internal fertilization.
It is found most often in animals that reproduce on land
and also found in some aquatic animals, such as sharks.
Internal fertilization requires a specialized sex organ to
carry sperm from the body of the male into the body of
the female.
Less number of eggs are produced
After fertilization, either the zygote is enclosed in a
protective shell and released by the female, or it remains
and develops within a special part of the female’s body.
Metamorphosis
In some animals that produce large number of eggs,
embryo hatches into nymph or larvae before it
completes its development. Nymphs or larvae complete
their development at the outside and become adults.
This series of changes is called metamorphosis.
Metamorphosis
REPRODUCTION IN
FISH AND AMPHIBIANS
• Eggs are not covered with a hard shell, instead
they are surrounded by a jellylike substance.
• Eggs that are produced in the ovaries of females
pass to the Müller’s duct through the
ciliated funnel (kirpikli huni) and then released
out of the body from the cloaca (kloak).
• Wolf’s duct carries both sperms and excretory
materials to the cloaca in males.
REPRODUCTION IN
FISH AND AMPHIBIANS
Testes
Egg
Kidney
Ciliated
funnel
Ovary
Muller’s
duct
Kidney
Wolf’s
duct
Urinary
bladder
Urinary
bladder
Ureter
Cloaca
Cloaca
Male fish and amphibian
urogenital system
Female fish and amphibian
urogenital system
REPRODUCTION IN
REPTILES AND BIRDS
•
•
•
•
•
Internal fertilization is mostly seen in reptiles and
birds.
Embryo found in the fertilized egg completes its
development inside the egg.
In females, eggs are transferred to the cloaca
through the Muller’s duct. Inside the Muller’s duct
egg white and shell are formed.
Wolf’s duct carries only sperms in males. Egg
shells of birds are harder than reptiles. Fertilization
occurs in Muller’s duct.
Excretory substances are transported from a
separate duct to the cloaca.
REPRODUCTION IN
REPTILES AND BIRDS
Testes
Kidney
Ovary
Ciliated
funnel
Muller’s
duct
Wolf’s
duct
Egg
Ureter
Urinary
bladder
Cloaca
Male Reptile and Bird
Urogenital system
Ureter
Urinary bladder
Cloaca
Female Reptile and Bird
Urogenital system
Bird Reproductive System
• After fertilization, the development of chordates
can be
oviparous, ovoviviparous or viviparous.
• In oviparous species, which include most
fishes and amphibians and all birds, the eggs
develop outside the mother’s body. Embryo
obtains nutrients from the egg.
In ovoviviparous animals, such as sharks, the
eggs develop within the mother’s body and the
embryos receive nutrients from the yolk in the egg.
The developing embryos of viviparous animals,
including most mammals, obtain nutrients
directly from the mother’s body.
EXTRAEMBRYONIC MEMBRANES IN
REPTILES AND BIRDS
1.
2.
3.
4.
Embryonic membranes formed during
the development of reptiles and birds
are;
Chorion (serosa)
Allantois
Amnion
Yolk sac (Vitellus sac)
EXTRAEMBRYONIC MEMBRANES IN
REPTILES AND BIRDS
1.CHORION: The outermost membrane lines the
inside of the shell and surrounds the embryo and
other three membranes.
***It aids in the exchange of gases between the
embryo and the environment.
***In mammals, chorion is involved in the formation
of placenta.
EXTRAEMBRYONIC MEMBRANES IN
REPTILES AND BIRDS
2. ALLANTOIS: is a saclike structure that grows
out of the digestive tract of the embryo. So that it
aids in the exchange of gases and collection of
waste materials.
*** In mammals, waste materials pass from
embryo to the mother, therefore allantois is
degenerated. (körelmiştir)
EXTRAEMBRYONIC MEMBRANES IN
REPTILES AND BIRDS
3. AMNION: The amniotic fluid within the
sac acts as a cushion to protect it from
shocks.
*** During developmental stages of fish and
frogs, amnion sac is not formed.
*** In mammals, amnion sac is involved in
the formation of umbilical cord (göbek
bağı).
EXTRAEMBRYONIC
MEMBRANES IN
EMBRİYO ZARLARI
REPTILES AND BIRDS
4. YOLK SAC (VITELLUS SAC):
It surrounds the yolk (vitellus) and it is the
source of food for the embryo.
*** Yolk sac of birds and reptiles are larger
than fish and frogs.
*** As there is little amount of vitellus in the
eggs of mammals, yolk sac is not
developed as much. The mother meets
the needs of the embryo.
REPRODUCTION IN MAMMALS
NONPLACENTAL MAMMALS
Egg-laying mammals
Pouched mammals (Marsupials)
Gagalı memelilerde
(platypus, ornithorenk)
(Keseli memelilerde)
*The egg of egg-laying
mammals contain a large
amount of yolk.
*The embryo completes its
development outside the
body of the mother and
feeds upon the mother’s
milk.
*Some internal development of the
embryo takes place in the uterus,
but no placenta is formed.
*The young animal crawls into a
pouch on the outside of the
mother’s body after birth and
attaches itself to a mammary
gland.
*Development is completed in the
pouch. Ex: kangaroo, opossum
(keseli ayı)
Pouched mammals
Egg-laying mammals
REPRODUCTION IN MAMMALS
PLACENTAL MAMMALS
Most mammals, including humans, are placental
mammals. (Ex: hedgehog (kirpi), bat, whale,
horse, donkey, elephant, seal, sheep)
In these mammals, the blood vessels of the
embryo’s circulatory system are in close contact
with the mother’s circulatory system. This contact
takes place in a specialized structure called the
placenta.
The placenta allows the exchange of nutrients
and wastes between the embryo and the mother.
In humans, the
chorion is the
outermost
extraembryonic
membranes.
Small fingerlike
projections called
chorionic villi form
on the outer surface
of the chorion and
extend into the
uterine lining.
( Chorionic Villus + uterus wall= Placenta)
In the human, the yolk sac and the allantois develop into
the umbilical cord. This rope like structure connects the
developing fetus to the placenta.
This structure contains blood vessels that transport waste
materials out of the embryo’s body. Veins inside the
umbilical cord carry oxygen and nutrients to the embryo.
(Umbilical cord = vitellus sac + allantois)
THE MALE REPRODUCTIVE
SYSTEM
SPERMATOGENESIS
Is the production of
sperm in testes by
meiotic division from
immature sex cells
called spermatogonia
(2n).
In humans, after a male
matures sexually , there
is a continual
development of some
spermatogonia into
functional sperm.
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1. Spermatogonium
increases in size to become a
primary spermatocyte.
2. The primary spermatocyte
undergoes the first meiotic
division, forming secondary
spermatocytes.
3. Each secondary
spermatocyte undergoes
second meiotic division,
forming 4 haploid spermatids.
4. Each of the spermatids
develops into a mature sperm
with flagellum inside the
epididimys.
THE MALE REPRODUCTIVE SYSTEM
• The male gonads are testes. The testes make
sperm cells, and the male sex hormone
testosterone.
• Testosterone causes development of the
secondary sex characters, such as, body hair,
muscle development and a deep voices.
• Secondary sex characteristics develop during
adolescence and are not involved in reproduction.
THE MALE REPRODUCTIVE SYSTEM
• Each testis is made up of coiled tubes called
seminiferious tubules. (300-600 tubules in each
testis)
• Immature sperm are made in these tubes and then
pass to the epididymis, a storage area on the
upper rear part of each testis.
• In the epididymis, the sperm mature and leave
through the vas deferens, a tube that leads
upward from each testis.
• The two vas deferens empty into the urethra.
Urethra is both the passageway for sperm and the
excretion of urine.
THE MALE REPRODUCTIVE SYSTEM
• In human male, urethra passes through the
penis to the outside of the body.
• As sperm enter the urethra, the
seminal vesicles, Cowper’s gland and
prostate gland all secrete seminal fluid into
the urethra.
• The mixture of sperm and fluid is called
semen.
HORMONAL CONTROL OF THE MALE
REPRODUCTIVE SYSTEM
• FSH (Follicle-stimulating hormone): In
males it controls the production of sperm
cells in testes by stimulating the
seminiferious tubules.
• LH (Luteinizing hormone): It stimulates
the testes and makes them secrete
testosterone
• FSH, LH are secreted from pituitary
gland (hipofiz) and
testosteron is
secreted from testes.
FEMALE REPRODUCTIVE SYSTEM
OOGENESIS
• Oogenesis is the production of eggs in the ovary.
• Eggs develop in the ovary from immature cells
called oogonia (2n) (sing:oogonium).
• Oogonium is surrounded by a follicle, a sac of
cells within which the mature egg develops.
• During the early development of the female, the
oogonia divide many times by mitosis to form a
supply of oogonia.
• Each human female is born with all the oogonia
she will ever have.
OOGENESIS
• Before birth and by the third month of
development of a human female, oogonia
within the baby’s ovaries begin to develop
into cells called primary oocytes.
• Meiosis stops at that point until the female
reaches to sexual maturity. Then, once a
month in women, one of these primary
oocytes finishes meiosis and develops into
an egg.
OOGENESIS
When the first meiotic division takes place in
the primary oocyte, the cytoplasm of the cell
divides unequally.
One of the daughter cells is large and called
secondary oocyte (n).
The other small daughter cell is called first
polar body (n). (l. kutup hücresi)
During the second meiotic division, the
secondary oocyte divides unequally into a
large cell called ootid and another polar
body.
The first polar body also divides into two
polar bodies. (ll. kutup hücresi)
The ootid grows into a mature egg(n).
The polar bodies break apart and die.
COMPARISON OF EGG AND SPERM
EGG
•Round and unable to
move
•Contains nucleus and
stored food in the form
of yolk
•Larger than sperm
SPERM
•is made up of head,a
middle piece and
flagellum
•head contains nucleus
and acrosome that
contains enzymes to
make sperm penetrate
the egg
•Middle piece contains
mitochondria
THE FEMALE REPRODUCTIVE SYSTEM
• The female gonads are the ovaries. The ovaries
makes eggs and secrete the female sex hormone
estrogen.
• Estrogen causes the development of female
secondary sex characteristics such as breasts, a
broadened pelvis, and distribution of body fat.
• Estrogen plays an important role in menstrual
cycle.
THE FEMALE REPRODUCTIVE SYSTEM
• There are two ovaries.
• Each ovary contains
about 200.000 tiny egg
sacs called follicles.
• In each follicle, there is
an immature egg.
• When an egg matures,
its follicle moves to the
surface of the ovary.
• The follicle than breaks, releasing the egg.
This process is called ovulation.
THE FEMALE REPRODUCTIVE SYSTEM
• Near each ovary, but not
connected to it, is an
oviduct or Fallopian
tube with a funnel-like
opening.
• Cilia lining the oviduct,
transports the released
egg into the tube. In the
oviduct, the egg may be
fertilized if any sperm are
peresent.
THE FEMALE REPRODUCTIVE SYSTEM
• From the oviduct, egg
passes into the uterus.
• If the egg has been
fertilized, it finishes its
development in th uterus
attached to it’s wall.
• The neck of the uterus is
called cervix and it opens
into the vagina (birth
canal), which leads to the
outside of the body.
• Unlike the male, in the mature female, the urinary
and reproductive tarcts are completely separete.
MENSTRUAL CYCLE
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• In human female, a mature egg develops and
leaves one of the ovaries about every 28 days.
• At this time uterus wall thickens and is prepared to
accept a fertilized egg.
• If the egg is not fertilized, the uterine wall breaks
down and along with the unfertilized egg passes
from the body.
• Then another egg matures and uterine wall builds
up again.
• This cycle is called menstrual cycle.
STAGES OF MENSTRUAL CYCLE
1. FOLLICLE STAGE:
 The pituitary gland secretes FSH (Follicle
stimulating hormone), which causes several
follicles in the ovary to begin developing.
Usually one follicle matures. As the follicle
develops, it secretes estrogen.
 The estrogen stimulates the uterine lining to
thicken with mucus to prepare for pregnancy.
This stage lasts 10 to14 days.
STAGES OF MENSTRUAL CYCLE
2. OVULATION:
 A high level of estrogen in the blood causes the
pituitary to decrease the secretion of FSH and
begin the secretion of luteinizing hormone (LH).

When the concentration of LH reaches a certain
level, ovulation takes place.

The follicle breaks and releases the mature egg.
STAGES OF MENSTRUAL CYCLE
3. CORPUS LUTEUM:
 After ovulation, LH causes the broken follicle to
fill with cells, forming a yellow body called the
corpus luteum.
 The corpus luteum begins to secrete
progesterone, which brings about the continued
growth of the uterine lining.
 Progesterone also stops the development of new
follicles in the ovary by inhibiting the release of
FSH. Fertilized egg attaches to the wall of uterus
by progesterone hormone.
 The corpus luteum stage lasts 10 to 14 days.
STAGES OF MENSTRUAL CYCLE
4. MENSTRUATION:
 If fertilization does not occur, secretion of LH
decreases, and the corpus luteum breaks down. This
causes a decrease in the level of progesterone.
 As the progesterone level decreases, uterine wall
breaks down. Layers of wall, unfertilized egg, and
small amount of blood pass out of the body. This is
called menstruation.
 It lasts about 3-5 days.
 During menstruation, estrogen level decreases.
The pituitary secretes more FSH and a new follicle
starts to mature.
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HORMONAL CONTROL OF THE MALE
REPRODUCTIVE SYSTEM
Hormones produced by hypothalamus called
releasing factors (RF), control the release of
hormones from the pituitary gland.
Pituitary gland secretes;
•
•
•
FSH (follicle stimulating hormone)
Luteinizing hormone (LH)
Luteotrophic hormone (prolactin)
**Secretions of pituitary effects directly the
ovary and ovary stimulates uterus activities.
Luteotrophic hormone (Prolactin)
• It maintains the continuity of corpus
luteum, and the secretion of progesterone
and estrogen.
•
It stimulates the secretion of milk by the
mammary glands of the female after she
gives birth. It is also known as prolactin.
 During pregnancy, placenta secretes a
hormone which acts like estrogen and
progesterone and corpus luteum continues the
secretion of progesterone.
 During pregnancy, progesterone helps uterine
activities continue until the childbirth. After birth,
placenta passes out of the body and secretion of
progesterone stops. Thus, uterine walls break
down and return to it’s position before birth.
OXYTOCIN:
•
It is secreted from the pituitary gland, and
stimulates contractions of the uterus muscles
during childbirth along with the estrogen.
•
After childbirth, it helps milk that is secreted
from the mammary glands of the female, fill the
milk channels.
OVARIES
FSH: stimulates the
development of egg cells in
follicles
LH: causes the release of egg
cells from ovaries of female
(ovulation ) After ovulation, it
causes the broken follicle to
form corpus luteum.
LTH: it maintains the continuity
of corpus luteum.
Also stimulates the secretion of
milk
ESTROGEN:
1.Stimulates the development of
female rep. system and
secondary sex characteristics
2.It increases the no. of ciliated
epithelium cells in fallopian
tubules
3. Increases the amount of blood
and tissue fluid in uterus
PROGESTRON:
1.It stimulates the development
of uterus
2.It ıncreases the amount of
glycogen and fat inside the
fallopian tubule
3.It helps embryo attach to the
wall of uterus
PITUITARY GLAND HORMONES
HORMONES SECRETED FROM
TESTES
FSH: controls the production of TESTOSTERON:
1.Stimulates development of male
sperm
LH: It stimulates testes to rep. system and secondary sex
characteristics
secrete testosteron
2. Stimulates development of
sperms