Transcript Reproductionx

Reproduction
ASEXUAL REPRODUCTION
Asexual Reproduction
• reproduction by MITOSIS
• only one parent
• offspring is genetically identical to parent
organism
• rapid and results in the production of large
numbers of offspring
Binary Fission
• Bacteria, some protists (ameba,
paramecium, algae)
• Parent organism divides into 2 equal parts
Budding
• parent organism divides into two UNEQUAL parts
• The buds may break off and live independently
• Some buds may remain attached to the parent
and form a colony
Spore formation (sporulation)
• Spores are single, specialized cells
produced by mitosis
• When spores are released from the parent
organism, the spores germinate and grow
to form new individuals
• Spore germination requires an environment
that is warm, has nutrients and moisture
Regeneration
• The ability of an organism to regrow lost
body parts
• Regeneration decreases as an animal
becomes more complex
Vegetative Propagation
• A type of regeneration that occurs in plants
• Complete new plants develop from a part of
the parent plant (root, stem, leaf)
1. Bulbs
• Enlarged underground stem surrounded by
leaves and contains stored food
• New bulbs form by the base of the leaf
2. Tuber
• Enlarged underground stem with stored food
• Buds (“eyes”) can develop into new plants
3. Runners
• Stems that grow along the ground
• New roots form where the stem meets the
ground and develop into a new plant
4. Rhizomes
• Stem that grows sideways underground or
underwater
Artificial Vegetative Propagation
1. Cuttings
• Any part of the plant (stem, leaf, root) is used
to produce a new individual
2. Grafting
• A stem is removed from one plant and joined
permanently to another plant
• Stock: provides the root system
• Scion: added piece
Advantages
• Plants that grow from seeds do not always
show the same characteristics
• Faster
• Higher yields of fruits
SEXUAL REPRODUCTION IN PLANTS
AND ANIMALS
Sexual Reproduction
• Reproduction by combining the female
gamete and male gamete
• Involves fertilization and meiosis
– Meiosis: formation of gametes
• Produces offspring that are genetically
different from both parents.
Advantages and Disadvantages
• Asexual Reproduction
– Advantages:
• Rapid Populating: produce large quantities of offspring
quickly
• No True Investment: quick and inexpensive process in
terms of time and number
– Disadvantages:
• No Diversity: All offspring are genetically identical
• Prone to Extinction: same traits = same weaknesses
• Can’t Adapt: can’t change due to environmental
changes
Advantages and Disadvantages
• Sexual Reproduction
– Advantages:
• Offspring are genetically different from one another
– Disadvantages:
• Requires two parents with a large expenditure of
energy
• Requires more time to produce offspring
TYPES OF FERTILIZATION
External Fertilization
• External fertilization is the process in which a
sperm joins with an egg outside of the body.
Internal Fertilization
• Internal fertilization is the process in which a
sperm joins with an egg inside of the body.
HUMAN REPRODUCTION
Male reproductive system
• Testes – the male gonad; produce sperm and
testosterone
• Located outside of the body in structure called
the scrotum
Lower temperature is best for sperm
production and storage
• Testes are 3°C lower than body temp
Male reproductive system
• Mature sperm are stored in the epididymis
• The sperm is transported from the testes
(testicles) to the vas deferens
• vas deferens: tubes that connect to urethra
Male reproductive system
• Glands that add fluid are the Cowper’s gland,
seminal vesicles and prostate
• Fluid nourishes and transports sperm, protects
sperm from acidity of female reproductive tract
• Sperm + seminal fluid = semen
Female reproductive system
• Ovaries – the female gonad; produce egg cells
(ova) and hormones estrogen and progesterone
• Oviduct (fallopian tube) - a tube that carries the
egg cell (ovum) to the uterus;
****site of fertilization of the egg cell
• Cilia draws ovulated egg cell into the oviduct
Female reproductive system
• Uterus – a thick,
muscular, pear shaped
organ (aka womb)
– A baby develops here
• Cervix – narrow neck
that is the opening to
the uterus
• Vagina – the birth canal
Menstruation
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Menstrual cycle – a series of changes controlled by
hormones that help prepare the female uterus for a possible
pregnancy
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The cycle is controlled by hormones of the pituitary
gland and ovaries
The menstrual cycle occurs in 4 stages
Menstrual Cycle
begins at puberty (usually between ages 10 &
14)
 usually lasts 28 days, but can vary due to illness
& other factors
 stops when a women is pregnant
 stops permanently during ages 45-55
(menopause)
 humans & primates are the only mammals to
have a menstrual cycle
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Stage 1 - Follicle stage (lasts~10-14
days)
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ovarian hormones (estrogen and progesterone) are in
low concentrations
pituitary produces FSH which causes a follicle (egg cell
capsule) to form
as the follicle grows it makes increased amounts of
estrogen
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estrogen has negative feedback on the pituitary to stop FSH
estrogen causes the uterine lining (endometrium) to grow
thicker
Stage 2 – Ovulation (middle of
cycle)
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increased estrogen from the
follicle stimulates the
pituitary gland to produce
LH
LH surge causes the follicle
to rupture and the egg cell is
sent to the
oviduct=ovulation
Stage 3 – Corpus Luteum

ruptured follicle heals inside
the ovary forming the
corpus luteum
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Yellow body
corpus luteum produces
progesterone
progesterone maintains the
added growth of the uterine
lining
If fertilization takes place:
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An embryo in the uterus will secrete a chemical
called hCG
hCG prevents the corpus luteum from decomposing
which maintains progesterone levels
The uterine lining is not shed
 hCG is the chemical that is detected by pregnancy
tests
Stage 4 - Menstruation
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if an embryo is not present, approximately 2 weeks after
ovulation the corpus luteum decomposes
estrogen & progesterone levels decrease
uterine lining is shed and moves out through the vagina
(menstruation)
pituitary increases the release of FSH & a new follicle
matures
Fertilization:
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IF fertilization takes
place, it occurs in the
oviduct
The egg cell is viable
for approximately 24
hours after ovulation
Implantation
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After approximately a
week, the developing
embryo is implanted
into the uterus
Embryo: conception
to 8 weeks
Embryonic Development
A
series of cell divisions and
differentiation into various tissues
and organ systems
Embryo: a multicellular organism
in the early stages of development
Differentiation
the changing of unspecialized embryonic cells
into the specialized cells, tissues and organs of
a multicellular animal
 The ectoderm, mesoderm, and endoderm
differentiates to form tissue and organs
systems
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Differentiation
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Each cell contains the same genes, but different genes
are expressed in different cells (embryonic cells use
different portions of their genetic information)
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The type of cell that forms through differentiation is
controlled by genes, hormones and cell location
Prenatal Development
zygote  multiple identical cells  differentiated cells
(tissues)  organs organ systems  individual
Prenatal Development
The single-celled zygote forms a multicellular
organism with specialized cells through the
processes of:
mitosis and differentiation
Prenatal development

When the zygote is
implanted in the
uterine wall a
temporary organ
called the placenta
is formed from
maternal and
embryonic tissues
Placenta
Prenatal development
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The developing embryo
is attached to the
placenta by the
umbilical cord
This cord contains
blood vessels
Placenta
Umbilical cord
Placenta: site of diffusion
Oxygen & nutrients diffuse from the mother’s
blood vessels, across the placenta, and into
the baby’s blood vessels
 Wastes diffuse from the baby’s blood vessels
into the mother’s blood vessels
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Prenatal development
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The fetus is surrounded
by a membrane called the
amnion which is filled
with amniotic fluid
The fluid protects the
fetus by giving it a stable
environment and
absorbing shock
Prenatal development
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By the end of the 8th
week of pregnancy
the embryo is called
a fetus and all of the
major structures are
present
Human gestation
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the period between
fertilization and birth
approximately 38-40
weeks
When gestation is
complete the baby
passes through the
cervix and then
through the vagina