Transcript The Reproductive System - Wappingers Central School

Reproduction
• Reproduction: the
creation of new
individuals from a
parental generation.
Two types:
• Asexual: one parent
• Sexual: two parents:
recombinant DNA
Couple types of asexual
reproduction
paramecium
1. Binary fission: parent
divides into two equal
organism
Organisms: bacteria and
single celled organisms
Similar to mitosis of
multi-cellular organisms
Binary fission animation
2. Budding: New individuals grow or bud on the
surface of the parent.
• may break off and live independently or remain
attached.
Organisms: Yeast, hydra, sponges
• Sexual reproduction involves DNA being
combine from two organism
• creates recombinant DNA and many genetic
variations.
• The DNA needs vehicles in order recombine.
EXAMPLE
• Humans: sperm and egg
• Flower: pollen and egg
• We will focus on human reproductive system
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Gametes: sex cells.
Male gamete: sperm
female gamete: egg
both are haploid
Haploid: single set of
chromosomes (23)
• Sperm + egg = zygote
• Zygote: union of sperm
and egg.
• Fertilization: Remember the sperm and egg are
haploid.
• Once they combine it’s the first diploid cell.
• It then divides into many diploid cells.
How are gametes created?
• Meiosis: The process of meiosis produces gametes or
sex cells.
1.
2.
3.
4.
Start with a diploid cell
DNA replicates
The cell divide into two cells
It then divides again into four haploid cells that are all
different.
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Similar but different to mitosis.
Differences between mitosis and meiosis:
1. Meiosis: creates gametes
Mitosis: creates body cells
2. Meiosis: Daughter cells have half the chromosomes as the
parent cell (haploid).
Mitosis: Daughter cell have the same number of
chromosomes as parent cell
3. Meiosis: Two divisions creates four daughter cells
Mitosis: One division creates two cells
4. Meiosis: all four cells are genetically different Mitosis:
two daughter cells are identical
Divisions
DNA
Meiosis
Mitosis
2
1
Half of parent Equal to parent
Nucleus
Haploid
diploid
Variations
All unique
All Identical
End
Four haploid
gametes
Two diploid
body cells
mitosis
meiosis
One division
One division
second division
2 genetically identical
diploid body cells
4 genetically different haploid
gametes
Meiosis
animation:
• starts with one
diploid cell.
• Two divisions
• Ends with four
different haploid
gametes
23
Chromosomes
23
Chromosomes
46
Chromosomes
23
Chromosomes
2nd division
1st division
23
Chromosomes
23
Chromosomes
23
Chromosomes
Complete the meiosis diagram
for an organism that has 8
chromosomes
1st division
2nd division
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Zygote: union of egg and sperm.
It is the first single diploid cell
Diploid: two set of chromosomes (46)
Zygote divides many times until the human
develops.
• Haploid is written: (n)
• Diploid is written: (2n)
Zygote divides
Male Reproductive
System
Main structures :
1. Testes
2. The epididymis
3. The vas deferens
4. The urethra
5. The penis
•
These structures work
together to produce
and deliver sperm.
• Male reproductive organs are on the outside of the
body.
• It is one to three degrees Celsius lower
• This temp difference is necessary for sperm
development.
• Males hormone: testosterone.
• Testosterone produces secondary sexual
characteristics in males
• Secondary sex characteristics are those that do not
include the sex organs: facial or body hair and
deepening of the voice.
• Puberty is complete when the testes have produced
enough functioning sperm.
Sperm
• A sperm is made of a head, midpiece, tail and
acrosome:
A. Head: had the nucleus with DNA
B. Mid-piece: has many mitochondria to make ATP,
energy.
C. Tail (flagellum): movement
D. Acrosome: Small cap on the head that contains an
enzyme needed for fertilization.
• Sperm are made in
the testicle
• Stored in the
epididymis.
• They exit the body
through the vas
deferens.
• The vas deferens
connects to the
urethra, a tube that
leads to the outside of
the body.
• Seminal fluid: nutrient rich fluid
• Semen: Seminal fluid and sperm
together
• There are between 50 and 130 million
sperm in 1 mL of semen.
Sperm Release
• Ejaculation: Sperm are ejected
from the penis by the
contractions of smooth muscle
lining
• About 2 to 6 mL of semen with
200 to 600 million sperm are
released
• They are released in the
reproductive tract of a female,
• These large numbers make the
chances of fertilization very
good.
Female Reproductive
System
Main structures:
1. The ovaries
2. The fallopian tubes
3. The uterus
4. The vagina
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Function: produce
eggs, prepare the
body to nourish a
developing embryo.
Egg development
• The ovary contains 400,000
eggs (primary follicles)
• Primary follicles: cluster of
cells (immature eggs)
surrounding a single egg.
• Function of a follicle: help
egg mature
• Females do not produce any
new eggs during her life time
• only about 400 of the 400,00
eggs will mature.
• Each month, one follicle
grows and passes
through the early stages
meiosis.
• Meiosis: how sperm and
egg divide.
• At the end of meiosis,
females have one large
haploid egg and three
smaller cells called polar
bodies.
Egg release
• Ovulation: When the follicle has
completely mature, the egg is
released
• The follicle breaks open, the egg
leaves the ovary into the opening
of one of the two fallopian tubes.
• The egg is often fertilized in the
fallopian tube
• The egg is then passed into the
uterus.
• The uterus is prepared to accept
the fertilized egg, if fertilization
has occurred.
• Cervix: outer end of the
uterus
• Beyond the cervix is a
canal called the vagina,
leading to the outside of
the body.
The Menstrual Cycle
• The reproductive and
endocrine systems in
females causes the
menstrual cycle.
• It takes about 28 days.
• During the cycle, an egg matures and is released from the
ovary.
• The wall of the uterus thickens in preparation to accept
the fertilized egg.
• If the egg is fertilized, it is implants in the uterus and
development begins.
• If its not fertilized, the egg is discharged along with the
lining of the uterus and blood: we call this her period.
• This is the menstruation cycle:
What is fertilization?
• During sexual intercourse,
semen is ejaculated from the
penis into the vagina.
• Sperm swim through the
uterus into the fallopian
tube.
• If an egg is present in the
fallopian tubes, it has a good
chance of being fertilized
because millions of sperm
are released.
• Only about one percent
reach this area however.
• The egg has a thick protective
covering.
• Acrosome: sac on the head of
the sperm has enzymes.
• When the sac hits the
protective coat on the egg, the
enzymes are released and
break it down.
• When the head of the sperm
(haploid) penetrates the egg
(haploid),
• the two nuclei are joined
together to form one diploid
cell (fertilized egg).
• Acrosome digests protective
coating of the egg.
• Zygote: the
fertilized diploid egg.
• The zygote then
divides by mitosis to
form a ball of cells.
The ball attaches to
the wall of the uterus
and continues to
divide.
• Implantation: ball of
cells attaching to
uterus.
Egg implanting in uterus
• Fertilization in
the fallopian
tubes
• implantation
Fertilization
• A zygote (fertilized egg)
smaller than a period on
this page divides by
mitosis to form a new
human being.
• Stem cells: first cluster of
cells that are unspecialized
• Differentiation: eventually
cells become specialized
organs like brain and
heart.
• The placenta
• The placenta is a connection
between the mother and the
embryo.
• It serves as a source of nutrients
and oxygen for the embryo.
• Also eliminates wastes such as
carbon dioxide
• The placenta is the embryo’s
organ of respiration,
nourishment, and excretion.
• Embryo does on get blood
directly from mother. Why?
• May have different blood types,
also protect from diseases.
• Some can pass such as rubella
(german measles)
• Alcohol and prescription drugs
can also be passed by the
placenta.
• After 8 weeks, the embryo is
called a fetus.
• Most organs and tissues are fully
developed (differentiation).
• Umbilical chord forms which
connects fetus to placenta.
Childbirth
• Nine months after fertilization,
a baby is born.
• When baby meets the outside,
he or she may begin to cry, this
rids the lungs of fluid.
• Breathing starts almost
immediately, and umbilical
chord is cut.
• Baby now leads an independent
existence and has own supply of
oxygen, and excretes own waste.
• Comparing Reproduction of different
species
• Species possess different adaptations for
reproduction and development.
Possibilities
• External fertilization
• Internal fertilization
• External development
• Internal development
• External Fertilization: The fertilization in water outside
the body
• External Development: Young organisms develop
outside the mother in the water
• Disadvantage: eggs and young have little or no
protection.
• Organisms: fish and amphibians
• Most of their babies are eaten by predators.
• Internal fertilization:
male inserts sperm
inside female.
• External development:
female lays fertilized
eggs for development
outside the body.
• Advantage: Lay fewer
eggs and provide more
protection for young.
• Organism: Reptiles
and birds
• Internal fertilization
• Internal development: baby develops within the female
womb.
• Advantage: release few eggs that are well protected by
parents.
• Organisms: mammals