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Transcript
Sexual Reproduction
-involves 2 parents
-Involves the process of meiosis
Background Vocabulary:
- gametes – sex cells – sperm and egg
- gonads – sex organs/glands – testes and ovaries
- zygote – fertilized egg
egg + sperm = zygote
- meiosis – process by which sex cells develop
- gametogenesis, oogenesis, &
spermatogenesis
- diploid (2n) – normal # of chromosomes (46 –
human)
- haploid or monoploid (n) – ½ the # of
chromosomes (23 – human)
Meiosis – results: 4 daughter cells with ½ the number of
chromosomes
Meiosis – result 4 daughter cells ½ the # of chromosomes
Gamete Formation (Gametogenesis)
Spermatogenesis
- testes produce sperm
- primary sex cell  meiosis  4 monoploid cells
- each usually matures into a motile sperm cell
Result 4 motile sperm – 4/4
Oogenesis
- ovaries produce eggs (ovum/ova)
- ovum: larger, non-motile
- only 1 monoploid ovum usually forms
- other 3 – polar bodies – die
- unequal cytoplasmic division
Result: 1 egg and 3 polar
bodies
Spermatogenesis
Oogenesis
Zygote Formation
- zygote  fertilized egg
- sperm + egg = zygote (fertilized egg)
- process is called fertilization
- recombination occurs (genes from mom and
dad come together)
- chromosomes from both parents
recombine – increases variety
Fertilization
Zygote
Cleavage
Internal Fertilization
- fertilization occurs inside the female
- usually terrestrial (land) organisms
- few eggs produced - protected
- could have either internal (mammals) or
external (birds) development
External Fertilization
- fertilization occurs outside the body of the
female
- usually aquatic (water) organisms
- many eggs – ensure survival
- only external development
Embryo Formation
- the zygote divides by mitosis (cleavage) to
an embryo
form
- zygote  embryo – divisions by mitosis (cleavage)
- Gastrulationembryo forms layers
- Differentiation occurs  cells become different
- take on their own identity (hair cell, skin
cell, etc.)
Embryo Formation –
zygote  morula(solid ball)  blastula (hollow
ball)  gastrula (3 germ layers – endoderm
mesoderm, ectoderm)
Fertilization
Sperm + egg
=
zygote
Cleavage
mitosis
Differentiation – Cells become
different or specialized
• Ectoderm (Outer Layer): Skin & Nerves
• Mesoderm (Middle Layer): Muscles & Blood
Vessels
• Endoderm (Inner Layer): Digestive Tract
Sequence of events in sexual
reproduction:
1.
2.
3.
4.
5.
Meiosis
Fertilization
Mitosis (Cleavage)
Gastrulation
Differentiation
Male Reproductive System
Male Reproductive System
2 major functions:
1. Make sperm
2. Deposit in female (internal fertilization)
Structures and Functions:
1. Testes: Male gonads
a. Sperm and testosterone production
b. Location  scrotum – keeps sperm 1 – 2 degrees
cooler than normal body temperature
2. Vas Deferens:
a. tube that connects testes to urethra
b. sperm transported here
c. along the way secretions from 3 glands
are picked up to make semen.
3. Semen: sperm + fluids
4. Testosterone: hormone secreted by
testes, regulates development of secondary
sex characteristics.
Male Reproductive System – Frontal View
Male Reproductive System
Female Reproductive System
Female Reproductive System
Structures and Functions
1. Ovaries:
a. female gonads
b. produce eggs (meiosis – oogenesis)
c. eggs enclosed in follicles
d. once a month egg is ovulated (released – into
fallopian tube)
2. Fallopian Tubes (oviducts):
a. connects ovary to uterus
b. fertilization here
3. Uterus:
a. implantation here (embryo embeds itself
into uterine wall
b. development from embryo to fetus here
4. Vagina:
a. birth canal (menstruate through here too)
5. Estrogen and progesterone:
a. female hormones (ovaries)
b. regulate secondary sex characteristics
c. menstrual cycle
Menstrual Cycle
Background information:
-series of changes in ovaries and uterus
-Begins at puberty
-Temporarily stops during pregnancy
-Menopause – cycle stops permanently
Stages of the Menstrual Cycle
Stages of the Menstrual Cycle
(Lasts about 28 days)
A. Stage 1: Follicle Stage (10 days)
a. Pituitary  FSH
b. Ovaries  estrogen – thickens uterus
c. Egg matures in follicle – swells
B. Stage 2: Ovulation (1 day – stays in tube 2 – 3
days)
a. Pituitary  LH
b. egg released from follicle
C. Stage 3: Corpus Luteum Stage (~ 14 days)
a. Follicle dies – forms a “scar”  corpus luteum
b. Corpus luteum  progesterone
c. Causes uterine lining to stay thick
D. Stage 4: Menstruation (4 days)
a. egg not fertilized – uterine lining breaks down
Internal Development: Placental Mammals
- development inside the female
- gestation- time period between fertilization
and birth
1. Placenta:
a. Forms in uterus
b. Feeds fetus - nutrition
c. Exchanges gases for fetus – respiration
d. Rids fetus of wastes – excretion
e. No direct connection of bloodstreams
between mother and fetus (Diffusion occurs
across the blood vessels)
Placenta
2. Umbilical Cord:
a. attaches placenta to fetus
b. food, wastes, gases, travel through here
3. Amniotic Sac:
a. filled with amniotic fluid
b. protects fetus
Multiple embryo’s:
Identical twins: 1 sperm 1 egg  splits  same placenta/sac
Fraternal twins: 2 eggs 2 sperm  separate sacs and placenta
R
e
s
u
l
t
1
P
a
g
e
:
2
3
4
5
6
7
8
9
1
0
N
7 weeks - Brain has the first
detectable brain waves, muscles
develop and get stronger
8 weeks - Eyes are well-developed,
Fingers lengthen while distinct
grooves (digital rays) form between
the fingers
12 weeks - Fetus begins to move around,
though the mother cannot yet sense these
movements.
14 weeks - Fetus is more flexible with
ability to move head, mouth, lips, arms,
wrists, hands, legs, feet, and toes.
18 weeks - Fetus has phases of sleep and
waking and may prefer a favorite sleep
position, temporary hair called lanugo
appears on the head
20 weeks - Fetus may suck on thumb.
Extremely rapid brain growth; eyebrows
and scalp hair become more visible and
fetus blinks more often.
24 weeks - Fetal brain waves begin to activate
auditory and visual systems, both mouth and
lips show more sensitivity. Eyes respond to
light, while ears respond to sounds
originating outside uterus.
32 weeks - Eyes open during alert times and
close during sleep. Eye color is usually blue,
regardless of the permanent color as
pigmentation is not fully
developed. Fingernails reach over finger tips
and fetus can scratch itself.
40 weeks
Vaginal Delivery
Cesarean Delivery (C-section)
Artificial Insemination: sperm artificially inserted into female.
In Vitro Fertilization: fertilization occurs in a petri
dish, then implanted in the uterus.
Amnioscentesis: removal of amniotic fluid from the
sac during gestation  chromosomes analyzed for
genetic disorders