Reproduction
System
Aaron, Keiah, Ryan
Why is reproduction important?
oYou only live once.
oA population transcends finite life only be
reproduction, the creation of new individuals from
existing ones.
Asexual Vs. Sexual Reproduction
Asexual reproduction is the creation of new individuals
whose genes all come from one parent without the
fusion of egg and sperm.
Sexual reproduction is the creation of offspring by the
fusion of haploid gametes to form a zygote (fertilized
egg), which is a diploid.
By producing offspring having a variety of phenotypes,
sexual reproduction may enhance the reproductive
success of parents when environmental factors
change relatively rapidly.
Asexual Reproduction
o Many invertebrates can reproduce asexually by
fission, the separation of a parent into two or more
individuals of approximately equal size, e.g. sea
anemone
o Or budding, in which new individuals arise from
outgrowths of existing ones, e.g. stony corals
o Another way is through fragmentation, the
breaking of the body into several pieces,
accompanied by regeneration, the regrowth of lost
body parts, e.g. many sponges, cnidarians
(jellyfish, corals)
Asexual Reproduction
Asexual reproduction has several potential
advantages such as enabling animals living in
isolation to produce offspring without locating
mates. It can also create numerous offspring
in a short amount of time, which is ideal for
colonizing a habitat rapidly.
Theoretically, asexual reproduction is most
advantageous in stable, favorable
environments.
Reproductive Cycles and Patterns
•The periodic nature of reproduction allows animals to conserve
resources and reproduce when more energy is available than is
needed for maintenance and when environmental conditions
favor the offspring.
•Reproductive cycles are controlled by a combination of
hormonal and environmental cues, the latter including seasonal
temperature, rainfall, day length, and lunar cycles.
•Asexual reproduction occurs under favorable conditions, and
sexual reproduction occurs during times of environmental
stress.
•Animals can switch between producing asexually and sexually,
or just be one.
Parthogenesis and Hermaphroditism
Parthogenesis is a process in which an egg develops without
being fertilized.
Male honeybees are produced parthogenetically whereas
females, both sterile workers and reproductive females
(queens) are developed from fertilized eggs.
Parthogenetic lizards, which evolved from species that have
two sexes, still require certain sexual stimuli for maximum
reproductive success.
Hermaphroditism is where each individual has both male and
female reproductive systems. Some hermaphrodites fertilize
themselves, but most mate with a member of the same
species. In this case, each animal serves as both male and
female, donating and receiving sperm. E.g. earthworms
Sequential hermaphroditism is where an individual reverses
its sex during its lifetime. E.g. Caribbean bluehead wrasse
 Parthogenic Lizards
Caribbean Bluehead Wrasse 
(Top is male, bottom is female)
 Earthworms
The Female
Reproductive
system
•• The Female Reproductive System. We have to draw and label it now.
•
http://www.ibguides.com/images/biology/female-reproductive-system.png
6.6.1
• IB has required the drawing of a Penis on an IB, this could be on the IB
Anatomy 6.6.1
Vagina-a thin-walled chamber that is the repository for
sperm during intercourse and is also the birth canal
Vulva- the external female genetalia including the labia
majora, labia minora, Bartholin's gland, clitoris, and the
vestibule
Cervix- The neck of the uterus that separates the uterus
and the vagina
Uterus- a thick muscular organ that can expand during
pregnancy to hold a 4-kg fetus we will talk about this more
during the pregnancy slide.
The vestibule is the area where the vaginal and urethral
openings are.
Anatomy
endometrium- the inner lining of the uterus which is filled
with blood vessels
Oviduct- (Fallopian Tubes) takes the egg cell out of the
abdominal space and moves the egg cell down to the
uterus
Ovary- the female gonads in the abdominal cavity on both
sides of the uterus and is attached to it by the mesentery. It
releases the egg cell to the abdominal cavity for the
Fallopian tube to pick up.
4 Stages of Sexual Response
Excitement- This is when the human body prepares for intercourse.
This can include myotonia (increase in muscle tone), increased breast
size, and vasocongestion (swelling caused by localized increase of
blood flow and blood pressure) of the reproductive organs. The uterus
elevates and the inner 2/3 of the vagina expands in response to the
possibility of fertilization. This can be affected by psychological factors.
Plateau- the sexual excitement before orgasm in which vasocongestion
continues and muscles begin to tighten.
Orgasm- it is believed that during the female orgasm, muscular spasms
help move the sperm up the vaginal walls into the uterus. During the
male orgasm, semen goes to the urethra by emission and expelled
from the urethra by expulsion. This is the shortest phase lasting a few
seconds.
Resolution- This is when the reproductive system of females and males
returns to its normal size and leaves the stages of sexual response.
This phase can be immediate, or it can last 12 to 24 hours
Ovary 11.4.4
Germinal Epithelium
Secondary
oocyte
•
•
http://www.biog1105-1106.org/demos/105/unit8/media/ovary-schematic.jpg
We will cover this in menstruation
Ovary
germinal epithelium- the epithelial layer covering the ovary
Primary oocytes- the cells that have the potential to ovulate and become an
egg cell. They are diploid cells (46 chromosomes). They begin as oogonia in
the womb and stop being produced at 5-6 months. At birth, a female baby will
have 1-2 million primary oocytes after they matured. By puberty a girl has
400,000 primary oocytes.
primary follicle- is a primary oocyte with one layer of follicle cells or a secondary
oocyte with many layers of follicular cells.
Mature follicle- A mass of follicular cells surrounding the secondary follicle and
follicular fluid which is mature enough to release the secondary follicle during
ovulation.
Secondary oocyte- after meiosis I, this is a haploid cell (23 chromosomes) that
will go through meiosis II and become an ovum and a second polar body.
Oogenesis 11.4.5
These are the basic steps of oogenesis:
1.A female fetus develops diploid oogonia (stem cells) which undergo mitosis
until they make thousands of primary oocytes (diploids) stopped at prophase I
of meiosis until puberty.
2.These cells will continue to grow and develop until they are needed
3.Female reaches puberty with around 400,000 primary oocytes.
4.Each month from that point until menopause a primary oocyte will begin
meiosis I and stop at metaphase II. This causes the diploid cell to divide the
cytoplasm unevenly resulting in a haploid polar body and a haploid secondary
oocyte in the Graafian follicle. The polar body degenerates in order to provide
a suitable amount of cytoplasm to the secondary oocyte and to reduce the
number of chromosomes.
5.Ovulation
6.If the secondary oocyte is fertilized, then it will go through meiosis II, dividing
the cytoplasm unevenly again resulting in a second polar body and an egg with
the final chromosome copy.
6 alternate. The secondary oocyte is not fertilized, then it is discarded and the
female body goes through menstruation.
http://1.bp.blogspot.com/VR3wPiFAptw/TgdL3gS9EaI/AAAAAAAAA0I/yH5mo2Hq0nM/s1600/Oogenesis.jpg
Oogenesis and follicular development
Egg Cell 11.4.6
http://click4biology.info/c4b/11/hum11.4.htm
Menstrual Hormones 6.6.2
Gonadotrophin Releasing Hormone (GnRH)- released by the hypothalamus, it
directs the pituitary glands to secrete FSH and LH into the blood stream.
Follicle Stimulating Hormone (FSH)- Stimulates the growth of follicles, the
growth of the primary oocyte, the production of follicular fluid, and the increase
in follicular cells which increases the amount of estrogen. This and the
Luteinizing Hormone are produced by the pituitary gland.
Luteinizing Hormone (LH)- surges day 12 (middle of the cycle) to bring
ovulation and to develop the corpus luteum.
Estrogen- produced by follicular cells. Produces negative feed back on the
pituitary gland and stimulates thickening and increased vascularization (more
blood vessels) in the endometrium. It also has positive feedback on the
hypothalamus later on. This and Progesterone are produced by the ovary.
Progesterone- produced by the corpus luteum, it maintains the endometrium
and the secretion of a glycogen solution to nourish an embreyo. It causes
negative feedback on the hypothalamus and the pituitary gland.
Menstrual Cycle 6.6.3.
•The menstrual cycle is a process in females in
which the a secondary oocyte is formed, released,
and not fertilized.
•Because it is unfertilized the body eventually
discards it along with a thickened endometrium
and blood ☹
•It is also associated with Premenstrual Syndrome,
which causes many different symptoms but its
cause is unknown. Scientists believe it could be
associated with a sudden drop of hormones.
The Menstrual
Cycle
http://www.merckmanuals.com/media/home/figures/MMHE_22_241
_03_eps.gif
The cycle has 3 phases:
•Follicular Phase/
menses
•Ovulation
•Luteal phase
Menstruation
1. On day 1, the hypothalamus releases GnRH to stimulate the pituitary
gland to secrete FSH and LH.
2. The increase of FSH stimulates the primary follicle to develop. This
causes the oocyte to grow, the follicular fluid to develop, and the increase
in follicular cells.
3. The follicular cells produce lots of estrogen which causes negative
feedback on the pituitary gland decreasing the production of FSH and LH.
It also causes the endometrium to thicken and vascularize which increases
the blood vessels. This continues into the ovulatory phase.
4. The peak of estrogen occurs around day 13 which causes positive
feedback on the hypothalamus saying the body is ready to ovulate. The
hypothalamus releases GnRH increasing the FSH and especially the LH.
5. The high LH allows for ovulation in the middle of the cycle and then the
LH maintains the Corpus Luteum (the body of follicular cells that exists
after ovulation). This enters the Luteal phase.
6. The Corpus Luteum continues the production of estogen and
progesterone which continues to stimulate the growth of the endometrium.
Menstruation Continued
7. The increase of progesterone and estrogen causes negative feedback
on the hypothalamus and the pituitary gland shutting of GnRH, FSH, and
LH production.
8. Because the LH maintained the Corpus Luteum, when LH falls the
Corpus Luteum disintegrates causing a harsh drop in estrogen and
progesterone around day 28.
9. The drop in estrogen and progesterone causes the endometrium to
loose its source of nourishment causing it to disintegrate and fall out and
bleed during menses between day 1 and day 7.
10. During menses the body begins the follicular phase on day 1 when the
hypothalamus begins to release GnRH again
Menstrual Cycle
Menstrual Cycle videos
http://www.youtube.com/watch?v=lYaZRR3G6pg
http://www.youtube.com/watch?v=l4X0QWcTIvk&feature=related