Title:
1Lets Talk About Sex-ual Reproduction
- Parts, their functions and Meiosis
2The Human Life CycleWhy do we reproduce?
http//www.biosci.uga.edu/almanac/bio_103/notes/ap
r_4.html
3Sexual Reproduction
- 2 parents are required and can produce 1 or more
offspring that are genetically different from
either parent - Benefits creates genetic variation in a
population which allows for evolution and
adaptation as well as being able to battle
parasites, viruses and bacterial pathogens some
species find it an enjoyable past-time! It also
ensures your genes are passed on, like leaving
something of yourself behind when you are gone! - Drawbacks requires more time and energy,
produces smaller numbers of offspring generally,
requires both parents be in the same place at the
same time (must find a mate!) - How does it happen?? You must learn a bit about
the human structures first..
4Male Reproductive Organs
5Male Reproductive Structures and their Functions
Structure Function
Testes (testis sing.) Site of male gamete formation spermatogenesis Produces testosterone
Scrotum Holds the testes outside the body
Epidydimus Where sperm is stored
Vas deferens Sperm travels through here
Seminal Vesicle Creates seminal fluid which adds nutrients to semen
Cowpers Gland Creates alkaline fluid to counteract acidity in vagina
Prostate Gland Creates secretions for semen
Urethra Semen and urine travel through this to the outside
6Female Reproductive Organs
7Female Reproductive Structures and their Functions
Structure Function
Ovary Site of oogenesis and estrogen and progesterone production
OviductsFallopian Tubes Site of egg fertilization, egg travels through to uterus if not fertilized
Uterus Zygote implants here, embryo grows via placenta
Cervix Creates mucin strands for sperm to travel up into uterus
Vagina Receives sperm, birth canal for fetus
Clitoris Sensory organ similar to glans penis
8Test Yourself.so to speak! Name that part!
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9Test Yourself.so to speak! Name that part!
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1. Testis 2. Cowpers Gland 3.Vas Deferens 4.
Urethra 5. Epididymus 6. Oviduct 7. Ovary
8. Vagina 9. Uterus 10. Prostate Gland
10Meiosis- The Process of making Gametes
- OVERVIEW
- 1st Division is very important as it reduces the
numbers of chromosomes by half . - Prophase I has the homologous chromosomes
(chromosomes that appear identical to one another
because they carry the same genes, one comes from
our mom, and the other comes from our dad.)
crossing over to exchange material - Metaphase I have the homologous pairs line up at
the equator of the cell and in Anaphase I, the
homologous chromosomes separate and thus reducing
the chromosome number in each cell. - 2nd Division of Meiosis is exactly like mitosis,
except that 2 cells start off in prophase 2 and
you end up with 4 daughter cells that are
completely different from each other.
11Meiosis in Detail
- Prophase I
- Homologous chromosomes thicken and attach to each
other in a chiasma (chiasmata- plural) - Crossing Over occurs between homologs
- The nuclear envelops disintegrates
- The spindle fibers form from centrioles that move
to the poles of the cell
12Meiosis in Detail (contd)
- Metaphase I
- Homologous chromosomes line up at the equator of
the cell - Spindle fibers attach to the chromosomes
13Meiosis in Detail (contd)
- Anaphase I
- Homologous chromosomes separate from each other
and go to opposite poles of the cell - Sister chromatids do not separate
14Meiosis in Detail (contd)
- Telophase I
- Spindle fibers disappear
- Nuclear envelope may reappear
- Cytokinesis occurs to create 2 cells having half
the number of chromosomes of the parent cell
15Meiosis in Detail (contd)
- Meiosis II
- Prophase II
- Same as mitosis nuclear envelop
disintegrates - Spindle fibers form and attach to each
chromatid and the centromere of the chromosome
16Meiosis in Detail (contd)
- Metaphase II
- Chromosomes line up at the equator of the cell
17Meiosis in Detail (contd)
- Anaphase II
- The sister chromatids separate and move to
opposite sides of the cell
18Meiosis in Detail (contd)
- Telophase II
- Nuclear envelopes reform and the spindle fibers
disappear - Chromosomes relax into fine threads
- Cytokinesis occurs
- BOTTOM LINE
- 4 different haploid cells have been formed!
19Meiosis Genetic Variability?
- This cell has 4 chromosomes 2N and creates 4
different possible gametes. - What happens when there are 6 chromosomes? How
many possible different gametes can arise? - Does it matter if there is crossing over, or not?
20Meiosis Spermatogenesis Making Sperm
- Notice that the outcome of this meiosis shows no
crossing over, only a shuffling of chromosomes
and the maturation of sperm (crossing over occurs
more often than not occurring at all) - There are 4 different cells that arise from
meiosis each having only ½ the original amount
of DNA
21Meiosis Oogenesis Making Eggs
- There are still 4 different cells created,
however, only 1 of them is used for fertilization - note the first meiotic division starts at
ovulation, while the second meiotic division is
not complete until fertilization occurs! - females are born with a preset number of
potential gametes prior to birth
22Comparing Mitosis and Meiosis
- Mitosis
- 1. begins with one cell
- 2. creates 2 identical diploid cells
- 3. has only 1 stage of division
- 4. DNA replicates before mitosis begins
- 5. Occurs in all body cells at some point of
life - 6. Crossing over is a rare event
- Meiosis
- 1. begins with one cell
- 2. creates 4 different haploid cells
- 3. has 2 stages of division
- 4. DNA replicates before meiosis begins
- 5. Occurs only in sex cells
- 6. Involves crossing over as a normal event
23Sexual vs Asexual Reproduction
- Sexual
- 1. Requires two parents
- 2. Creates offspring that are different than the
parents - 3. Process occurs by meiosis, fertilization and
then birth - 4. Harmful pathogens cannot wipe out entire
populations as there is a variety in genetic
make-up - 5. Increases the organisms chance of survival
and evolution - 6. Usually occurs in organisms that are more
complex - 7. Requires more energy and time in raising the
offspring
- Asexual
- 1. Requires only one parent
- 2. Creates offspring that are identical to the
parent - 3. Process may be by mitosis, spore formation,
budding etc. - 4. Harmful pathogens can wipe out entire
colonies of organisms due to the same genetic
make-up e.g bananas! - 5. May decrease the organisms evolutionary
capacity - 6. Usually occurs in organisms that are less
complex - 7. Requires less energy and time in raising the
offspring
24Bibliography and Credits
- http//www.biosci.uga.edu/almanac/bio_103/notes/ap
r_4.html - Audesirk et al. Biology Life on Earth. Sixth
Edition. Prentice Hall. 2002. - http//www.accessexcellence.org/RC/VL/GG/index.htm
l - http//www.grad.ttuhsc.edu/courses/histo/notes/fem
ale.html - http//www.biosci.uga.edu/almanac/bio_103/notes/ap
r_8.html - http//www4.ncsu.edu/unity/users/b/bnchorle/www/in
dex.htm