Asexual
vs.
Sexual
Reproduction
Our Objective
Compare and contrast the processes of asexual
and sexual reproduction, including the type and
number of cells involved (one body cell in
asexual, two sex cells in sexual), and the
number of gene sets (body cell has 2 sets, sex
cells have 1 set each) passed from parent(s) to
offspring. (3.3.A.a)
Let's talk a moment about ASEXUAL
reproduction.
Remember how many parents are
involved?
That's right........just ONE
This type of reproduction is great if all you want
are clones because asexual reproduction does
not provide any variety in the offspring...............
Every offspring has the same characteristics as
the parent.
Of course,
humans can't
asexually
reproduce, as you
learned last time,
but you get the
idea...
Now, when it comes to sexual
reproduction every offspring is
unique.
It happens that way because in sexual reproduction
you get part of mom's characteristics and part of dad's
characteristics.
Dad's part comes from the sperm cell
Mom's part comes from the egg cell
The Sperm Cell
Each sperm cell develops in the testes and has
three parts: a head, middle piece, and tail.
An acrosome at the head tip produces enzymes
that help penetrate the female egg. During
fertilization, genetic material in the nucleus join
with genetic material in the egg.
The middle piece (body) contains mitochondria,
structures that provide energy for the sperm. The
mitochondria are tightly spiraled around the top of
the tail.
The tail moves the sperm toward the egg. An
average amount of sperm has 300 to 500 million
sperm.
The Egg Cell
Developing Egg Cell in the
ovary (takes about 2 weeks)
Mature Egg Cell
Nucleus
with
genetic
material
How long does it keep going???
The ovary continues to produce eggs until the woman
reaches age 51 (on average).
Some women may produce their last egg at a much
earlier age but the average is age 51.
This time of a woman's life is called
menopause.
Men can continue to produce sperm cells all their life.
Fertilization
Once the sperm gets inside the egg the genetic
material from each combine to create a unique
offspring. (Look at the kids and look at mom and dad)
Once the first sperm
cell
penetrates the egg a
chemical reaction
occurs
that prevents any
more
sperm from entering
the egg.
Sexual or Asexual?