Transcript asexual_vs_sexual_reproductionx

Asexual vs Sexual Reproduction
• http://educationportal.com/academy/lesson/asexual-versussexual-reproduction.html#lesson
Reproduction:
The Continuity of Life
Reproduction
Sexual
Reproduction
Asexual
Reproduction
Question
• How might the asexual reproduction of
genetically identical plants be useful to humans?
• Answer We could theoretically grow a particular
plant in abundance
• How could it prove harmful to our food supply?
• Answer: if condition change a significant portion
of our food supply could be adversely affected.
Asexual Reproduction:
Identical Offspring
• Budding
• Regeneration
• Parthenogenesis
… Cloning???
Genetically
Binary fission is similar in function to
mitosis.
• Asexual reproduction is the creation of offspring
from a single parent.
– Binary fission produces two daughter cells genetically
identical to the parent cell.
parent cell
– Binary fission occurs in
prokaryotes.
DNA
duplicates
cell begins
to divide
daughter
cells
Budding…
• New Organisms Arise
as an Outgrowth from
the Parent Organism
• Seen Mostly in Marine
Animals
– Examples Include;
Sponges, Corals and
Jellyfish…
Coral Polyp Photo courtesy Jeffrey N. Jeffords
http://oceanworld.tamu.edu/students/coral/coral1.htm
Some eukaryotes reproduce through
mitosis.
• Budding forms a new organism from a small
projection growing on the surface of the parent.
Hydra
bud
Yeast
• Yeast cell cycle including budding:
• http://brodylab.eng.uci.edu/cgibin/jpbrody/animation/files/13977277560.html
Can I have some spore?
• Spore Formation – spores = small
specialized cells that contain a
nucleus and cytoplasm
surrounded by a thick outside
wall which protects the spore.
Under the right conditions the
spore can rise to a new organism.
Found in bacteria, molds, yeast,
mushrooms, mosses, ferns and
some protozoans.
Regeneration…
• This refers to the ability
of some animals to
re-grow severed parts.
• Some of these animals
can also grow new
organisms from the
severed pieces
(Segmented Worms
and Sea Stars)
VEGETATIVE REPRODUCTION
• Fragmentation is the
splitting of the parent
into pieces that each
grow into a new
organism.
• Vegetative reproduction
forms a new plant from
the modification of a stem
or underground structure
on the parent plant.
• Bulb = Short
underground stem
surrounded by thick
leaves. Contain
stored food. As the
plant grows it
produces new bulbs
which will grow into
new plants. Tulips,
onions, and lilies.
• Corms =
Similar to
bulbs but
do not
contain
leaves, just
undergroun
d stems.
Water
chestnuts.
• Tuber = enlarged
part of an
underground stem
that contains
stored food.
Potatoes are
tubers. “Eyes” =
tiny buds that can
form a new potato
plant. How you
plant potatoes.
Great potato
famine.
• Runner or stolon =
horizontal stem above
the ground with buds.
If a bud touches the
ground it will form
roots and stems and
start a new plant.
Strawberries.
• Rhizome = horizontal
stem that grows
underground. Thick
and contains stored
food. Upper portion
form nodes which will
form buds which will
form new plants.
Lower portion forms
roots. Ferns, cattails,
and water lilies.
ARTIFICIAL VEGATATIVE
REPRODUCTION
Watch out for those old ladies.
• Cutting = use a portion of a
developed plant to make a
new plant. Roses, ivy, and
grapevines are reproduced
in this way.
• Layering = a stem is
bent so that it is
covered with soil.
Once the branch forms
roots it is
disconnected from the
original plant.
• Raspberries and roses.
• Grafting = Bud or
stem of one plant is
permanently
attached to the
stem or trunk of a
very similar plant.
The cambium layers
grow together and
form a single plant.
Apple trees.
Why Bother??
• Advantages to artificial vegetative propagation:
1. Plants that grow from seed are not always exactly
the same as their parents.
2. Takes less time to artificially propagate.
3. Can create seedless fruits.
4. Grafting can be used to generate higher levels of
fruit and nut production.
Parthenogenesis…
• Offspring can arise
from unfertilized eggs.
• Includes some Fish,
Reptiles, Amphibians
and Aphids.
• Most of these species
can switch between
Sexual and Asexual
Reproduction.
http://aolsearch.aol.com/aol/imageDetails?invo
cationType=imageResults&query=photos+of+pa
rthenogenic+species&img
http://www.duke.edu/%7Ejsr6/H
awaiipics/Rhampho.jpg
(depending on conditions)
http://spot.colorado.edu/~noyesr/TEACHING/480
0%20Fall%202002.%20Biology%20and%20Evolutio
n%20of%20Sex/Gynogenesis.Poecilia.pdf
www.ag.ndsu.nodak.edu
WHY???
• Why would these organisms prefer asexual
reproduction in stable conditions and sexual
reproduction in more uncertain or less
favorable conditions?
Imagine…
• Imagine that a particular organism within a
species lacks a certain gene (or ability to
express a certain gene) necessary to break
down a specific type of food, yet others of the
same species within the population are able
to break down that food.
• What happens if the uncertain or less
favorable conditions lead to that being the
primary food source?
Death…
• The parent organism and all of their offspring
produced through parthenogenesis would die!
• But, with the genetic diversity that comes
from sexual reproduction the possibility of the
offspring surviving is enhanced.
• Environment determines what form of reproduction is
most advantageous.
– Asexual reproduction
is an advantage in
consistently favorable
conditions.
– Sexual reproduction is
an advantage in
changing conditions.
Stem Cells—multicelluar life
Multicellular organisms depend on
interactions among different cell types.
CELL
TISSUE
stem
shoot system
leaf
vascular
tissue
ORGAN
lateral
roots
primary
root
root system
• Tissues are groups of cells that perform
a similar function.
• Organs are groups of tissues that
perform a specific or related function.
• Organ systems are groups of organs
that carry out similar functions.
SYSTEMS
Specialized cells perform
specific functions.
• Cells develop into their mature forms through the process
of cell differentiation.
• Cells differ because different combinations of genes are
expressed.
• A cell’s location in an embryo helps determine how it will
differentiate.
Outer: skin cells
Middle: bone cells
Inner: intestines
Question
• Why is regulation of the differentiation
process during the early stages of
development so critical?
• The early stages lead to the development of
progressively more specialized tissues and
organs. Distribution of cell differentiation in
the early stages could cause severe
abnormalities in an organism’s body structure.
Stem cells are unique body cells.
• Stem cells have the ability to
– divide and renew themselves
– remain undifferentiated in form
– develop into a variety of specialized cell types
Stem cell video
• http://www.youtube.com/watch?v=tPulEAryP
O0
• Stem cells are classified into three types.
– totipotent, or growing into any other cell type
– pluripotent, or growing into any cell type but a totipotent cell
– multipotent, or growing into cells of a closely related cell
family
• Stem cells come from adults and embryos.
– Adult stem cells can be hard to isolate and grow.
– The use of adult stem cells may prevent transplant rejection.
– The use of embryonic
stem cells raises
ethical issues
– Embryonic stem cells
are pluripotent and
can be grown indefinitely
in culture.
First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner
cell mass. These cells are then removed and grown with nutrients. Scientists try to
control how the cells specialize by adding or removing certain molecules.
• The use of stem cells offers many currently realized and
potential benefits.
– Stem cells are used to treat leukemia and lymphoma.
– Stem cells may cure disease or replace damaged organs.
– Stem cells may revolutionize the drug development process.