Transcript Asexual Reproduction:

Asexual Reproduction:
It takes only one!
What is it and what’s it’s function?
• Asexual Reproduction is: when 1 organism gives
rise to 2 identical organisms ( this is essentially
cloning!)
• Organisms reproduce asexually when there is
an abundance of food, and when other
environmental conditions are very good
• Asexual reproduction does not take a lot of
energy in terms of raising the offspring or going
through mating rituals; and allows populations to
grow quite large in a short amount of time.
There are 5 types of Asexual
Reproduction:
1.
2.
3.
4.
5.
Binary Fission
Budding
Fragmentation
Spore Formation
Vegetative
Reproduction
Binary Fission
Protist: Paramecium
Bacteria!
• Virtually the same
as mitosis, binary
fission causes one
cell to divide into 2
after all its
organelles and
DNA have
replicated.
• Binary fission takes
place in singlecelled organisms
such as bacteria
and most protists
Budding
•
http://Hollenhorst and Catherine Fox
• A miniature of the original
parent comes off of the
parent by an out
pouching of cells or
cytoplasm from the
parent
• A new organism forms
eventually and breaks
away from the parent
• Occurs in yeast, hydra
and some plants
Fragmentation
• Pieces from the parent break
off and form a new organism
identical to the original parent
• Occurs in planaria (a freeliving flatworm) and sea stars.
• Often fragments of these
seastars must include part of
the middle disc to create a new
organism.
• Regeneration typical in sea
stars, demonstrates a similar
mechanism – in the photo here
only one arm is being
recreated.
Spore Formation
• When a bacterial cell senses
harmful or inhospitable
conditions, this vegetative cell
replicates its DNA and its cell
wall begins to surround the
new DNA copy. A durable
spore coat forms around the
developing spore and
eventually will await better
conditions for growth.
• Occurs in bacteria
(endospores), some protists,
fungi, ferns and mosses.
Vegetative Propagation
• Stolons travel above
ground and land in
another viable place
where soil is good
enough that another
crown and root system
can be made
• Occurs in strawberry
plants, spider plants,
grasses, lilacs, and ferns.
What are the benefits to
reproducing asexually?
1.
2.
3.
4.
5.
You don’t need a partner!
You can reproduce faster in good conditions
You use less energy
You increase the population of your species
You can make an exact replica of yourself (for
those of you who are vain!) and thus know
exactly what the offspring will be.
* Farmers use seeds that are genetically identical when
they plant their crops….. How does this benefit
them?
What are the costs or
disadvantages to reproducing
asexually?
• There is no exchange of genetic information and
so no genetic variation will exist in the
population – evolution of a species may not
occur
• Usually occurs only when environmental
conditions are good.
• Organisms that have developed from asexual
reproduction are prone to diseases and viruses
or other environmental problems because of a
lack of variability in the genetic make-up of the
population
Matching: Which organism would
use which type of asexual
reproduction?
• ___ Yeast
• 1. Spore Formation
• ___ Bacteria
• ___ Strawberries
• 2. Vegetative
Reproduction
• 3. Binary Fission
• ___ Planaria
• 4. Budding
• ___ Hydra
• 5. Fragmentation
Ans: Yeast – 1 & 4; Bacteria – 1 & 3; Strawberries – 2; Planaria – 5; Hydra – 4
Bibliography and Credits
•
•
•
•
http://sciences.aum.edu/bi/BI2033/thomson/binaryfission.html
http://biology.about.com/library/weekly/aa090700a.htm
http://biology.about.com/gi/dynamic/offsite.htm?site
http://www.cs.tufts.edu/%7Ecabotsch/bulloughs/invertebrates/worms/fl
atworm.html
• http://plantphys.info/Plants_Human/vegprop/vegpropn.html
• http://www.microbe.org/microbes/spores.asp