Asexual Reproduction

Asexual Reproduction Reproductive process that involves only one parent and produces offspring that are identical to the parent Well, what does that mean??

Asexual Reproduction Reproductive process that involves only (1.) one parent and produces (2.) offspring that are identical to the parent Well, what does that mean??

What types of asexual reproduction are there?

Bacteria Split by binary fission: they make a copy of their DNA and then split in half. What can you assume about the two new cells’ DNA? The two cells are exactly the same!

Asexual Reproduction Requires only one parent Offspring have 100% the same chromosomes as the parent. In other words, the offspring are exact “clones” of the parent. Most unicellular organisms reproduce this way. Mitosis Movie

Amoebas reproduce by binary fission

Hydra Microscopic organism that live in freshwater Reproduce by budding (when the offspring just grows off the side of the parent.)

Asexual Reproduction Budding Hydra Movie Budding is a means of asexual reproduction whereby a new individual develops from an outgrowth of a parent, splits off, and lives independently.

Asexual Reproduction video: Hydra Hydra Video

What is the difference between the DNA of the two hydra? Can you think of any other organisms that can do this?

Spider Plants are an example of an organism that reproduces by budding

Sponges also can reproduce by budding, regeneration and sexually too

Planarian Flatworm Live in ponds, streams and oceans Flatworms have eyespots that distinguish between light and dark They feed on dead or decaying material

Reproduce by regeneration--when a flatworm is cut in half, they reproduce into two new flatworms. What is special about the DNA of the two new worms? Any others you can think of that do this?

Regeneration of planarian worms Asexual Reproduction of Planarian Worms

Some Sea Stars can reproduce by regeneration

Parthenogenesis A form of reproduction in which an unfertilized egg develops into a new individual, occurring commonly among insects and certain other arthropods. http://bioteaching.wordpress.com/2010/12/25/parthenogenesis/ Parthenogenesis literally means a virgin birth; in biological terms, it simply means that an unfertilized ovum will give rise to a fully-functioning adult. That’s the broadest definition, and the one we will be using in this post; keep in mind that in the narrowest sense, parthenogenesis implies unisexual populations of virgin females producing clones (as seen in some lizards). A species can be obligately parthenogenic (can’t reproduce sexually at all) or facultatively parthenogenic (has the ability to switch between sexual and parthenogenic reproduction). In all, there are about 2000 species recorded to reproduce at least facultatively parthenogenetically under natural conditions and many more definitely exist, but remain unobserved/unsampled. Of the vertebrates, parthenogenesis has never been reported for mammals; bird eggs reported as being of parthenogenic origins never hatch. It’s only found in several unique fish, amphibians and lizards. In those, it is present due to polyploidy and hybridisation. At the cellular level, the difference between parthenogens and sexuals is that in the latter, meiosis is followed by fusion of a male and female gamete. In parthenogenesis, meiosis is changed so that only one particular set of chromosomes is transferred in a non-random fashion. Before going on to look at examples from the invertebrates, let’s examine the cytological underpinnings of parthenogenesis in vertebrates, just to see why the ‘Virgin’ Mary is a liar (or why Joseph is a gullible idiot).

Komodo Dragon parthenogenesis http://www.youtube.com/watch?v=G41EANkcMvg

cloning

Advantages of Asexual reproduction? More offspring Partners are not necessary

Disadvantages to asexual reproduction? Small gene pool Less able to adapt to environment A single disease could wipe out the entire population