Reproduction: The Continuity of Life Reproduction Sexual Asexual

Methods Advantages Disadvantages Sexual Internal fertilization Offspring less likely to have mutations show up Successful traits can be selected and failed traits can be prevented from passing on Does require a mate to reproduce Population increases are limited External fertilization Asexual Budding Uniformity in offspring Can increase populations rapidly Does not require a mate for reproduction to take place Lack of diversity in offspring Because they reproduce offspring genetically identical to parents, the offspring inherit any mutations of the parent. Regeneration Fission Parthenogenesis

Asexual Reproduction: Genetically Identical Offspring Budding Regeneration Fission Fragmentation Vegetative Propagation Parthenogenesis … Cloning???

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

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)

Fission This is the type of reproduction all prokaryotes go through. The DNA is copied, the cell enlarges and splits in 2. Both cells then have the ability to grow as large as the original cell.

Vegetative Propagation Asexual reproduction in plants when a piece of the original plant can result in another organism without seeds or spores.

Fragmentation When pieces of the parent organism are broken off and grow in to genetically identical organisms.

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. (depending on conditions) http://aolsearch.aol.com/aol/imageDetails?invocationType=imageResults&query=photos+of+parthenogenic+species&img http://www.duke.edu/%7Ejsr6/Hawaiipics/Rhampho.jpg http://spot.colorado.edu/~noyesr/TEACHING/4800%20Fall%202002.%20Biology%20and%20Evolution%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.