Reproduction:The Continuity of Life

Reproduction

Sexual Reproduction

AsexualReproduction

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…Budding…

New Organisms New Organisms Arise as an Arise as an Outgrowth from the Outgrowth from the Parent OrganismParent Organism

Seen Mostly in Seen Mostly in Marine AnimalsMarine Animals Examples Include; Examples Include;

Sponges, Corals and Sponges, Corals and Jellyfish…Jellyfish…

Coral Polyp Photo courtesy Jeffrey N. Jeffords http://oceanworld.tamu.edu/students/coral/coral1.htm

Regeneration…Regeneration…

This refers to the ability This refers to the ability of some animals to of some animals to re-grow severed parts.re-grow severed parts.

Some of these animals Some of these animals can also grow new can also grow new organisms from the organisms from the severed pieces severed pieces (Segmented Worms (Segmented Worms and Sea Stars)and Sea Stars)

FissionFission

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

Vegetative PropagationVegetative Propagation

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

FragmentationFragmentation

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

Parthenogenesis…Parthenogenesis…

Offspring can arise Offspring can arise from unfertilized eggs.from unfertilized eggs.

Includes some Fish, Includes some Fish, Reptiles, Amphibians Reptiles, Amphibians and Aphids.and Aphids.

Most of these species Most of these species can switch between can switch between Sexual and Asexual Sexual and Asexual Reproduction. Reproduction.

(depending on conditions)(depending on conditions)

http://www.duke.edu/%7Ejsr6/Hawaiipics/Rhampho.jpg

http://aolsearch.aol.com/aol/imageDetails?invocationType=imageResults&query=photos+of+parthenogenic+species&img

http://spot.colorado.edu/~noyesr/TEACHING/4800%20Fall%202002.%20Biology%20and%20Evolution%20of%20Sex/Gynogenesis.Poecilia.pdf

www.ag.ndsu.nodak.edu

WHY???WHY???

Why would these organisms prefer Why would these organisms prefer asexual reproduction in stable conditions asexual reproduction in stable conditions and sexual reproduction in more and sexual reproduction in more uncertain or less favorable conditions?uncertain or less favorable conditions?

Imagine…Imagine…

Imagine that a particular organism within a Imagine that a particular organism within a species lacks a certain gene (or ability to species lacks a certain gene (or ability to express a certain gene) necessary to break express a certain gene) necessary to break down a specific type of food, yet others of the down a specific type of food, yet others of the same species within the population are able same species within the population are able to break down that food. to break down that food.

What happens if the uncertain or less What happens if the uncertain or less favorable conditions lead to that being the favorable conditions lead to that being the primary food source?primary food source?

Death…Death… The parent organism and all of their The parent organism and all of their

offspring produced through offspring produced through parthenogenesis would die! parthenogenesis would die!

But, with the genetic diversity that comes But, with the genetic diversity that comes from sexual reproduction the possibility of from sexual reproduction the possibility of the offspring surviving is enhanced.the offspring surviving is enhanced.