Reproduction typesWHY DO CERTAIN ORGANISMS REPRODUCE THE WAY THEY DO?

Asexual reproduction• Fission• Budding• Vegetative Propagation• Spore formation• Fragmentation• Parthenogenesis• Cutting

• Benefits of Asexual reproduction– Quick

• Bacteria, for example can reproduce very quickly.

• 1 bacteria can multiply to thousands in days!

– Easy - No Need to spend lots of resources finding a suitable mate. Requires only one parent

– Produces identical offspring

So how do asexually reproducing organisms ward of baddies?

– Well, generally they don’t– Plague, competition, and changes in environment are devastating to these

creatures.– Mutations in genetic code really are the only way these organisms survive

epidemics or changes in their surroundings.

Fission– Fission is basically Mitosis– Organism matures, grows,

synthesizes it’s own DNA, splits, then repeats the process.

– Some examples of single cell organisms that use fission for Mitosis are

• Bacteria• Algae• Protozoa

Budding– Budding is a type of asexual

reproduction that starts with a little growth on the original organism

– The growth on the outside of the original cell gets larger and larger, until it can break off from the original organism

– Once it’s free from the original organism, it’s free to grow and get larger and live its own life

– Examples• Yeast• Hydra

Lets look at a video of budding

Vegetative Propagation

– Many plants can be cut from their main plant body and will sprout roots

– Spider plants do this well, place the baby sprouts in water, and they’ll end up growing roots, so that you can plant them

Spore formation– Spores are formed as “gametes”

through mitosis asexually and released.

– Likely catch in the wind and blow through the air until meeting an opposite “gamete”

These “gametes” fertilize each other and form more multicellular organisms to carry out the same process.

The following diagram shows the lifecycle of a sporophyte (spore producing organism)

Fragmentation– Think starfish

• Starfish can have one of its legs cut off, and it will grow back.

• Not that uncommon, happens in our livers too.

• What’s more uncommon is that the leg that was cut off will grow into a new starfish!

• Could be because some starfish have developed special organs or zones that can be broken off due to damage or predators.

Parthenogenesis

– These girls go through parthenogenesis, which literally means “virgin birth” meaning, they don’t need to mate to form an embryo.

– We can say they’re girls, because these reptiles, whiptail lizards, are all girls.

– No males known to be in existence.

– They make two female gametes that can fertilize each other.

Cutting

Sexual reproduction– There are surprisingly few organisms

that, in some time during their lives don’t reproduce sexually.

– In fact about 99 percent of organisms on earth reproduce sexually at least some time during their lives.

– Leads to a great deal of diversity– Diversity leads to a more sustainable

population that is better suited to ward off competition and plague.

– Requires 2 parents– Produces different offspring

– There are how many types of asexual reproduction?

– Yeast performs what type of sexual reproduction

– How do organisms who reproduce asexually defend against plague or competition?