Asexual Reproduction

Producing Identical Offspring

Asexual Reproduction

• Unicellular organisms, many simple animals, and many plants reproduce asexually, at least during part of their life cycles.

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Asexual Reproduction

• Because asexual reproduction takes place only by mitotic cell division, every offspring has the same exact DNA as its parent.

http://www.phoenix5.org/glossary/graphics/mitosis.jpg

Check for Understanding

• Would you expect offspring produced asexually to show much variation? Why?

Asexual Reproduction

• Usually rapid and often results in the production of large numbers of offspring.

Methods of Asexual Reproduction

• There are several methods of asexual reproduction, including:

1. Binary Fission2. Budding3. Spore Formation4. Regeneration5. Vegetative Reproduction

Binary Fission

• Binary fission is the simplest form of asexual reproduction.• Parent organism

divides into two equal parts.

Binary Fission

• Binary fission is the usual method of reproduction in one celled organisms, including bacteria, protozoa, and many algae.

http://www.biology-resources.com/images/paramecium-dividing-big.jpg

Budding

• Budding is a method of asexual reproduction in which the parent divides into two unequal parts.

Budding

• The new individuals develop as small outgrowths, or buds, on the outer surface of the parent.

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Budding

• The buds may break off to live as an individual, or they may remain attached, eventually forming a colony. http://farm3.static.flickr.com/

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Budding

• Budding differs from binary fission in that the parent and offspring are not the same size.

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Budding

• Budding takes place in yeast and hydra, as well as in sponges and some worms.

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Budding in Yeast and Hydra Video

Budding in Yeast and

Hydra Video

Spore Formation

• Spores are single, specialized cells that are produced by certain organisms.• Can be formed

sexually or asexually.http://medicineworld.org/images/blogs/mold-spores214412.jpg

Spores

• Although spores can vary greatly in appearance, they all function as single units of reproduction.• Often surrounded with a thick hard

outer wall.• May sometimes have a flagella.

Spores• Asexually formed

spores are a common method of reproduction in many simple organisms, such as fungi, algae, and protozoa.

http://www.sixwise.com/images/articles/2005/10/26/fungusPIL.gif

Spores

• These spores are produced through mitotic cell division.• They are formed within and released

from a single cell structure that is the remains of the original parent cell from which they are formed.

Spore Formation in Bread Mold

• Bread mold is a fungus, and can sometimes be seen growing as a dark mass on bread or other food. http://www.buzzle.com/img/articleImages/375982-2387-

34.jpg

Bread Mold• Spores are

produced by mitotic cell division in spore cases on specialized stalks that grow upward from the surface.

Bread Mold

• Thousands of black spores develop within each spore case.• When fully grown, the

walls break down, and the tiny light spores are swept away by air currents.

http://www.skidmore.edu/academics/biology/plant_bio/fungi/Rhizopus%20-%20bread%20mold.jpg

Spores• When a spore lands

in a warm, moist environment, where nutrients are available, it germinates and grows to form a new mass of mold.

http://www.scienceprojectlab.com/image-files/mold-on-bread.jpg

Bread Mold

• Bread mold also reproduces sexually, which we will discuss later.

Bread Mold Video(click photo above)

Bread Mold

• In the space provided on your worksheet, draw and label a diagram showing the main structures of bread mold.

Regeneration

• Regeneration is the ability of an organism to re-grow lost body parts. http://www.biosulf.org/1/images/newt-regeneration.jpg

Regeneration

• Relatively simple animals can regenerate lost body parts. For example:

* Hydra* Planaria* Starfish* Earthworm

http://www.scientificillustrator.com/art/microscopic/hydra.jpg

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http://campus.albion.edu/wjwilson/files/2010/12/regenlabel.jpg

Regeneration

• The power of regeneration decreases in more complex organisms.• For example: While a crab

can re-grow a lost claw, it cannot regenerate an entire animal from pieces.

http://newsliteimgs.s3.amazonaws.com/100429_crab1.jpg

Sea star regeneration video (click photo above)

Vegetative Reproduction

• Although most plants reproduce sexually by means of seeds, asexual reproduction involving roots, stems, and leaves also occurs.

http://www.localdelicious.com/wp-content/uploads/2010/09/strawberry-runners.jpg

Vegetative Reproduction

• Roots, stems, and leaves are called vegetative structures.• They normally play a

role in the nutrition and growth of plants.

http://extension.oregonstate.edu/mg/botany/images/fig1.gif

Vegetative Reproduction

• When these structures give rise to new plants, the process is known as vegetative reproduction, or vegetative propogation.

Check for Understanding

• Give three examples of vegetative structures.• Roots, stems, leaves

• When these structures give rise to new plants, the process is known as what?• Vegetative Reproduction (propogation).

Vegetative Propagation• In vegetative

reproduction, cells divide mitotically, then differentiate to produce another plant.• The new plant has the

same hereditary characteristics as the parent plant.

http://plantphys.info/plants_human/vegprop/root.gif

Vegetative Propagation

• Vegetative propagation occurs naturally and can be produced artificially.

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Natural Vegetative Propagation

• A bulb is a short underground stem surrounded by thick fleshy leaves that contain stored food.

Bulbs• As the plant grows,

small new bulbs sprout from the old one.• Each of the new bulbs

can give rise to another plant.

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Bulbs

• Examples of plants that reproduce with bulbs are:

* Tulips* Onions* Lillies

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http://www.mdidea.com/products/proper/lily_bulb10.jpg

Tubers

• A tuber is an enlarged part of an underground stem that contains stored food.

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Tubers

• White potatoes are tubers.• Along the surface of

the tuber are indentations called “eyes”.

http://food.evilwalrus.net/wp-content/uploads/2008/07/potatoes-white.jpg

Tubers

• The eyes are tiny buds that grows into a shoot.• The young shoot uses

food stored in the tuber until it can carry on photosynthesis.

Runners

• A runner or stolen, is a stem that grows sideways and has buds.• Usually grows along

the surface of the ground.

Runners

• Where buds from the runner touch the ground, new plants develop.• These new plants will

send out runners that will repeat the process.

http://forum.sensiseeds.com/uploads/19197/wildstrawberryrunners.jpg

Runners

• Strawberry plants and many grasses that reproduce quickly use runners.

http://living-country-life.com/wp-content/uploads/2009/05/strawberry-plant2.jpg

http://i.ehow.com/images/a06/20/81/plant-grass-runners-200X200.jpg

Rhizome

• A rhizome is a stem that grows sideways underground.• Usually thick and

fleshy and contains stored food. http://www.rhizomesystems.com/images/

rhizome_example.png

Rhizome

• Along the rhizome are enlarged portions called nodes.• Buds along the upper

surface of the rhizome give rise to leaf-bearing branches.

http://www.turfgrass.ncsu.edu/images/Plants/bermudagrass/Web/rhizome.jpg

Artificial Vegetative Propagation

• Farmers and gardeners have developed ways to grow plants with desirable traits.• They do this through artificial

vegetative propagation.

Cuttings

• A cutting is any vegetative part of the plant used to produce a new individual.

http://www.instructables.com/image/F520ALBP7REP27QGYD/Rooting-plant-cuttings.jpg

Cuttings• Cuttings are usually

placed in water and allowed to grow roots.• Once roots develop,

the cutting is planted in soil and grows as a new plant.http://www.happynews.com/living/

livingimages/cuttings-plants-trees.jpg

Grafting

• In grafting, a stem or bud is removed from one plant and permanently joined to the stem of a closely related plant. http://www.bodwen-nursery.co.uk/Resources/

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Grafting

The added piece is called the scion

Part of the combination providing the roots is known as the stock

Grafting

• In the space provided on your worksheet, draw and label a typical grafting set up.

Advantages of Artificial Vegetative Propagation

• Plants grown from seeds do not always show the same characteristics as the parent plant.• Vegetative propagation produces

plants identical to the parent.

Advantages of Artificial Vegetative Propagation

• Example 1: Seedless fruit can only be

grown through vegetative propagation.

• Example 2:Scions of a desirable plant

can be grafted onto plants with a disease resistant root system.

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