KEY CONCEPT Many organisms reproduce by cell division

5.4 Asexual Reproduction

KEY CONCEPTMany organisms reproduce by cell division.


Binary fission is similar in function to mitosis.(PN under Asexual Reproduction section)

• Asexual reproduction is the creation of genetically identical offspring from a single parent that does not involve joining of gametes (sex cells: egg and sperm cells)– Binary means “consisting of two parts.”– Fission means “the act or process of splitting into two parts.”– Binary fission is asexual reproduction that produces two daughter

cells genetically identical to the parent cell.– Binary fission occurs in single-celled prokaryotes only.


Do you have one of these at home?

• This is a common household plant, which produces little plantlets.

• It is called a Spider Plant (gross name, cool plant, however).

• Why is this considered asexual reproduction?


Binary fission is similar in function to mitosis.(PN under Binary Fission section)

Remember: •Prokaryotes have DNA, but not a lot of it•The DNA is found within the cytoplasm of the cell. •The DNA is a circular chromosome.•There are no spindle fibers in the prokaryotic cell.


Binary Fission Steps: (Study Guide, Page 77 – draw and explain).

1. (#2 on SG) The bacterial chromosome is copied; both copies attach to the cell membrane (draw the diagram that shows DNA duplicating in your SG)


Binary Fission Steps:

2. (#3 on SG) as the cell elongates, the chromosomes separate (draw the diagram that shows the cells beginning to divide)


Binary Fission Steps:

3. (#4 on SG) The cell grows twice its size and undergoes cytokinesis; the membrane is pinched inward and a new cell wall is created; the new chromosomes become two new identical daughter cells


• Environment determines what form of reproduction is most advantageous.

– Asexual reproduction is an advantage in consistently favorable conditions.

– Sexual reproduction is an advantage in changing conditions.

– Let’s do some math.

Hands-On Activity!– You do the math.– You are a bacteria

reproducing asexually. Using the beads I have given you, how many cycles did you go through before you ran out of beads?


Advantages to Asexual Species:Asexual reproduction can be more efficient if organisms are

well suited to their environment or there are ideal circumstances.

All organisms can potentially reproduce.Organisms do not need to spend resources like time and

energy finding or attracting a mate.Disadvantages to Asexual Species:Organisms may lack adaptability to survive in changing or

harsh conditions.The ability of all organisms potentially being able to

reproduce is not necessarily more efficient than sexual reproduction.

All identical organisms respond the same way to the environment, which might limit their overall survival.


Some eukaryotes reproduce through mitosis. This is called mitotic reproduction. Common in simple plants and animals. Three types are:

1. (On your PN) Budding forms a new organism from a small projection growing on the surface of the parent.

The new plant is genetically identical to the parent plant.

Can live alone or part of a colony.

Examples: Hydras and yeast

bud

Hydra

Yeast


2. Fragmentation is the splitting of the parent into pieces that each grow into a new organism.

Examples: flatworms, sea stars (starfish)

3. Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

Examples: See the pic to the right – what is it?

Also strawberries


What organism can reproduce asexually AND sexually?

• The sea anemone!• How??????

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KEY CONCEPT Many organisms reproduce by cell division