Transcript 5.4 Asexual Reproduction

5.4 Asexual Reproduction
Chapter 5 Cell Growth and Division
Mr. Shilala
DAHS
KEY CONCEPT
Many organisms reproduce by cell division.
Purpose of Reproduction
• To make sure a species can continue.
– Definition: Reproduction is the process by
which an organism produces others of its
same kind. 2 ways
• Asexual or sexual
• Asexual reproduction is the creation of offspring
from a single parent. There are several types
Binary Fission and Mitosis
1. Binary fission is similar in function to mitosis
– Binary Fission occurs in most Prokaryotes
– Binary fission produces two daughter cells
genetically identical to the parent cell.
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells
Binary Fission and Mitosis
• Prokaryotes have no
nucleus but do have
DNA
– DNA in the shape of
single circular
chromosome
– Chromosome copied
and attached to cell
wall
– When cell is twice as
large membrane
pinches inward –
cytokinesis
– Cell wall forms
Advantages and Disadvantages of
Asexual Reproduction
• Environment determines what form of
reproduction is most advantageous.
– Advantages of Asexual reproduction
• Favorable in environments that don’t
change much.
• Can be more efficient
– Disadvantages
• In environments that do change, identical
offspring respond the same to changes in
environment
• Extinction can occur if genetic variation
is needed
– Sexual reproduction
• Increases genetic diversity
• 1 or more individual may survive change
• Asexual reproduction itself is not more
efficient, rather the associated costs of
sexual reproduction are greater
– Example
• Two organisms each have 10 offspring
• 1 reproduces asexually
– All 10 can have offspring of their own
• The other 1 reproduces sexually
– 5 males and 5 females are produced
– Only females can bear offspring
– Must attract a mate
» Involves energy, signals, and behaviors
Some eukaryotes reproduce through
mitosis.
• Budding
– Forms a new organism from a small projection growing
on the surface of the parent.
– Very common in plants
Hydra
bud
Yeast
• Fragmentation
– Splitting of the
parent into pieces
that each grow into
a new organism.
– Sea Stars and
Flatworms
• Vegetative
reproduction
– Forms a new plant
from the modification
of a stem or
underground
structure on the
parent plant
– Sometimes referred
to as cloning
– Strawberries and
potatoes
• Regeneration
– The ability to
restore lost or
damaged tissues,
organs or limbs.
– It is a common
feature in
invertebrates, like
worms and
starfish.