Asexual Reproduction
Some organisms can reproduceasexually,meaning that the offspring have a single parent
and share the exact same genetic material as the parent. The advantage of asexual repro-
duction is that it can be very quick and does not require the meeting of two individuals
of the opposite sexes. The disadvantage of asexual reproduction is that it does not involve
genetic recombination, a process that can result in an adaptive new set of traits. For ex-
ample, you might inherit one advantageous trait from your maternal grandmother, another
adaptive trait from your paternal grandmother, and other adaptive traits from your paternal
grandfather. You have the benefit of the many genes from two lineages combining in a new
way. An organism that is born through asexual reproduction, however, only has the DNA
from one parent, and it is the exact copy of that parent. Therefore, no new combinations of
traits can happen.
Prokaryotic organisms, which as you might recall are single-celled, reproduce asexually.
Bacteria reproduce throughbinary fission,where they basically divide in half (Figure
5.6). First, their chromosome replicates and the cell enlarges. After cell division, the two
new cells each have one identical chromosome. Mitosis is not necessary as there is no nucleus.
Then new membranes form to separate the two cells. This simple process is beneficial to the
bacteria, allowing very rapid reproduction.
Figure 5.6: Bacteria reproduce by binary fission. Shown is one bacterium reproducing and
becoming two bacteria. ( 1 )
There are also several animals that can reproduce asexually. Flatworms can divide in two,
then each half regenerates into a new flatworm identical to the original. Many types of
insects, fish, and lizards (Figure 5.7)can reproduce asexually through parthenogenesis.