Thanks for the great question!
The ultimate goal of the DNA that makes up our
genes is to reproduce: to transmit copies
of DNA into the future.
Different living things use different
strategies to reproduce. Asexual
organisms, such as many species of single cell
bacteria, reproduce by forming clones, or
exact copies, of themselves which split off
from the parent. On the other hand
multicellular organisms, such as plants and
animals, reproduce sexually -- through the
fusion of sex cells. Species evolved to use
whichever strategy worked best in their
Also, many living things have evolved to use
both asexual and sexual means of reproduction. For
example aphids, slime molds, sea anemones, and
some starfish are capable of both asexual and
sexual reproduction. Typically, when the
environment is rich and abundant with resources,
these species will undergo asexual
reproduction. However, when environments
become harsh, and resources are scarce, these
species may switch to sexual reproduction.
This is because sexual reproduction increases the
genetic variability within a species, perhaps
allowing them to adapt with their changing
There are far too many to list them all. All
animals can reproduce sexually, but some can do
both ways. Colonial animals such as
siphonophores, corals, and bryozoans are
particularly good at asexual reproduction, but
like everything else they can reproduce sexually.
However, asexual reproduction is known in some
lizards, some molluscs, many parasites, and some
other animals, too.
In the future, humans might join the club if we
start going in for cloning in a big way.
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