Video Transcript
Brittle stars are small aquatic
organisms, formed of a central disk and multiple arms. Brittle stars can break off their
arms and then regrow them. Which method of asexual
reproduction is used by brittle stars? (A) Binary fission, (B) budding,
(C) vegetative propagation, or (D) regeneration.
We are told that brittle stars can
regrow their arms by an asexual method of reproduction and asked to work out which
method they use to accomplish this.
Remember, reproduction is the
process by which an organism, or organisms, produce offspring. Some important, distinguishing
features of asexual reproduction are that it only involves one parent and produces
offspring that are genetically identical to that parent. Let’s discuss each answer option
and eliminate the incorrect choices.
Binary fission is a type of asexual
reproduction in which a cell divides into two genetically identical cells. This process is used mainly by
single-celled organisms, like bacteria, and is not the method that brittle stars use
to regrow their arms. So, answer (A) binary fission is
incorrect.
Budding is another method of
asexual reproduction in which an organism is produced from an outgrowth, or bud, on
the surface of the parent cell or body. The outgrowth eventually detaches
to form two genetically identical organisms. This is not the method utilized by
brittle stars to regrow an arm, because it requires the offspring detach from the
parent. So, answer (B) budding is incorrect
as well.
Vegetative propagation is a method
of reproduction used by plants in which a new, genetically identical plant grows
from part of the parent plant. This method is used exclusively by
plants. And as brittle stars are animals,
it cannot be used to regrow brittle star arms. As a result, we can eliminate
answer (C) vegetative propagation.
Regeneration is the ability of an
organism to repair or regrow damaged or missing parts of their bodies. For example, brittle stars can use
this process to regenerate, repair, and regrow lost arms. This is sometimes referred to as a
method of asexual reproduction, as some species can use regeneration to regrow the
detached part into a whole, new, genetically identical organism.
Using this information, we can
deduce the method of asexual reproduction used by brittle stars to regrow arms that
are broken off their body. The correct answer is (D)
regeneration.
