Video Transcript
Salmonella bacteria are
responsible for causing food poisoning in humans. The bacteria reproduce when a
single bacterium divides into two. This happens repeatedly and rapidly
in the right conditions. Which method of asexual
reproduction is used by Salmonella? (A) Vegetative propagation, (B)
budding, (C) binary fission, or (D) regeneration.
We are being asked to identify the
correct method of asexual reproduction used by Salmonella bacteria. You may remember that asexual
reproduction involves a single parent and does not involve the fusion of
gametes. It results in offspring that are
typically genetically identical to their parent and their siblings. We call these genetically identical
individuals clones.
The answer choices give four
different methods of reproduction. Let’s look at each of them to make
sure they are asexual methods and to determine which of them most closely matches
the description of the method used by Salmonella.
Vegetative propagation occurs when
a new plant develops from a piece of a parent plant. The new plants can come from
leaves, special roots, stems, or fruits. In prickly pear cactus, shown in
the diagram, new plants are formed when fallen stem segments and fruits send out
their own roots If environmental conditions are right, the stems and fruits will
grow into new plants and will eventually form clusters of clones around the parent
plant.
Vegetative propagation involves a
single parent and results in offspring that are clones, so it is a method of asexual
reproduction. However, it is exclusive to plants
and does not match the description given for Salmonella. So, we can rule this answer choice
out.
Budding occurs when a new organism
develops from a bulge or bud attached to the parent. It is found in both unicellular
organisms, such as yeast, and multicellular organisms, such as hydra and coral. The buds grow to maturity while
still attached to the parent. They then detach from the parent
and continue their lives as independent clones. Budding is a type of asexual
reproduction, but the parent does not split into two as described in the
question. So, we can rule it out.
Binary fission is a process in
which a cell duplicates its genetic material and then undergoes cytokinesis to
produce two daughter cells. Binary fission involves a single
parent cell, and the two daughter cells are genetically identical. So, it is a method of asexual
reproduction. It also matches the description
given for Salmonella in the question. So, this could be the correct
answer. But just to be sure, let’s have a
look at our final answer choice.
Regeneration is used by organisms
to regrow damaged or missing body parts. In most cases, regeneration does
not create offspring, so it is not a method of reproduction. However, there are cases where two
or more fragments of an organism each develop into a fully functioning
individual. This type of regeneration is often
referred to as fragmentation, and it is found in simple multicellular organisms,
including sea stars, sponges, and annelids, like this earthworm. Fragmentation needs just one parent
to produce offspring that are clones, so it does qualify as asexual
reproduction. It also involves the splitting of
the parent into two parts.
So, how can we choose between
answers (C) and (D)? Well, the term fragmentation is
typically used to refer to the process of creating offspring from two or more
fragments of multicellular organisms. And binary fission is used to refer
to the splitting of unicellular organisms, such as bacteria, into two equal daughter
cells. Therefore, the correct answer is
(C). The method of asexual reproduction
used by Salmonella is binary fission.
