Video Transcript
Most species of fungi can produce a haploid cell that undergoes a series of mitotic
divisions to form a haploid organism. What name is given to this haploid cell? (A) Gamete, (B) bud, (C) seed, (D) spore, or (E) ovule.
This question asks us about fungi, which are eukaryotic organisms. So each of their cells contains genetic material in the form of chromosomes within a
membrane-bound nucleus. Some examples of fungi that you might be familiar with include yeasts, molds that
grow on food like fruit, and even edible mushrooms. Let’s take a closer look at how fungi can reproduce so that we can work out the
correct answer to this question.
Reproduction is the biological process through which an organism or organisms produce
offspring. There are two main types of reproduction, and many fungi are capable of carrying out
both: sexual reproduction and asexual reproduction. Asexual reproduction involves only one parent and can occur through different
mechanisms depending on species. Some single-celled fungi like yeast can reproduce asexually through a process called
budding, which is a form of mitosis. When budding, a parent cell develops an outgrowth. The parent cell will replicate its genetic material and partition one nucleus to the
outgrowth. The outgrowth or bud eventually detaches, producing two yeast cells that are
genetically identical to each other.
Yeast display an interesting example of reproduction in fungi as the parent cell can
either be haploid or diploid when it buds depending on environmental conditions. When one yeast cell undergoes a single round of budding, this is just one mitotic
division and produces two new cells, which might be diploid or haploid, depending on
the chromosome number in the parent cell. However, this question is specifically asking about a process that produces a haploid
cell that can then grow into a single multicellular organism full of haploid cells
through many mitotic divisions, not just one new haploid cell like budding
produces. This suggests that the haploid cell that is being described in the question is not a
bud.
Let’s take a look at another method of fungal reproduction, which occurs in most
molds and edible mushrooms, the production of spores. What we observe as mold on bread or fruit or the mushrooms that grow above ground are
actually just the reproductive parts of certain species of multicellular fungi. Most of the fungus is in fact found below the surface of the structure it grows on in
the form of vast networks of threadlike fungal filaments called hyphae. The reproductive structures, which are called fruiting bodies, are formed by the
hyphae when the fungus is ready to reproduce. The fruiting bodies of fungi can undergo a reproductive process called sporogenesis,
which can either be a form of sexual or asexual reproduction, which, like in
budding, often depends on environmental conditions.
When sporogenesis is carried out by fungi, the fruiting bodies produce and release
single-celled structures called spores. Interestingly, other species such as nonflowering plants like mosses and ferns and
many species of algae can also carry out sporogenesis to produce and release
spores. But it occurs slightly differently in these organisms. Similarly to the cells produced in budding, fungal spores can either be haploid or
diploid, but they are usually haploid. Regardless of their haploid or diploid nature, once released, the fungal spores
disperse. Those that land on a suitable surface can start to divide through mitosis to produce
many genetically identical cells, eventually growing into a new network of hyphae
and thus forming a new multicellular organism, which is usually full of haploid
cells.
Having explored fungal reproduction in more detail, we can now answer this question
correctly. The name of the haploid cell produced by fungi that can then undergo mitotic
divisions to form a haploid organism is a (D) spore.
