Video Transcript
Which genus reproduces by
conjugation? (A) Polypodium, ornamental
fern. (B) Plasmodium, protist and
malaria parasite. (C) Spirogyra, a filamentous
algae. (D) Sclerophrys, Egyptian
toad. Or (E) Synodontis, Nile
catfish.
Reproduction is a biological
process by which offspring are produced by a parent or parents. Reproduction can either occur
sexually or asexually. Conjugation, which is the method of
reproduction of importance to us in this question, is a type of sexual
reproduction. Let’s take a look at how the
different organisms mentioned in the answer options reproduce in order to work out
which genus uses conjugation for sexual reproduction.
Most mammals reproduce through
internal fertilization, a process which usually involves a biological male’s sperm
cell fertilizing a biological female’s egg cell within the female’s body. The fusion of the male and female
gametes in fertilization usually produces a zygote that develops into a new
organism. Amphibians and many fish often
reproduce through external fertilization, which also involves the fusion of gametes
to form a zygote, but fertilization happens outside the female’s body.
Sclerophrys, the Egyptian
toad, is an amphibian. So we can eliminate answer option
(D) as organisms in this genus will reproduce through external fertilization.
Answer option (E),
Synodontis, the Nile catfish, can also be eliminated as these organisms
will also reproduce through external fertilization.
Another method of reproduction is
called alternation of generations, which is a phenomenon that involves an organism
alternating between two distinct forms, usually sexual and asexual or haploid and
diploid. Some examples of organisms that
carry out alternation of generations within their life cycle are the ornamental fern
Polypodium and a unicellular protist called Plasmodium, which can
cause malaria in humans. As both of these genera listed in
options (A) and (B), respectively, use alternation of generations and not
conjugation, these choices can be eliminated.
Conjugation occurs when two
organisms combine their genetic material through direct cell-to-cell contact. Many organisms, such as some
bacteria, fungi, and protists, like the filamentous algae Spirogyra, can
utilize conjugation in their reproduction. During one type of conjugation, two
adjacent filaments from two different individuals grow a conjugation tube that
connects one cell to another in a different filament. A special type of gamete is moved
from one cell in the male filament to the other female filament through the
conjugation tube, where the two haploid cells can combine to produce a zygote.
This means that we have found the
correct answer to this question. The genus that reproduces by
conjugation is (C) Spirogyra, a filamentous algae.
