Video Transcript
Which of the following is not an
example of a group that a heterotrophic organism could be classified into? (A) Holozoic, (B) parasites, (C)
saprophytes, or (D) prototrophs.
This question asks us to identify
the answer choice which is not a subdivision within the heterotrophic type of
nutrition. Let’s start by defining what a
heterotrophic organism is before we explore the different types to work out the
correct answer to this question.
A heterotrophic organism, sometimes
simply referred to as a heterotroph, is an organism that must obtain its nutrition
by consuming other organisms or the organic matter from a once-living organism. Humans are an example of organisms
that rely on other living or once-living organisms to obtain our nutrition. Everything we eat, whether it is
plant matter like fruit and vegetables, fungal matter like mushrooms, or animal
matter like meat and fish, was once a living organism.
Humans belong to an even more
specific class of heterotroph: holozoic heterotrophs. Holozoic organisms are those that
obtain nutrition by ingesting and internally digesting solid, liquid, or gaseous
food particles within their bodies. Remember that this question asks us
to find an example of a group that a heterotrophic organism could not be classified
into. As holozoic is an example of a
group that a heterotrophic organism could be classified into, we can eliminate
answer choice (A).
Another group of heterotrophs are
parasites, which obtain their nutrition by feeding on a host organism. Parasites tend to obtain their
nutrition at their host’s expense. For example, leeches obtain their
nutrition by feeding on another organism’s blood, which would definitely be
detrimental to the health of the host. With this information, we can also
eliminate answer choice (B).
A third type of heterotrophic
organisms are saprophytes. The prefix sapro- means rotting,
while “phyte” means feeding. So saprophytes, like most fungi and
some bacteria, feed off dead or rotting tissues to obtain their nutrition. For example, fungi usually feed by
releasing extracellular enzymes out of their cells to digest organisms that are
often dead and decaying and then absorbing the smaller molecules that the organic
matter is broken down into. Knowing this, we can also eliminate
answer choice (C).
This means that we have found the
correct answer to this question. The option that is not an example
of a group that a heterotrophic organism could be classified into is (D),
prototrophs.
