Video Transcript
A botanist used the diagram shown
below to identify certain species. Which of the following statements
is true about this diagram? (A) The diagram refers to a
binomial nomenclature system. (B) The diagram is organized in a
set of triplets of characteristics of living organisms. (C) The diagram uses a series of
questions that can have two possible answers. Or (D) the diagram refers to a
hierarchical taxonomic system.
This question asks us about a
diagram that is used to identify different groups of plants by answering a series of
contrasting questions. These diagrams are called
dichotomous keys, since the prefix di- means two and there are two possible answers
to each question at each juncture of the diagram. For instance, at the first
juncture, the plant groups are separated by whether they have specialized vascular
tissue or not. These are very important tools for
identifying organisms based on their observable characteristics. However, they do not necessarily
show evolutionary relationships between different organisms. Let’s take a look through the
different answer options so we can figure out which is true about this diagram of a
dichotomous key.
Binomial nomenclature describes a
system scientists can use to name organisms using both their genus and species. The prefix bi- also means two,
while the suffix -nomial describes the name. So organisms named in this way have
two parts to their name. For example, the genus humans
belong to is Homo, while our species is sapiens, so our scientific
name using binomial nomenclature is Homo sapiens. The final groupings in this
particular dichotomous key only consist of one word, not two. And in fact, these groups do not
refer to the genus or the species of any particular organism but instead larger
divisions that contain many different genera and species. This means that we can eliminate
answer choice (A).
Answer choice (B) suggests that the
diagram is organized in a set of triplets of characteristics of living
organisms. This option can also be excluded as
dichotomous keys use one characteristic with two possible answers, like having seeds
or not having seeds, to separate organisms at each juncture, not three.
Answer choice (C) suggests that the
diagram uses a series of questions that can have two possible answers. This seems to be the correct answer
as we just learned that dichotomous keys use two statements at each juncture, like
the final statement which decides whether the plant has flowers or no flowers. But let’s make sure that the final
answer is incorrect.
Answer choice (D) suggests that the
diagram refers to a hierarchical taxonomic system. Hierarchical taxonomic systems are
based on evolutionary and genetic relationships between organisms, while a
dichotomous key like this one usually are not. Therefore, this statement is also
incorrect.
Now we know which of the statements
is true about this diagram of a dichotomous key. The correct answer is (C). The diagram uses a series of
questions that can have two possible answers.
