Video Transcript
A simple dichotomous key used to
identify different groups of mammals is provided. An organism that does not give
birth to live young and is covered in smooth fur is discovered. Using this dichotomous key,
determine which group it is most likely to belong to.
This question asks us to use a
dichotomous key to determine the group a newly discovered organism belongs to based
on certain characteristics. Dichotomous keys can be used to
identify an organism by responding to a series of contrasting statements. The prefix di- in dichotomous means
two, indicating that each successive statement in the dichotomous key can only have
two answers, gradually separating broad groups of organisms into smaller more
specific groups. It is important to note that
dichotomous keys are not a mechanism for accurate scientific classification, as they
are not based on evolutionary or genetic relationships between organisms but instead
simply group them based on easily observable characteristics.
Let’s take a look at the
dichotomous key we’re given, starting at the top with the broadest grouping we are
provided with, mammals. Moving down to the first junction,
we encounter our first statement that we need to respond to concerning the mammal
which we are attempting to identify. If the mammal in question lays
eggs, we follow the branch to the left. And if it instead gives birth to
live young, we follow the branch to the right. From the information given in our
question prompt, we know that our mystery organism does not give birth to live
young, so we can deduce that it must lay eggs. This means that we can follow the
left branch, which leads to the group Prototheria.
To narrow the group down further,
next we need to determine if the organism has smooth fur or spines. The organism discovered is said to
have smooth fur, so we should follow the left branch which leads to the group
Platypoda. As there are no more junctions or
branches past this grouping, this is as specific as our particular dichotomous key
gets.
Now that we have investigated the
characteristics of the unknown organism using this dichotomous key, we know the
correct answer to our question. The group that the mystery organism
that has been discovered is most likely to belong to is Platypoda.
