Complete question:
The dichotomous key below provides a way to classify some animals into groups according to their physical characteristics.
Dichotomous Key
I wings------------------go to II
no wings------------- group A
II feathers---------------group B
no feathers----------go to III
III two legs------------- group C
six legs---------------group D
The key can be used to classify each of the four animals represented below ⇒ wasp, ant, tiger, bird
Which row in the chart shows the correct classification group for each animal?
Row Wasp Ant Tiger Bird
(1) group D group D group A group B
(2) group B group A group D group C
(3) group B group D group A group C
(4) group D group A group A group B
Answer:
Row Wasp Ant Tiger Bird
(4) group D group A group A group B
- Group A: Tiger and Ant → They do not have wings
- Group B: Bird → It has wings and feathers
- Group D: Wasp → It has wings, does not have feathers, and has six legs
Explanation:
When analyzing a dichotomous key, you just need to pay attention to the given descriptions and carefully observe the organisms you have.
The key describes specific morphological traits of each organism that are useful to differentiate it from other organisms. So all you need to do is to follow the instructions given in each step, and the key will guide you directly to the answer.
In the exposed example you have four organisms: wasp, ant, tiger, bird
The provided key gives you three steps: I, II, III.
Step I:
wings------------------go to II
no wings------------- group A
Here the key tells you to separate, from your group of organisms, the ones that have wings from the ones that do not have wings.
- wasp and bird have wings → So you need to go to step II
- tiger and ant do not have wings → So they belong to Group A
Step II:
feathers---------------group B
no feathers----------go to III
Now you only need to consider the bird and the wasp, which are the two organisms that have wings.
Here the key tells you to separate the one that has feathers from the one that does not have feathers.
- Bird has feathers → So it belongs to the group B
- The Wasp does not have feathers → So you need to go to step III
Step III:
two legs------------- group C
six legs---------------group D
In this last step, the key takes you to two possible groups. But you only have one left organisms, which is the wasp. So what you need to do is to observe how many legs your wasp has. It is an insect, so it has six legs. The wasp belongs to Group D.
You do not have any organism that belongs to group C.
To sum up, according to the given information you could group the group of organisms as follows:
- Group A: Tiger and Ant → They do not have wings
- Group B: Bird → It has wings and feathers
- Group D: Wasp → It has wings, does not have feathers, and has six legs
