Question 1
Multiple choiceMedium1 markThe key is used for three local pond species. A field team identifies an observed animal and compares a barcode from pond-water environmental DNA (eDNA) with reference barcodes. The animal has no shell and six legs; the sample barcode is CTAG. Which pair gives the animal’s key identification and the species detected in the water sample, respectively?
Dichotomous key
| Feature | Identification or route |
|---|---|
| Shell present | Pond snail |
| Shell absent | Go to 2 |
| Six legs | Water beetle |
| More than six legs | Freshwater shrimp |
Reference barcodes
| Species | Barcode |
|---|---|
| Pond snail | GACT |
| Water beetle | TGCA |
| Freshwater shrimp | CTAG |
Show answer and explanation
Answer: A. The key routes an animal with no shell to the next distinction, where six legs identifies a water beetle. The eDNA barcode CTAG matches the freshwater shrimp reference barcode.
B: identifies the observed animal correctly but assigns the sample barcode to the pond snail, whose barcode is GACT.
C: matches the sample barcode correctly but selects the shell-present route for the observed animal.
D: swaps the key identification and the species identified from the eDNA barcode.
Remember: a dichotomous key uses observable features; an eDNA barcode is compared with reference barcodes.