Which of the following is NOT a protostome?Group of answer choicessand dollarsnailbarnaclespiderlobster

To determine which of the organisms listed is NOT a protostome, we first need to classify each of the animals based on their developmental characteristics.

Step 1: Identify the Groups

1. Protostomes are animals in which the mouth develops before the anus during embryonic development. This group includes animals in the phyla Mollusca (like snails), Arthropoda (like lobsters and spiders), and Annelida.
2. Deuterostomes, on the other hand, are characterized by the anus developing before the mouth. This group includes animals in the phyla Chordata (like vertebrates) and Echinodermata (like starfish).

Step 2: Analyze Each Option

1. Sand Dollar - Sand dollars are echinoderms and belong to the Deuterostome group.
2. Snail - Snails are mollusks and therefore are protostomes.
3. Barnacle - Barnacles are crustaceans, which fall under the protostome classification as well.
4. Spider - Spiders are arachnids, categorized under protostomes.
5. Lobster - Lobsters are also crustaceans, hence they are protostomes too.

Step 3: Conclusion

From the analysis, the sand dollar is the only organism listed that is NOT a protostome, as it belongs to the Deuterostome group.

Final Answer

The organism that is NOT a protostome is the sand dollar.