Question

models: drawing animal body plans 2 of 4 points g \true\ or \false\ to the end of each statement. show instructions 1. since none of these phyla have a head, none have an anterior end. false 2. nematoda is the only phylum of the three with a cuticle. 3. platyhelminthes uses the same opening as a \mouth\ and an \anus.\ 4. all three models show cross sections. 5. annelida is the only phylum of the three with segmentation. 6. these three phyla of worms are the same size.

Explanation:

1. (Already answered correctly: False) Anterior end refers to the front/head region, but even without a distinct head, many worms have an anterior (front) end where sensory structures are concentrated.
2. Arthropoda also have a cuticle, so Nematoda is not the only one.
3. Platyhelminthes are acoelomates with a gastrovascular cavity that has only one opening, serving as both mouth and anus.
4. The image shows a longitudinal (lengthwise) section, not cross sections, so not all models are cross sections.
5. Annelida (segmented worms) are the only major worm phylum with true metameric segmentation; Nematoda and Platyhelminthes are unsegmented.
6. The three phyla (Platyhelminthes, Nematoda, Annelida) include species with a wide range of sizes, from microscopic to large, so they are not the same size.

Answer:

1. False
2. False
3. True
4. False
5. True
6. False