Table of Contents
In what ways are the flatworms more complex than the sponges?
Although the flatworm body plan is relatively simple, it is a great deal more complex than that of a sponge or cnidarian. Flatworms have a middle tissue layer, the mesoderm. And unlike sponges and cnidarians, the flatworm has tissues that are organized into organs.
What main characteristic do worms have?
bilaterally symmetrical
Characteristics. All worms are bilaterally symmetrical, meaning that the two sides of their bodies are identical. They lack scales and true limbs, though they may have appendages such as fins and bristles. Many worms have sense organs to detect chemical changes in their environments, and some have light-sensing organs.
How are worms different to cnidarians?
They all have long, narrow bodies without legs. All worms also have tissues, organs, and organ systems. Worms have bilateral symmetry. Unlike sponges or cnidarians, worms have distinct head and tail ends.
How are worms more advanced than cnidarians?
Flatworms are more complex than cnidarians. Cnidarians have two layers of cells, the ectoderm and the endoderm; flatworms have a middle layer called the mesoderm between the other two layers (Fig. 3.16). The cells of the ectoderm and endoderm are also more organized than similar cells of cnidarians.
What makes worms unique?
An earthworm has a streamlined body with no antennae or fins or arms or legs! This streamlined shape is an adaptation to living in narrow burrows underground and the need to move easily through the soil. An earthworm has circular muscles that surround each body segment.
How are nematodes more complex than Platyhelminthes?
Species of nematodes are higher than that of Platyhelminthes. Platyhelminthes have an incomplete gut whereas nematodes have a complete one. Unlike in nematodes, Platyhelminthes have flame cells to do the excretory functions. Unlike flatworms, most roundworms are microscopic.