Which Feature Characterizes the Sea Urchin Archenteron

question 96

Multiple Choice

Which feature characterizes the sea urchin archenteron?

• A) It requires the primary mesenchyme to form.
• B) It is derived from mesoderm.
• C) It is elongated by contraction of filopodia extending from secondary mesenchyme.
• D) The anus forms as a secondary opening.
• E) Its open end is the blastopore, which becomes the mouth.

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Definitions:

Absolute Threshold

The absolute threshold refers to the smallest level of stimulus intensity needed for the stimulus to be correctly detected at least half the time.

Difference Threshold

The minimum difference in stimulation that a person can detect 50 percent of the time, also known as the just noticeable difference.

Stimulus

Anything in the environment that is detectable by an organism and can elicit a physical or behavioral response.

Receptor Cells

Receptor cells are specialized cells found in the senses (like those for taste, smell, and sight) that respond to specific stimuli by triggering an electrical signal.