Hemichordates Live

question 6

Multiple Choice

Hemichordates live

• A)in the open ocean with a similar lifestyle to arrow-worms (which is why they are considered related).
• B)in kelp beds.
• C)in deep oceans,especially the rich and oxygenated Arctic Ocean.
• D)on the bottom of shallow oceans,sometimes colonially and in secreted tubes.
• E)just around thermal vents.

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Definitions:

Secretion

The process by which substances are produced and discharged from a cell, gland, or organ for a particular function in the organism or for excretion.

Terminal Cisternae

Enlarged areas of the sarcoplasmic reticulum around the myofibrils of muscle cells, involved in calcium ion storage.

T-tubules

Tubular extensions of the plasma membrane that penetrate into the center of skeletal and cardiac muscle cells, facilitating the transmission of electrical impulses.

Sarcolemma

The sarcolemma is the fine transparent tubular sheath that envelops the fibers of skeletal muscles.