"Their habitats may range from the surface water to the ocean trenches. Marine organisms are classified<span> by how they move and where they live."
Hope This somehow helps~
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A. I am pretty sue that the answer is A.
Responding to the environment.
Answer:
foreign cells.
Explanation:
Humoral and Cell-Mediated Immune Responses The immune system distinguishes two groups of foreign substances. One group consists of antigens that are freely circulating in the body. These include molecules, viruses, and foreign cells.
Chordates
Chordates have the 4 unique characteristics, postanal tail, notorchord, pharyngeal gill slits and dorsal-hollow nerve cord. Lancelets is the group of chordates that has a notochord and includes separate males and females.
Lancelet exhibits the four basic characteristics of phylum Chordata. It has a dorsal nerve, a notochord, a post annul tail, and pharyngiall gill slit.
Jawless fish, cartilaginous fish, and bony fish have notochord when they were still young but it was replaced by a vertebral column as they mature.
<span>Lancelets are included in the subphylum cephalochordata. Cephalochordates are gonochoristics. It means that the sexes are separate. Both sperm and eggs cells are released in the water where fertilization occurs.</span>