Answer:
A unicellular organism is formed by a single cell. ... The circulation in unicellular organisms is carried out by the movement of the cytoplasm of the cell called cyclosis.
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Answer:
Helper T cells are arguably the most important cells in adaptive immunity, as they are required for almost all adaptive immune responses. They not only help activate B cells to secrete antibodies and macrophages to destroy ingested microbes, but they also help activate cytotoxic T cells to kill infected target cells.
Explanation:
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete cytokines that regulate or assist the immune response.
I think the answer is sexual reproduction to carry out selective breeding.
Answer:
I. evolved from ancestors that walked
Explanation:
Whales and pythons have vestigial structures, which are structures (hind legs) which are no longer useful to them since they have evolved. The ancestors of the whale and python did use the hind legs but over generations the whale and snake have adapted to new environments and they no longer need them.
