The outer layer of the sponge is covered by flattened cells that sometimes contract in response to potentially harmful stimuli to protect the inner cells of the sponge. One type of inner cells are , flagellated and collared cells that help circulate water through the sponge and collect food particles. Various types of cells are found in the mesohyl and may secrete structural components such as spicules or spongin fibers

Embryonic stem cells are cells derived from an embryo. these cells can be used to create new tissues for patients suffering from certain illnesses and disorders. which statement best summarizes why the use of embryonic stem cells could be seen as unethical? a. some people consider embryos to possess rights equal to those of fully developed human beings. b. extracting stem cells from embryos is a very energy-intensive process, which consumes resources that could be used elsewhere. c. embryos are difficult to obtain, so the monetary cost of using them for research outweighs their benefit. d. the process of extracting stem cells from embryos generates biohazardous waste that cannot be safely disposed of.