B A zygote undergoes cell ^division to produce a hollow ^sphere of cells called ______.^A) Gastrula B) Blastula ^A In mammals, ectoderm cells ^will form the outer layer of ^skin. ^A) True B) False ^B The alimentary tract ^develops from which germ ^layer? ^A) Ectoderm B) Endoderm ^A Sponges may reproduce ^asexually by forming ^gemmules or by _______. ^A) Buds B) Collar Cells ^A Sponges and Hydras are ^able to regenerate missing ^parts when damaged. ^A) True B) False ^A What are the stinging cells ^of the Hydra called? ^A) Nematocysts B) Choanacytes^ ^B The hydra possesses a higher ^specialization than the ^sponge due to its _______. ^A) Spicules B) Nerve Net ^B A marine invertebrate ^which is not free-swimming ^is said to be ________. ^A) Spiracle B) Sessile ^A Hydras attach themselves ^to rocks by their _______. ^A) Basal Disks B) Buds ^ ^B Specialized tissues ^develop from three germ ^layers. One is the: ^A) Mesoglea B) Mesoderm ^ ^ ^ ^ ^
