You are watching: Which animal phylum lacks true tissues?
Most animals...have muscle and nerve cells, room diploid (embryo is created by haploid sex cells), thrive through a collection of developmental stages.
Animal advancement from the Cambrian Explosion: pets probably advanced from a early american flagellated protist that lived in Precambrian seas about 600-700 million year ago.
Under the Cambrian Period, about 542 million year ago, animal diversity exploded and also all current body develops evolved.
Theories the Cambrian Explosion: -Predator-prey theory, pets continued to evolve and also adapt to feed, move, and ultimately survive.-Evo-devo theory, the advancement of master manage genes in organisms (genes managing growth and adulthood features in animals).
Animal Phyla: Sponges (lack true tissue), Cnidarians (have radial symetry, not bilateral symmetry), Molluscs, Flatworms, Annelids, Roundworms, Arthropods, Echinoderms, Chodates (have a spinal cord: chordata).
Radial Symmetry: an pet that has identical human body structures roughly a main axis (jellyfish).Bilateral Symmetry: symmetry halves that the human body when separation in two (humans, starfish).
Body Cavity Formations: Pseudocoelem (partial lining of tissue acquired from the mesoderm), True Coelem (complete lining of tissue in the human body cavity), Aceolem (no lining of the human body cavity).
Songes: absence true tissues.Choanocytes: cells that draw water and also nutrients right into sponge.Amoebocytes: cells the digest food, carry nutrients, and also prodcue bones fibers.
Cnidarians: existence of body tissues, show radial symmetry, have tentacles through stinging cell (cnidocytes), has actually a central gastrovascular area v one human body opening.
Cnidarian body Plans:-Polyp kind (sessile, no locomotion, tentacles on top) (hydra)-Medusa kind (tentacles on bottom, provided for locomotion) (jellyfish)
Molluscs: have a tough outer covering protecting your soft inner bodies, numerous have a radula (tongue like body organ that scrapes up food).
Molluscs human body Parts: Foot (muscle used for movement), Visceral mass (houses inner organs), and also the Mantle (secretes the outer shell).
Major Mollusca Groups: Gastropods (snail, slugs), Bivalves (clam, oyster), and also Cephalopods (squids).
Gastropods have one single, spiraled external shell.Bivalves have actually a hinged shell.Cephalopods have actually a pronounced brain and tentacles because that movement and hunting.
Flatworms (Phyla Platyhelminthes): have no body cavity (aceolomates), room the most basic bilateral animals, and can be parasitic or cost-free living in moist habitats. Examples include tapeworms and also blood flukes.
Planarian: free living flatworm v a very branched digestive mechanism for the optimum absorb of nutrients.
Tapeworms: have actually no cradle system, they simply absorb their nutrient from a host.Blood Fluke: likewise has extremely branched digestive device like the planarian.
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Annelids: identified by human body segmentation, have a coelem (completely lined human body cavity), and also a complete digestive street (two body openings, food moves just one direction).