650 million years ago to 530 million years ago, animal phyla {invertebrate} evolved from protozoa.
types
Invertebrate types include anthozoans, crustaceans, ctenophors, echinoderms, insects, mollusks, stars, and worms. Lower invertebrates include ctenophors, coelenterates, flatworms, gastrotricha, proboscis worms, rotifers, roundworms, sipunculans, and sponges. Higher invertebrates include acorn worms, annelids, arthropods, clictors, lampshells, molluscs, moss animals, onychophora, phoronids, and starfish.
stimuli
Invertebrates sense chemical stimuli. Invertebrates can learn by touch but cannot distinguish shapes. Invertebrates have no joint receptors or proprioceptors, do not know muscle contraction or relaxation degree, and do not know body position. Invertebrates do not feel motivations, such as hunger or thirst.
learning
Invertebrates can learn to manipulate objects.
650 million years ago to 530 million years ago, early invertebrates {lower invertebrate} {marine invertebrate} {marine metazoa} had receptors, nerves, muscles, and glands. Enzyme, transmitter, hormone, messenger, and electrical-signal patterns coordinated behavior.
600 million years ago, body structures {coelom, invertebrate}| had a mesoderm cavity {schizocoelom} or had gut-cavity pouches {enterocoelom}.
Later invertebrates {Bilateria} were bilaterally symmetric [-590000000], with front and back and right and left. Bilateria include protostomes and deuterostomes. Body parts were in pairs, one right and one left {bilateral symmetry, body}, and body had front and back.
The first Bilateria (Urbilateria) included rounded flatworms {roundish flat worm}| (RFW). Chordates split from roundish flatworms 530 million years ago.
530 million years ago to 440 million years ago, later invertebrates {higher invertebrate} had ganglia, separate mouth and anus, muscular guts, developed circulatory systems, and coeloms. Chordates split from roundish flatworms 530 million years ago. For example, arthropods have nervous system on front, and vertebrates have nervous system on back. Both animal groups use same two genes for front and back, but chordate dorsal side is homologous with arthropod ventral side.
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0225