BIOL 1002 Midterm: EXAM #2
Document Summary
Animals possess all of the following characteristics. They are motile at some point in the life cycle. They are able to respond rapidly to external stimuli. Tissue: are groups of similar cells that carry out a specific function (e. g. muscle: difference b/w radial and bilateral symmetry. Symmetrical animals have upper (dorsal) surface and lower (ventral) surface. Animals with radial symmetry can be divided into roughly equal halves by any plane that passes through the central axis. Animals with bilateral symmetry can be divided into mirror-image halves only along one plane that runs down the midline: the major animal phyla. Animals probably originated from ancestral protistists protists. Present day biologists recognize 27 phyla of animals. Most animals are invertebrates (lack a vertebral column) Less than 3% of all known animals are vertebrates (possess a vertebral column) Sponges belong to the phylum porifera and are found in most marine environments.
