chordate animals
31Tunicate — Temporal range: Cambrian stage 3–Recent …
32Deuterostome — Deuterostomes Temporal range: Late Ediacaran – Recent …
33animal — animalic /an euh mal ik/, animalian /an euh may lee euhn, mayl yeuhn/, adj. /an euh meuhl/, n. 1. any member of the kingdom Animalia, comprising multicellular organisms that have a well defined shape and usually limited growth, can move… …
34Cambrian explosion — The Cambrian explosion or Cambrian radiation was the seemingly rapid appearance of most major groups of complex animals around Ma|530, as evidenced by the fossil record. [http://www.ucmp.berkeley.edu/cambrian/camb.html The Cambrian Period] ]… …
35animal development — Introduction the processes that lead eventually to the formation of a new animal starting from cells derived from one or more parent individuals. Development thus occurs following the process by which a new generation of organisms is produced by …
36Fish — are aquatic vertebrate animals that are typically ectothermic (previously cold blooded), covered with scales, and equipped with two sets of paired fins and several unpaired fins. Fish are abundant in the sea and in fresh water, with species being …
37skeleton — skeletonless, adj. skeletonlike, adj. /skel i tn/, n. 1. Anat., Zool. the bones of a human or an animal considered as a whole, together forming the framework of the body. 2. any of various structures forming a rigid framework in an invertebrate.… …
38nervous system — Anat., Zool. 1. the system of nerves and nerve centers in an animal or human, including the brain, spinal cord, nerves, and ganglia. 2. a particular part of this system. Cf. autonomic nervous system, central nervous system, peripheral nervous… …
39endocrine system — Group of ductless glands that secrete hormones necessary for normal growth and development, reproduction, and homeostasis. The major endocrine glands are the hypothalamus, pituitary, thyroid, islets of Langerhans, adrenals, parathyroids, ovaries …
40Ordovician Period — Interval of geologic time, 490–443 million years ago, the second oldest period of the Paleozoic Era. It follows the Cambrian and precedes the Silurian. During the Ordovician, many of the landmasses were aligned in the tropics. Life was dominated… …
