 Introduction to Animals Chapter 34

What makes an animal an animal?  Multicellular  Heterotrophy  Sexual reproduction & development  Movement

Body Symmetry  Radial symmetry- a body plan in which the parts are organized in circle around an axis.

Body Symmetry  Bilateral symmetry- two similar halves on either side of a central plane

Body Symmetry  Asymmetry- no organization

Body Cavity  Body cavity- fluid filled space that forms between the digestive tract and the outer wall of the body.  Aids in movement and acts as a reservoir and medium of transport for nutrients and wastes.

Animal Kingdom Invertebrates  Animals without a Backbone or Spinal Column Vertebrates  Animals with a Backbone or Spinal Column: (All these animals are in the phyla Chordata and the subphyla Vertebrata.)

Vertebrates  Vertebrates are a subphylum of chordates.  Chordates comes from notochord which is a firm, flexible rod of tissue located in the dorsal part of the body.  In vertebrates the notochord develops into a brain and spinal cord.

Invertebrates  Most invertebrates have bilateral symmetry which is an adaptation to a more motile lifestyle.  It allows for cephalization.  Radial symmetry are not very motile and drift along, allows for more access to food sources.

Cell to Embryo Cleavage- the series of cell divisions that occurs immediately following fertilization Blastula- dividing cells become a hollow ball Gastrulation- transforms the blastula into a multilaytered embryo called the gastrula

Germ Layers  Ectoderm- outer layer of the gastrula  Forms the outer layer of skin, hair, nails and the nervous system  Mesoderm- middle layer  Forms the skeleton, muscles, inner layer of skin, circulatory system and the lining of the body cavity  Endoderm- inner layer  Forms the urinary and reproductive systems, and the digestive tract; pancreas, liver, lungs and gills