Introduction to AnimalsChapter 34

What makes ananimal 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