Chapter 32 – Animal Diversity

Animals have the following characteristics: 32.1 – Animals are multicellular, heterotrophic eukaryotes with tissues that develop from embryonic layers Animals have the following characteristics: Multicellular heterotrophs Most have muscle & nervous tissue Most reproduce sexually, with a flagellated sperm & a large egg which unite to form a diploid ZYGOTE The diploid stage dominates the life cycle 1.3 million living species

Vocab Zygote Cleavages Blastula Fertilized egg Successive mitotic cell divisions without cell growth between cycles Blastula Hollow ball of cells surrounding a cavity called the blastocoel

Gastrula Ectoderm Endoderm As the blastula is “punched in”, the embryonic tissue layers will form Ectoderm The outer tissue layer Endoderm The inner tissue layer

Blastopore Archenteron Opening into the gastrula Becomes the mouth in protosomes Becomes the anus in deuterostomes Archenteron Blind pouch formed by gastrulation

Some animals have larvae Immature form distinct from the adult stage they will undergo metamorphosis Animals share HOX GENES Unique family of genes that play important roles in development Can produce a wide diversity of animal morphology

32.3 – Animals & Their “Body Plans” Symmetry None (sponges) Radial Bilateral

Radial occurs in: Jellyfish Any cut through the central axis would produce mirror images

Bilateral occurs in - Lobsters Humans Have a right & left side Single cut would divide the animal into 2 mirror image halves Dorsal side (back) Ventral side (belly) Anterior (head) Posterior (tail) Cephalization

Tissues Animal body plans vary according to the organization of the animal’s tissues Tissues are collections of specialized cells isolated from other tissues by membranous layers During development, three germ layers give rise to the tissues and organs of the animal embryo

Ectoderm is the germ layer covering the embryo’s surface Endoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron Mesoderm is the middle layer

Diploblastic animals have ectoderm and endoderm Triploblastic animals also have an intervening mesoderm layer; these include all bilaterians

Body Cavities Most triploblastic animals possess a body cavity 3 types: 1) A coelomate possesses a true body cavity Derived from mesoderm Filled with fluid Separates an animal’s digestive tract from the outer wall Earthworms

2) Pseudocoelomate Triploblastic animals Cavity formed from mesoderm & endoderm Roundworms

----- Meeting Notes (3/30/12 15:00) ----- Mr.Norman joey joseph donald

3) Acoelomates No cavities between alimentary canal & outer wall of body Flatworms

Functions of Body Cavities 1) Cushion suspended organs 2) Act as a hydrostatic skeleton 3) Enable internal organs to grow & move independently

Protostome & Deuterostome Development 3 major differences: 1) Cleavage 2) Coelom formation 3) Fate of the blastopore

Cleavage: P = begins with spiral, determinate cleavage D = radial, indeterminate cleavage

Begins in the gastrula stage Coelom Formation: Begins in the gastrula stage P = coelom forms from splits in the mesoderm D = coelom forms from mesodermal outpocketings of the archenteron

Fate of the Blastospore: P = mouth forms from the blastopore D = mouth forms from a secondary opening