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Chapter 32 – Animal Diversity. 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 - PowerPoint PPT Presentation
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Chapter 32 – Animal
Diversity
32.1 – Animals are multicellular, heterotrophic eukaryotes
with tissues that develop from embryonic layers
Animals have the following characteristics:Multicellular heterotrophsMost have muscle & nervous tissueMost reproduce sexually, with a flagellated sperm & a large egg which unite to form a diploid ZYGOTEThe diploid stage dominates the life cycle1.3 million living species
VocabZygote
Fertilized eggCleavages
Successive mitotic cell divisions without cell growth between cycles
BlastulaHollow ball of cells surrounding a cavity called the blastocoel
GastrulaAs the blastula is “punched in”, the embryonic tissue layers will form
EctodermThe outer tissue layer
Endoderm The inner tissue layer
BlastoporeOpening into the gastrula Becomes the mouth in protosomesBecomes the anus in deuterostomes
ArchenteronBlind pouch formed by gastrulation
Some animals have larvaeImmature form distinct from the adult stage they will undergo metamorphosis
Animals share HOX GENESUnique family of genes that play important roles in developmentCan produce a wide diversity of animal morphology
32.3 – Animals & Their “Body Plans”
SymmetryNone (sponges)RadialBilateral
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
TissuesAnimal body plans vary according to the organization of the animal’s tissuesTissues are collections of specialized cells isolated from other tissues by membranous layersDuring development, three germ layers give rise to the tissues and organs of the animal embryo
Ectoderm is the germ layer covering the embryo’s surfaceEndoderm is the innermost germ layer and lines the developing digestive tube, called the archenteron
Mesoderm is the middle layer
Diploblastic animals have ectoderm and endodermTriploblastic animals also have an intervening mesoderm layer; these include all bilaterians
Body CavitiesMost triploblastic animals possess a body cavity
3 types:1) A coelomate possesses a true body cavity
Derived from mesodermFilled with fluidSeparates an animal’s digestive tract from the outer wallEarthworms
2) PseudocoelomateTriploblastic animalsCavity formed from mesoderm & endodermRoundworms
3) AcoelomatesNo cavities between alimentary canal & outer wall of bodyFlatworms
Functions of Body Cavities
1) Cushion suspended organs2) Act as a hydrostatic skeleton3) Enable internal organs to grow & move independently
Protostome & Deuterostome Development
3 major differences:1) Cleavage2) Coelom formation3) Fate of the blastopore
Cleavage:P = begins with spiral, determinate cleavageD = radial, indeterminate cleavage
Coelom Formation:Begins in the gastrula stage
P = coelom forms from splits in the mesodermD = 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