Evolution of vertebrates

characteristics animals share

• multicellular

• heterotrophic

• eukaryotic

• no cell wall

• ingestion and digestion tract

animal development

• begin life as a single cell divides and forms blastula

• blastula becomes inverted through gastrulation

• form future digestive tract (mouth / anus)

Durring stage

embryonic tissues (germ layers form)

germ layers: ectoderm (skin) endoderm (digestive) mesoderm (other organs)

sponges

• most have no true tissue layers

• most are asymmetrical

• some inverts are radially symmetrical

• many inverts and verts are bilateral symmetrical

diploblastic

2 germ layers (endoderm and ectoderm)

• jelly fish and coral

triploblastic

most inverts and all verts have mesoderm —> 3 layers of germ layers

coelom

• fluid filled body cavity within mesoderm where some organs are housed

• some inverts have mesoderm but are acoelomates (EX: flatworms)

• some inverts and all verts are coelomates

protostome

blastopore forms mouth first

deuterostomes

blastopore forms anus first

What is a chordate?

-bilateral, 3 embryonic tissue, coelom, deuterostomes (pleiomorphism)

• notochord, dorsal hollow nerve cord, past anal tail, endostyle (synapomorphies)

notochord

• found in embryonic stage

• - between digestive and nerve cord

• replaced with vertebral column

dorsal hollow nerve cord

ventral solid nerve cord

• in verts, develops into brain and spinal cord

post anal tail

body extends past anus

-bone/cartilage and muscle

endostyle/ thyroid gland

• develops as pocket of the pharynx

• structure that binds iodine to creates thyroxine hormone
  - regulates body metabolic rate