Intro into Eukaryotes and Animals

five characteristics of an animal

multicellular, eukaryote, heterotroph, move at some point in life, no cell wall

how do we study innovations?

fossils, comparative morphology, comparative development, and comparative genomes

multicellularity

composed of many cells that adhere to each other and do not express the same genes

endoderm

internal tissue layers- digestive system

ectoderm

external tissue layer- skin and nervous system

mesoderm

middle tissue layer- muscles, bone, organs, and circulatory system

dipoblast

two tissue layers- endoderm and ectoderm

triploblast

three tissue layers

symmetry

HOX genes determine anterior and posterior ends; other genes determine dorsal-ventral axis

asymmetry

no plane of symmetry

bilateral

two planes of symmetry

radial

multiple planes of symmetry

coelom

fluid filled cavity completely lined with mesoderm

acoelom

no fluid filled cavity, block of mesoderm

pseudcoelom

fluid filled cavity partially lined with mesoderms

protostome

mouth first- spiral cleavage is unique

deuterostome

anus first, mouth second- radial cleavage

segmentation

body or part of body divided into series of similar structures; segment identity determined by HOX genes

nerve net

neurons are diffuse instead of being clustered into large ganglia or tracts; radially symmetric and bilateral symmetric animals

CNS

aggregation of large numbers of neurons into ganglia; bilaterally symmetric animals

cephalization

head where structures for feeding, sensing environment, and processing information are concentrated; bilaterally symmetric animals