Intro to Animals

the embryonic/germ layers

• have 2 germ layers (ectoderm and endoderm)
• includes cnidarians (jelly fish and anemone) and comb jellies

• have 3 germ layers (ecto, endo and mesoderm)
• includes: flatworms, arthropods (have an exoskleteton), vertebrates and others

• a true body cavity (derived from mesoderm)
• fluid or air filled space
• internal organs are suspended in

body cavity derived from meso and endoderm

Pseudocoelomate

acelomates

Protostome and deuterostome

• spiral (cells are not parallel)
• have a determinate cleavage
• fate of cell is determined early

• Radial (form parallel/perpendicularly)
• indeterminate cleavage
• each cell can complete an embryo (can from identical twins)

• Animalia: monophyletic
• All animals share the common ancestor colonial flagellate
• sponges are basal animals
• Eutetazoa is a clade with true tissues
• most animal phyla belong to the clade Bilateria
• chordates belong to the clade Deuterostomia

old: divides bilaterian into the clades deuterostomes and protostomes

New uses three clades: deuterostomia, ecdysozoa and Lophotrochozoa

• old= morphology
• new= molecular evidence

choanoflagellates

• Heterotrophic protist
• single flagellum surrounded by collar of microvilli
• fingerlike projections of cell membrane
• similar cell morphology to sponges

• complex life, including those with skeletons appeared (most major phyla appeared)
• 535-525 mya
• during Paleozoic era (542-251 mya)

• 251-65.5 mya
• first mammals emerged
• dinosaurs were dominant terrestrial vertebrates
• coral reefs emerged
• plants and insects became more diverse

• 65.5 mya-present
• began with mass extinction of animals
• mammals became dominant
• global cooling