animals exam2

Mesoderm cells

Germ layers that form in development and line things.

Acoelomates: no mesoderm

Pseudocielomates: mesoderm in cavity but not organs

Coelomates: cavity and organs surrounded by mesoderm

Segmentation

No segments: nematodes

Hella segments: annelids and arthropods

Some segments: normal animals

Metamerism

Repeating body segments to generate new body plans in evolution

Imagine spine or centipedes

Nervous system

No centralized nervous system: sponge

Diffuse nervous nerve nets: cnidarians

Organized into ganglia in different body sections: arthropods

Vertebrates have a highly organized central and peripheral nervous system

Polytomy

A node on phylogeny where more than 2 lineages descent from one node.

Animals split into no nerves (sponge) nerve nets (insects and ish) and complex nerves (normal animals)

Sister Taxa to all other animals

Believed to be either sponges (no nerves muscles or gut) or ctenphores (do have nerves muscles and gut)

Sponge sister

More parsimonious

(Simpler so they like this one more)

Ctenophore sister

New data says this has more support because sponges are more similar to other animals than ctenophores (chromosomally)

Protostomes

Opening develops first into the mouth as an embryo (annelids mollusks and arthropods)

Deuterostomes

Opening first develops into butt hole (vertebrates echinodermata hemichordates etc)

Radially symmetrical animals are diploblastic (2 cell layers)

Endoderm (inner layer)

Lung cells thyroid cells digestive Cells

Ectoderm (outer layer)

Skin cells, neurons, pigments

Bilaterally symmetrical animals are triploblastic (3 cell layers)

Ectoderm (outside layer)

Endoderm (inner layer)

Mesoderm (middle layer)

Cardiac skeletal and smooth muscle

Tubule and red blood cells

Triploblast blastopore development

Diploplast vs deuterospome blastopore

Proto vs deuterostomes digestive and nerve cord

Protostomes:

Dorsal (on back) digestive tract and heart nerve cord is ventral (on belly)

Deuterostomes

Ventral digestive tract and heart dorsal nerve cord