Animals = invertebrates and vertebrates (95% of all animals are invertebrates)

Animal Characteristics The bodies of animals are multicellular. It is responsible for the enormous variety of animals. All animals are heterotrophs. Most animals reproduce sexually, and some can also reproduce asexually.

In all but the simplest animals, there is a division of labor among cells called cell specialization. (This aids internal body organization.) Most animals can move about their environment.

One or Two Houses Monoecious – (“One House”) hermaphroditic animals – both male and female sex organs Dioecious – (“Two Houses”) separate sexes

Body Symmetry: None – Sponge (asymmetrical) Radial –similar parts branch in all directions. -Hydra, Jellyfish,

Pentaradial

Bilateral, two similar halves in either side of a central plane of symmetry moth, primates etc. Bilaterally symmetrical

Animals tend to exhibit cephalization. Cephalization: – concentration of sensory and brain structures in the anterior end (a cephalized animal has a head). The more complex an animal the more pronounced the degree of cephalization. It is an advantage because a more complex animal can respond to an environment more quickly.

Germ Layers:- (p 683 – 684) As a result of gastrulation, three primary layers form: (Fundamental tissue types found in embryos of all animals except sponges which have no true tissues) Endoderm – inner layer Mesoderm – middle layer Ectoderm – outer layer

endoderm inner layer - The archenteron, surrounded by endoderm forms the throat passage, gills, lungs and gut and associated organs such as pancreas, and liver. (lines digestive tract & much of respiratory system.)

ectoderm – outer layer – forms skin, hair, nails, and nervous system

mesoderm which forms between the other layers, forms skeleton, muscles, inner layer of skin, circulatory system, and lining of the body cavity (also reproductive system & excretory system).

Deuterostomes & Protostomes: Deuterostomes – “second mouth” radial cleavage of developing embryo, blastopore (indentation of the blastula) becomes the anus, second opening becomes the mouth. (examples - echinoderms – such as star fish, chordates and vertebrates as well)

Protostomes – “first mouth” spiral cleavage of developing embryo, blastopore becomes the mouth, second opening becomes the anus (occurs in most animal phyla).

Animals & Body Cavities: (pg 686) acoelomate – no body cavity example: flatworms

pseudocoelomate – “false body cavity” mesoderm lines an endodermic gut suspended in a fluid filled coelom cavity.

coelomate – true body cavity - An endodermic gut – is surrounded & supported by a body cavity of mesoderm. The mesoderm forms tissues or attachments for organs located in the true body cavity, such as the liver, lungs, etc. Mollusks, arthropods, chordates, & echinoderms are coelomate animals.

coelom a) a true hollow, fluid-filled cavity completely surrounded by mesoderm. b) The muscles of the body wall are separated from those of the gut. c) The body walls can contract without hindering t movement of food in the gut (digestive tract).