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).