Kingdom Animalia
Characteristics
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no cell walls
sexual reproduction is common
most are mobile
multicellular, heterotrophic
Specialized tissue develop in the embryo during GASTRULATION
A fertilized egg divides and becomes a BLASTULA (hollow ball of cells) which then
pinches inward to form a GASTRULA which has the 3 germ layers
Endoderm - becomes the lining of the gut
Ectoderm - becomes the skin and outer layer, including nervous tissue
Mesoderm - the middle layer, the muscles and bones
The common ancestor of animals is thought to be the CHOANOFLAGELLATES, from
which all major animal groups branch from
Definitions
Parazoa - sponges, organisms with no true tissues (cells within sponges are called
Choanocytes, which absorb nutrients)
Eumetazoa - all other animals with true tissues
Radiata - animals with radial symmetry (hydra, jellyfish)
Bilateria - animals with bilateral symmetry ( dogs, worms, humans). They have a top
(dorsal) and a bottom (ventral), front end (anterior) and behind (posterior)
Acoelomates - have no blood vascular system, and lack a cavity between the gut and
outer body wall (flatworms)
Pseudocoelomates - animals that have a fluid filled body cavity, but not enclosed by
mesoderm
Coelomates - have a true coelom (body cavity)
Protostomes - first embryonic indentation becomes the mouth Ex. annalids, arthropods,
mollusks
Deuterostomes - the first indentation develops into the anus Ex. chordates and
echinoderms (starfish)
Major Animal Taxa
1. Porifera - sponges
2. Cnidaria - jellyfish, hydra. They lack a mesoderm and are radially symmetrical
3. Platyhelminthes - flatworms (flukes, planarians, tapeworms), cephalization (to have a
head end)
4. Rotifera - tiny worm like creatures, with a complete digestive tract
5. Nematoda - roundworms
6. Molluska - clams, squid, snails, slugs.
7. Annalids - segmented worms, earthworms and leeches
8. Arthropods - have hard exoskeletons made of chitin. Lobsters, crabs, insects, isopods
9. Echinodermata - starfish
10. Chordata - includes a couple of nonvertebrates (lancelets and sea squirts) and then all
the vertebrates
There are four features common to chordates
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dorsal nerve cord - forms the nervous system and becomes the brain and spinal
cord in vertebrates
notochord - long support rod that is replace by bone in most
Pharyngeal slits - slits in the pharynx area that become respiratory structures
(gills)
Tail - extension past the anus, though it is lost in most