Kingdom Animalia

The World of Animals

Kingdom Animalia

• Animal life began in the Precambrian seas– Approx. 750 million years ago

• Major characteristics of Kingdom Animalia– Multicellular– Heterotrophic – by ingestion– Eukaryotic– No cell wall around cells

Kingdom Animalia

– Collagen and other structural proteins found in and outside of cells

– Unique cellular junctions – tight junctions, gap junctions, desmosomes

– Tissues (in all but one phyla) for impulse conduction and movement

– Sexual reproduction, with diploid stage dominating life cycle

Kingdom Animalia– Sexually formed zygote undergoes cleavage

• Blastula gastrula etc..

Kingdom Animalia

– Hox genes present – regulatory genes responsible for the transformation of a zygote to an animal of a specific form.

Evolution of animals • Most taxonomists now agree

that animals evolved from a colonial, flagellated protistduring the late Precambrian– It is speculated that this protist

was related to the choanoflagellates

Traditional systematics uses body plans (called grades) to group animals

• Body plans are formed by the presence or absence of:

1. Tissues• Grade Parazoa – no true tissues• Grade Eumetazoa – with true tissues

2. Symmetry• Grade Radiata –

radial symmetry• Dorsal, ventral

• Grade Bilateria –bilateral symmetry• Dorsal, ventral,

anterior, posterior head

• Cephalization –evolutionary trend toward the concentration of sensory structures towards the anterior of the animal.

3. End result of gastrulation• Radiata – gastrulation produces two tissue layers

(diploblastic)• Ectoderm – covering of animal and, in some, central nervous

system• Endoderm – lining of digestive tract (archenteron)

• Bilateria – gastrulation produces three tissue layers (triplobalstic)

• Ectoderm• Endoderm• Mesoderm – muscle and other organs

4. Solid or tube body – presence of cavities in

Bilateria– Acoelomate –

(a=without; koilos=hollow)

– Pseudocoelomate(pseudo=false) –cavity, filled with fluid not lined completely with mesoderm tissue

– Coelomate – fluid filled cavity completely lined with mesoderm tissue

5. Protostome –Deuterostomein Coelomates

The current classification of the animal phyla is a hotly debated topic among

zoologists• Traditional zoologists tend to lean towards

morphological evidence, while new technologies in molecular biology have produced slightly different phylogenetictrees.

• For this course we will utilize the traditional classification system to study the major animal phyla

Traditional view of animal

classification

Kingdom Animalia (with approx. number of extant species)

• Phylum Porifera – the sponges; 5,500 spp.• Phylum Cnidaria – the cnidarians; 10,000 spp.• Phylum Platyhelminthes – the flatworms; 20,000 spp.• Phylum Nematoda – the roundworms; 25,000 spp.• Phylum Annelida – segmented worms; 16,500 spp.• Phylum Mollusca – the mollusks; 93,000 spp.• Phylum Arthropoda – the arthropods; 1,000,000+ spp.• Phylum Echinodermata – the echinoderms; 7,000 spp.• Phylum Chordata – the Chordates; 52,000 spp.

Animal Classificationfor

BIOL1407