ANIMAL KINGDOM

MAIN CHARACTERISTICS Multicellular, eukaryotic, heterotrophs Specialized cells; most have tissues Response to stimuli by nervous and muscular tissue Most capable of locomotion; few sessile Most diploid and reproduce sexually

ANIMALS LIVE IN DIVERSE HABITATS Marine Origin of animal life Provides buouyancy Body fluids isotonic to environment Plankton, nekton, sessile

Freshwater Cells hypertonic to environment Osmoregulation More challenging than marine: food, oxygen, sunlight, temperature

Terrestrial – Threat of Dessication : Body covering to reduce evaporation Respiratory organs deep in body cavity Reproduction Eggs Means of thermoregulation

EVOLUTION OF ANIMALS Common protist ancestor: choanoflagellate Evo-Devo Diversity Hox genes

CHARACTERISTICS USED TO FURTHER CLASSIFY ANIMALS…

BODY SYMMETRY Asymmetry Radial symmetry Bilateral symmetry

CEPHALIZATION Concentration of sensory structures in a head Nerve cells concentrate in head  brain Nerve cord extends toward rear Found in bilaterally symmetrical organisms Adaptations to locomotion

EMBRYONIC DEVELOPMENT Zygote Undergoes cleavage Develops into blastula Undergoes gastrulation

Radial Parallel or right angles to axis Indeterminate Spiral Diagonal to axis Determinate 2 TYPES OF CLEAVAGE PATTERNS

GERM LAYERS Form in all animals except sponges 3 layers: Ectoderm – outer layer Endoderm – inner layer Mesoderm – middle layer DIPLOBLASTIC TRIPLOBLASTIC

OVERVIEW OF ANIMAL TYPES Sponges – loose arrangement of different types of cells; do not have tissues Diploblastic Cnidarians and Ctenophores Only have 2 germ layers Triploblastic Have 3 rd germ layer - mesoderm

Triploblastic organisms further grouped base on presence and type of coelom – fluid-filled cavity between digestive tract and body wall BODY CAVITY

BODY CAVITY CLASSIFICATION Acoelomates Solid body; no cavity Flatworms and ribbon worms

Pseudocoelomates Have a body cavity but it is not completely lined with mesoderm Nematodes and rotifers Coelomates Tube-within-a-tube body plan Coelom completely lined with mesoderm Comparison

2 MAIN GROUPS OF BILATERAL ANIMALS: During gastrulation, group of cells move in forming sac … embryonic gut If blastopore becomes mouth – organism is a protostome If blastopores becomes anus - deuterostome

PROTOSTOMES Flatworms, annelids, arthropods, mollusks Spiral, determinant cleavage Schizocoely DEUTEROSTOMES Echinoderms and chordates Radial, indeterminate cleavage Enterocoely PROTOSTOMES VS. DEUTEROSTOMES

Fig. 29-7, p. 627