What is an animal?

• Mulcellular heterotrophs: feed by ingeson. • How does this differ from plants, fungi, prosts? What is an animal?

• Carbohydrates stored as glycogen • Polysaccharide of glucose • (no, you do not need to know this structure) What is an animal?

• No cell walls • Cells supported by structural proteins: collagen – Extracellular matrix, supports ssues, gives cells structure from outside – Triple-helix structural protein What is an animal?

• Nerve and muscle ssue • Impulse & movement What is an animal?

• Generally, most have sexual reproducon from anisogamous or heterogamous gametes. What is an animal?

Development • Egg + Sperm ⇒ • Zygote ⇒cleavage ⇒ • Blastula ⇒ • Gastrula ⇒ • Larva or juvenile ⇒ • Adult

• This development regulated by Hox genes Animal Diversity • The vast majority of animal species are marine • Only truly terrestrial* animals come from 5 phyla – Mollusca – Annelida – Onychophora – Arthropoda – Chordata • *Does not include internal parasites nor taxa needing constant external moisture Animal Origins

• Monophylec • Sister taxon Choanoflagellates (prost protozoan) • Colonial, flagellated prost ancestor Animal Origins

• Gastrula-like infolding into two layers • Increased specializaon of cells and ssues beginning with somac vs reproducve Animal Origins • Molecular evidence: – Suggests divergence from fungi ~1 bya – Common ancestor of animals 675-875 mya

Animal Origins

• Fossil evidence: – Possible trace fossils ~900 mya – Ediacaran fauna 610-550 mya • Animals??? – Definite animal fossils (about 1/2 of phyla) appear during Cambrian Explosion.

Animal Origins

The Cambrian Explosion • Why so sudden? 1. Predator-Prey interacons and coevoluonary arms races. 2. Increase in atmospheric oxygen allows for larger animals with higher metabolic rates. 3. Key innovaon of Hox genes allows rapid diversificaon of developmental pathways.

Morphological Trends Symmetry • Radial vs bilateral • Radial – Top and boom only-- no le or right – Likely ancestral trait: Cnidarians, Ctenophores Morphological Trends

Symmetry • Radial vs bilateral • Bilateral – Top-boom, forward- backward, le-right – Allowed cephalizaon, more acve lifestyle. Morphological Trends

Tissues • Porifera or Parazoa (sponges) lack true ssues (this is a unique development) Gastrulaon

• Germ layers are formed by the process of gastrulaon • One end of blastula folds inward, eventually produces layers of embryonic ssue Gastrulaon

• Blastula is a mul- cellular embryonic stage that is typically a hollow ball of cells that surrounds a cavity called a blastocoel Gastrulaon

• The invaginaon or gastrulaon results in the gastrula stage • The pouch formed is called the archenteron and the opening to the outside is called the blastopore Gastrulaon

• Animals with only ectoderm and endoderm have only gastrulaon as germ layer formaon • Cnidaria (jellies) and Ctenophora (comb jellies) • Diploblasc Gastrulaon

• All bilateral animals have a third germ layer, the mesoderm • Forms muscles and most organs between digesve tract and the outer covering. • Triploblasc Body Cavity: The Coelom

• Most triploblasc animals have a body cavity – Fluid- or air-filled space separang the digesve tract from the outer body wall. • This is the coelom Body Cavity: The Coelom

• The coelom forms from ssue derived from mesoderm • COELOMATES: – Mesoderm connects dorsally and ventrally and provides a complete lining of the coelom Body Cavity: The Coelom

• The coelom forms from ssue derived from mesoderm • PSEUDO- COELOMATES: – Coelom is lined with mesoderm (outside) and endoderm (inside) Body Cavity: The Coelom

• The coelom forms from ssue derived from mesoderm • ACOELOMATES: – No true body cavity – Oen so-bodied organisms. Body Cavity: The Coelom

• All three groups (Coelomates, Pseudocoelomates, and Acoelomates) are polyphylec. • Body cavity (coelom) also coincides with complete digesve tract (mouth, anus) and circulatory system (vessels or sinuses) Coelomates: Protostomes & Deuterostomes Classic division in Bilateria

Differences • Paern of early cell division • Topotency in early cell development • The formaon of the coelom • Fate of the blastopore Coelomates: Protostomes & Deuterostomes Protostomes • Early cell division is via spiral cleavage

Deuterostomes • Early cell division is via radial cleavage Coelomates: Protostomes & Deuterostomes Protostomes • Fate of cells is determined at early cleavage stages: Determinate cleavage

Deuterostomes • Cells at early cleavage stages remain topotent: Indeterminate cleavage Coelomates: Protostomes & Deuterostomes Protostomes • Solid mass of mesoderm splits to form coelom: schizocoelous

Deuterostomes • Coelom forms from mesodermal outpockengs of the archenteron: enterocoelous Coelomates: Protostomes & Deuterostomes Protostomes • Blastopore becomes mouth

Deuterostomes • Blastopore becomes anus General Classificaon of Animalia

• Currently considerable debate on relaonships between animal phyla. • Remember, Animalia is monophylec. General Classificaon of Animalia

• Sponges branch first, form the Porifera or Parazoa. – Morphology and molecules disagree about monophyly – Generally considered paraphylec – Animalia without true ssues • Everything else form Eumetazoa – Animalia with true ssues General Classificaon of Animalia

• Radiata are paraphylec: Cnidaria & Ctenophora – Radial symmetry – Diploblasc • Bilateria are monophylec – Bilateral symmetry – Triploblasc General Classificaon of Animalia

• Bilateria divided into four groups: – Acoela – Deuterostomia • Echinodermata • Chordata – Ecdysozoa • Nematoda • Arthropoda – Lophotrochozoa • Platyhelminthes • Rofera • Ectoprocta • Brachiopoda • Mollusca