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What is an animal?
• Mul.cellular heterotrophs: feed by inges&on.
• How does this differ from plants, fungi, pro.sts?
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 reproduc.on 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
• Monophyle&c • Sister taxon Choanoflagellates (pro.st protozoan) • Colonial, flagellated pro.st ancestor
Animal Origins
• Gastrula-‐like infolding into two layers
• Increased specializa.on of cells and .ssues beginning with soma&c vs reproduc&ve
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 interac.ons and
coevolu.onary arms races. 2. Increase in atmospheric oxygen
allows for larger animals with higher metabolic rates.
3. Key innova&on of Hox genes allows rapid diversifica.on of developmental pathways.
Morphological Trends Symmetry
• Radial vs bilateral • Radial – Top and bofom only-‐-‐no leg or right
– Likely ancestral trait: Cnidarians, Ctenophores
Morphological Trends
Symmetry • Radial vs bilateral • Bilateral – Top-‐bofom, forward-‐backward, leg-‐right
– Allowed cephaliza&on, more ac.ve lifestyle.
Morphological Trends
Tissues • Porifera or Parazoa (sponges) lack true .ssues (this is a unique development)
Gastrula.on
• Germ layers are formed by the process of gastrula&on
• One end of blastula folds inward, eventually produces layers of embryonic .ssue
Gastrula.on
• Blastula is a mul.-‐cellular embryonic stage that is typically a hollow ball of cells that surrounds a cavity called a blastocoel
Gastrula.on
• The invagina.on or gastrula.on results in the gastrula stage
• The pouch formed is called the archenteron and the opening to the outside is called the blastopore
Gastrula.on
• Animals with only ectoderm and endoderm have only gastrula.on as germ layer forma.on
• Cnidaria (jellies) and Ctenophora (comb jellies)
• Diploblas&c
Gastrula.on
• All bilateral animals have a third germ layer, the mesoderm
• Forms muscles and most organs between diges.ve tract and the outer covering.
• Triploblas&c
Body Cavity: The Coelom
• Most triploblas.c animals have a body cavity – Fluid-‐ or air-‐filled space separa.ng the diges.ve 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 – Ogen sog-‐bodied organisms.
Body Cavity: The Coelom
• All three groups (Coelomates, Pseudocoelomates, and Acoelomates) are polyphyle&c.
• Body cavity (coelom) also coincides with complete diges.ve tract (mouth, anus) and circulatory system (vessels or sinuses)
Coelomates: Protostomes & Deuterostomes
Classic division in Bilateria
Differences • Pafern of early cell division • To&potency in early cell development • The forma.on 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 to&potent: Indeterminate cleavage
Coelomates: Protostomes & Deuterostomes
Protostomes • Solid mass of
mesoderm splits to form coelom: schizocoelous
Deuterostomes • Coelom forms from
mesodermal outpocke.ngs of the archenteron: enterocoelous
Coelomates: Protostomes & Deuterostomes
Protostomes • Blastopore
becomes mouth
Deuterostomes • Blastopore
becomes anus
General Classifica.on of Animalia
• Currently considerable debate on rela.onships between animal phyla.
• Remember, Animalia is monophyle.c.
General Classifica.on of Animalia
• Sponges branch first, form the Porifera or Parazoa. – Morphology and
molecules disagree about monophyly
– Generally considered paraphyle.c
– Animalia without true .ssues
• Everything else form Eumetazoa – Animalia with true .ssues
General Classifica.on of Animalia
• Radiata are paraphyle.c: Cnidaria & Ctenophora – Radial symmetry – Diploblas.c
• Bilateria are monophyle.c – Bilateral symmetry – Triploblas.c
General Classifica.on of Animalia • Bilateria divided into four
groups: – Acoela – Deuterostomia
• Echinodermata • Chordata
– Ecdysozoa • Nematoda • Arthropoda
– Lophotrochozoa • Platyhelminthes • Ro.fera • Ectoprocta • Brachiopoda • Mollusca