Chapter 32 & 33

Kingdom Animilia

• Over 1.5 million species
  • Estimated 73 million
• 35 Phylums
  • Over half are insects
• More similarities within animal genomes than other kingdoms

Characteristics 

• Multicellular
• Lack of cell wall
• Sexual reproduction
  • mobile sperm
  • larger non-motile egg
• Nervous Tissue
  • Complexity
  • Responsiveness
• Hox Genes
  • Special clusters of genes associated with the planning of the body

Metazoans

• All animals
• Multicellular animals
• Paratoans
  • Sponges
• Eumetazoans
  • "true" multicellular animals

Classification/Systematics

• Old
  • Morphology
  • Embryonic Development
• Recent
  • Molecular genetics

Body Plans

Morphological and Developmental Features

1. Body Symmetry
2. Number of tissue Layers
3. Patterns of Embryonic development 

Symmetry

• Eumetazoa
  • Divided by symmetry
• Radiata
  • Radial symmetry
  • Often Circular or tubular
• Bilateria
  • Bilateral symmetry
  • Dorsal
    • Back
  • Ventral
    • Front
  • Anterior
  • Posterior
  • cephalization
    • enlarged head

Tissues

• Metazoa
  • all animals
  • divided on weather or not they have specialized tissues
• Parazoa
  • Porfera
    • sponges
    • may have distinct cell types
• Enmetazoa
  • more than one type of tissue
  • organs
  • all other animals

Germ Layers

• Radial
  • 2 layers
  • Diploblastic
    • endoderm
    • ectoderm
• Bilateral
  • 3 layers
  • Triploblastic
    • endoderm
    • ectoderm
    • mesoderm

Embryonic Development

• Protostome
  • Blastopore becomes mouth
  • cleavage is determinate
    • fate of embryonic cells are determined early
• Deuterostome (second opening)
  • Blastopore becomes anus
  • cleavage is indeterminate
  • each cell produced by early cleavage can develop into a complete embryo 

Other Morphological Characteristics

Used in classification

• Presence or absence or coelom
• Body segmentation

Molecular data suggest these features are unreliable in terms of understanding evolutionary history

Body Cavity

Coelom

• • a fluid-filled body cavity
• Coelomate or eucolemate
  • true coelom
  • coelom completely lined with mesoderm
• Pseudocoelom
  • coelom only partially lined with mesoderm
  • rotifers and roundworms
• Acoelomate
  • lack of a body cavity and instead have mesenchyme
  • flatworms

Flatworm has no mesoderm

Functions of the Coelom

• Cushions internal organs
• Enables movements and growth of internal organs independent of the body wall
• Fluid acts as a simple circulatory system

Segmentation

• Body may be divided into regions called segments
• occurs in annelid worms, arthropods, and chordates
• allows specialization of body region

DO NOT worry about the number of species

Molecular views of Animal Diversity

• Scientist now use molecular techniques to classify animals
  • Compare similarities in DNA, rRNA, and Amino Acids
  • Closely related organisms have fewer differences than those more distantly related
• Advantages over morphological data in that genetic sequences are easier to quantify and compare
  • Example: A,T,G, and C in DNA

Genes used in Molecular Systematics

• Studies often focus on ribosomal RNA (rRNA)
  • Universal in all organisms
  • changes slowly over time
• Hox genes also studied often
  • Found in all animals
  • duplications in these genes may have led to evolution of body form
• Phylogenies constructed using rRNA and Hox genes are similar and often agree with those based on morphology

Invertebrates

• "without backbone"
• +95% of all species

Phylum Porifera

• Sponges
• lack tissues (organs)
• multicellular
• pores
  • filter H2O and food
• Invertebrates

Phylum Cnidaria

• Jelly fish, corals, anemones 
• Diploblastic development
  • Two tissue layers
• Mesoclea 
  • gelatinous covering
• Nerve net
  • interconnected nerve cells 
  • no brain
• One opening with gastrovascular cavity
• Protostomes
• Invertebrates
• Radial symmetry
• Salt and fresh water
• Stingers

Phylum Ctenophora

• Comb jellies
• Same characteristics as Cnidaria
• Strictly salt water
• No Stingers

Phylum Platyhelminthes

• Flatworms, tapeworms, flukes
• Triploblastic
• Organs and organ systems
• Enhanced nerve net
  • 2 cerebral ganglia
• One opening with gastrovascular cavity
• Protostomes
• invertebrates
• bilateral symmetry
• Acoelomate

Phylum Rotifera

• rotifers
• pseudocoelomate
• Triploblastic
• Two openings
  • complete gut tract
  • alimentary canal
• Protostomes 
• Corona
• simple brain
• invertebrates

Phylum Mollusea

• Snails, slugs, oysters, octopus, squid, clams, muscles
• Triploblastic
• Eucoelomate
• Complete gut tract
• Protostomes
• Invertebrates
• Three part Body
  • Foot
  • Visceral mass
  • Mantle
    • Many have outer shells

Phylum Annelida

• Segmented ring worms
• Triploblastic
• Eucoelomate
• Complete gut tract
• Protostomes
• Enhanced nervous system
• Invertebrates

Phylum Nematoda

• Roundworms
• Triploblastic
• Pseudocoelomate
• Complete gut tract
• Protostomes
• Invertebrates

Phylum Anthropoda

• Insects, crustaceans, spiders, ticks
• Highest diversity of animals
  • >1.5 million species
• Hardened Exoskeleton
• Protostomes
• Invertebrates
• Eucoelomate
• Triploblastic
• Complete gut tract
• Enhanced nervous system
  • Insects, in particular, have an enhanced brain
• segmented appendages

Phylum Echinodermata

• sea stars, urchins, sea cucumbers, sand dollars
• Triploblastic
• Eucoelomate
• Complete gut tract
• Deuterostomes
• Simple nervous system
• Endoskeleton
  • series of plates

Phylum Chordata

• Deuterstomes
• Complete gut tract
• Endoskeleton
• Few invertebrates
  • Mostly vertebrates
• Eucloemates
• Triploblastic

Four Critical Innovations of Chordate Body Design

1. Notochord
2. Dorsal, hollow nerve cord
3. Pharyngeal gill pouches
4. Post-anal tail

• These four features are exhibited at some point of life history/development
  • Only some Fishes exhibit all four

Notochord

• Cartilaginous supporting rod along the dorsal axis
• Replaced by jointed "backbone"
  • Vertebral column of hardened cartilage or bone

Dorsal, hollow nerve cord

• Expanded at the anterior end
  • Brian
• Enclosed/supported/protected by the Notochord

Pharyngeal gill pouches

• Gill slits
• pharynx
  • back of mouth cavity

Post-anal Tail

• Tail extends posterior of the anus

Humans

Notochord

• replaced by vertebrae
• only pieces left are the inter-vertebral discs between vertebrae 

Nerve cord

• Dorsal, hollow with largest brain capacity (compared to body size)

Pharyngeal Pouches

• Embryonic Development
• 1 pair retained as Eustachian tubes

Post-anal Tail

• One vertebra as a tail bone (coccyx)

Subphylum Urochordata

• tunicates
• invertebrates
• ~3000 species
• Marine
• Filter feeders

Subphylum Cephalochordata

• Lancelets
• Invertebrates
• 25 species
• marine
• Filter feeders