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

Body Symmetry
Number of tissue Layers
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

Notochord
Dorsal, hollow nerve cord
Pharyngeal gill pouches
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

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