ANIMAL KINGDOM

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ANIMAL KINGDOM
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Main Characteristics

• Multicellular eukaryotes
• 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

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Animals live in diverse habitats

• Marine
• Origin of animal life
• Provides buouyancy
• Body fluids isotonic to environment
• Plankton, nekton, sessile
• Freshwater
• Requires osmoregulation
• More challenging than marine food, oxygen,
  sunlight, temperature

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• Terrestrial avoid dessication
• Body covering to reduce evaporation
• Respiratory organs deep in body cavity
• Reproduction
• Return to water
• Internal fertilization
• Eggs with coverings
• Means of thermoregulation

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Evolution of Animals

• All animals have a common protist ancestor
  choanoflagellate
• Cells of colony became specialized
• Division of labor resulted in single organism
• Diversity results from changes in development
  that lead to changes in body plans
• Hox genes control early development

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Animals can be Classified According to Body
Symmetry

• Asymmetry
• no regular arrangement
• Radial symmetry
• similar structures arranged around central axis
• Bilateral symmetry
• can only be divided through one plane (midline)
• get roughly left and right halves

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Cephalization

• Found in bilaterally symmetrical organisms
• Concentration of sensory structures in a head
• Nerve cells concentrate in head ? brain
• Nerve cord extends toward rear
• Bilateral symmetry and cephalization are
  adaptations to locomotion

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Embryonic Development

• Zygote formed through fertilization
• Undergoes cleavage series of mitotic division
• Develops into blastula hollow ball of cells
• Undergoes gastrulation formation of specific
  layers of tissue called germ layers

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2 Types of Cleavage Patterns

• Radial
• Parallel or right angles to axis
• Fate of cell comes later
• Indeterminate
• Spiral
• Diagonal to axis
• Fate of cell fixed early
• Determinate

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Germ Layers

• Form in all animals except sponges
• 3 layers
• Ectoderm outer layer
• Endoderm inner layer
• Mesoderm middle layer

DIPLOBLASTIC
TRIPLOBLASTIC
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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 endo and ectoderm
• Triploblastic
• Have 3rd germ layer - mesoderm

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Body Cavity

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

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Body Cavity Classification

• Acoelomates
• Solid body no cavity
• Flatworms and ribbon worms

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• 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

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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

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Protostomes vs. Deuterostomes

• PROTOSTOMES
• Flatworms, annelids, arthropods, mollusks
• SPIRAL CLEAVAGE
• Developmental fate of embryo fixed early
  determinate

• DEUTEROSTOMES
• Echinoderms and chordates
• RADIAL CLEAVAGE
• Fate of embryo occurs later indeterminate

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Fig. 29-7, p. 627