Chapter 29- Comparing Invertebrates

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Chapter 29- Comparing Invertebrates
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I. Invertebrate Evolution

• Origin of the Invertebrates
• 1. Invertebrates fossils have been found to
  date between 610-570 million years ago.
• 2. Now molecular paleontology studies the
  fossils DNA.

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• 3. The Ediacaran fossils include some of the
  earliest and most primitive animals.

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• The Cambrian period, 544 million years ago has
  many different fossils.
• 5. Example Burgess Shale animals.

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B. Invertebrate Phylogeny

• Some features evolved over time also.
• 2. These features include tissues, and organs,
  patters of early development, body symmetry,
  cephalization, segmentation and the formation of
  three germ layers and a coelom.

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C. Evolutionary Trends

• Specialized cells, tissues and organs.
• Body symmetry- Sponges lack symmetry BUT all
  other invertebrates have some type of body
  symmetry.

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• 3. Cephalization-Invertebrates with
  cephalization can respond to the environment in
  more sophisticated ways than can simpler
  invertebrates.

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• Segmentation
• Coelom formation- most complex animals have a
  true coelom that is lined completely with tissue
  derived from the mesoderm.

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• Embryological development- Some of them are
  deuterostomes, meaning they have an anus.

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II. Form and function in invertebrates

• Feeding and Digestion
• 1. Intracellular and extracellular digestion-
  the simplest animals break down food primarily
  through intracellular digestion, but more complex
  animals use extracellular digestion.

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• 2. Extracellular digestion- Food is broken down
  outside the cells in a digestive cavity and then
  absorbed into the body cavity.

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• Respiration
• 1. Respiratory organs have large surface areas
  that are in contact with the air or water. Also,
  for diffusion to occur the respiratory surfaces
  must be moist.

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• Circulation
• 1. Most complex animals move blood through
  their bodies using one or more hearts and either
  an open or closed circulatory system.

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• Open circulatory- blood is only partially
  contained within a system of blood vessels.
• 3. Closed circulatory- a heart or something like
  it forces blood through vessels within the body.

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• D. Response-invertebrates show three trends in
  the evolution of the nervous system
  centralization, cephalization and specialization.

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• Cephalization- where if any sense organs the
  animal has are located at the front of the head.
• 2. Specialization- cells with particular cells.

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• Movement and Support
• 1. Invertebrates have one of three main kinds
  of skeletal systems hydrostatic skeleton,
  exoskeleton, or endoskeleton.

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• 2. Hydrostatic skeleton- muscles are surrounded
  by a fluid filled body cavity.

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• Exoskeleton- External skeleton.
• 4. Endoskeleton- A structural support located
  inside the body.

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• Sexual and Asexual Reproduction.
• 1. Most invertebrates reproduce sexually during
  at least part of their life cycle. Depending on
  environmental conditions, many invertebrates may
  also reproduce asexually.

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• External fertilization- fertilization outside of
  the body.
• 3. Internal fertilization- fertilization inside
  of the body.

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The End