Opener Chapter 7

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Opener Chapter 7
Chapter 7 Animal Classification, Phylogeny,
and Organization
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• Common names
• Crawdads, crayfish, or crawfish?
• English sparrow, barn sparrow, or a house
  sparrow?
• Problem with common names
• Vary from region to region
• Common names often does not specify particular
  species

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• Binomial system of Nomenclature brings order to a
  chaotic world of common names
• Universal
• Clearly indicates the level of classification
• No two kinds of animals have the same binomial
  name
• Every animal has one correct name International
  Code of Zoological Nomenclature

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• Genus begins with a Capital letter
• Entire name italicized or underlined
• Homo sapien or H. sapien

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The three domains

• Arhaea- prokaryotic microbes live in extreme
  environments, inhabit anaerobic environments
• Reflect the conditions of early life
• Archaea the most primitive life form
• Archaea give rise to two other domains
• Eubacteria- true bacteria and are prokaryotic
  microorganisms
• Eukarya- include all eukaryotic organisms,
  diverged more recently thus more closely related
  to archae (protists, fungi, plants and animals)

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Figure 7.2 (b)
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Kingdom of Life

• 1969 R. Whittaker- five kingdom classification
• System of classification that distinguished b/w
  kingdoms according to
• cellular organization
• mode of nutrition

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Figure 7.2 (a)
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• Monera- bacteria and cyanobacteria are prokaryotic

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• Protista- single or colonies of eukaryotic cells
  (Ameoba, Paramecium)

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• Plantae- eukaryotic, multicellular, and
  photosynthtic. Have cell wall, and usually
  nonmotile

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• Fungi-eukaryotic and multicellular. Have cell
  wall and nonmotile. Mode of nutrition
  distiguishes fungi from plant- fungi digest
  extracellularly and absorb the breakdown products

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• Animalia- eukaryotic and multicellular, usually
  feed by ingesting other organisms, cell lack cell
  walls, and usually motile

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Text devoted to animals

• Except for Chapter 8 Animal like protists (Amoeba
  and Paramecium)
• The inclusion of protozoa is part of a tradition
• Once considered a phylum (Protozoa) in the animal
  kingdom

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Pattern of Organization

• Asymmetry i.e. ameoba
• Symmetry
• Radial symmetry- tube coral pulp
• Bilateral symmetry- insects

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Figure 7.7 Asymmetry red encrusting sponge
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Figure 7.8
Radial symmetry tube coral pulp
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Part 2
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Bilateral animals

• Bilateral symmetry important evolutionary
  advancement
• Important for active, directed movement
• Anterior, posterior ends
• One side of body kept up (dorsal) vs. down
  (ventral)

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• Directed movement evolved with anterior sense
  organs? cephalization
• Cephalization
• specialization of sense organs in head end of
  animals

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Bilateral Symmetry

• Divided along sagittal plane into two mirror
  images
• sagittal divides bilateral organisms into right
  and left halves

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• Anterior head end
• Posterior tail end
• Dorsal back side
• Ventral belly side

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• Symmetry, fig. 7.9
• Median sagittal

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Other Patterns of Organization may reflect
evolutionary trends

• Unicellular (cytoplasmic)- organisms consist of
  single cells or cellular aggregates,
• provide functions of locomotion, food
  acquisition, digestion, water and ion regulation,
  sensory perception and reproduction in a single
  cell.

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• Cellular aggregates consist of loose association,
  cells that exhibit little interdependence,
  cooperation, or coordination of function
• Some cells may be specialized for reproduction,
  nutritive or structural function

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• The analogy of a clock
• Can be used to place major events in the Earths
  history in the context of the geological record

500 million years ago
Algea fossils
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• Larger organisms do not appear in the fossil
  record
• Until several hundred million years later
• Chinese paleontologists recently described
  570-million-year-old fossils
• That are probably animal embryos

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The Colonial Connection

• The first multicellular organisms were colonies
• Collections of autonomously replicating cells

May Lead to Cell Specialization
Figure 26.16
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• Organisms can have more than one tissue layer
• Diploblastic- two layers

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• What about Tripoblastic three layers?

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• Diploblastic Organization- Two tissue layers
• Cells are organized into tissues in most animal
  phyla
• Body parts are organized into layers derived from
  two embryonic tissue layers.
• Ectoderm- Gr. ektos, outside derm, skin gives
  rise to the epidermis the outer layer of the body
  wall
• Endoderm- Gr. Endo, within, gives rise to the
  gastrodermis that lines the gut

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• Mesoglea- between the ecto and endo and may or
  may not contain cells
• Derived from ecto and/or endo
• Cells form middle layer (mesenchyme)
• Layers are functionally inderdependent, yet
  cooperate showing tissue level organization i.e.
  feeding movements of Hydra or swimming movements
  of a jellyfish

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Figure 7.10
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The Triploblastic (treis, three blaste, sprout)

• Animals described in chapters 10-22
• Tissues derived from three embryological layers
• Ectoderm- outer layer
• Endoderm- lines the gut
• Mesoderm- meso, middle, Third layer between Ecto
  and Endo
• Give rise to supportive cells

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Figure 7.11
Diploblastic
Triploblastic
Diploblastic or Triploblastic?
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• Triploblastic animal

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• Most have an organ system level of organization
• Usually bilaterally symmetrical or evolved from
  bilateral ancestors
• Organized into several groups based on the
  presence or absence of body cavity and for those
  that posses one, the kind of body cavity present.
• Body cavity- fluid filled space in which the
  internal organs can be suspended and separated
  from the body wall

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Body cavities are advantageous

1. Provide more room for organ development
2. Provide more surface area for diffusion of gases,
   nutrients, and waste into and out of organs
3. Provide area for storage
4. Often act as hydrostatic skeletons (supportive
   yet flexible)
5. Provide a vehicle for eliminating wastes and
   reproductive products from the body
6. Facilitate increase in body size

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What does acoelomate mean?

• No coelom

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Acoelomate a, without kilos, hollow

• Mesoderm relatively solid mass
• No cavity formed between ecto and endo
• These cells within mesoderm often called
  parenchymal cells
• Parenchymal cells not speciallized for a
  particular fnc.

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Whats a coelom?

• coelom
• true body cavity
• Fluid-filled
• lined by mesoderm-derived epithelium

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• Acoelomates lack a true body cavity
• Solid body
• no cavity b/w the digestive tract and outer body
  wall

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Do these questions now

• Think about aceolomate bilateral animals
• To what domain do they belong
• kingdom
• What phyla include these organisms
• What is bilateral symmetry, and why was it an
  important evolutionary advantage

movie
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Acoelomate Bilateral Animals

• Consist of phyla
• Phylum Platyhelminthes
• Phylum Nemertea
• Others

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Acoelomate Bilateral Animals

1. Simplest organisms to have bilateral symmetry
2. Triploblastic
3. Lack a coelom
4. Organ-system level of organization
5. Cephalization
6. Elongated, without appendages

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Acoelomate Bilateral Animals

1. Simplest organisms to have bilateral symmetry
2. Triploblastic
3. Lack a coelom
4. Organ-system level of organization
5. Cephalization
6. Elongated, without appendages

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Triploblastic Pseudocoelomate pseudes, false

• Body cavity not entirely lined by mesoderm
• No muscle or connective tissue associated with
  gut
• No mesodermal

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The Triploblastic Coelomate Pattern

• Coelom is a body cavity completely surrounded by
  mesoderm
• Peritoneum- mesodermal sheet that lines the inner
  body wall and serosa (outer covering of visceral
  organs)
• Having mesodermally derived tissue (muscle,
  connective tissue) enhances the function of all
  internal body systems.

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Figure 7.12
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