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Opener Chapter 7. Chapter 7 Animal Classification, Phylogeny, and Organization. Common names Crawdads , crayfish , or crawfish ? English sparrow , barn sparrow , or a house sparrow? Problem with common names Vary from region to region

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opener chapter 7
Opener Chapter 7

Chapter 7

Animal Classification, Phylogeny, and Organization

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
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
Genus begins with a Capital letter
  • Entire name italicized or underlined
  • Homo sapien or H. sapien
kingdom of life
Kingdom of Life

1969 R. Whittaker- five kingdom classification

System of classification that distinguished b/w kingdoms according to

  • cellular organization
  • mode of nutrition
Fungi-eukaryotic and multicellular. Have cell wall and nonmotile. Mode of nutrition distiguishes fungi from plant- fungi digest extracellularly and absorb the breakdown products
Animalia- eukaryotic and multicellular, usually feed by ingesting other organisms, cell lack cell walls, and usually motile
challenge of the five class system
Challenge of the five class system
  • Ribosomal RNA excellent for studying evolution
  • rRNA changes very slow (evolutionary conservation)
  • Closely related organisms have similar rRNAs
  • Comparison of rRNA of different organisms concludes
  • All life shares a common ancestor
  • Three major evolutionary lineage (domains) and supersedes the kingdom as the broadest taxonomic grouping
the three domains
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)
text devoted to animals
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
pattern of organization
Pattern of Organization
  • Symmetry
  • Asymmetry
  • Radial symmetry
  • Bilateral symmetry
figure 7 8
Figure 7.8

Radial symmetry tube coral pulp

bilateral animals
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)
Directed movement evolved with anterior sense organscephalization


  • specialization of sense organs in head end of animals
bilateral symmetry
Bilateral Symmetry
  • Divided along sagittal plane into two mirror images
    • sagittal= divides bilateral organisms into right and left halves
Anterior= head end
  • Posterior= tail end
  • Dorsal= back side
  • Ventral= belly side
Symmetry, fig. 7.9
    • Median= sagittal
other patterns of organization may reflect evolutionary trends
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.
    • 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
Diploblastic Organization
    • 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
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
the triploblastic treis three blaste sprout
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
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
body cavities are advantageous
Body cavities are advantageous
  • Provide more room for organ development
  • Provide more surface area for diffusion of gases, nutrients, and waste into and out of organs
  • Provide area for storage
  • Often act as hydrostatic skeletons (supportive yet flexible)
  • Provide a vehicle for eliminating wastes and reproductive products from the body
  • Facilitate increase in body size
acoelomate a without kilos hollow
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.
what s a coelom
What’s a coelom?


  • coelom=
    • true body cavity
    • Fluid-filled
    • lined by mesoderm-derived epithelium
Acoelomates lack a true body cavity
    • Solid body
    • no cavity b/w the digestive tract and outer body wall
do these questions now
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


acoelomate bilateral animals
Acoelomate Bilateral Animals
  • Consist of phyla:
    • Phylum Platyhelminthes
    • Phylum Nemertea
    • Others…
acoelomate bilateral animals1
Acoelomate Bilateral Animals

Reproductive and osmoregulatory systems

  • Simplest organisms to have bilateral symmetry
  • Triploblastic
  • Lack a coelom
  • Organ-system level of organization
  • Cephalization
  • Elongated, without appendages
acoelomate bilateral animals2
Acoelomate Bilateral Animals

Reproductive and osmoregulatory systems

  • Simplest organisms to have bilateral symmetry
  • Triploblastic
  • Lack a coelom
  • Organ-system level of organization
  • Cephalization
  • Elongated, without appendages
triploblastic pseudocoelomate pseudes false
Triploblastic Pseudocoelomate pseudes, false
  • Body cavity not entirely lined by mesoderm
  • No muscle or connective tissue associated with gut
  • No mesodermal
the triploblastic coelomate pattern
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.
figure 7 3
Figure 7.3

Groups traced to separate ancestors

All descendants of a single ancestor

Includes some but not all of a members of a lineage

Fig 7.3 Evolutionary groups

figure 7 4
Figure 7.4

Fig 7.4 Vertebrate Phylogenetic tree depicts the degree of divergence from a common ancestor

figure 7 5
Figure 7.5

Fig 7.5 Interpreting Cladograms

Five taxa (1-5) and characteristics (A-H)

Symplesiomorphies- common characters in a group