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Introduction to Animals

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Title: Introduction to Animals


1
Introduction to Animals
2
To be an animal means
  • Multicellular
  • humans have 50 - 100 trillion cells
  • Ingestive heterotroph
  • Lacking a cell wall
  • Specialization of cells
  • (except Porifera)
  • May involve movement sexual reproduction
    (formation of a zygote)

3
Phylogenetic tree of animal kingdom
  • Based on
  • Body symmetry
  • Patterns of embryo development
  • Comparing fossils
  • rRNA

4
Symmetry
  • Overall pattern of structure
  • Asymmetric - No symmetry as with the Porifera
  • Radial symmetry even cut along a diameter.
    Echinodermata and Cnidaria
  • Bilateral symmetry even cut along a central
    plane. Worms, Arthropods, Mollusks, Echinoderms,
    and Vertebrates

5
Trends in Animal Evolution
  • As you go up the phylogenetic tree, you will see
    a greater tendency towards bilateral symmetry.
  • Also a concentration of nerves (sensory organs)
    towards the front of the organisms known as
    cephalization

6
Body views
  1. Dorsal top/back
  2. Ventral belly/bottom
  3. Anterior front/head
  4. Posterior tail/rear

Anterior (front)
Dorsal (top)
Ventral (bottom)
Posterior (tail end)
7
Cleavage
  • A series of cell divisions that occurs
    immediately following fertilization
  • Mitosis occurs but cells do not grow in size.

8
Stages in Cleavage
Gastrula Indented ball stage
Blastula Hollow ball stage
Morula Solid ball stage
Zygote
                                                
                                                  
              
During gastrulation, an indentation occurs.
A multi-layer embryo is formed with 3 germ layers
Blastopore opening of indentation
9
  • Protostome
  • Blastopore developes into the oral opening
    (mouth)
  • Mollusks, arthropods and annelids
  • Deuterostomes
  • Blastopore developes into anus
  • Echinoderms and Chordates (thats us)

10
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11
Germ Layers
  • Fundamental tissue types found in embryos of
    animals (but not sponges)
  • Gives rise to every body feature, organs
    tissues
  • 2 germ layers in Cnidaria 3 in all others
  • Endoderm forms throat, gills, lungs and
    digestive tract (with pancreas and liver)
  • Ectoderm forms outer skin, hair, nails and
    nervous system
  • Mesoderm skeleton, muscles, inner skin layer,
    circulatory system and lining of the body cavity

12
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13
Body Cavities
  • Acoelomates Body cavity is absent. As in
    Flatworms . Endoderm is connected solidly to
    mesodermal tissue
  • Pseudocoelomates Body cavity contains three
    distinct layers but endoderm is not connected to
    mesoderm. Free floating in fluid. Found in
    roundworms.
  • Coelomates True body cavity. Mesoderm lines
    body cavity while supporting endodermic.
    Mollusks, annelids, arthropods, chordates and
    echinoderms

14
Systems through the Phyla
  • Circulatory systems
  • Closed Circulatory System
  • One in which blood is always contained within a
    vessel. Heart serves as a pump. Found in
    annelids, chordates
  • Open Circulatory System
  • Pumps blood into spaces around the body tissues.
    From there the blood makes its way back to
    vessels that will carry it back to the heart, or
    possibly to holes in the heart itself. Found in
    Arthropods and some mollusks

15
Skeletons
  • Exoskeleton Rigid, outer covering protecting
    soft internal tissue. Found in Arthropods and
    mollusks. Needs to be shed (molt) as animal
    grows.
  • Endoskeleton Internal skeleton. Best for
    larger organism. Found in echinoderms and
    vertebrates. Grows as animal grows.

16
Reproduction
  • Asexually by budding (Porifera, Cnidarians) or
    regeneration (Porifera, Planaria, Sea stars)
  • Sexually
  • Hermaphroditic contains both sexes (but not
    self fertilization necessarily). Think of your
    earthworm
  • Separate sexes as you go up the phylogenetic
    tree

17
Development
  • Incomplete metamorphosis Direct development
    young animal is born or hatched looking like
    adult but smaller. No larval stage. Mantids,
    Grasshoppers, us
  • Complete metamorphosis Indirect development
    intermediate larval stages appearing different
    from adult.
  • Butterfly, flies, moths
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