Follow the written procedure being sure to answer any by benbenzhou

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									                                     Biology 212: Fall 2007; Lab 1

Laboratory Objectives
I.    To become familiar with the key characteristics of the following animal phyla: Porifera, Cnidaria,
      Platyhelminthes, Nematoda.
II.   To compare members of these phyla in terms of symmetry, embryonic tissue layers and associated
      structures, presence/absence of a true body cavity, and other aspects of their body plans.
III.  To understand how these animals meet their basic need (feeding, gas exchange, etc…)
IV.   To understand the relationship of structure to function.
V.    NOTE: Anything covered in the laboratory is fair game for the lecture exam and the lab practical.

Methods (working your way through the lab!)
I.   Exercise 17: Introduction. The lab introduction provides a useful overview of this topic.
     A.     The 13 characteristics described in the introduction will be a recurrent theme in both
            lecture and lab. Note these categories are on Table 18.1, which you will complete as you
            go through the lab.

II.    Exercise 17.1: Phylum Porifera
       A.    Follow the written procedure, being sure to answer any questions embedded in the text.
       B.    Sketch the longitudinal section of Scypha (viewing through the compound microscope),
             and label
             1.      ostia (can’t see)
             2.      incurrent canal (lined with choanocytes)
             3.      choanocytes
             4.      spongocoel (=central cavity)
             5.      osculum
             6.      amoebocytes (if seen: could also comment about where they would be if not seen)
             7.      collagen (forming amorphic “matrix” of sponge)
       C.    Sketch the cross section of Scypha and label
             1.      incurrent canal (lined with choanocytes)
             2.      choanocytes
             3.      spongocoel (=central cavity)
             4.      amoebocytes (if seen: could also comment about where they would be if not seen)
       D.    Fill out table 18.1 for the sponge
       E.    We will regroup and review the lab (including the appropriate part of table 18.1) before
             moving to the next section.

III.   Exercise 17.2, Phylum Cnidaria
       A.    Follow the written procedure, being sure to answer any questions embedded in the text.
             1.      Procedure #9 is tricky. It works best if you actually “draw through” the drop of
                     methylene blue and the acetic acid by placing the edge of a Kimwipe on the side of
                     the coverslip opposite to where you placed the drop. If you get a good prep, give a
                     shout!
       B.    Sketch a cross section of Hydra, labeling
             1.      epidermis derived from ectoderm
             2.      gastrodermis derived from endoderm
             3.      mesoglia
             4.      gastrovascular cavity
             5.      cnidocytes (if you can’t see, at least note that they are specialized epidermal cells)
       C.    Fill out table 18.1 for the Hydra
       D.    We will regroup and review the lab (including the appropriate part of table 18.1) as well as
             view some additional slides before moving to the next section.
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VI.    Exercise 17.3: Phylum Platyhelminthes-Planaria
       A.    Follow the written procedure, being sure to answer any questions embedded in the text.
             1.      For Procedure #2, feed the Planaria a bit of egg rather than liver. I will have a
                     separate container for “used” Planaria to avoid contamination from the eggs.
       B.    Sketch the cross-section at the level of the pharynx (choose carefully from the multiple
             sections on the slide) on the separate paper provided rather than in the lab notebook, as
             these will be collected. . Be sure to label:
             1.      epidermis derived from ectoderm (multiple places in cross-section)
             2.      muscles derived from mesoderm (multiple places in cross-section)
             3.      gastrodermis derived from endoderm (multiple places in cross-section)
             4.      pharynx
             5.      pharyngeal chamber
             6.      gastrovascular cavity (multiple places in cross-section)
             **This is actually a rather tricky sketch because there are multiple places where there are
             epidermis (from ectoderm), gastrodermis (from endoderm), and muscle (from mesoderm).
       E.    Fill out table 18.1 for the Planaria
       F.    We will regroup and review the lab as before moving to the next section.

VII.   Exercise 18.1: Phylum Nematoda
       A.    Follow the written procedure, being sure to answer any questions embedded in the text.
       B.    Sketch the cross section of a female Ascaris, being sure to include the following parts:
             1.      cuticle composed of chitin
             2.      epidermis derived from ectoderm
             3.      longitudinal muscles derived from mesoderm
             4.      pseudocoelom (a type of body cavity)
             5.      gastrodermis derived from endoderm
             6.      intestine (or “digestive tract”)
             7.      ovaries
             8.      oviducts
             9.      uteri (paired)
             10.     nerve cord (not always visible)
       C.    Fill out table 18.1 for Ascaris
       D.    We will regroup and review the lab as before moving to the next section.

IV.    Lab summary: Write a paragraph for each of the features listed in part B, comparing their
       presence among the four groups, and briefly discussing the significance of these differences.
       HINT: You should use your text, lab book and lectures to help you with this assignment,
       but also be creative and speculative!
       A.     Sample paragraph: Symmetry. Members of Phylum Porifera are asymmetrical, while
              Cnidarians are radially symmetrical and both Platyhelminthes and Nematoda are
              bilaterally symmetrical. Radial symmetry provides Cnidarians a 360 view of the world
              and the ability to move equally in any direction, while bilateral symmetry allows the
              flatworm and roundworm to concentrate sensory organs at one end and move decisively in
              one direction. Porifera are sessile; symmetry is thus likely to be less important to them.
       B.     Features to discuss in your own summary:
              1.      Embryonic tissue layers present, and what they become.
              2.      Body cavity (pseudocoelom or coelom present?)
              3.      Complete digestive system (with two openings)
              4.      Nervous system
              5.      Gas exchange

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                                    Biology 212: Fall 2007; Lab 1

To turn in (on Friday by noon for Tuesday labs; on Monday in lecture for Thursday labs)
1. Labeled sketches as indicated in this handout
    a. If you would like more time to examine the slides, they will also be available during non-lab
         times (M,W,F all day).
2. Essay comparing the key features of the invertebrate phyla examined in class today.




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