Thursday, March 30, 2006

Hello. Here are your notes from today's lesson.

Today in class we discussed Section 2 of Chapter 25.

  • Symmetry- A balance in proportions of an object or organisms; close agreement in size, shape, and relative position of parts arranged on opposite sides of a dividing line or plane or around a central point.
  • There are three different types of symmetry. Spherical, Radial, and Bilateral symmetry.

  • Spherical symmetry- occurs when any plane divides the body into mirrored halves.
  • Radial symmetry- occurs when any longitudinal plane passes through a central axis divides the body into mirrored halves.
  • Bilateral symmetry- occurs when an organism can be divided down its length(midline) into similar right and left halves.

  • Asymmetry- is an animal that has an irregular shape. (has no symmetry)

  • Body Regions
  • Planes of animal symmetry

  • Body Regions
  1. Anterior indicates the head end; the opposite or tail end is Posterior.
  2. Dorsal is the back side and Ventral is the front or belly side.
  3. Medial is the midline of the body; Lateral is the sides.
  4. A Frontal plane divides the body into Dorsal and Ventral halves.
  5. A Sagittal plane divides the body into right and left halves.
  6. A Transverse plane separates Anterior and Posterior portions.
  7. In vertebrates, Pectoral is the chest region or area supported by forelimbs.
  8. Pelvic refers to the hip region or area supported by hind limbs.

Comparison of body plans.

Coelom- a fluid filled space

3 Types of Body Plans

  1. Acoelomate- no cavity.(flatworm)
  2. Pseudocoelomate- False body cavity, surrounded on one side by mesoderm ( round worm)
  3. Coelomate- true body cavity. surrounded on both sides by mesoderm ( segmented worm)


Exoskeleton- Hard, waxy covering on the outside of the body that provides a framework for support. Exoskeletons are found on animals that are invertebrates. Their exoskeletons Do not grow with the animal, so they have to shed it. Exoskeletons are a good source of protection.

Molting- The process of shedding the exoskeleton.

Endoskeleton- internal skeleton that provides support inside an animals body. Endoskeletons are found within vertebrates, animals with a backbone. and it grows with the animal.

For homework Do the section 2 assessment for chapter 25.

Next person to scribe will be Nicole Norton.. Love you all.... See ya. O, and Nicole have FUN with the next scribe......


Post a Comment

Links to this post:

Create a Link

<< Home