Lab 10 – Animal Diversity 2 Deuterostomes

Lab Objectives

• Compare anatomy of representative deuterostomes (similarities and differences in organs).

• Discuss impact of molecular studies on phylogenetic trees.

• Analyze relationship between body form and organism lifestyle.

Overview of Deuterostomes

• Includes diverse animals like sea stars and humans.

• Morphological comparisons can be misleading; developmental and molecular data are crucial for classification.

• Key distinction: Stage of embryo development (deuterostomes vs. protostomes).

Phylum Echinodermata: Sea Stars

• Marine animals with spiny endoskeleton.

• Unique water-vascular system for movement through tube feet.

• Anatomy Observations:

  • Aboral surface (top) and oral surface (bottom).

  • Central disk and pentamerous (five-armed) structure.

  • Madreporite: water entry point into vascular system.

  • Skin gills: for respiration and waste removal.

  • Stomach can extend out for feeding; contains digestive glands and gonads.

Phylum Chordata: Lancelets and Rats

Lancelets (Cephalochordata)

• Burrowing marine animals with distinct anatomical features compared to fish.

• Key structures: pharynx with gill slits, notochord, dorsal nerve cord, and post-anal tail.

Norway Rat (Rattus norvegicus)

• Distinguished features of mammals:

  • Covered in hair, mammary glands, four-chambered heart.

  • Endothermic with a diaphragm for efficient breathing.

Internal Anatomy Observations:

1. Digestive System:

   • Muscular diaphragm separates thoracic and abdominal cavities.

   • Stomach with cardiac and pyloric regions, small and large intestines, cecum.

2. Circulatory System:

   • Heart with 4 chambers: right and left atrium, left and right ventricle.

   • Key vessels include vena cavae and pulmonary arteries.

3. Nervous System:

   • Composed of central (brain and spinal cord) and peripheral systems.

   • Brain dissection highlights cerebrum, cerebellum, and cranial nerves.

Comparative Anatomy

• Analyze differences in digestive structures between rats and humans (e.g., cecum, intestinal lengths).

Note: Always cover tools post-dissection and properly return specimens as instructed.