Bio Lab 13 lecture 5/20: Animal Diversity, Human Anatomy, and Frog Dissection

Phylum Classification and Diversity

• Phylum Porphyria

  • Spelling note: The name contains the letter "c," but it is silent and not pronounced (similar to the "p" in psychology).
  • Identification: Students will answer specific questions in their handout regarding this phylum.

• Phylum Platychelnippis (Flatworms)

  • Common name: Flatworms.
  • Physical characteristics: These animals are worms that are physically flat.
  • Parasitic nature: Some species are parasites that inhabit the human intestine and cause illness.
  • Clinical/Literal scenario: A parasite may exit the body through the intestine; medical intervention is required because the head usually remains inside and can regrow or continue the infection.
  • Flukes: This group includes flukes, which can be found in meat that humans consume, potentially leading to liver problems.

• Phylum Arthropod

  • Diversity: This phylum contains the most species of animals in the world.
  • Common name: Arthroglots.
  • Included groups: Insects and various edible sea creatures.
  • Physical structure: They possess an exoskeleton, meaning they are hard on the outside and soft on the inside (the opposite of human anatomy).
  • Examples: Lobsters, shrimp, and crabs. These must have their outer shells removed to eat the soft interior. They produce a "crunch" sound if stepped upon.

• Phylum Chordata

  • Classification: These are the vertebrates.
  • Defining characteristic: They possess a backbone.
  • Human relation: Humans belong to this phylum; the speaker refers to other chordates as "our cousins" and the most familiar group to us.

• Practical Identification Tips

  • Jellies: Belong to the group characterized by "gellets."
  • Coral: The speaker identifies coral as a "really tricky" specimen and explicitly notes that it belongs to the same group as the jellies.

Anatomy of Human Systems

• The Heart

  • Medical context: Heart disease is the leading cause of death in the United States, making heart anatomy a priority for study.

• The Digestive System

  • Key components: Mouth, esophagus, stomach, liver, and intestines.
  • Positional detail: The pancreas is located behind the stomach.

• The Reproductive System

  • Expectations: Students must identify parts of both male and female reproductive systems for the final exam and upcoming quiz.
  • Male-specific anatomy: Includes the testicles and the vas deferens.
  • Female-specific anatomy: Includes the uterus.
  • Distinction: While humans remain largely the same in terms of bones and muscles regardless of sex, the reproductive systems are fundamentally different.

Skeletal Systems and Comparative Anatomy

• Human Skeletal Facts

  • Quantity: There are more than $200$ bones in the human body.
  • Study requirement: Students are only required to learn the specific bones listed in their lab handout, not all $200+$ bones.
  • Lab materials: The bones used in class are plastic models, not real human remains.

• Comparative Anatomy: Humans vs. Frogs

  • Observation: Human and frog skeletons are fundamentally similar with differences only in size and slight shape variation.
  • Structural similarities: Both typically feature five fingers and a limb structure consisting of one upper bone and two lower bones.
  • Evolutionary significance: These similarities exist because humans and frogs share a common ancestor that possessed these specific bone structures, which were then inherited by both lineages.

Frog Dissection Procedures and Internal Anatomy

• Preparation and Safety

  • Order of operations: Students must complete the anatomy portion of the lab before beginning the dissection.
  • Safety gear: Sterile gloves from the provided boxes must be worn.

• External and Muscle Incisions

  1. The frog should be placed on its back in the dissection tray.
  2. Use scissors to cut the skin down the middle of the torso.
  3. Make horizontal cuts across the top and the bottom.
  4. Peel the skin back and cut it away to prevent it from falling back over the work area.
  5. Muscle layer: Underneath the skin is a yellow layer of muscle. The speaker notes frogs appear to have an "$8$ or $10$ pack" of abdominal muscles.
  6. Repeat the same incision pattern on the muscle layer to reveal the internal organs.

• Internal Organ Identification

  • Primary organs to locate: Heart, liver, stomach, intestines, kidneys, and spleen.
  • Sex-specific organs: Testicles (male) or egg masses (female).
  • Positional Note: The kidneys are located "all the way in the back" and are typically the last organs to be examined.

• Dietary Analysis

  • Stomach: To determine the frog's last meal, the stomach must be removed, sliced open, and folded inside out to find remains of insects.
  • Cloaca: This is a combined structure where the digestive and urinary tracts meet (frogs do not have a separate large intestine and bladder).
    • Definition: A combined bladder and intestine.
    • Examination: One can squish out feces from the cloaca to feel the hard, undigested parts of insects.

Logistics and Assessment

• Lab Rotation Schedule

  • Group A (Two groups): Anatomy part first $\rightarrow$ Dissection $\rightarrow$ Diversity part.
  • Group B (Three groups): Diversity part first $\rightarrow$ Anatomy part $\rightarrow$ Dissection.
  • Reasoning: This staggered schedule allows the instructor to assist with dissections without all five groups needing help simultaneously.

• Upcoming Quiz Details

  • Scientific Naming: The first page of the handout explains how to write scientific names. The quiz will require students to identify $5$ scientific names in Latin.
  • Visual Identification: The quiz will include pictures of the heart, bones, digestive system, and reproductive system (e.g., identifying the arrow pointing to the vas deferens).

• Final Exam Details

  • Practical Format: The instructor will place stickers on specific bones or organs and ask the students to name them correctly.