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Key Terms

  • Amniotic Egg:

    • Structure: Membranes forming an amniotic sac surrounding the embryo.

    • Example Species: Turtles, snakes, lizards, and crocodiles lay eggs on land; these have leathery shells protecting embryos from dehydration.

    • Humans: Do not lay eggs but possess amniotic membranes for the embryo.

    • Non-amniotic taxa: Frogs, salamanders, and fish lay eggs in water; even live-bearing fish are not amniotes.

  • Bony Skeleton:

    • Definition: An internal skeleton composed of calcium and phosphate.

    • Presence: Found in bony fish, reptiles, birds, mammals, and amphibians.

    • Comparison: Sharks have cartilage skeletons, making them more flexible.

  • Cladogram:

    • Purpose: Illustrates evolutionary relationships by showing speciation events.

    • Nodes: Each split indicates a speciation event.

    • Taxa: Located at the ends of the branches.

    • Common Ancestor: All species in a grouping must share a common ancestor.

    • Monophyletic Group: Includes all species derived from a common ancestor (valid).

    • Paraphyletic Group: Shares a common ancestor but excludes some derived species (e.g., "reptiles" excluding birds, not valid).

  • Lungs:

    • Evolution: Evolved in some vertebrates around 400 million years ago.

    • Adaptation: Enabled breathing air and living on dry land; present in amphibians, reptiles, birds, and mammals.

Mammals

  • Definition: Monophyletic group characterized by shared derived character of producing milk to offspring.

  • Types of Mammals:

    • Monotremes: Lay eggs and lack nipples; provide milk through skin glands.

      • Examples: Platypus, Echidna.

    • Marsupials: Short gestation period with rudimentary placenta; babies obtain milk from nipples in a ventral pouch.

      • Examples: Kangaroo, Wallaby, Koala, Opossum.

    • Placental (Eutherian) Mammals: Possess a complex placenta; give birth to more developed young.

      • Examples: Elephant, Bat, Lion, Human, Whale, Dog, Cow, Mouse.

  • Opposable Thumb:

    • Definition: Thumb can touch other fingers, allowing grasping and object manipulation.

    • Presence: Found in primates and some marsupials.

  • Tetrapod:

    • Definition: Vertebrates with four limbs or limb-like appendages.

    • Examples: Amphibians, lizards, snakes, crocodilians, turtles, birds, mammals (including whales), and their extinct relatives.

Practice Questions

  1. Identify the Class of the specimen on the instructor table.

  2. Determine the Phylum of the specimen.

  3. Identify the Domain of the organism.

  4. Determine the Kingdom of the specimen.

  5. List three tetrapod specimens by common name from the provided samples.

  6. Identify four taxa that possess an amniotic egg using common names.

  7. List all specimens with mammary glands present in females.

  8. Which taxa have an opposable thumb?