Terminology, Vertebrate Story, Chordates

Compare and contrast homology, analogy, and homoplasy.

• Homology: Similarity due to shared ancestry (e.g., vertebrate limbs).

• Analogy: Similar function, but not derived from a common ancestor (e.g., wings of birds and insects).

• Homoplasy: Similar appearance or traits that evolved independently (e.g., dorsal fins in sharks and dolphins). These concepts can overlap.

Define radial and bilateral symmetry.

• Radial symmetry: Body parts arranged around a central axis; multiple planes of symmetry (e.g., jellyfish).

• Bilateral symmetry: Body divided into right and left halves along one plane (e.g., humans).

Describe the three body planes (sagittal, frontal, and transverse).

• Sagittal: Divides body into left and right.

  • Midsagittal: Directly along the midline.

  • Parasagittal: Off-center from the midline.

• Frontal (coronal): Divides body into dorsal (back) and ventral (front).

• Transverse: Divides body into cranial (head) and caudal (tail) portions.

Define the following relative directional terms: cranial, rostral, caudal, medial, lateral, proximal, and distal.

• Cranial: Toward the head.

• Rostral: Toward the nose (on the head).

• Caudal: Toward the tail.

• Medial: Toward the midline.

• Lateral: Away from the midline.

• Proximal: Closer to the body core.

• Distal: Farther from the body core.

What are the five fundamental features shared by all chordates at some point in their life cycle? Know the basic structure and purpose of these features.

1. Notochord: Flexible rod for support.

2. Pharyngeal pouches/slits: Feeding and respiration.

3. Endostyle/Thyroid gland: Filter feeding or hormone production.

4. Dorsal hollow nerve cord: Becomes CNS in vertebrates.

5. Post-anal tail: Locomotion.

Is the notochord the same as the spinal cord in later vertebrates? If not, what structure does it form?

• No. The notochord is not the spinal cord. It becomes part of the vertebral column, specifically the intervertebral discs.

Describe the structure and function of the vertebral column. Name the basic components of a vertebra.

• Structure: Series of vertebrae protecting the spinal cord and providing support.

• Components: Centrum, neural arch/spine (dorsal), hemal arch/spine (ventral), intervertebral discs.

Describe the key features of "prevertebrates". What adaptation allowed for increased feeding/respiratory efficiency?

• Prevertebrates had pharyngeal musculature and springy cartilage forming a muscular pump, improving feeding and respiration.

What are Agnathans? Describe their feeding mechanisms.

• Jawless vertebrates (e.g., hagfish, lampreys).

• Use muscular pharyngeal pump and tongue-like structures for feeding.

How do the vertebral columns of hagfish and lampreys differ? What is a unique characteristic of many lampreys?

• Hagfish: Vertebra-like elements in larvae, lost in adults.

• Lampreys: Cartilaginous vertebrae.

• Unique trait: Many are parasitic.

Describe the development and significance of jaws in Gnathostomes.

• Jaws evolved from rostral pharyngeal arches.

• Allowed for improved prey capture and feeding efficiency.

What are the distinguishing features of Chondrichthyes? What are the two major groups within Chondrichthyes? What adaptations do they have for buoyancy?

• Features: Cartilaginous skeleton, placoid scales, electroreceptors, paired fins, 5–7 gill slits.

• Groups:

  • Holocephalans (chimeras): Upper jaw fused to braincase, grinding plates.

  • Elasmobranchs (sharks, skates, rays): More diverse.

• Buoyancy: Oil-filled liver and reduced bone density.

What are the main differences between Actinopterygii and Sarcopterygii?

• Actinopterygii: Ray-finned, lighter scales, swim bladder.

• Sarcopterygii: Lobe-finned, internal bones in fins, paired lungs (lungfish), prominent notochord.

Describe the structure and composition of ganoid scales.

• Hard, enamel-like, mineralized scales.

• Interlocking and inflexible.

• Found in primitive ray-finned fish like sturgeon and gar.

What are the two types of swim bladders? How do they differ in their mechanism of gas exchange?

• Physostomous: Connected to esophagus, gas exchange via gulping air.

• Physoclistous: Closed system, gas diffuses from blood.

What features of Tiktaalik roseae make it a transitional example between fish and tetrapods?

• Flat head with dorsal eyes.

• Robust pectoral fins.

• No bony connection between skull and pectoral girdle.

What are Lissamphibians? List their key characteristics and provide examples.

• Modern amphibians: Frogs, salamanders, caecilians.

• Traits: Paired lungs, gills in larvae, skin respiration, mostly scaleless.

  • Urodela: Salamanders

  • Anurans: Frogs, toads

  • Apoda: Caecilians

What is the key innovation of Amniotes?

• Amniotic egg: Protects embryo, allows terrestrial reproduction.

Name the three groups of mammals and provide an example of each.

• Monotremes: Platypus

• Metatherians: Kangaroo (marsupials)

• Eutherians: Humans (placental mammals)

What are the three primary germ layers in organogenesis, and what tissues/organs do they give rise to?

• Ectoderm: Epidermis, nervous tissue, cranial muscles.

• Mesoderm: Dermis, skeletal/muscle tissue, circulatory system, kidneys.

• Endoderm: GI/respiratory lining, liver, pancreas.

How does body size relate to surface area and volume? What are the consequences of this relationship for physiological processes?

• As body size increases, surface area grows slower than volume.

• Larger organisms need specialized structures (lungs, intestines) for efficient exchange.

Why is surface area important for material exchange?

• Greater surface area allows more efficient diffusion of gases, nutrients, and waste.

Define phylogenetic groups: monophyletic, paraphyletic, polyphyletic.

• Monophyletic: Includes ancestor and all descendants.

• Paraphyletic: Includes ancestor but not all descendants.

• Polyphyletic: Grouped by traits, not common ancestry.

What are neural crest cells and ectodermal placodes?

• Neural crest cells: Stem cells forming diverse structures (e.g., cranial nerves, pigment cells).

• Ectodermal placodes: Thickenings that give rise to sensory organs.

What are placoid scales and their function?

• Found in Chondrichthyes.

• Tooth-like, reduce drag, protect skin.

What is the function of the cranium in vertebrates?

• Protects brain and sensory organs.

• Derived from neural tube and cartilage/bone.