Terminology, Vertebrate Story, Chordates

Homology

Similarity due to shared ancestry.

Analogy

Similar function but not derived from a common ancestor.

Homoplasy

Similar appearance or traits that evolved independently.

Radial symmetry

Body parts arranged around a central axis; multiple planes of symmetry.

Bilateral symmetry

Body divided into right and left halves along one plane.

Sagittal plane

Divides body into left and right.

Frontal (coronal) plane

Divides body into dorsal (back) and ventral (front).

Transverse plane

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

Cranial

Towards the head.

Rostral

Towards the nose (on the head).

Caudal

Towards the tail.

Medial

Toward the midline.

Lateral

Away from the midline.

Proximal

Closer to the body core.

Distal

Farther from the body core.

Notochord

Flexible rod providing support in chordates.

Pharyngeal pouches/slits

Used for feeding and respiration in chordates.

Dorsal hollow nerve cord

Becomes central nervous system in vertebrates.

Post-anal tail

Structure used for locomotion in chordates.

Agnathans

Jawless vertebrates such as hagfish and lampreys.

Gnathostomes

Jawed vertebrates with jaws evolved from rostral pharyngeal arches.

Chondrichthyes

Class of cartilaginous fish, including sharks and rays.

Actinopterygii

Ray-finned fish with a swim bladder.

Sarcopterygii

Lobe-finned fish with internal bones in fins.

Ganoid scales

Hard, mineralized scales found in primitive ray-finned fish.

Physostomous swim bladder

Connected to esophagus; gas exchange occurs by gulping air.

Physoclistous swim bladder

Closed system; gas diffuses from blood.

Tiktaalik roseae

Transitional fossil with features between fish and tetrapods.

Lissamphibians

Modern amphibians, including frogs, salamanders, and caecilians.

Amniotic egg

Key innovation of amniotes that allows terrestrial reproduction.

Monotremes

Egg-laying mammals, such as the platypus.

Metatherians

Marsupials, such as kangaroos.

Eutherians

Placental mammals, such as humans.

Ectoderm

Germ layer that develops into epidermis and nervous tissue.

Mesoderm

Germ layer that forms skeletal/muscle tissue and circulatory system.

Endoderm

Germ layer that becomes the lining of the GI tract and respiratory system.

Surface area to volume relationship

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

Importance of surface area

Greater surface area allows for more efficient material exchange.

Monophyletic group

Includes ancestor and all descendants.

Paraphyletic group

Includes ancestor but not all descendants.

Polyphyletic group

Grouped by traits, not by common ancestry.

Neural crest cells

Stem cells that give rise to various structures in vertebrates.

Ectodermal placodes

Thickenings of ectoderm that develop into sensory organs.

Placoid scales

Tooth-like scales that reduce drag and protect skin in Chondrichthyes.

Cranium function

Protects the brain and sensory organs in vertebrates.