Anatomy lecture 3

Flashcards covering key vocabulary related to the evolutionary history and characteristics of primitive chordates (Amphioxus, Tunicates) and early vertebrates (Agnathans like lampreys, hagfishes, ostracoderms, and conodonts).

Amphioxus Anterior End

The 'head' region containing sensory systems, an ocellus, feeding mechanism, endostyle, and pigment spot.

Ocellus (Amphioxus)

A light-sensitive organ found in amphioxus.

Endostyle (Amphioxus)

A primitive 'thyroid' gland in amphioxus.

Pigment Spot (Amphioxus)

A rudimentary 'proto-eye' in amphioxus.

Biological Role of Slits in Amphioxus

To filter food, acting as a sieve to bring in specific sized food particles.

Hatschek’s Pit

A ciliated structure in amphioxus that secretes mucus to help collect food, functioning as a proto-pituitary with endocrine capabilities.

Velum (Amphioxus)

A structure acting like a 'partial diaphragm' in amphioxus.

Pharyngeal Slit (Amphioxus)

A filter-feeding organ in amphioxus that collects iodine.

Oral Hood (Amphioxus)

A structure that encloses the anterior entrance to the pharynx in amphioxus.

Amphioxus Circulatory System

Features colorless blood lacking blood cells and oxygen-carrying pigments, and no true 'heart' as found in vertebrates.

Pharyngeal Arch Complexes (Amphioxus)

Structures analogous to the afferent and efferent arteries of gills, involved in blood filtration.

Sinus Venosus (Amphioxus)

A blood vessel positioned like a vertebrate heart but lacking a pulse.

Amphioxus Blood Movement

Achieved by the major blood vessels themselves through peristaltic movement, as there is no true heart.

Cephalization

The developmental process of forming a 'head' region.

Urochordata

Also known as 'tunicates' or 'sea squirts,' an important chordate group.

Tunicate Larval Anatomy

Crucial for identifying tunicates as chordates, characterized by a notochord and organized nerve cord.

Hermaphrodites (Monoecious)

Organisms in which both sexes occur in each individual.

Dioecious

Organisms with separate sexes (male and female).

Free Swimming Larva (Tunicate)

An 'ascidian tadpole,' which is bilaterally symmetrical and phylogenetically significant.

Amoebocytes (Tunicate)

Cells with pseudopodia found in tunicate blood, resembling certain vertebrate lymphocytes.

Body Inversion (Deuterostomes)

A developmental process influenced by the ventral expression of BMP and dorsal expression of chordin.

Chordin

A protein that is antagonistic to BMP (Bone Morphogenetic Protein).

BMP (Bone Morphogenetic Protein)

A multifunctional growth factor involved in development.

Vertebrate Synapomorphies

Shared derived characteristics of vertebrates, including vertebral column, olfactory epithelium, pineal/parietal eye, lateral paired eyes, electroreception, visceral and aortic arches, sophisticated heart, and mineralized tissues like dentine, enamel, and bone.

Electroreception

The ability to detect electrical stimuli, present in some vertebrates but lost in most reptiles, birds, and mammals (except monotremes).

Endochondral Skeleton

An internal skeleton of mesodermal origin, formed from a cartilaginous precursor.

Dermal Bone

Bone of mesodermal origin that forms part of the 'external skeleton,' such as parts of the skull and jaw.

Permian-Triassic Boundary Extinction

A mass extinction event linked to massive volcanic eruptions in Siberia, leading to high CO2, increased temperatures, and anoxic conditions, particularly in marine environments.

Ostracoderms

Extinct jawless armored fish-like animals.

Evolution of Jaws

A critical evolutionary development that facilitated prey capture and a more active lifestyle, leading to jawed fishes.

Agnathan Vertebrates

Jawless vertebrates, including lampreys, hagfish, ostracoderms, and conodonts.

Cyclostomes

Extant jawless vertebrates, comprising lampreys and hagfish.

Lampreys and Hagfishes

Extant jawless vertebrates characterized by a cartilaginous skeleton, keratin, eyes (including a median eye), neural arches, and a large notochord.

Myxinodea (Hagfishes)

Deep-sea, burrowing marine animals that feed on dead or dying organisms, known for their single wide nostril and body fluid salinity matching seawater.

Petromyzontiformes (Lampreys)

A group with both parasitic and free-living adult forms; all species spawn in fresh water, and their larvae are suspension feeders.

Hagfish Defense Mechanism

Involves releasing extreme amounts of mucus and a 'gill clogging' slime, and using a 'knotting' behavior to escape predators.

Larval Lamprey Gills

Used for filter feeding, displaying a convergent evolutionary pattern with amphioxus.

Adult Lamprey Gills

Used primarily for breathing.

Keratins

Largely insoluble proteins formed within the cytoplasm of epidermal cells, originating from the ectoderm.

Lamprey Horny Teeth

Keratinized structures in lampreys that are not homologous to true vertebrate teeth but serve a similar role in feeding.

Arginine-Vasotocin (AVT)

An oligopeptide hormone homologous to oxytocin and vasopressin, found in all non-mammalian vertebrates and a major regulator of water balance, osmotic homeostasis, and social/sexual behavior.

Pleiotropy

A phenomenon where one gene influences more than one phenotypic trait, exemplified by the vasotocin receptor gene impacting multiple organ systems.

Conodonts

Small, soft-bodied early vertebrates characterized by mineralized dental tissues ('teeth') used to crush food, important for dating geological strata.