Lecture 27-

single, pair, digits.

Tetrapod limbs three-parted: 1. Upper, ______ long bone hinged to; 2. A _____ of parallel long bones; 3. Terminal hand/foot with jointed _______.

plants

Tetrapods (~365 MYA) preceded by ______ & invertebrates move to land (~475-500 MYA).

Digits

Tetrapods are vertebrates with two pairs of sturdy, skeleton-supporting limbs with __________ (synapomorphy).

jawed

Three lineages of_______ vertebrates (Gnathostomes) survive today: chondrichthyans, ray- finned fishes, and lobe-fins.

Transition

Why ___________ to Life on Land? • Continental drift: - Convergence → Pangaea: coastal regions became land-locked, • LOTS OF FOOD Plants, arthropods, and other invertebrates colonizied land ~100 million years prior to tetrapods • Competition and predation in aquatic ecosystems. → Escape predators & few competitors. • New terrestrial niches!

Simple lung

dorsal outpocketing of gut filled with gas.

vertebrates.

craniates that have a backbone - Allowed development of more complex nervous system.

Fins to limbs

some skeletal elements in lobe-finned fish are homologous to bones in tetrapod limbs. - Pectoral fins developed into forelegs; pelvic fins developed into hind legs.

Myllokunmingia

had parts of a braincase and was a true craniate

Bony Fish $$

important to fishing economy. Overfishing → collapse of many fish stock Aquarium trade.

Acanthostega (Early Tetrapod)

- 4 limbs w/ numerous (>5) DIGITS. - Pelvis weakly attached to vertebrate. • Pelvis attached to vertebrae → support, weight-bearing - Long fin rays around the tail. - No true elbows, knees, wrists or ankles (i.e. not weight-bearing). - Internal gills and lungs, but ribs were too short to support chest cavity out of water. - Acanthostega primarily aquatic. • What were limbs used for? - Suitable for paddling (digits webbed), or for holding on to aquatic plants.

Neural crest

- Collection of cells near dorsal margins of closing neural tube in embryo. - cells give rise to variety of structures, including some of the bones and cartilage of skull.

Hagfish

- Feed on soft-bodied worms or on decaying corpses of larger animals → rasping action of tooth-like plates strips flesh from carrion. - Bury themselves in a corpse → absorb the carcass's nutrients through their skin.

Plant adaptations for life on land:

- Waxy cuticle - waterproof epidermis. - Vascular tissue - transports water to tissues; supports structures against gravity. - Stomata - regulate gas exchange, minimizing drying out. - Pollen, seeds, fruit - new reproductive strategies for life on land.

Animals evolved (to adapt to life on land)

-Waterproof external layers -internal gas exchange system -reproduction independent of water -strong support systems ( endoskeletons and exoskeletons) that allowed them to move about on land.

Sharks

-streamlined bodies -Pectoral fins add lift. - Do not have gas-filled swim bladder. - Buoyancy via storing oil in liver.(SINK WHEN NOT SWIMMING) -most carnivores -short digestive tract

Challenges of terrestrial life

1. Gravity 2. Desiccation 3. Respiration 4. Reproduction 5. Locomotion 6. Senses 7. Temperature

Gnathostome (jawed vertebrates) synapomorphies

1. Opposing Jaws 2. Mineralization of skeleton 3. 2 pairs of appendages 4. 2nd genome duplication, incl. duplication of Hox genes (4 clusters). 5. An enlarged forebrain → enhanced smell and vision.

Classes of bony fish

Actinopterygii (Ray-fin fish (actin = ray) Sarcopterygii (Lobe-finned bony fish)

Desiccation (Challenges of terrestrial life)

Air is drier than water! Terrestrial animals need some form of skin/coat to stop tissues from desiccating (incl. protecting embryos).

Neck

Allows tetrapod to move head independently of body, up-down and side-to-side.

lancelets

Ancestral chordates may have resembled ________.

Locomotion (Challenges of terrestrial life)

Aquatic animals can swim, or otherwise move through the water. These motions have to be modified in the terrestrial realm.

Gravity (Challenges of terrestrial life)

Aquatic life is buoyed by water. Air is not buoyant! Terrestrial animals needed supporting tissue.

Respiration (Challenges of terrestrial life)

Aquatic organisms exchange O2 & CO2 dissolved in water. In air, these substances are gases, so new structures are needed to breath.

Reproduction (Challenges of terrestrial life)

Aquatic organisms often release gametes directly into water (EXTERNAL FERTILIZATION). This approach is much less effective in air, so other solutions evolve.

Ectoparasitic

As adults, many lampreys ___________ of fish. - Clamp on fish by funnel-like sucking mouth. - Scrape skin with rasping tongue (keratin spines) → suck blood. - All lampreys can also feed on small invertebrates.

Endoskeleton/Cephalization

Brain encased in protective plates (cranium, not jaw). Endoskeleton of cartilage or bone • Includes paired eyes & other sensory organs (from neural crest cells).

(Class) Chondrichthyans (sharks, rays, etc)

Cartilaginous fishes Endoskeleton made of cartilage. - But have BONY teeth.

bony fishes

Characteristics of ______ • Fully ossified (bony) endoskeleton. • Dermal armor is reduced to relatively thin, plate-like bony scales. • external fertilization common.

two, metabolism

Circulatory system modified: - Closed circulatory systems, including a heart with at least ____ chambers. - Haemoglobin in red blood cells; oxygenated via gills or lungs. - Kidneys - removal of waste products of metabolism from blood. → Support higher ________________ and more muscularity than tunicates and lancelets.

Ray-fin

Class Actinopterygii: _______fish Fins supported by long, flexible RAYS→ for maneuvering, defense, etc. All commercially important bony fish are in this group.

Lobe-finned

Class Sarcopterygii: ________________ bony fish. fleshy, muscular pectoral and pelvic fins supported by BONY ELEMENTS in the base. Single basal skeletal element (humerus/femur) + central supporting elements.

Hox Genes

Craniates have two clusters of_______________ - Non-craniate chordates (lancelets & tunicates) have 1 cluster.

Oviparous

Eggs hatch outside mother's body.

Ovoviviparous

Embryo develops within uterus and nourished by egg yolk.

Viviparous

Embryo develops within uterus and nourished through a yolk sac placenta from mother's blood.

pharyngeal clefts

Embryonic ___________ ________ develop into 'active' organs. - Functions associated with muscles and nerves (cf. invertebrate chordates). → Gill slits (aquatic species) → Parts of ear (terrestrial species)

Stepwise

Evolution of tetrapods from lobe-fins represented a significant change in body plan Fossil record provides evidence of ____________ changes → series of fossil forms that lived between about 390 and 360 MYA.

Gills

Extant bony fish descended from ancestors living in brackish water that had simple lungs and ________.

Connection

For swim bladders: - __________ to the gut via pneumatic duct present in more "primitive" ray-finned fish. - __________ lost in most ray-finned fish (closed swim bladder).

Senses (Challenges of terrestrial life)

Light, sound, and smell transmit differently in water than in air. Some senses (e.g. electric sense, lateral line) don't work in air at all. Terrestrial animals have to evolve new adaptations to deal with these differences.

bony

Lobe-fins have fleshy, muscular pectoral and pelvic fins supported by ________ elements in the base. ***Tetrapods are 1 of 3 surviving lobe-fin lineage***

Mouthparts

Mineralization (with calcium) appears to have originated with vertebrate _______________.

Monophyletic

Modern classification includes all bony vertebrates in _____________ clade Osteichthyans. *Nearly all extant osteichthyans have a BONY (ossified) endoskeleton*. - Clade includes bony fish and tetrapods (amphibians, avian and non- avian reptiles, and mammals).

Origin of Jaws

Modifications of 2 pairs of skeletal rods that had supported pharyngeal slits. The mouth could then grow bigger and wider → capture larger prey.

HOMOLOGOUS

Most extant lungfish species have two lungs. - Lungs of lungfish are _______________ to lungs of tetrapods. - Lungs of lungfish and tetrapods extend from the ventral surface of the esophagus.

prior

Most traits critical to the move to land evolved _______ to tetrapods exiting water (Simple lungs, internal nostrils (for breathing), feet)

limbs, feet

One of most significant events in vertebrate history was when fins of some lobe-fins evolved into _____ and ______ of tetrapods.

Swim Bladder

Original simple lung modified into __________________ in most extant bony fish. -maintains neutral buoyancy of fish = "float" @ desired depth (NOT found in Chondrichthyes)

tetrapods

Osteichthyans (traditional) is paraphyletic if restricted to fish. - Common ancestor of Osteichthyes (BONY FISH) includes _____________ as descendants.

teeth

Placoid scales structurally homologous with vertebrate _______ *Shark continuously shed and replace teeth.

cloaca

Reproductive tract, excretory system, and digestive tract empty into a common ________

electrical fields, vibrations

Shark Senses: -acute senses of sight and smell (noses!). -Can detect __________ _________ from muscular movement of nearby animals. Can detect ______________ in water. - via lateral line.

Placoid

Skin rough → dermal ____________ scales. Scales have spines (feels rough when stroked backwards). reduce hydrodynamic drag .

Claspers

Sperm transfer through copulation. - Make Shark holds female with ___________ to help guide sperm

Lungfish

Sub-class Dipnoi (__________) (<Class Sarcopterygii) - Two modes of RESPIRATION: gills and lungs - Gulp air into lungs from water's surface by lowering and raising floor of mouth cavity (buccal pump).

Actinistia

Sub-class__________ (<Class Sarcopterygii) - One extant genus: Coelacanths "Living fossil";

Homologous (same evolutionary origin)

Swim bladder is _______________ to the lungs. - Lungs (paired) → respiration. - Swim bladders (single) → maintain neutral buoyancy.

Craniates

Synapomorphies of _____________ 1. Two clusters of Hox Genes 2. Neural crest. 3. Endoskeleton and pronounced Cephalization 4. Circulatory system modified. 5. Embryonic pharyngeal clefts develop into 'active' organs.

Temperature (Challenges of terrestrial life)

Temperature fluctuate more in air than in water. Terrestrial animals have to evolve adaptations to deal with these fluctuations.

agnathans

Two extant classes of craniates LACK jaws (look like eels) - Hagfishes and Lampreys. *paraphyletic group

Amphibia, Amniota

Two groups of extant tetrapods

Maneuverable fins.

Unique pattern of dermal bones in head (e.g. operculum) and pectoral girdle

Lungs

_________ or ________ derivatives synapomorphic (shared, derived) character for Osteichthyans.

Genome

__________ sequencing suggests: - Genes associated with heart and thyroid common to all chordates. - Genes associated with transmission of nerve impulses unique to vertebrates. - Early whole-genome duplication in chordate evolution.

Cartilaginous

___________ skeleton is NOT a primitive character state. -Derived from ancestors with bony skeletons. Development of most vertebrates: skeleton is first cartilaginous and then becomes ossified. Mineralization of cartilage by calcium phosphate. (SHARKS SKIP THIS STEP)

Osteichthyan (BONY FISH)

_____________ Synapomorphies: 1. Lungs or lung derivatives. 2. Operculum 3. Maneuverable fins

Transitional

________________ tetrapods had legs and both lungs and gills, but were still primarily aquatic and unsuited to life on land:

Craniata

are animals in Chordata with a head. MOST = vertebrates. - Skull of hard bone or cartilage (cranium = skull). - Evolution of a head enabled chordates to coordinate more complex movement and feeding behaviours.

vertebral column)

chain of skeletal elements (cartilage or bone) surrounding and protecting nerve cord. • Replaces function of notochord

Conodonts

first vertebrates with mineralized skeletal elements in their mouth and pharynx. *Vertebrate endoskeleton became fully mineralized much later*

Haikouella

had a well-formed brain, eyes, and muscular segments, but not a braincase. *transition to craniates*

Lampreys (Class Petromyzontida)

oldest living lineage of vertebrates. Notochord in adults surrounded by cartilaginous tube = Primitive vertebral column no jaws or paired limbs.

Monoaxial fin:

single basal skeletal element (humerus/femur) + central supporting elements

Operculum

single plate of dermal bone that covers and protects the gills. *Breathe by drawing water over operculum-protected gills, use it as a pump!*

Gnathostomes

vertebrates that have jaws. *sharks & their relatives, ray-finned fishes, lobe-finned fishes, amphibians, reptiles (incl. birds), and mammals.*

placoderms.

• Earliest gnathostomes fossils: extinct lineage of armored vertebrate fish Among the first jawed fish. First fish to develop pelvic fins

Tiktaalik (Transitional tetrapod)

• Fish features: scales, fins without digits, and gills + lungs. • Tetrapod features: neck (Shoulder (pectoral girdle) not fused to skull ), ribs, limb skeleton, eyes on top of head Shape and size of the hip socket (pelvis) = could partially support its own weight (but still more fish-like)

Hagfishes (Myxini)

• Only known living animals that have a skull but NO vertebral column. - cartilaginous cranium; no jaws. - Well-developed notochord: axial rod of cartilage; no vertebrae.

Rays and Skates

• Similar to sharks in most respects. • But most swim by flapping large pectoral fins. Dorso-ventrally flattened.

fish

• paraphyletic group of aquatic craniates that use gills for respiration. • Includes jawless fishes, cartilaginous fishes, and bony fishes, but excludes tetrapods.