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Fishes

What major group of vertebrates has the most species?

500 mya

When did the first vertebrates appear?

Notochord; dorsal, hollow nerve cord; Postanal tail; Pharyngeal slits

What are the 4 characteristics that chordates share at some point?

Paedomorphosis

retention of larval characteristics into

adulthood

Key evolutionary features of vertebrates

endoskeleton; link between pharynx and breathing; well developed nervous system; Paired limbs

Cephalochordata

Lancelets or amphioxus. Tiny eel-like marine animals. Adults present all chordate characteristics

Urochordata

(Tunicates or Sea Squirts). Sessile marine animals. Attach to rocks and filter feed. Adults do not resemble a chordate. Tadpole larval stage has all 4 chordate characteristics.

Systematics

the scientific study of the kinds and diversity of

organisms, and their evolutionary relationships

Taxonomy

discipline in charge of providing names for groups of

organisms and establishing rules by which organisms are named

Binomial nomenclature

Every organism (species) is assigned a two-part name 1st

word genus, 2nd word species (e.g., Homo sapiens)

Hierarchical classification

System of grouping species

Lower levels nested within higher levels

Current system contains 7 primary taxonomic ranks

Homologous structures

similarity due to shared ancestry

Analogous structures

similarity not from shared ancestry

Monophyletic

Paraphyletic

Polyphyletic

Allopatric Speciation

The formation of new species in populations that are geographically isolated from one another.

Sympatric Speciation

The formation of new species in populations that live in the same geographic area

Vicariant speciation

Original population becomes separated. Each allopatric group is subject to different environmental stresses and diverges via natural selection leading to reproductive isolation

Founder effect

Few individuals move far out of normal range and found a new population

Ecological Segregation

Species live in the same area, but segregate relative to specific habitat types

Bergmann's Rule

endotherms tend to be larger in colder

climates

Allen's Rule

extremities of endotherms vary inversely

w/body size

Gloger's Rule

endotherms living in arid regions tend to be

lighter in coloration

Cyclostoma

jawless fish

Gnathostoma

jawed vertebrates

Species

'types' of organisms, members of the same species have similar characteristics, reproductively isolated from other groups

Devonian

Age of Fishes

Mixini

Hagfish

Petromyzontiformes

Lampreys

Osteognathostomes

- Armored carapace made of bone

- Appeared in Devonian

- No paired fins

- More derived than extant cyclostomes

Evolution of hinged jaws

Allowed for more diverse prey types, predatory lifestyles, ect.

Placodermi

- Extinct group

- Often armored

- Jaws with teeth *

- Pectoral fins

- Heterocercal tail

- Speculated ties to sharks

Chondrichthyes

Sharks, skates, rays, chimera

- Cartilaginous skeleton

- Two sets of paired fins

- Heterocercal tail

- Placoid scales

- Inferior mouth

- No swim bladder

Acanthodii

- Extinct group

- Lived during 2nd half Paleozoic

- Jaws with teeth

- Heterocercal tail

- Multiple sets of paired fins

- Most Small

Osteichthyes

(Bony fish)

- Appeared during Silurian

- Skeleton of bone

- Thin, overlapping scales

- Paired fins

- Swim bladder

Actinopterygii

(ray-finned fish)

- Fins supported by rays

- Date back to devonian

- 2 main subgroups (Chondrostei and Neopterygii)

Chondrostei

- Primitive bony fish (sturgeon, paddlefish)

- Skeleton mostly cartilage (secondary bone loss)

- Body either naked or with thick, plate like scales

- Rostrum projects past the mouth

Neopterygii

- Modern bony fish

- Most species of fishes (over 32,500)

- Incredibly diverse in form, function, and habitat

Sarcopterygii

(Lobe-finned fish)

- Fins have fleshy base

- Smallest group

- 2 main groups Actinista and Dipnoi

- Precursors to tetrapods

Actinistia

(Coelacanths)

- Common in Devonian

- Coelacanth one of the most important finds in recent biological history

- Thought extinct; rediscovered in 1938 off coast of Africa

Dipnoi

(lungfish)

- Date to Paleozoic and Devonian

- Double breathers

- 6 living species

- During dry periods form cocoon, aestivate in mud

- Closest living relatives to tetrapods!!

Rhipidistians

- Predaceous, large, and often armored

- Died out shortly after Devonian

- Ancestral precursors to tetrapods

Amphibians

- Terrestrial, aquatic, or both

- Legless and or gilled larval stage

- Smooth permeable skin

- Egg without shell

- Generally oviparous with external fertilization

Carboniferous

Age of Amphibians

Acanthostega

- More aquatic than terrestrial

- Presence of ceratobrachials

- Tail long and fishlike, with fin rays

- Polydactyly

- Implies 5-toed tetrapod condition is derived

- Limbs

Ichthyostega

- 1st good fossil of land vertebrate

- Vertebrae fishlike

- Tail long and fishlike with fin rays

- Pectoral and pelvic girdles strong

- Polydactyly

Whatcheeria

Early tetrapod from Iowa

Temnospondyli

- More aquatic lifestyle

- Flat, immobile skulls

- Hand reduced to 4 fingers

- Gave rise for Lissamphibia

Tiktaalik roseae

- Transitional fossil with mixed features

- Fish features: Bony scales, fin rays, fish tail, gill arches, fish-like jaw

- Tetrapod features: Shortened skull, modified ear, mobile neck, functional wrist

Gymnophiona

(Caecilians)

- Tropical

- Burrow underground or in leaf litter

- Legless and tailless

- Retain a few scales in neck

- Poorly studied

Urodela

(Salamanders)

- Generally have legs

- Show great deal of bone loss

- Can be long-lived (20 years)

- Most do not metamorphose

Anura

(Frogs and toads)

- Live in tropical, temperate, sub-artic, and even desert

- Large hind legs for leaping

- Metamorphic life cycle

- No tails as adults

Basal Reptilimorphs

- More terrestrial than Temnospondyls

- Generally robust and combination of amphibian and reptilian characteristics (5 fingered hands)

- Domed skulls with some skull movement

- Recent member of this lineage is genus Seymouria

Cotylosaurs

- Extinct most basal reptiles

- Lizard like insect eaters

- Skull is slightly amphibian

- Nearly all other skeletal characteristics reptilian

Lissamphibia

(Modern Amphibians)

- Loss of bone in skull

- Loss of scales

- Most with 4 digits (not 5)

- 2 middle ear bones

- Weak teeth

- 3 chambered heart

Mesozoic

Age of Reptiles

Reptilian Characteristics

- Amniotic egg with yolk

- Lack larval stages

- Impermeable skin

- Breathe via lungs

- Ectotherms?

- Generally 3-chambered hearts

Anapsid

no opening behind eye

Synapsid

1 opening behind eye

Diapsid

2 openings behind eye

Circulatory system

Transports gases, nutrients, wastes, hormones, and antibodies; regulates temperature; maintains a stable internal environment

Vascular system

Includes the heart, blood vessels, and blood

Atrium

Thinner-walled heart chamber that receives blood through veins

Ventricle

Thick-walled heart chamber that pumps blood out into arteries

Arteries

Blood vessels that carry blood away from the heart

Arterioles

Small blood vessels that carry blood throughout the body

Veins

Blood vessels that carry blood back to the heart; usually larger in diameter but thinner-walled than arteries

Venules

Small vessels that collect blood and lead into larger vessels (veins)

Capillaries

Very narrow vessels where exchange of materials occurs between blood and tissue cells

Plasma

Mostly water; also contains nutrients, salts, hormones, proteins, wastes, and antibodies

Erythrocytes

Red blood cells that contain hemoglobin

Leucocytes

White blood cells involved in immune function

Thrombocytes

Blood cells involved in blood clotting

Open circulatory system

Blood is emptied into the body cavity

Closed circulatory system

Blood remains inside blood vessels

Lymphatic system

Returns tissue fluid (lymph) to the cardiovascular system and filters foreign particles through lymph nodes

Fish heart

Two-chambered heart with one atrium and one ventricle

Fish circulation

Single circulation: Heart → Gills → Body

Amphibian heart

Three-chambered heart with two atria and one ventricle

Pulmonary circuit

Heart → Lungs → Heart

Systemic circuit

Heart → Body → Heart

Lepidosauria

(most living reptiles)

- Plesiosaurs, tuatara, lizards, snakes

Archosauria

Thecodonts, non-avian dinosaurs, pterosaurs, crocodilians, birds

Ichthyosauria

- Extinct diapsid

- Highly specialized marine species

- Similar in form to dolphins and porpoises

Plesiosauria

- Extinct diapsid

- Aquatic marine

- Limbs oar-like

- Long thin neck with small head

Rhynchocephalia

- Tuatara

- 1 species in New Zeland

- Fossil forms date to Triassic

- Considered living fossils

- Most primitive living reptiles

Squamata

- Lizards, snakes, and worm lizards

- Similar scale patters and paired hemipenes

- Primarily terrestrial

- Multiple groups have lost limbs

Crocodilia

- Alligators and crocodiles

- Date to Triassic

- Lots of sharp teeth

- Long, tubular body, and long snout tipped with nostrils

- Semi-aquatic, with long tail for propulsion in water

Pterosauria

- Date to Triassic

- Extinct flying reptiles

- Wing membrane (patagium) supported by 4th digit

- Hollow, air filled bones, elongate jaws

- large unkeeled sternum

- Probably lived in Iowa!

Ornithischia

- Date to Late Triassic

- Bird-hipped herbivorous dinosaurs

- Some quadrupedal

- Some bipedal

- Many were prey for theropods

Theropods

bipedal carnivores

Sauropods

Largest terrestrial vertebrates, quadrupedal herbivores

The _____ present in tetrapods is homologous to "stapes" in mammals

Columella

Dromaesaurs

- Stem paraves

- Flexible and rotating wrist structure

- Shift in shoulder joint

- Beginnings of keeled sternum

- arms capable of flapping

Archeopteryx

- First true bird

- Could fly

- Had a wishbone

- Many intermediate features between theropods and birds

Denatary bone

Single lower jaw in mammals

Diphyodonty

Two sets of teeth

Heterodont dentition

Different shaped teeth for different jobs

Pelycosaurs

- Sailbacks

- Common in late Carboniferous and Permain

- Carnivores with large sharp teeth

- Arched palate Sail of Dimetrodon derived from enlarged neural spines

- Evidence of blood vessels on spines