Exam 1 - comparative anatomy

Common ancestry

Homology

Similar function

Analogy

Similar appearance

homoplasy

Chordate characteristics

Notochord, dorsal hollow nerve chord, pharyngeal slits, post anal tail, endostyle

Hemichordates food movement

Dorsal to ventral

Cephalochordate food movement

Ventral to dorsal

Urochordates

Larval notochord shows phylogenetic relationship to chordates

Larvae getting bigger 2 advantages

Locomotion changes, feeding changes

Paedomorphosis

Juvenile form reproduces, how echinoderms maybe became chordates

Echinoderms and chordates

Common ancestor

Axial skeleton

Vertebral column and skull

Somites

Segments

Resegmentation

Differentiates vertebrae

Rhacitomous

Multiple pieces, flexible

Lepospondyl

Firm, weight bearing

Appendicular skeleton

Limbs and girdles

Fins and girdles 2 functions

Stabilize fin, muscle attachment

Limbs and girdles 3 functions

Stabilize limbs, carry propulsive force, muscle attachment

Fins evolved because

Resist roll, pitch and yaw

Evolutionary change in pelvic/pectoral girdles

Support muscles in sarcopterygian attached to skull to weight bearing limbs in tetrapods

Endochondrial component

Basal fin elements, articulation

Dermal component

Brace and support

Lobe fins pre adapted with form and function to become

Limbs

3 piece girdle

Scapula, coracoid, procoracoid

3 Traits of early mammal girdle

Excavation, orientation, pubis reduced

Bone forces

Compression, tension, shear

3 ways of preventing bone breaks

Counter weight, bigger bones, brace

Immobilized

Atrophy

Exercised

Increased bone density

Wolf's law

New mechanical stress causes thicker compact bone

2 problems in bipedalism

Most weight above center of gravity, distributes weight over two points of contact

Bipedal adaptations

Shorter pelvis at 180, s curve spine for shock absorption

Piezoelectricity

Bone deposited along stress trajectories

Neural spines

Resist compression

Muscles/ligaments

Resist tension

Nodal

Middle of vertebral column, reversal of stress forces

Counter balance function

Reduces compression/tension forces

Direction of neural spine

Towards centrum, resists compression

Neural spine height

Taller has better muscle leverage

Separate lumbar vertebrae

No rib interference in hind legs

Streamlining

Reduces drag

Fossorial

digging

6 Modes of locomotion

Fossorial, arboreal, saltitorial, scansorial, aerial, cursorial

Arboreal

Climbing with grip

Scansorial

Climbing with claws

Saltitorial

jumping

Aerial

Through air

Cursorial

Running

Therapsids

Overhand swing, limbs rotated forwards

Lateral sequence gait

3/4 limbs on the ground

Speed

Stride length x stride rate

4 ways to Increase stride length

Longer distal elements, less distal elements, change in foot posture, added joint

Plantigrade

Humans

Unguligrade

Hooves

Digitigrade

Cat

3 traits of stride rate

Muscle location, lighten distal limb, shorten limb by flexing

Amble

Fore and hind on the same side

Trot

Diagonal

Half bound

Hind at the same time, leading fore

Gallop

Leading and trailing pattern

Pronk/bound

All 4