Lecture Exam 2 Essay Q Flashcards
Why did the sacral and cervical vertebral regions develop during the transition to land?
The sacral and cervical regions developed with the pelvic and pectoral girdles and fused to bear more load
Why was the regionalization of the cervical vertebrae important?
Allowed for the head to be separate from the pectoral girdle
What is the advantage of having a distinct lumbar region?
As the hindlimbs swing forward to take longer strides, there is no risk of ribs in the lumbar region contacting one another
What are the types of loads a material can be exposed to?
Compression, Tension, Shearing, and Torsion
How well does bone resist the types of loads?
Bone is very strong against compression, fairly strong against tension and torsion, and somewhat weak to shearing
How well do tendons resist the different types of loads?
Tendon is very strong against tension and torsion, but weak to compression
How well does cartilage resist the different types of loads?
Cartilage is very resistant to compression and tension
Define stress
internal resistance exhibited by a body or material when an external force is applied to it – measured in N/cm^2
Define strain
The deformation in a material when mechanical stress is applied – dimensionless
Elasticity
How quickly materials fully return to original shape
Plasticity
Point at which materials yield to permanent deformation
Step 1 of endochondral ossification
Chondrocytes at the center of the cartilage model grow and die as the matrix calcifies
Step 2 of endochondral ossification
New osteocytes cover the shaft of the cartilage in a thin layer of bone
Step 3 of endochondral ossification
Blood vessels invade the cartilage; new osteocytes form a primary ossification center
Step 4 of endochondral ossification
The bone of the shaft thickens, and the cartilage near the epiphyses is replaced by bone
Step 5 of endochondral ossification
Blood vessels invade the epiphyses and osteoblasts form the secondary ossification centers
Axial skeleton in fish
Specialized for undulatory motion; spine extended into lobed tails
Axial skeleton in early tetrapods
Under a lot of torsion – not designed for walking; eventually evolved zygapophyses
Zygapophyses
lateral processes of the vertebrae that interlock with adjacent vertebrae to prevent torsion
Axial skeleton in modern therapsids
Fusion of sacral and cervical vertebrae; removal of lumbar ribs; elongated cervical region
How is the hyoid apparatus important in fish?
Hyoid arch is involved in jaw suspension; in sharks and rays, jaws are attached to hyoid arch instead of directly to skull
How is the hyoid apparatus important in amphibians?
hyoid apparatus supports tongue – in lingual feeding, muscles squeezes hyoid out of mouth (like squeezing wet bar of soap)
How is the hyoid apparatus important in birds?
hyoid apparatus assists in tongue protrusion in woodpeckers and hummingbirds
Synarcual
In batoids and ratfishes; fused vertebrae meant to stiffen the surrounding area and support fins
Urostyle
In frogs; fused vertebral element providing more pelvic stability for muscle attachment for saltation
Synsacrum
In birds; fused vertebral elements that allow for greater load to be placed on pelvic girdle when bipedal
List four lineages that exhibit limb loss
In fish: seahorses, sunfish, catfish, and true eels; Caecilians; Snakes; Aquatic mammals
What lifestyles are associated with limb loss?
Fossoriality (burrowing) and aquatic lifestyles
What materials are teeth made of?
Enamel, dentine, and cementum in mammals
How are scales similar to teeth?
Early scales were composed of enamel and dentine; In chondrichthyans, placoid scales have pulp cavity as well
Evidence of inside-out hypothesis
Requires evidence of odontodes forming from endoderm
Evidence of outside-in hypothesis
requires evidence that odontodes form from ectoderm
Best hypothesis for tooth evolution
modified outside-in: teeth form from ectoderm-endoderm boundaries; denticles were precursors to teeth
Gegenbaum theory of fin evolution
Limbs are derived from gill arches
Balfour & Thacher theory of fin evolution
Fin-folds (like in Amphioxus) give rise to fins
Yonei-Tamura theory of fin evolution
Medial fin programming migrated to lateral mesoderm
Supporting evidence for Balfour & Thacher
Metapleural folds in cephalochordates, wide fins in embryonic elasmobranchs, accessory lateral fins in acanthodians, possible fossil evidence – however, lack of embryonic evidence
Supporting evidence for Yonei-Tamura
Lots of embryonic evidence – however, no way to validate with fossils
Suspension feeding
feeding on suspended plankton by filtering it from the water column
Suction feeding
generating negative pressure by rapidly expanding the pharynx to suck prey into mouth
Ram feeding
overtaking prey by outpacing it and swallowing it whole
Inertial feeding
rapid movement of head and jaws causes prey to be transported further into oral cavity
What role do pharyngeal jaws perform?
Assist in transporting prey into mouth and down throat
What are the different types of cranial kinesis?
jaw suspension and intracranial joints
Types of jaw suspension
Autostyly, Amphistyly, Hyostyly, Metautostyly, and Craniostyly
Types of intracranial joints
Metakinesis, Mesokinesis, Prokinesis, Streptostyly
Autostyly
Jaw suspension in which the upper jaw is connected directly to the cranium
Amphistyly
Jaw suspension in which the upper jaw is braced against the cranium in two places: anteriorly near the orbital capsule and by the hyomandibulae
Hyostyly
Jaw suspension in which the upper jaw is connected to the cranium only by means of ligaments and the hyomandibulae
Metautostyly
Autostyly in amphibians, ‘reptiles’, and birds
Craniostyly
Autostyly in mammals
Metakinesis
cranial kinesis arising from a joint between the braincase and dermal bones of the cranial vault – found in squamates
Mesokinesis
cranial kinesis arising from a join tin the middle of the dermocranium, posterior to orbit – also found in squamates; mesokinetic are also metakinetic
Prokinesis
cranial kinesis arising from a joint anterior to the orbit of the dermocranium – found in snakes and birds
Streptostyly
dislocation of jaws to eat larger prey
Common adaptations for fluid feeders
long tongue, tongue bristles
Why are hypsodont teeth important for grazing?
Hypsodont teeth are very resistant to abrasion resulting from grazing
What are some materials that plants use as herbivory defenses?
calcium oxalates/druse and silicates
Difference between browsers and grazers
browsers eat mostly dicots (woody vegetation like shrubs) and are smaller, grazers eat mostly monocots (grass) and are larger
Chewing vs Mastication
Many animals chew/bite, but only mammals truly masticate
Why does mastication require precise occlusion?
The repeated chewing motion requires the teeth to return to the same spot
Salivary gland modifications
Snakes: toxins injected by fangs; vampire bats: anti-coagulants; insectivores: toxins - submaxillary and sublingual glands
How do ungulates extract the most nutrients out of their food?
Chewing cud for extra mechanical processing; symbiotic bacteria for cellulose fermentation – requires large storage capacity and slow passage time
What are the three component tissues of the integument?
epidermis (from ectoderm), dermis (from mesoderm), Basement membrane (composed of basal lamina from ectoderm and reticular lamina from mesoderm)
Which integument layers can give rise to bone?
The dermis gave rise to dermal bone and bony scales in ancient fish; dermis is responsible for most facial bones
What tissues arise from skin?
scales, feathers, hair, baleen, vibrissae (whiskers), nails, claws, horns, and hooves
Glands in the integument
Salt glands in crocs, turtles, and birds help excrete excess salt; uropygial gland in birds produces oils to waterproof feathers; musk glands in snakes and turtles produce noxious odors to deter predators; sebaceous glands, and mammary glands
Functions of integument
insulation/thermoregulation, osmoregulation, respiration, protection, feeding (like baleen, teeth, claws), reproduction (like feathers for display)
