what is the order of evolution to tetrapods from cartilaginous fishes?
- cartilaginous fishes
- nonteleost ray-finned fishes
- teleosts
- lungfish
- tetrapods
differences between living on land than in water and the evolutionary developments that came with these differences
- air is less viscous and less dense
- need to overcome gravity so terrestrial tetrapods have a skeleton to support the body - gills collapse in air
- need a tidal flow system with a sac like lung - heat capacity and conductivity
adaptations for support and locomotion for terrestrial tetrapods
fish are weightless in water, skeletal structure on avg is lighter and force of gravity is less in water
- skeleton must be rigid (overcome gravity)
- light as possible (need to save energy)
what are tetrapods skeletal systems made up of
cartilage and bone (more dense)
why are tetrapods’ skeletons dynamic?
so internal structure can adjust to changing demand
this is why older people need to keep exercising - if they just sit around then bones atrophy and lose rigidity/strength
how are bones arranged in amniotes, what types of bone are there?
in concentric layers around blood vessels
cylindrical units are called haversian systems
external layers of bone are dense/compact
internal layers are spongy: cancellous bone
haversian systems
cylindrical units in bones
supply nutrients to bone
cancellous bone
spongy bone in bones, internal layer of bones, bordered by haversian systems
joint structure in amniotes
covered by articular cartilage which covers cancellous bone
entire joint is enclosed in a joint capsule which contains synovial fluid - keeps space between bones smooth so they move easily
axial skeleton
skull, vertebral column, ribs, sternum: long axis of body
appendicular skeleton
bones of pectoral girdle, pelvic girdle, and limbs
zygapophyses
vertebrates have them
interlock and prevent bending/twisting and facilitates transfer of weight to limbs
ex. horse’s back is straight even tho there is a lot of force being pulled down by tummy, due to zygapophyses
parts of the zygapophyses
prezygapophysis, postzygapophysis
name major bones in pelvic girdle
ilium, femur, ischium, pubis
name major bones in pectoral girdle
scapula, cleithrum, humerus, clavicle, sternum, coracoid, interclavicle
roles of axial muscles in tetrapods
main roles:
1. postural support of axial skeleton
2. ventilation (hypaxial muscles in diaphragm)
maintain posture
locomotion
examples of axial muscle significance in locomotion
lateral bending in salamanders, lepidosaurs and crocodylians
dorsoventral flexion in mammals
powering of tail in aquatic mammals
lateral bending
dual movement of pectoral limb with opposite side’s pelvic limb
ex. salamanders move by moving right foot and left arm and vice versa
