W11 L2 Flashcards
(19 cards)
What is bipedalism?
form of terrestrial locomotion in which the organism moves by using its two rear limbs
What is the difference between facultative and obligate bipeds?
facultative can move bipedal but don’t have to while obligate bipeds have no other option besides bipedalism
what are some advantages to bipedalism?
increases in stride length, more efficient in speed increase
Why E. cursoris probably evolve the biped gait?
to evade predators
What is the traditional explanation for bipedalism in dinosaurs?
to free up the forearms from locomotion for other purposes like grasping prey
What is the new theory for why dinosaurs evolved bipedalism?
implicates the caudofemoralis which became enlarged and gave the back legs extra strength. this reduced the front legs and shifted the center of gravity making dinosaurs become obligate bipeds. was a way to escape predators rather than catch prey
from whom was the crouched posture of extant birds inherited from?
ornithischians dinosaur ancestors
What is the theory that explains bipedalism in birds?
size and weight of the forelimbs changed, as well as the tail becoming lighter which shifted the center of gravity.
Why is the position of the femur in birds almost horizontal?
to maintain balance with a heavier front end, animals feet has to stay forward. horizontal position of the femur allows for this balance
What does the modified version of a digitigrade posture take more of?
energy and is less efficient
What is the advantage to a digitigrade posture?
improves the economy of running and storage & energy recovery of tendons and muscles
what is the advantage to plantigrade posture?
in aggressive encounter, a fully planted foot allows for more power to be generated
How do red kangaroos move?
bipedal ricochet
At slower speeds what locomotion do red kangaroos use?
pentapedal locomotion
What is the genetic basis for limb loss in pythons?
a weak signal from one of the enhancers to the SHH gene
what are the pelvic spurs of boas and pythons?
remnants of the femur protruding from the skin
Explain the relationship of SHH and limb loss in snakes?
snakes with vestigial limbs, had the SHH enhancer turned on for a brief moment before turning off. in snakes with no vestigial limbs, the SHH enhancer was not found
What are the 4 gaits of snakes?
concertina
serpentine
sidewinding
caterpillar (rectilinear)
What upstream regulator of SHH is lost in Cetaceans?
Hand2
