Tetrapods Flashcards
What is the sister taxon of tetrapods? Why?
Dipnoi (Lungfish)
They exhibit underwater walking on pectoral and pelvic fins and air breathe using modified lungs
What two features did tetrapods evolve from Lungfish that allowed them to move on land?
Lungs (originally air sacs)
Limbs (originally lobe-fins)
What are the derived characteristics for specific adaptations for living on land
four limbs: with feet and digits for walking on land
ears: for detecting airborne sounds
neck: allows head “swinging”
pelvic bones fused to Vertebrae: allowed force of pushing against ground to propel whole body
ribs: support lungs to help breathe on land
What is the amphibian clade heavily dependent on? Why?
Water
The need the moist skin to supplement gas exchange since lungs are inefficient
reproduction requires water since eggs lack shells and dry out and fertilization occurs externally
What do amphibians undergo during development?
metamorphosis from water to land
What is the amniote clade?
evolved from amphibia to survive and reproduce away from water
Why does the amniote clade not need water?
They have a rib cage to ventilate lungs for increased breathing efficiency
This removes the need to conduct gas exchange across the skin
could evolve impermeable skin to help prevent water loss
What is the most important feature of the amniotes?
amniotes evolved an embryonic support system that allow development away from water using the amniotic egg
What is the amniotic egg?
contains four special membranes to protect the embryo
allows total departure from an aquatic environment
Has three roles: embryo development in water, protection (shock-absorber) and hydration (contains water)
Shell: offers additional protection and water loss prevention
What are the members of the amniote clade?
reptiles and mammals
even humans, but substantial evolution has taken place in amniotic eggs
What is predominant feature of reptiles?
most reptiles have scales for protection and waterproofing
they lay amniotic eggs with protective hard shells
What is ectothermic?
absorption of external heat from the environment as the main source of body heat
reduces energy needs of organism
susceptible to external conditions
most reptiles like turtles (incubators during growth)
What is endothermic?
maintain a constant body temperature by employing internal metabolic processes
sustained, high-energy activities
high energy cost to organism
What are birds related to?
reptiles
however, almost every feature has been modified
Why are birds different from reptiles?
flight most modifications of reptile features involved adapting to flying, such as wings and feathers forelimbs to wings scales to feathers weight reduction light bones endothermic metabolism
