Honors Biology
Vertebrate Evolution
Study Sheet
Explain the importance of the following transitional organisms to vertebrate evolution.
Sponges: first animals. Has cell-cell communication and collagen, a form of
protein possessed only by animals.
Tunicates: first chordate (possessing a notochord), made the transition from
invertebrate life to chordate life.
Lungfish: Extant species example of a link between fish and amphibians.
This is a lungfish which has lungs as well as skeletal rods in its muscular fins
that would allow it to crawl from a desiccating pond to more substantial water
source.
Artist’s rendition of one of the first tetrapods. Based on the fossil remains of
Tiktaalik which, unlike fish, had a neck, horizontally flat head, and limbs.
Archaeopteryx: Reptile that shows the transition from scaly, flightless
animals to flying animals with feathers. Feathers are believed to be an
exaptation from scales modified for into feathery insulation to being selected
for my nature for flight resulting in modern feathers.
The duck-billed platypus is a monotreme mammal which is the oldest line of
mammals. It lays leathery-shelled eggs (like reptiles), but they have hair and
primitive mammary glands which are the hallmarks of mammals.
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7/12/2016