BILD 3 Lecture Notes - Lecture 3: Venus Flytrap, Wisdom Tooth, Bild
13 Jun 2018
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BILD 3 Lecture 3
4/6/2018
• Fossil: any trace of an organism that live in the past
o Shows commonalities between living and extinct creatures
o Fossils can be used to test evolutionary hypotheses (macroevolution)
• Succession: fossils from one region similar to extant organisms from that same region
• First hypothesis: evolution of fish to tetrapods
o If you were just looking at the relationship/commonalities between a fish alive
toda ad us, ou ould’t thik this ould hold true
o If you add in all of the related extant animals, you get a better connection
o Look for transition fossils that make connections between species (like between
fish-like and more tetrapod-like animals to show the connection/descent)
▪ A transition fossil would have characteristics of both lobe-finned fish and
tetrapods
▪ Each species is a snapshot of a continuum→there are still many more
fossils left to be discovered
• Not every species in the fossil record makes a direct ancestral link
▪ By finding the right place in the right geological time made discovering a
transition fossil easier→athig the age of the oks to hat ou’e
looking for
• Another transition state hypotheses: connection between birds and therapod dinosaurs
(e.g. chickens and T-rex’s
o Connections seen in bone morphology and, recently, the discovery that many
dinosaurs may have had feathers
o Purpose of feathers in birds
▪ Thermoregulation, nesting, keeping eggs warm, color to attract
mates/camouflage, and power flight
o Transition bird form between dinosaurs and birds
▪ Like a bird: long feathers
▪ Like a dinosaur: had teeth, 3-proper digits with claws, a bony tail
o Leads to uestio: hat is a patiall futioal ig ad hat eefit does it
have that natural selection would give it advantage towards?
o Hypothesis for the origin of flight: wing assisted incline running
▪ Using partially functioning wings to help run up a steep hill
• Hypothesis 3: transition animal between most mammals and primitive whales in the
case of ankle bones
o These transition of fossils connect species together to their ancestor
o Whales with hind limbs found with ankle bones that were very similar to ankle
bones of cows, deer, and pigs
• Transitional forms provide evidence of intermediate phenotypes
o Transitional forms are not necessarily the direct ancestors of extant forms
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