Class Notes (808,382)
Canada (493,172)
BIOB51H3 (184)
Lecture 3

Lecture 3 Notes

9 Pages
Unlock Document

University of Toronto Scarborough
Biological Sciences
Maydianne Andrade

BIOB51 st SEP 21 , 2010 Lecture 3 & 4: Evidence for Evolution  Evidence for Evolution - Some evidence was available to Darwin while some wasn’t - Evidence from various different fields are consistent with evolution and ideas relating to it - Evidence for Darwinian evolution would include any sort of evidence that suggests that the lower model [DESCENT WITH MODIFICATION] is a better explanation for life on Earth than the upper model [SPECIAL CREATION] - Darwin made analogies with artificial selection imposed by humans and Natural Selection BIOB51 SEP 21 , 2010 - He looked at domestic plants and animals [people breeding them for certain traits] - The analogy was then that Natural Selection could work in the same way with ecological conditions/social conditions imposing the selection on the lineages - E.g. dogs = originated from a wolf-like ancestor [for every breed] - Somewhere between 15000 or 100 000 years ago, humans started domesticating wolfs:  Results are a stunning range of different body forms, physiologies, temperaments, furs, and lifespan  So impressive range of changes in morphology, physiology and etc through artificial selection - Skeletal evidence - Selective breeding has changed the shape of skull and snout –> leads to radical changes in morphology - Molecular origins: Much of the variation is the results of the increases in the number of tandem repeats of bases in the DNA sequences - These repeats it turns out -> have developmental implications [so in morphology –skull!] - Linear relationship! [graph] - Larger # of repeats –> changes in the bends [upwards/downwards] [for snouts] - Closely correlated to the # of tandem repeats that are in this particular developmental gene BIOB51 st SEP 21 , 2010 - Rapidly evolving characteristics of the DNA that lead to the type of morphological changes that we see in these lineages  & selection on the morphology has lead to the changes in DNA –> and that then is inherited and results in all these different forms You’ve to have variation for selection to have any effect! - Evidence not just from artificial breeding done by humans but evidence that’s available about what actually happened on Earth outside of human control BIOB51 st SEP 21 , 2010 - Even before Darwin –> geologists had recognized that there was evidence [when you look at the earth’s crust] that species had changed through time - And that there was a way you could look at the earth’s crust and get a timeline of species appearance - This evidence was available to Darwin but was not discovered by him - He just pointed to and said that it was consistent with his ideas of evolution - Critically –> you can find characteristic fossils: that is the type of fossils that you find in the deep layers of rock, have a different composition [organisms] than the ones you find in the top layers of rock - That the layers of fossils had characteristics that changed as you moved through the geologic column. - Using either relative dating or radiometric dating: the deeper layers of rock are more ancient and layers on the BIOB51st SEP 21 , 2010 surface are more recent in terms of when they were deposited. As fossils are formed, you would expect the ancient fossils to be down in deeper layers and the recent ones closer to the surface. - It was not the case that you see one layer of rock with no organisms and a layer that is completely full of every organism that we now see on Earth today. - The fossils that you find in the most ancient rocks tend to be those organisms that are closer to the proposed original species  So single-celled organisms come first then multi-cellular life starts showing up in those layers and then larger organisms later  Bacterial fossils found throughout the record  Ex: Horses are never found in the most ancient layers –
More Less

Related notes for BIOB51H3

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.