BIOB51 Lecture 3 Notes
Answers to these big questions of life being special creation.
Species are created by supernatural force. All species created at the same time.
Humans have been selectively breeding organisms for 10s of thousands of years. This we
The variations that have existed between the original ancestor of all of these kinds have been
exaggerated through selective breeding. Selective breeding continues today.
Example of how phenotypes are consistently changing along with breeding patterns even in
recent times. Can look at their genetics and see better how evolution is happening.
Tandem repeat loci (t.r.l)=little bits of DNA that can be repeated over and over. ie. CGGAT -->
this section can be repeated several times. The number of times it's repeated is common to alot
of related organisms. Humans have a certain amount of tandem repeat loci of their DNA and
generally the same number of repeats are present in each human.
Phenotype of bull terrier has changed quite alot due to selective breeding and dog breeders
picking out particular characteristics. Skull of bull terrier has also changed.
These people were looking to see if these t.r.l were more variable than they thought originally
and dogs. Whether it was the length of these/number of these repeats that had anything to do
with these rapid changes in phenotype.
The gene length (# of repeats) was positively correlated to the degree in weirdness of dog nose
shape. the weirder, the more convex the dog's nose, the longer the gene, the more tandem
repeats that existed. Dogs were more variable in the # of these repeats loci then they originally
thought and that if we're constantly selecting for the individuals that have the longest genes or
roundest noses then we're going to create a really rapid phenotypic evolution.
Wild mustard is a plant that became domesticated and was artificially selected for a bunch of
different traits. Wild mustard same as all the veggies in slide. The variations in the traits we see
in wild mustard, people have capitalized on that variation, selectively bred wild mustard seeds for particular traits. ie. broccoli for having a large flower head. Cabbage for having large leaves
and no flower head. Single ancestor, many varieties.
Why is artificial selection such a great demonstration of descent with modification and
-See a lot of the same principles at work in artificial selection than we do in natural selection
But in the case of artificial selection, human breeders are the ones imposing the selective force
and deciding who’s going to be the most successful; have the most lifetime reproductive
success. Whereas in natural selection, it’s the environment that’s putting that selective pressure
on the individuals.
Conscious intent with artificial selection (we are the ones directing it) but no conscious intent
with natural selection.
Reinforces the idea that even things that appear to be phenotypically very different can have a
Selection is the force that transforms phenotypes.
Deposition: fossils deposited into rocks
River through time eroded away lots of layers of rocks revealing older and older layers. Find
fossil evidence of newer species in newest rocks and fossil evidence of older species in older
Evidence of bacteria about 3600 ma. In middle age rocks, we find land plants, of fish, insects
and reptiles. Finally in the new layers of rocks find evidence of larger land, species of land
animals, dinosaurs, birds, flowering plants and then the rise of mammals.
There has been time for this descent with modification and diversity to be created.
Inference: living organisms are descendants of these extinct organisms Slide 28
Glyptodont: four legged mammal whose fossilized remains were found in South America.
Roughly the size and shape of a Volkswagen Beatle. The armadillo is a living relative today.
similar adaptations to the glyptodont (ie. Shell proectection).
Diprotodon: giant hippo wombat was a marsupial as other species in Australia. We see
descendants today of marsupials that don’t live all over the world. They live particularly in
Main point of finding animals in the fossil records that aren’t living today is that it reinforces this
idea that ancestors give rise to new species. So we would expect to find in the fossil record
evidence of species that no longer exist that used to exist that gave rise to stuff that is alive
Irish elk: fossil remains found in irish bogs
Enable us to connect our living species to older extinct species. Ie. Archaeopteryx helped
connect reptiles to birds.
*Living transitional form p.50-51* ON EXAM!
After discovery of Archaeopteryx, other feathered dinosaurs were found. Found in the ash lakes
in China. Different types of rocks can give rise to different types of fossils.
Bottom is ancestor of all the horse species. These fossilized remains show a transition from 4
digits to one hoof. Intermediate forms similar to bottom ancestor. that’s how you know they’re
Problems with using fossil record as evidence for evolution. Gaps do exist in the fossil record
because not every animal that dies gets fossilized. Requires a really particular geological
conditions for fossilization to occur.
Illegal fossil trade in Brazil since there are limestone rocks that are fossil rich, which people can
find and sell.
Old idea: Feathers evolved from scales. As scales elongated and widened, individuals were
able to glide better and feathers evolved from that pathway. New idea: Feathers evolved from filaments and not sca