lec 6- Paleontology Flashcards
what are the 4 types of evidence that support Darwins ideas?
-comparative anatomy
-embryology
-artificial selection
-fossils
what are homologous traits?
similar structures resulting due to inheritance from a common ancestor
(e.g. homology of the forelimb bone of tetrapods)
what are Darwins four postulates?
- individual variation- individuals vary in their traits
- inheritance- traits are passed on from parents to offspring
- overproduction- more individuals are born than can survive in a stable population
- competition- individuals compete for resources, struggle for survival
what is natural selection?
a natural process, not random, that selects for surviving individuals based off of their heritable traits
what is the difference between artificial selection and natural selection?
instead of it being the breeder who selects for the individuals that will breed and pass on traits in artificial selection, its the organisms themselves that select for traits and adaptations to survive and reproduce
what is the difference in middle eastern sheep and regular sheep?
middle eastern is bred for fat and oil while regular is bred for wool
after natural selection, what was Darwins second mechanism?
sexual selection
what is sexual selection?
when members of the same biological sex compete with one another to mate with members of the opposite sex
what is genetic drift?
random changes to the gene pool resulting from chance events in small populations
(can play a role in rapidly changing gene frequencies)
who confirmed that fossils are remnants of formerly living organisms?
Nicolaus Steno
Darwin predicted transitional fossils (links) would be found between species, what species link connected the dinosaurs to the birds?
archaeopteryx, found in 1861 and supported Darwin’s theories
what is a taxon?
any formal taxonomic category: species, genus, family etc.
when did archaeopteryx live?
during the upper Jurassic, 150 Ma old
what did Darwin recognize that evolution required?
an old earth, billions of years old
who disputed Darwin that the earth was not billions of years old and how did he come to his conclusion?
Lord Kelvin, proposed the earth was no more than 20 million years old based on temperature of rocks (later was found out to be flawed cause radioactive heating deep inside earth keeps the temp high and reduces cooling)
how is radiometric dating done?
-when magma cools, it forms hard crystals like zircons which trap elements present in the lava, that can be used as rocks
-crystals contain atoms that slowly radioactively decay into daughter elements, when comparing decay products relative to radioactive ones, and known ratios of isotopes, time elapsed since crystal was formed can be found out.
-summarized: radiometric dating is done by looking at trapped elements and seeing how long it took them to radioactively decay
how was earth dated?
rubidium/strontium of 38 different meteorites all produced a coherent isochron (equal time) , with a slope saying the earth is 4.5 Ba old
do organisms fossilize well? what are the requirements needed for good fossilization?
-No
-those with hard parts like bones and teeth have best chance, and if near sedimentary environments like oceans, lakes, and rivers
-and if the organisms are numerically abundant in broad distributions
what is the “sleeping dragon mummy”?
a nodosaur that was perfectly preserved in Alberta oil sand mines and a whole mummified fossil was found
was the nodosaur countershaded?
yes
what is laggerstaette?
sites with unusually excellent preservation
