tracing phylogeny Flashcards
how do some fossils form?
form as sand, rock, silt us weathered and eroded from the land and carried by rivers to seas and swamps where the particles settle to the bottom
deposits pile up and compress the older sediments below into the rock - imprint fossil
what part of the organism gets preserved as a fossil?
the hard parts as the soft tissue decays
what sometimes happens with the tissue in fossils?
sometimes minerals seep into the tissues and replace its organic material as is done with petrified wood
what is another way fossils form besides imprinting?
by leaving an empty mold that becomes filled with mineral (other half=cast)
what do trace fossils leave behind?
trace fossils lie coprolites (fossilized dung) footprints or burrows that show the animal’s behavior
where can entire preserved organisms be found?
in amber - fossilized tree sap
frozen in ice
in acid bog where decomposition is slowed down
2 methods to date fossils
relative dating
absolute dating
what is relative dating?
dating relies on the position of fossils in strata
the deeper it is, the older
what does relative dating tell us?
the order in which groups of species existed but not the age of the fossil
what does absolute dating tell us?
does not tell us the absolute/errorless age but a close number
what is used for absolute dating?
aid of radiometric dating that relies on the fact that all fossils contained isotopes when they were alive and those isotopes decay at a fixed rate
half life of C 14? what does this mean?
5600 years
takes that long for 50% of the original sample to decay since isotopes are radioactive
what is C-14 used to date?
relatively young fossils
what isotope is used to date older rocks?
U-238
what can the geological time scale be divided into?
4 eras
many periods
many epoches
4 eras oldest to youngest
precambrian
paleozoic
mesozoic
cenozoic
what does the geological time scale correspond to?
is not divided arbitrarily, but corresponds to times of great change
are continents fixed in place?
no, they are drifting on plates above a hot mantle
what does the movement of plates lead to?
mountain buildings, volcanoes, and earthquakes
when was Pangea formed?
about 250 mya when plate movements brought the land masses on earth together into the supercontinent Pangea
what happened to the species on land when Pangea formed?
species that had evolved in solation were now together
shorelines reduced, causing a dry continental interior
mass extinction
when did the 6th mass extinction happen ? why?
today as a result of anthropogenic activities
what does the fossil record reveal?
an episodic history with long periods punctuated by a turnover in species composition
what does the episodes in fossil records include?
mass extinctions and adaptive/explosive reaction
what was an impressive adaptive radiatino?
Cambrian explosion between the Precambrian and Paleozoic eras
what did the cambrian explosion create a drastic change in?
change in sea life
the cambrian animals were the first to?
have hard body parts like shells, skeletons and claws
what did the hard bodies allow for?
for many new complex body designs and altered many predator-prey relationships
what do many believe emerged from the Cambrian explosion?
all animal phyla that exist today evolved during this time
what did the organism Pikaia first show signs of?
first signs of a notochord and may be the ancestor of all vertebrates
what most often follows mass extinctions?
adaptive radiation
what are the 2 most notable mass extinctions?
the Permian extinction and another that happened in the cretaceous period
what happened in the permian extinction?
250 mya when pangea came together
90% of life was destroyed allowing for mammals and dinosaurs to flourish
what happened in the extinction in the cretaceous period?
65 mya
marked the end of the dinosaurs
furthered the evolution of angiosperms
why did the mass extinction happen in the cretaceous period?
volcanic eruptions in India blocking out the sun
an asteroid colliding in the Yucatan Peninsula sending a great cloud of dust into the air and also blocking out the sun for possibly years and setting of a fire storm across NA continent killing most life there upon impact
what did the species that managed to survive the mass extinction do?
adaptively radiated to fill the vacant zones caused by the extinction
how do we know the asteroid struck the Gulf of Mexico?
1) crater
2) Ir= Iridium (more common in space)
what is phylogeny?
evolutionary history of a species
what is reconstructing phylogeny done with the aid of?
systemics - the study of biological diversity in an evolutionary context
how do biologists represent the genealogies of organisms of organisms with?
phylogenetic trees - diagrams that trace evolutionary relationships as best that can be determined
how to systematics arrange organisms? through what techniques?
taxonomy, the identification and classification of species, in their attempts to arrange organism in categories that reflect their evolutionary history/phylogeny
what are hypothesis of past history on available data?
phylogenetic trees
what are phylogenetic trees based upon?
fossil evidence, comparative anatomy, embryology, and comparing DNA and proteins
comparing DNA and/or proteins is the most?
precise method in constructing evolutionary relationships if they are available
how can DNA be analyzed by the use of?
gel electrophoresis or DNA sequence analysis - comparing the actual nucleotide sequences of DNA segments
how do you measure the differences between two species when analyzing DNA?
identify nucleotides found in both species and determine if they have common ancestry
what are cladograms?
type of phylogenetic tree
what is homology?
likeness attributed to shared ancestry
is all likeness inherited from a common ancestor?
no
how may species from different evolutionary branches resemble on another?
if they have similar ecological roles “environmental pressure”
and natural selection has shaped similar adaptations
convergent evolution
different evolutionary branches but similar features based on analogous structures
analogy
similarity due to convergence
what similarities should we use to develop phylogenetic trees and classify organisms?
homologous similarities
what happens to relatedness as the number of homologous part increase?
more related the two species are
what happens to relatedness as the complex number of homologous part increase?
the higher the chance they evolved from one common ancestor
divergent evolution
same ancestor and branched out
based on homologous structures
when a frozen or dried fossil is recovered, what is rare?
the fact that the DNA is intact
what is fossil DNA contaminated with?
viruses or bacteria or has changed shape/broken down
pieces of DNA mined from any fossil represent what?
only fractions of an organism’s whole genome
what are the 2 significant features of a phylogenetic tree?
1) the location of branch points along the tree symbolize the relative time of origin of diff organisms
2) the extent of divergence between branches represents how different 2 organisms have become since branching from a common ancestor
with cladograms, how are actual organisms treated as?
terminal nodes
what is the branching structure of cladograms determined by?
solely by shared derived characteristics - homologous structures that evolved in an ancestor that are common to all species on one branch of a fork in the tree, but not common on the other branches
what is the main difference between phylogenetic trees and cladograms?
phylogenetic trees - length of branch is proportional to time/divergence from a branch point
cladograms - the length of branches is not important and only order is significant
