midterm 2 Flashcards
monophyletic group
common ancestor and all descendant species
polyphyletic group
doesn’t include a common ancestor
paraphyletic group
doesn’t include all descendant species
how does continental shift impact flora/fauna? (ex. why are marsupials in australia and south america?)
plants and animals used to live on several continents when they were connected (pangea). When the continents shifted, the species stayed on those continents and evolved.
how do scientists determine the start/end of a time period
based on biological events (mass extinctions)
What do geologists use to figure out when something happened? How is this different from evolutionary biology?
geologists use dating with isotopes and their half-lives (ex. packrat waste; pre-contact dog bone; C3/C4 grasses and horse teeth). phylogeny uses molecular clock theory.
where does the energy for continental movement come from?
magma under the earth’s crust
what are the two pieces of evidence that prove there was a supercontinent and then the continents moved?
mid atlantic ridge; earthquakes, mountains, volcanoes
convergent plate movement
plates crash into each other
divergent plate movement
plates move away from each other
transformational plate movement
plates slide past each other
consequence of oceanic-oceanic convergence
one goes up, other goes down, creates mountains
consequence of continental-oceanic convergence
oceanic goes down, continental goes up, creates mountains
consequence of continental-continental convergence
one goes up, one goes down, creates mountains
How did scientists track the extinction of irish elks and mammoths? What pattern did they find?
used isotope dating to track their fossils. the large mammals went extinct as human moved across eurasia.
dispersal
movement of individuals across areas
vicariance
breakup of continents/areas
what is pleistocene overkill?
the idea that humans overhunted megafauna for food, severely decreasing their abundance and diversity
why is it hard to figure out what caused mass extinctions?
humans and asteroids only caused one mass extinction each. evidence about what caused the others gets lost through plate tectonics
what is thought to have caused the permian/triassic mass extinction?
The supercontinent, pangea, was very far north and heavily glaciated. this caused ocean levels to drop. plate tectonic activity under the ice carbon dioxide and sulfur dioxide into the air (what is now known as the siberian trap).
How was the early atmosphere like?
no ozone layer, no oxygen
How have humans changed the environment leading to the anthropocene era?
platic/pollution/great pacific garbage patch, change in atmospheric C14, increased nitrogen and methane in atmosphere
what three processes changed the composition fo the early atmosphere?
photosynthesis - released O2 as waste. volcanic activity - released water vapor, CO2, and nitrogen. Other chemical reactions produced CO2 which turned into acid and dissolved rock into soil
consequences of oxygen in the environment/atmosphere
environment became aerobic; caused the oxygen catastrophe: first mass extinction (wiped out anaerobic life); ozone layer blocked UV rays and allowed for larger organisms with more complex genomes (lesser chance of mutations now)
why can’t we study the origin of life with phylogenies?
no fossils to track homologous traits (homologous traits show common ancestors). the origin of life has to be determined experimentally
What three things does life need?
accurate replication, metabolism, cell structure
what are the two components of a cell
cell membrane/micelle (container) and genetic material (RNA)
how do we know RNA was the first prebiotic molecule? (what are the 5 criteria for the first prebiotic molecule)?
1- must be able to encode information
2- all functions must be encoded in a “jack of all trades” molecule
3- the molecule’s individual monomer units must be obtainable by natural organic chemistry
4- must be able to catalyze its own reactions
5- must be able to catalyze other reactions
what is a micelle?
a self-assembling membrane of fatty acids. it grows and divides through osmotic pressure.
How did this first protocell/protobiont align with the conditions for natural selection?
Different protobionts had different RNA/genetic material and different success rates in organizing amino acids which affected their stability and metabolism, which affected their survival and reproductive success
what are the two things NS considers?
stability and replication rate
what did the miller urey experiment test?
could life originate fro the conditions that were present on early earth? (shocked water with an electrical source; produced amino acids, purines, pyrimidines)
criticisms of miller urey experiment
used an unrealistic amount of energy, did not have the correct atmosphere replication, how would the necessary molecules and reactive phosphorous be concentrated enough to produce anything?
what are the two theories for sources of reactive phosphorous
1- reactive phosphorous came to earth via meteorites (pre-atmosphre) or lightning (post-atmosphere)
2- deep sea vents (black-smokers) have necessary conditions (reducing environment) for the origin of life
what are the two problems with RNA (why does DNA predominate now)?
1- it’s not self correcting like DNA
2- enzymatic catalysis by RNA is very slow
the 7 synapomorphies of all living things
1- citric acid cycle
2- cell membrane
3- ribosomes
4- universal genetic code
5- DNA replication
6- DNA –> RNA –> proteins (central dogma)
7- membrane bound proteins that convert ADP to ATP
what are the two endosymbiotic events between bacteria and eukarya
mitochondria and chloroplasts
most important distinction between bacteria and archaea
bacterial cell wall has peptidoglycan; archaea cell wall is made of polysaccharides
how do bacteria reproduce?
binary fission (replicate and divide); differs from mitosis because they divide based on environmental conditions
how can bacteria exchange genetic material
transformation- taking genetic material from the environment. transduction- phages (bacterial parasites) transfer genetic material between bacteria. conjugation- form pillis between two bacteria and transfer genetic material
bacterial xenologous genes
bacteria can transfer genes to distantly related groups (lateral gene transfer)
what did louis pasteur prove?
life can’t come from nothing (spontaneous generation); life has to come from other life (biogenesis)
what did ignaz semmelweis prove?
hospitals/people should practice better hygeine (wash hands after doing autopsies to prevent women from developing infections after childbirth in a hospital setting)
koch’s 4 postulates
1- pathogen may be considered cause of disease if found in every P with the disease
2- pathogen should theoretically grow on a culture medium
3- if pathogen is taken from culture plate and introduces to a susceptible organism, it should cause disease
4- a pathogen extracted from an ill P should grow and produce pure strains of the same bacilli
how can DNA replication occur in prokaryotes in extreme environments?
scientists found thermus aquaticus bacteria in a hot spring (used for PCR) *DNA thermal cyclers also important innovation for PCR
what is the evidence that bacteria were the first domain?
sequence genes that duplicated before the 3 domains originated (paralogs). F ATP-ase gene of archaea and eukarya clump together suggesting they’re a monophyletic group. bacteria are separate suggesting they evolved first
unifying features of bacteria and archaea
unicellular; no nuclear membrane
unifying feature of bacteria
peptidoglycan in cell wall; unique protein synthesis machinery
