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
unifying factors of archaea
cell wall of polysaccharides; same protein synthesis machinery as eukarya
why is it hard to determine bacterial species? what do we do and why?
they exchange genes frequently so we compare a gene that evolves slowly (ribosomal 16s); 97% similar = same species. can also distinguish between gram positive and gram negative
Why 16s?
- ribosomes are in everything (were in the first ancestor of life)
- important in translation –> 16s is conservative (not a lot of lateral gene transfer) & it evolves very slowly
how many species of bacteria are in our mouth?
~500
how many bacteria are in our GI tract?
10^14
how many bacteria are on our skin?
10^12
What is the human microbiome?
the bacteria living in and on our bodies (some bacteria only live in certain places in/on our bodies)
what’s the difference between genes that originated in bacteria and bacterial genes?
bacterial genes are in bacteria right now. genes that originated in bacteria evolved in bacteria but can be in another organism
What percent of human genes originated in bacteria?
37%
What does the baby poop graph show?
Different types of bacterias’ relationships determined by 16s. Our microbiome is dynamic; babies acquire bacteria through life. Baby took antibiotics –> dip in microbiome diversity.
consequences of taking antibiotics/being too clean
disturbs microbiome; kills good and bad bacteria –> digestive/immune system problems
how did bacteria cause global change
they photosynthesize –> produces oxygen –> makes ozone layer –> decrease UV mutagenic rays –> evolution of multicellular and eukaryotic organisms
6 pieces of evidence mitochondria and chloroplasts were bacteria
1- divide independent from rest of cell
2- only come from other mito/chloroplasts
3- 2 or more plasma membranes
4- have their own circular genome
5- no histones
6- own protein synthesis machinery (eukaryotic/archaic protein synthesis inhibitor does not affect mito/chloroplasts)
How many times did mitochondria evolve? How do we know? When did it happen?
They evolved once. mitochondria are monophyletic. it happened when O2 arrived in the atmosphere; at the same time as eukarya evolution
how did mitochondria end up in another bacteria?
mitochondrion was pulled in during feeding and wasn’t broken down.
in endosymbiosis, what engulfs what?
heterotroph engulfs autotroph
how many times did photosynthesis evolve?
Many
what are the three major types of plastids
chloroplasts, rhodoplasts, apicoplasts (apicoplasts are non-photosynthetic; monoplyletic; cause disease; ex toxoplasma - changes host behavior/malaria)
How many times did plastids evolve?
once
how many times did photosynthesis evolve?
multiple
what had to happen for endosymbiosis?
bacteria had to lose tough cell wall (peptidoglycan) –> flexible cell membrane that folds on itself –> nuclear envelope, ER, golgi, tansport vesicles; bacteria need to acquire actin
What are protists?
groups with eukaryotic cells that are not fungi, animalia, or plants (paraphyletic group)
how many times did multicellularity evolve?
multiple
problems with large size
diffusion is slow; need to obey fick’s law
what’s fick’s law
rate of diffusion increases when thickness decreases
6 ways to manipulate flux to obey fick’s law
1- eukaryotes increase SA by folding membranes; 2- volvox increase surface area bc they’re hollow; 3- sponges have good SA:V ratio bc only 2 cell layers; 4- flatworms increase SA by being flat; 5- large animals developed circulatory systems; 6- fish have gills to increase SA
6 characteristics of metazoa
1- collagen; 2- multicellular; 3- heteroptrophs; 4- unique muscle/nerve tissue; 5- lifecycle where diploid phase is dominant; 6- gene arrangement controlled by Hox genes
what are choanoflagellates
closest relative to animalia
consequence of large body size
need to eat more food
6 advantages of large body size
1- better for filter feeding (water around you is turbulent)
2- can move faster and in many directions
3- more prey options and less predators
4- need more food but amt of food/unit body mass decreases
5- specialization of cells –> tissues and organs
charles linnaeus’ classes in animalia kingdom
1- ambhibia
2- aves
3- mammalia
4- pisces
5- insecta
6- vermes (anything w/o legs)
metazoa synapomorphy
multicellularity
porifera (sponges) synapomorphy
choanocytes
cnidaria (jellyfish/sea anemones) synapomorphy
nematocysts (stinging cells)
ctenophora (comb jellies) synapomorphy
colloblasts (sticky adhesive structures attached to tentacles)
syanpomorphies after porifera
1- radial symmetry
2- two germ layers (diploblasts)
synapomorphies after ctenophora
1- bilateral symmetry
2- cephalization
3- triploblastic (three germ layers)
protostomes synapomorphies
1- blastopore = mouth
2- positional info at 8 cell stage
two groups under protostomes
ecdysozoa; lophotrochozoa
ecdysozoa synapomorphy
molting/exoskeletons
ecdysozoa phyla
nematodes (roundworms, c.elegans, trichinella); arthropoda
what are the big 4 subphyla in arthropoda
1- insects
2- crustaceans
3- spiders
4- mites
features of insects
1- segmented
2- undergo tagmosis (fusion of segments
3- exoskeleton made of cuticle –> stepwise growth/molting
4- open citculatory system
5- dorsal heart
3 reasons why insects are so successful
1- evolution of wings
2- methods to protect their wings
3- complete metamorphosis (holometabola); allows babies and adults to eat different things/not compete for food
lophothrochozoa synapomorphies
1- spiral cleavage
2- distinct form of larvae
lophotrochozoa phyla
1- annelida (ex. leeches)
2- mollusca
3- platyhilmenthes (flat worms)
annelida synapomorphy
segmentation (easy way to get big)
mollusca synapomorphy and three main body regions
synapomorphy: mantle (secretes the shell)
3 main regions: mantle, foot, visceral body mass (digestive and circulatory tracts)
platyhilmenthes features (no synapomorphy)
- parasitic (reproduce in definitive host; born in indefinitive host)
- no coelom
-triploblastic - can regrow entire body from neoblast cells (totipotent –> can become any body cell)
deuterostomes synapomorphies
1- blastopore = anus
2- no positional info at 8 cell stage
3- symmetrical cleavage
deuterostoma phyla/sub phyla
1- chordata (–> urochordata (tunicata), cephalochordata, craniada –>vertebrata)
2- echidnodermata (starfish/sea urchins/sea cucumbers)
echinodermata synapomorphy + features
synapomorphy: water vascular system (tube feet operated by hydrostatic pressure)
1- adult stage reverts to radial symmetry
2- larval stage has bilateral symmetry
3- calcium carbonate endoskeleton covered by skin (epidermis)
chordata synapomorphies
1- notochord (located between gut and nerve cord in embryo; support and locomotion functions)
2- dorsal hollow nerve cord (becomes brain and nervous system)
urochordata
tunicates; larva have notochord, adults don’t/are filter feeders; produce anti-cancer drugs
cephalochordata (lancets/amphioxus)
closest relative to humans because they didn’t have massive gene loss like other chordata subphyla (craniata/urochordata)
craniata
deuterostomes with heads (ex. hagfish - cartilaginous skull, body stiffened by notochord, no jaw); brain and other organs are encased in bone or cartilage
vertebrata
subgroup of craniata; consists of hyperoartia/gnathostomata (lampreys and jawed vertebrates); rigid internal skeleton, vertebral column encloses spinal cord, internal organs suspended in coelom, well-developed circulatory system
lampreys
group of vertebrata; very reduced notochord
gnathostomata
group of vertebrata with jaws
what influenced the diversification of insects?
flowering plants evolved during the cretacious period; insects diversified to survive the plants’ defensive chemicals
chordata plesiomorphy
pharyngeal slits (originally used for filter feeding) –> later in evolution becomes jaw
coelom
fluid-filled cavity in come metazoa; forms three germ layers (triploblast) during embryonic development; advantage is getting bigger without feeding everything on the inside
acoelomates
don’t have a coelom
pseudocoelom
body cavity between the meso and endoderm –> not completely surrounded by mesoderm like a true coelom (ex.
blastula
early embryo stage; hollow ball of cells
blastocoel
space in the middle of the blastula
gastrulation
blastula pushing in on one side to make the gut
gastrula
early embryo stage after blastopore with two tissue layers (endoderm/ectoderm) + blastopore (hole/gut opening)
distance method for phylogeny
ancestors and species that have the least number of differences are most closely related
parsimony
favors the tree with the fewest convergent traits (assumes that homologous traits are more common than convergent traits)
ancestral traits/plesiomorphies
ancestral/primitive trait that applies to many groups
derived traits/synapomorphies
trait shared between two or more groups from a common ancestor
uniformatarianism
slow processes, given enough time, can create big changes/structures
apomorphy
derived trait in one group (new for that group - was not in CA)
