Week 5: Emerging Complex Life and Intelligence Flashcards
What is the Proterozoic eon? What changes characterize its start?
2.5 billion - 541 million years ago
where fossil record begins
simple life proliferates + multicellular life emerges
rise of eukaryotic cells + aerobic respiration
begins with huronian glaciation - temperatures decrease and glaciers cover earth’s surface
What is the huronian glaciation?
2.4-2.1 billion years ago
first snowball earth
period of low temperatures and glaciers covering earth’s surface
What caused the huronian glaciation?
oxygen from photosynthesis dilutes greenhouse gases in atmosphere and decreases the greenhouse effect
feedback loop where snow + ice reflect sunlight and lead to more cooling, which leads to the formation of more snow and ice
How does aerobic comparison compare to anaerobic respiration?
requires oxygen
produces 18x more energy!! much more efficient
How did the rise of oxygen levels impact organisms using anaerobic respiration?
oxygen has oxidizing and corrosive effects
free oxygen reacts with molecules to produce free radicals, which can cause cell damage
True or false: aerobic respiration was first used by prokaryotic cells and allowed eukaryotic cells to develop.
false
eukaryotic cells started it
How did eukaryotic cells form in theory?
prokaryotes form symbiotic relationships with each other and eventually one absorbs the other
become chimeric cells
absorbed cells become membrane bound organelles
When did eukaryotic cells emerge?
2.1 - 1.6 billion years ago
How are eukaryotic cells stronger than prokaryotes?
able to adapt to a wider range of environments due to specialized organelles
How did the huronian glaciation period end?
volcanic activity revived greenhouse effect + warmed the planet
How did the end of the huronian glaciation period impact life on earth?
prokaryotic and eukaryotic life thrives and diversifies
When did multicellular life begin?
2 billion years after huronian glaciation period
575 million years ago
When did sexual reproduction emerge? How did it benefit life?
in Proterozoic era
allows mixing of genetic material -> increased genetic diversity
allows complex information to be passed on
How does the structure of DNA allow for sexual reproduction?
double helix with rungs made of paired nucleotides
pairs allow for replication
What nucleotides bond to which nucleotides?
cytosine bonds to guanine
adenine bonds to thymine
What is a genetic code?
sequence of base pairs (DNA)
What is a codon?
three base pairs (DNA)
What is a gene?
sequence of codons (DNA)
What is a genome?
set of genes
What is the purpose of genes?
instruct assembly of proteins
What is a chromosome?
condensed genome
used for sexual reproduction
What is a gamete?
male/female reproductive cell
contain half of their organism’s chromosomes (make up a complete set when combined)
True or false: sexual reproduction is less energy intensive than asexual reproduction.
false
it requires a lot more energy
What is the Cryogenian glaciation?
720-635 million years ago
2nd snowball earth
glaciers covered earth
emergence of first multicellular organisms during this period
what is the cambrian explosion?
20-25 million year period where “burst of evolutionary innovation” occurred
What is the phanerozoic eon?
began with cambrian explosion
What is a chordate? When did they emerge?
ancestors of vertebrates
during cambrian explosion
True or false: genetically most organisms are very similar to each other
true
sequences of base pairs are different, but at the cellular level they are mostly the same
What are hox genes?
code for proteins specific to certain species that regulate genetic expression
differentiate different species
determine what structures form in a developing embryo
what motivated the evolution of hox genes?
mobility is good for survival
hox genes allow species to replicate previously evolved body plans instead of coming up with them freshly
What is the ordovician period?
488 million years ago
plants begin to colonize land
What is the carboniferous period?
359-299 million years ago
plant growth covers land and becomes modern day coal deposits
pangaea forms
oxygen levels reach peak concentrations
What is a biosignature?
object, substance, or pattern that requires life in order to form
Give three examples of potential biosignatures:
temporal variability of atmosphere composition (ex. oxygen)
change of planet surface reflectance due to biological life / activity
technosignatures indicating intelligent civilization
What are the two main aspects of modern evolutionary biology?
studying lines of DNA and fossils
What types of mutations are preserved by natural selection?
those that allow organisms to:
survive long enough to produce
produce offspring that are more likely to survive
hunt or scavenge more effectively
evade predators more effectively
What two main environmental factors drive natural selection?
survival
competition for resources
How have earth organisms adapted to the energy emitted by the sun?
sight has adapted to the wavelengths which the sun emits the most of (visible light wavelengths)
true or false: by looking at the genomes of modern day species, we can accurately estimate a timeline for when species emerged
false
timeline part is not accurate
What is LUCA?
last common universal ancestor
hypothetical organism with first genetic information that eventually led to all other life
What three categories make up the tree of life?
bacteria
archaea
eukarya (includes plants and animals as small branches)
What are mass extinction events?
events which apply natural selection forces to the whole planet at once
rapid decrease in biodiversity
spike in biodiversity caused by end of these events
What is the KT extinction?
mass extinction event
66 million years ago
caused by asteroid
killed of dinosaurs :(
how did mammals survive the KT extinction?
burrowing underground to avoid harsh surface conditions
omnivorous so they could continue to find food
what are primates? When did they emerge?
mammals evolved for life in trees
65.5-55.8 million years ago
in early paleocene epoch
What is the eocene epoch?
55.8-33.9 million years ago
emergence of early placental mammals
When did the first human ancestor emerge?
7-5 million years ago
True or false: the evolution of bipedalism happened gradually and linearly over time
false
it was not linear at all!!
When did neanderthal humans exist?
400,000 - 40,000 years ago
true or false: neanderthals coexisted with homo sapiens for a time
true
for about 5,000 years
probably some genetic mixing between the species
What is EQ?
encephalization quotient
ratio of brain mass to body mass
correlatd with intelligence
humans have the highest (7.4-7.8)
