Topic 6 - Fossil record and First Life Flashcards
What are the four requirements for life?
1: metabolism
2: response to stimuli
3: homeostasis
4: reproduction with the potential for error
what is metabolism?
a system of management of energy and materials via chemical reactions
What constitutes a response to stimuli?
Response can be changed in growth, in chemical, or movement.
What is homeostasis?
Maintenance of some internal chemical and/or thermal consistency relative to variation outside of the entity
Are Viruses Alive?
- viruses have nucleic acids that can mutate and respond to selection, and can reproduce themselves with error.
- viruses lack metabolism and homeostasis and cannot reproduce without using the cellular machinery of a host cell.
- therefore, VIRUSES ARE NOT ALIVE.
what is a fossil and what does it provide?
- fossils provide the most striking evidence of how life changed over time.
- Fossil is preserved evidence of an organism that lived in the past.
- fossilis =dug up
- Sedimentary rocks have fossils associated with them, they are rocks formed through the accumulation of mud, slit or snow. The distant layers of rocks are called strata.
What is fossilization more likely in?
- in hard bodies organisms than soft-bodied organisms
- in aquatic than terrestrial environments, because sedimentary rocks form more often in aquatic environments.
-in inshore marine than offshore marine, because death happens in inshore marine. ( inshore meaning –> shore)
- if decomposing organisms are absent after death.
Based off of the fossil records, how complete is our knowledge of past diversity and distribution of life?
it is very biased and incomplete
What are trace fossils?
- record evidence of behaviour
a. tracks
b. burrows
c. feces (poop)
The study of trace fossils is called?
- ichnology (study evidence form past life)
- ichnos = track, tail
What are cast fossils?
- formed when minerals fill space in sediment where an organism slowly decayed after having been buried.
-Sometimes when an animal dies and its body decays, it can leave an imprint in the sediment. If this imprint fills in with minerals from sediment and groundwater, it can harden to form a fossil.
what are petrified fossils?
- have had their tissues replaced by minerals.
- petra= rock
ex. ammolite
Can you find fossilized organic material?
-they can be found as
a. thin carbon films
b. in amber
c. in tar or peat
d. frozen
e. as persistent biomolecules.
What is a sub-fossil?
-Fossil has most organic parts replaced by mineral; sub-fossil has high % organic matter.
- if it stinks then it is a sub-fossil.
Relative dating is done via what method?
Sedimentary Stratigraphy
what does stratum mean ?
layer
what does graph mean?
write and record
what is relative dating?
the process of determining if one rock or geologic event is older or younger than another, without knowing their specific ages.
- rock layer beneath a layer will be older which helps depict age.
what is a gap?
- is caused by erosion or a temporary halt in sediment deposition.
- these gaps will cause on part of the rock to be in one part of the world while the other part on the other part of the world.
What are widespread common index fossils?
Fossils that can help read incomplete or scrambled layers.
What makes a good index fossil?
The best index fossils are those that existed form only a brief time but that made a wide geographic distribution at that time.
How are geological time scales made?
created based on the occurrence and disappearance of major taxa, including index fossils.
Why are geological time scales commonly linked with changes in eon, era, period, and epoch?
Because these time scales are often at the same time as major changes in taxa, due to the dependence on fossil record
How do you determine the absolute age of different scales?
radiometric dating
what is radiometric dating?
- measurement of radioactive isotopes in fossils and rocks.
-certain elements decay form one isotopic form into another at a constant rate.
ex. carbon 12 to carbon 14
what is a isotope?
members of a family of an element that all have the same number of protons but different numbers of neutrons
what is half life?
is when 50% of atoms in a given starting amount of radioactive substance have decayed
Example of radiometric dating in plants
- plants take up both C-12 and C-14 during photosynthesis
- animals also get the same ratio of C-12 and C-14 by eating plants and veggies.
-the C-12 stays but the C-14 atoms are unstable and decay back into nitrogen. - increasing the ratio of C-12:C-14 in follis allows fossils to be dated.
is carbon dating good for old or young fossils ?
-carbon is only good for young fossils (only up to 75000 years old)
What do we use for older fossils than 75,000 years old?
-we use uranium isotopes for older fossils.
- the half-life of uranium is 4.5 billion years old.
- it is created in molten volcanic rock
-fossils sandwiched between layers of volcanic rock can be dated this way.
what is the first evidence of continental drift?
- location of fossils in place
- land masses are not constant in location, they move around on plates floating on hot mantle.
what are tectonic boundaries?
- sites of earthquakes and volcanoes.
what was the name of the supposed paleo continent?
- Pangea
- pan=everywhere or everything.
- Gaia = Earth
What has movement of continent’s led to?
- they have led to diversification of life (develop locally evolved species) and mass extinctions
what is diversification?
the cumulative changes that occur in the heritable character of a population.
what is mass extinction?
- the dying or disappearing of a large number of species and higher taxa in a short period of time.
What are the two most famous events of mass extinctions?
- end Permian extinction
- end-cretaceous extinction
what is end Permian extinction ?
- occurred at 252 million years ago
- 60% of all families and 90% marine species.
-occurred at the same time as formation of supercontinent Pangaea- increased volcanism
- oceanic anoxia (lack of oxygen)
- reduced amount of shallow shoreline.
What is end-cretaceous extinction?
- occurred 66 million years ago
- 20% of all families
- included spectacular land animals and some diverse marine animals.
What did the paleontologists think caused mass extinctions?
- they believed that asteroid or comet strike caused massive fires and smoke that blocked the sunlight for months, thus leading to climate change and extinction.
how long ago did earth form?
it formed 4.6 billion years ago.
What is the oldest evidence of life from?
3.5 billion years ago.
what were the first organism on earth?
-Prokaryotes.
- They lack membrane bound organelles and the DNA is not contained in the nucleus.
how long were Prokaryotic cells the only evidence for on earth?
- 1.5 billion years
In what structures are the oldest prokaryotic fossils found?
- Stromatolites.
- stroma = sheet
-lith=rock.
How are banded rocks created?
-1.sediments accumulate top
-2. Prokaryotes grow through sediments
-3. Sediments bound by exudated
When did oxygen begin to accumulate in the earths atmosphere, and what caused this?
- oxygen accumulated 2.7 billion years ago.
- photosynthetic bacteria started using suns energy to split into hydrogen and oxygen.
- if you added H to co2 –> carbohydrate
what is another name for cyanobacteria?
blue-green algae
What were the first oxygen markers that we could observe?
- banded iron rock.
- eventually the rust from all the iron precipitated and allowed oxygen gas to begin accumulating in atmosphere.
Was oxygen toxic to most early life on earth (prokaryotes)?
True
what are obligate anaerobes?
-an = not
-aerob =reference to oxygen
- they are organisms that can grow and survive only in the absence of oxygen.
What are prokaryotes that are adapted to oxygen rich atmospheres and began respiring______
aerobically
up until the 1800’s what was the primary theory of how life began
-microbes arose through spontaneous generation form non-living material.
- idea that life arose from nonliving matter
- Pasteur: found that the liquid was spoiled by the particles in the air rather than the air itself.
in more recent time we have been able to replicate earths early conditions, producing amino acids and RNA, although these cannot act like cells. What is the current explanation?
- spontaneous formation of hollow lipid vesicles suggest how early cell-like structures may have arisen.
- they have a bi-layered structure.
Experiments conducted found that vesicles form faster in the presence of ___________, a type of ________ thought to be common 4 billion years ago
- Montmorllonite
- volcanic clay
Where did scientist first think life started?
- thought life around shallow water bodies or hot, mineral-rich deep sea vents, or from space.
What is the Panspermia hypothesis?
- that life migrates trough space, or first life came from space.
- pan =everywhere
-sperm=seed
The Panspermia theory gained traction in the 1990’s when they found _____ structures looking like bacteria inside of a meteorite
- nanobes - filament structure first found in rocks and sediments.
What has been discovered in meteorites that gives some credit to the panspermia theory?
- amino acids
What is (as far as we know) the most important step in fostering early life?
liquid water
