Fossil record and First life Flashcards
What are the four requirements for life?
1: Metabolism
2: Response to stimuli
3: Homeostasis
4: reproduction with 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?
No, they lack metabolism and homeostasis and cannot reproduce without using the cellular machinery of the host cell.
What is a fossil?
Is a preserved remnant/evidence of organisms that lived in the past
What is a fossilis?
A fossil that is dug up, usually within sedimentary rocks
What are distinct levels of rock called?
Strata
Whether an organism or part thereof is fossilized depends a great deal on chance.
What chance?
- More likely if hard - than if soft bodied
- More likely if aquatic than terrestrial
- More likely if inshore marine than offshore.
- More likely of decomposing organisms 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?
Evidence of behaviors
- tracks
- burrows
- faeces
The study of trace fossils is called?
Ichnology
- ichnos = track, trail
What does Ichnos mean?
- ichnos = track, trail
What are cast fossils?
A cast forms when minerals fill the space in sediment where organism decay after being berried
What are petrified fossils?
fossils have had their tissues replaced by minerals
What does Petra mean?
Rock
Can you find fossilized organic material?
Yes you can:
Thin carbon films
In amber
In tar peat
Frozen
What is a sub-fossil?
Fossil has most organic parts replaced by mineral; sub-fossil has high % organic matter.
Relative dating is done via what method?
Sedimentary stratigraphy
What does Stratum mean?
Layer
What does Graph mean?
Write/record
what is relative dating?
The process of seeing the age of fossils by using the principles of super position to determine age.
Can sediments be moved or rearranged naturally?
Yes, through mass geological moments
Ie earth quakes
True or false:
It is common to have gaps in Sedimentary sequence.
True
Due to erosion and/or a temporary stop in sedimentary deposition.
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?
Becasue 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?
It involves measurements of the radioactive isotopes in fossils or rocks.
They decay at a fixed rate “half life” and based on the concentration of daughter element we can see how long the rock/fossil is.
What is a isotope?
An element that can exist in many different states.
C12 C14
What makes a isotope?
The difference in neutrons in the element.
What is the most common element used in radiometric dating?
Carbon 14 - decays into nitrogen 14
What is a half life?
when an radioactive element transmuted half of its mass into a daughter element. Due to radioactive decay
Why and how do we use Carbon 14 for radiometric dating?
Plants take in C12 and C14 during photosynthesis
Animals get the same ratio of C12 and C14 through eating plants or herabavours
Once the organism dies they no longer take in C12 or C14
C12 stays but C14 decays
What is the half life of Carbon 14
5730
is carbon dating good for old or young fossils ?
Young
only good up to 75,000 years old
What do we use for older fossils than 75,000 years old?
We use Uranium
What is the half life of U-238?
4.5 Billion years old
The location of fossil both in place and in time is important. What is the challenge with the “place” of fossils?
There is Continental drift, meaning land masses are not always in the same place or same environment.
What was the first evedance of Continental drift?
Fossils within the same genus of plant found in Australia, Antarctica, and south america produced evedance for a Palaeo-Continent
What was the name of the supposed Palaeo continent?
Gondwana
What is Pangaea?
The Super Continent
What are mass extinctions?
Sudden periods in which large numbers of species and higher taxa disappeared
When was the end-Permain mass extinction?
It was around 245 million years ago
What else happed during the end-permain mass extinction?
Pangaea was formed
How many species and families died during the end-permain mass extinction?
60% of all families
90% of all marine species
When was the end-Cretaceous mass extinction?
65 million years ago.
at the Cretaceous-Paleogene boundary
how many families went extinct during the cretaceous mass extinction?
20% of all families
What are the two main theories that are held about the end-cretaceous mass extinction?
Some say that it was an asteroid or comet that caused it.
Others say that it was more slow and gradual, and being caused by climate change. With the asteroid being the final straw.
How long ago did earth form?
4.6 BILLION years ago
What is the oldest fossil record evidence that we have uncovered
3.5 billion years old
What was the first fossil record of?
Single celled prokaryotes that LACKED membrane bound organelles.
How long were Prokaryotic cells the only evidence of life on earth?
1.5 Billion years
Where are the oldest prokaryotic fossils found?
In stromatolites
What is the definition of Stroma?
sheet
What is the definition of Lith?
Rock
How are banded rocks created?
- prokaryotes live on sediment
- Sediment accumulated on top of them
- Prokaryotes grow up through the sediment leaving layers
When did oxygen begin to accumulate in the earths atmosphere, and what caused this?
It started to accumulate roughly 2.7 billion years ago.
It was caused by photosynthetic cyanobacteria who used the suns energy to split water into hydrogen and oxygen
What is another name for cyanobacteria?
Blue-green algae (even though they are not algea)
What were the first oxygen markers that we could observe?
iron oxide percipated out and resulted in banded iron rock that we analyze today.
True or false:
O2 was toxic to most early life on earth.
True.
It was the waste product.
What are obligate anaerobes?
Species of prokaryotes that are adapted to survive in a low oxygen environment
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?
Spontaneous generation:
ie - life just kinda appeared
in more recent time we have been able to replicate earths early conditions, producing amino acids, although these cannot act like cells. What is the current explanation?
Spontaneous formation of hollow lipid vesicles
Experiments conducted found that vesicles form faster in the presence of ___________, a type of ________ thought to be common 4 billion years ago
Montmorillonite
volcanic clay
Where did scientist first think life started?
In shallow water bodies that are exposed to atmosphere.
Where do scientist now think life first started?
They think it arose near or around hot, mineral-rich deep sea vents
What is the Panspermia hypothesis?
That prokaryotes came from space on a comet
What does pan mean?
Everywhere
What does sperm mean?
Seed
the Panspermia theory gained traction in the 1990’s when they found _____ structures looking like bacteria inside of a meteorite
Nanobes
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?
free, non-toxic water
