fossils Flashcards
What are 2 ways we date earth’s events in history?
- relative dating, 2. radiometric dating
Fossils provide vital information about…?
extinct species
Why is the fossil record incomplete throughout time?
Many organisms die without leaving a trace
Researchers who study fossils are called?
Paleontologists
extinct? (definition)
species that have died out
Is a fossil a whole organism or fragments of an organism?
both
In what rock are fossils usually found?
sedimentary - if sand builds up quickly, it can bury an organism/fragment.
Fossils are usually formed from hard structures such as teeth, bones…but how can soft tissue be preserved?
If the organism is buried quickly
What 4 things do fossils reveal about ancient life?
- its structural make-up. 2. the sequencing of groups ver time, 3. how organisms evolved, 4. ecology of the life around these organisms
Give an example of how a fossils reveals information about ecology?
fossilized plants can indicate desserts, lakes and forests at the time in that location.
Give an example of how a fossil can suggest an organism’s structural make-up?
fossilized footprints can indicate how the organism walked/ crawled.
What is relative dating?
judging the age of a fossil based on its location in the ground
How are index fossils used for dating?
these fossils are uniquely found in only certain time periods, and can be used to determine the age of the ground layer
What are 2 important qualifications a fossil must have in order to be considered an index fossil?
- be easy to recognize, 2. occur in only a few rock layers (unique to a small time period)
give 1 example of an index fossil
trilobites
what is radiometric dating?
it provides information on the fossil’s absolute age by measuring the decay of isotopes within the fossil.
half-life (definition)?
time required for half the radioactive atoms to decay
Different radioactive isotopes decay at different rates. Name 1 element with a long half-life and 1 with a short half-life.
long- potassium. short - carbon 14
when would you want to measure elements with long half lives?
for older fossils (such as rocks) and useful for figuring out whole time periods
where does carbon 14 come from?
its in the atmosphere…plants absorb it….organisms eat it….and it begins to decay when the organism dies
How was the geological timetable established?
using both relative and absolute dating to determine rock layer boundaries. These boundaries established the eons and periods.
Name the 4 major geological divisions (eons).
- Hadean, 2. Archean, 3. Proterozoic, 4. Phanerozoic
In which eon did the stable continents form?
3rd eon, Proterozoic
Which is the first eon?
Hadean
Which is our present eon?
Phanerozoic
In which eon did life first appear?
2nd eon, Archean
In which eon did eukaryotic cells form
Proterozoic (3rd eon)
How many eras are in the Phanerozoic eon
3 eras (Palaeozoic, Mesozoic, Cenozoic - current)
Eons are divided into…?
eras
Eras are subdivided into…?
periods
What is the range of years a PERIOD can be (in millions)?
between 2 million and 100 million
What period and era do we live in now?
Cenozoic era and the Quaternary period
How many of the 4 eons are in the Precambrian time?
the first 3 (Hadean, Archean and Proterozoic)
What percent of time does the Precambrian take up of earth’s existence?
90% of earth’s life has been spent in Precambrian time. Another 5% was in Paleozoic, 4 % spent in Mesozoic, 1% in Cenozoic.
What are 4 of earth’s changes that have shaped history?
- climate change, 2. plate tectonics, 3. volcanos, 4. meteors (mass extinction)
What are some of the effects on life due to climate change, plate tectonics, volcanos and meteors?
- natural selection, 2. new organisms created even more changes (ex. they increased the amount of oxygen and nitrogen in the atmosphere) An increase in oxygen led to decrease in carbon dioxide which allowed temperatures to go down and change the climate and ocean chemistry dramatically.
