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Flashcards in fossils Deck (36)
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1
Q

What are 2 ways we date earth’s events in history?

A
  1. relative dating, 2. radiometric dating
2
Q

Fossils provide vital information about…?

A

extinct species

3
Q

Why is the fossil record incomplete throughout time?

A

Many organisms die without leaving a trace

4
Q

Researchers who study fossils are called?

A

Paleontologists

5
Q

extinct? (definition)

A

species that have died out

6
Q

Is a fossil a whole organism or fragments of an organism?

A

both

7
Q

In what rock are fossils usually found?

A

sedimentary - if sand builds up quickly, it can bury an organism/fragment.

8
Q

Fossils are usually formed from hard structures such as teeth, bones…but how can soft tissue be preserved?

A

If the organism is buried quickly

9
Q

What 4 things do fossils reveal about ancient life?

A
  1. its structural make-up. 2. the sequencing of groups ver time, 3. how organisms evolved, 4. ecology of the life around these organisms
10
Q

Give an example of how a fossils reveals information about ecology?

A

fossilized plants can indicate desserts, lakes and forests at the time in that location.

11
Q

Give an example of how a fossil can suggest an organism’s structural make-up?

A

fossilized footprints can indicate how the organism walked/ crawled.

12
Q

What is relative dating?

A

judging the age of a fossil based on its location in the ground

13
Q

How are index fossils used for dating?

A

these fossils are uniquely found in only certain time periods, and can be used to determine the age of the ground layer

14
Q

What are 2 important qualifications a fossil must have in order to be considered an index fossil?

A
  1. be easy to recognize, 2. occur in only a few rock layers (unique to a small time period)
15
Q

give 1 example of an index fossil

A

trilobites

16
Q

what is radiometric dating?

A

it provides information on the fossil’s absolute age by measuring the decay of isotopes within the fossil.

17
Q

half-life (definition)?

A

time required for half the radioactive atoms to decay

18
Q

Different radioactive isotopes decay at different rates. Name 1 element with a long half-life and 1 with a short half-life.

A

long- potassium. short - carbon 14

19
Q

when would you want to measure elements with long half lives?

A

for older fossils (such as rocks) and useful for figuring out whole time periods

20
Q

where does carbon 14 come from?

A

its in the atmosphere…plants absorb it….organisms eat it….and it begins to decay when the organism dies

21
Q

How was the geological timetable established?

A

using both relative and absolute dating to determine rock layer boundaries. These boundaries established the eons and periods.

22
Q

Name the 4 major geological divisions (eons).

A
  1. Hadean, 2. Archean, 3. Proterozoic, 4. Phanerozoic
23
Q

In which eon did the stable continents form?

A

3rd eon, Proterozoic

24
Q

Which is the first eon?

A

Hadean

25
Q

Which is our present eon?

A

Phanerozoic

26
Q

In which eon did life first appear?

A

2nd eon, Archean

27
Q

In which eon did eukaryotic cells form

A

Proterozoic (3rd eon)

28
Q

How many eras are in the Phanerozoic eon

A

3 eras (Palaeozoic, Mesozoic, Cenozoic - current)

29
Q

Eons are divided into…?

A

eras

30
Q

Eras are subdivided into…?

A

periods

31
Q

What is the range of years a PERIOD can be (in millions)?

A

between 2 million and 100 million

32
Q

What period and era do we live in now?

A

Cenozoic era and the Quaternary period

33
Q

How many of the 4 eons are in the Precambrian time?

A

the first 3 (Hadean, Archean and Proterozoic)

34
Q

What percent of time does the Precambrian take up of earth’s existence?

A

90% of earth’s life has been spent in Precambrian time. Another 5% was in Paleozoic, 4 % spent in Mesozoic, 1% in Cenozoic.

35
Q

What are 4 of earth’s changes that have shaped history?

A
  1. climate change, 2. plate tectonics, 3. volcanos, 4. meteors (mass extinction)
36
Q

What are some of the effects on life due to climate change, plate tectonics, volcanos and meteors?

A
  1. 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.