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Organic Evolution > Mod 5/6 History of Life > Flashcards

Mod 5/6 History of Life Flashcards

1
Q

How old is earth?

A

4.6 Billion y.o.

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2
Q

Before he was a renowned evolutionary biologist, Charles Darwin accomplished in another field. What was it?

A

Geology

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3
Q

What was the estimate of the age of the earth?

A

70,000

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4
Q

What area in england did Darwin study?

A

The Weald

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5
Q

Who worked on heat and used heat modeling to estimate Earth at <20 myo? And what did he believe?

A

William Kelvin
Measured changes in temperature of rock and modeled using rocks in minesDid not know that the Earth was not a constant (heat flows up and down)Mine rocks were warmer than they should be due to heat flow

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6
Q

Did darwin agree with kelvin?

A

No.

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7
Q

What didn’t Kelvin know when forming his hypothesis about the cooling Earth?

A

Molten rock in the mantle and core rise and fall as their temperature changes

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8
Q

Atoms are

A

either stable or unstable•Instability was at different levels, depending on atom•Due to variation in number of neutrons

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9
Q

Most common isotope

A

Carbon 12 (6 p + 6 n)

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10
Q

Most rare isotope?

A

Carbon 14 (6 P + 8 N)

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11
Q

What is Half-Life equation?

A 
𝑁=𝑁0𝑒−λ 𝑡 
𝑁= number of unstable atoms
N0= remaining number of unstable atoms
λ= probability of decay
𝑡= time
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12
Q

What defines an element?

A

Number of protons

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13
Q

Radioisotopes

A

Some can be formed by cosmic rays •Sometimes convert nitrogen into carbon-14•Other examples•Most have been around since Earth formed•Isotopes in rocks have half-lives > 80 million years•By examining how much is left, we get an age

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14
Q

So earth is

A

4.568 billion years (4,568,000,000 years)

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15
Q

Radiometric dating

A

If you know the half-life (decay rate)
And you know how much of a radioisotope still remains
Compared to how much is stable
You can determine how much time has passed

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16
Q

Rubidium-87

A

37 protons and 50 neutrons•Half-life of 48.8 billion years
Decays into strontium-87 (Sr-87, stable)
When rocks are formed,
Contain various minerals
Each mineral contains different amounts of Rb and Sr

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17
Q

What do all rocks have upon formation?

A

All rocks have same ratio of Sr-87 to Sr-86•Regardless of ratio of Rb-87 to Sr-86

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18
Q

What decays to what overtime?

A

As Rb-87 decays to Sr-87•And as Sr-86 stays the same (it is stable)
The ratio Rb-87/Sr-86 decreases (in all rocks)
If this is plotted (as an isochron)
For all rock types
Slope of line is 𝑒𝑒λ𝑡𝑡−1
Used to determine time since formation

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19
Q

Rubidium -87 decays by

A

a neutron degrading to a proton and electron

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20
Q

What can this dating be used on?

A

Meteorites. Overall helped solve the age of the Earth.

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21
Q

Why did darwin think fossills were difficult to make?

A 
Are eaten
Smaller organisms consume them at microscopic level
Weather erodes them
Some do fossilize though
Must have the right conditions
Still water where silt can be deposited
Mudslide that is anoxic
Volcanic ash, etc.
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22
Q

Mineralization of organic matter can happen by?

A

Minerals from water fill spaces and settle

Original organic material dissolves away

Original spaces filled with other minerals

23
Q

Why are fossils never safe?

A

Can later be exposed

Degraded by weather erosion

People come along and pick them up!

24
Q

Previous organic fossils

A

Do not tend to have rubidium and strontium

Radiometric dating not possible

Can use nearby rock for dating

25
Q

If you were to find mineralized fossils from previously organic matter, what technique could you use to date their age?

A

Radioisotopic dating of nearby rock strata

26
Q

What can fossils tell us?

A

Morphology
Evolutionary relationships
Behavioral ecology
Mating, Reproduction, Feeding

27
Q

What can fossils tell us?

A

Morphology

Evolutionary relationships

Behavioral ecology:
Mating, Reproduction, Feeding

Developmental Biology

28
Q

What PHYSICAL techniques can we use to see fossil cellular structure?

A

SEM Scanning electron microscopes and Energy-dispersive X-ray spectroscopy of Borealopeltia

Showed: More melanin on dorsal surfaces
Indicated countershading
Seems it was preyed on by other dinosaurs

Computed tomography –allows mapping of three-dimensional characteristics of living (and fossil) organisms

29
Q

What two pieces of evidence indicated that hadrosaurs used their head crests for communication?

A

Connected to nasal openings
Area of brain for olfaction is small
Morphology – ear bones indicated they picked up frequencies produced by resonating crests

30
Q

Lagerstätten

A

•Deposit of well-preserved fossils

Usually due to an anoxic environment

Example: the Burgess shale (65k fossils, >93 species)•~505 to 510 mya

31
Q

Biomarkers

A

Molecules in the fossil record that indicate the presence of life

Some larger molecules can only form through organic pathways

Some are unique to certain groups of organisms

Okenane– only made by purple sulfur bacteria

32
Q

Okenane example

A

Found in 1.64 billion year old rocks in Australia

-indicates biological life
•Also anoxic, sulfidic ocean
•Waters would have been toxic to many organisms

33
Q

Are different isotopes found in fresh and sea waters?

A

Yes.

34
Q

Where do plants get carbon from?

A

Atmosphere, take up C12 better than C13

35
Q

Because plants get carbon from atmospheric CO….

A

We Can test rock to determine if plant material is present

36
Q

C3 vs C4 plants

A

C4 photosynthesizing plants have higher ratios of 13C/12C

Can help to determine diet in animals

Shift in human diets

37
Q

What was the shift in human diets?

A

More C4 plants more recently

Or feeding on animals that ate C4 plants

38
Q

Which of the following statements about “molecular paleontology” is true?

A

More recent humans appear to have shifted their diets from C3 to C4 plants (or to animals that consume C4 plants)

39
Q

How long has life been on Earth?

A

It started as molten rock
Many pieces came together
•Formed a crust by cooling over millions of years
•Denser crust rock sank
•Lighter crust rock formed the continents
•Rocks released gases, including water vapor
•Oceans began to form

40
Q

Eras

A
  1. Hadean
  2. Archaean
  3. Proterozoic
  4. Paleozoic
  5. Mesozoic
  6. Cenozoic
41
Q

How old is life?

A

Potential evidence of carbon-12 enriched inclusions in a 4.1 billion year old zircon

Not conclusive

  • At Darwin’s time, oldest known fossils were from Cambrian, 541 mya
  • Since then, fossils have been found possibly up to 3.5 bya
42
Q

What original rock can persist?

A

Original rock destroyed by impacts, plate tectonics
•Zircons can persist
•Sometimes have isotopes that give age
•Some show the composition from ancient Earth

43
Q

Stromatolites

A

sedimentary rock form by layers of cyanobacteria

44
Q

How does stromatolites form?

A

Combine with sand and other small rocks
•Build up by layers over a long time
•Rare now (because they are consumed)
•Common in Precambrian times

45
Q

First single-celled life?

A

Stromatolites
•3.5 billion years ago
•Only life for 1.5 billion years

46
Q

At Darwin’s time, oldest known fossils were from

A

Cambrian, 541 mya

47
Q

Photosynthesis revolution?

A

~2.7 billion years ago

•Increase O2 in the atmosphere

48
Q

Movement of Earth’s crust alter and influences what?

A

Climate and influences species survival

49
Q

Plate movement has Changes in?

A 
Climate
•Atmosphere
•Land size
•Flooding
•Glaciation
•Volcanic activity
•Meteor impact
50
Q

First eukaryotes

A

Had membrane-bound organelles
•Endosymbiotic theory
•~1.8 billion years ago

51
Q

Multicellular eukaryotes

A

~2.1 to 1.2 billion years ago
•Evolved from either: Aggregation
Sticky offspring
Probably colonial at first

52
Q

When did animals come?

A

635 to 585 my
•Ediacaran fauna
Precambrian ~570 mya

53
Q

Many organisms common now are “new”

A 
Dinosaurs – 240 to 66 mya(except birds)
•Mammals – 160 mya
•Flowering plants – 136 mya
•Grasses – 100 mya.
•Early human ancestors – 7   mya•
Homo sapiens – 300 kya

Organic Evolution (5 decks)

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