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Earth Science 1B > Life and Death > Flashcards

Life and Death Flashcards

1
Q

What is a fossil

A

Naturally preserved remains/traces of animals/plants
Is actually quite rare but reasonable ampunt has been preserved

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2
Q

In what environment are you most likely to find fossils?

A

Low energy environments eg deep ocean, lake eg not mountain stream
Sedimentary rocks

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3
Q

3 ways to increase chances of fossilization

A
  1. Burial soon after death
  2. Environmental conditions with little exposure to O2, light and minimal bacterial decay
  3. Organism made of geoliogicall stable materilas
    Sub 0 temps and low O2 also sometimes allow fossilization of soft bodied animals
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4
Q

Trace fossils vs Body fossils

A

Trace fossils are the REMAINS OF ACTIVITY, so anything made/produces by the animal: burrow, footprints, poop…
Body fossils are fossilized PARTS OF THE ORGANISM: teeth, leaves, bark, bone…

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5
Q

Mold vs cast

A

Mold: An imprint has been made into the sediment/rock and this imprint has been preserved
Cast: Stencil/mould has been filled up so the shape of the original organism is recreated and has been preserved

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6
Q

Lagerstätten

A

Rocks containing both soft and hard bodied animals

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7
Q

Impressions in carbon

A

Organism squashed by layers of sediment/rock so after its decay, all thats left is a thin layer of carbon imprints because the rest of the organis materila has decayed,

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8
Q
  1. Precambrian
    4600 - 540 million years ago
A

Mostly simple organisms, disc shaped, but since they didnt have shells, preservation potential small

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9
Q
  1. Paleozoic
    540 - 250 million years ago
A

Animals with shells

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10
Q

3.Mesozoic
250 - 66 million years ago

A

Evolution of reptiles/ complex forms of life

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11
Q
  1. Cenozoic
    66 million years ago - present
A

Mammals

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12
Q

Earths early atmosphere

A

Composed of water, carbon dioxide, carbon monoxide, methane, nitrogen and sulphur

Building blocks of life

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13
Q

Stromatolites

A

Earliest fossils (though a bit controversial)
Stromatolites are rocks with a very fine layering of carbonate made by cyanobacteria (excreted O2) trapping and binding sediment particles.

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14
Q

Evidence of bacterial life 3500 million years ago

A

Presence of light isotope of carbon in minerals in rocks dated from 3500 million years ago
C12 is preferred by living organisms (>C13, C14) eg during photosynthesis, so presence of C12 is evdience for bacterila photosynthesis

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15
Q

The Great Oxidation Event
3500 - 2000 million years ago
(Precambrian)

A

1) Oxygen produced by cyanobacteria reacts with dissolved iron in water to produce iron oxide –> banded iron formations
2) around 2400 million years ago, tipping point is reached where oxygen is no longer just reacting with iron to produce iron oxide in oceans, it is gathering in the atmosphere–> concentrations remained low until about 580 million years ago, allowign complex life to develop

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16
Q

Ediacran fauna
(Precambrian)

A

-Disc shaped organisms with radial ridges
-Preserved as impressions (no shells, because no such thing as predators yet)
-Produce cholesterol so animal rather than plant

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17
Q

The Cambrain Explosion

A

-replace ediacran fauna –> much more diverse
-complex body parts (eyes, brain, shell, skeleton…)

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18
Q

Lagerstätten

A

Rocks that contain fossils of plants and animals that are rarely preserved, usually because they are soft bodied

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19
Q

What is the Burgess Shale

A

is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At 508 million years old, it is one of the earliest fossil beds containing soft-part imprints.

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20
Q

How have the soft bodied animals in the Burgess Shale been preserved?

A

-Oxygen poor sea floor preventing bacterial decay and scavenging
-flattened and preserved as thin films of carbon

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21
Q

Why did the animals in the Burgess Shale develop spines and armored scales?

A

Some animals were predators (as can be seen in fossil remains in which gut and last meal have been preserved), so animals needed to evolve strategies to avoid being eaten

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22
Q

Significance of the Burgess Shale

A

Some animals in the burgess shale are unlike any others in the paleozoic era and even the modern day. Burgess shale almost like an evolutionary experiment–> animals experimenting with the types of forms they can take on and only the best adapted niches continued to develop

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23
Q

Conondont (Cambrian- mid triassic)

A

-Micro fossil
-Eel like predator

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24
Q

Brachiopod (Paleozoic- Cenozoic)

A

-particularly abundant prior to Permian/Great Dying)

-Mode of life: filter feeding–> water comes in, goes through LOPHOPHORE (feeding FILTER) where nutrients are absorbed and rest is shot out of organism. PEDICLE (stalk like structure) allows brachiopod to attach itself to rocks, corals and seafloor

Plane of symmetry: cuts through two shells rather than between shells

-

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25
Q

Crinoids (Paleozoic- Cenozoic)

A

-comprised of arms (filter feeding) and stalk.
-commonly found in limestone
-Stalk made of calcite discs with central hole (like polo candy)

Stalk ossicles/discs:
Carboniferous –> like polo mints
Jurassic –> more star shaped

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26
Q

Graptolite (Paleozoic)

A
  • Looks like pencil marking on rock
  • Saw-like shape
  • Form large colonies and every “tooth” is an organism
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27
Q

Colonial tabulate corals vs solitary rugose corals (Paleozoic)

A

Tabulate corals: Honeycomb morphology
-Polyp occupied each corralite

Rugose corals:
Ice cream cones

28
Q

Why the change in number of growth lines in rugose corals during Paleozoic era?

A

Each line is a DAY of growth
Regular variations in the size and spacing of growth lines reflects lunar, seasonal and annual cycles. The number of growth lines/year can be measured

29
Q

Trilobites (Paleozoic)
Anatomy and Morphology

A
  1. Cephalon (head): some with eyes on either side, some without
  2. Thorax (body): divided into many pleurae (segments) that enabled them to roll up
  3. Pygdium (butt/tail end): looks segemented but not flexible like thorax

Name comes from the three lobes (perpendicular to the cephalon, thorax and pygdium)

30
Q

Trilobites (Paleozoic)
Defense mechnisms

A

Exoskeleton made of hard calcite making them hard to chew well rolled up into a ball

Some developed curvy/extravagent spines

31
Q

Trilobites (Paleozoic)
Mode of life

A

-Float
-Swim
-Crawled or burrowed in the soft sea floor, leaving trace fossils

32
Q

Trilobites (Paleozoic)
Morphology/ functioning of eyes/ lenses

A

2 Eyes made up of thousands of individual calcite lenses

-Eyes on stalks because crawled just below the sediment surface
-Those in deep ocean were blind
-eyes curving downwards –> ability to see straight ahead and below, probably a predator to see whats swimming below

33
Q

Trilobites (Paleozoic)
Exoskeleton

A

The exoskeleton as well as the eyes moulted
-Temporarily blind creature
+abundant fossils because of exoskeleton fossils

34
Q

Rhynie Chert (Devonian/Paleozoic)

A

Lagerstatten from 410 million years ago, Scotland
Appearance of first vascular plants (plants with vessels to transport water and nutrients)

35
Q

Rhynie Chert (Devonian/Paleozoic):
Permineralisation

A

All the cells have been infilled with silica/plant matter replaced at the cellular level by silica

36
Q

Rhynie Chert (Devonian/Paleozoic):
How have they been preserved

A

Plants and insects lived near a hot spring, so very soon after death, organisms inundated by silica rich hot water and fossilised
Fossilisation so rapid that eve most delicate features preserved

37
Q

Fossil Grove (Carboniferous/ Mesozoic)

A

Scotland, while it was near the equator (tropical climate)

Lepidodendron (tree-like plants) have been preserved in sedimnet filled casts, its like an internal mould of the plant

38
Q

Fossil Grove (Carboniferous/ Mesozoic): environment and impact on Earths atmosphere

A

Lepidodendron grew in a subtropical setting like a swamp forest.

The plant reamins in the swamp is what accumulated to make large coal deposits to fuel industrial revolution

Burial of plant material removed a lot of CO2 from the atmosphere + Plant growth adds O2 to atmosphere = Carboniferous atmosphere had 35% O2 (current day has 21%) which allowed insects to grow huge

39
Q

Solnhofen limestone (Jurassic/Mesozoic)

A

Lagerstatten from 150 million years ago, Germany

Development of birds

Bones and impressions left are very detailed because deposited in very fine grained limestone

40
Q

Solnhofen limestone (Jurassic/Mesozoic):
Depositional environment and preservation

A

Depositional environement: lagoons near shallow tropical sea
+not much current to disturb remains at bottom
+Bottom fairly stagnant, salt and anoxic, good for preservation
+ toxic floor environment means predators and scavengers absent

41
Q

Solnhofen limestone (Jurassic/Mesozoic):
Archaeopteryx

A

Has beak, feathers, claws, teeth and solid bones: bird or dino?

“Dino-bird” that evolved from small carnivorous dinosaurs

Could probably fly/glide short distances

42
Q

Solnhofen limestone (Jurassic/Mesozoic):
Archaeopteryx relevance

A

The first skeeton was found 2 years after Darwin published “The Origin of Species” thus supporting his ideas

Close relative of the true ancestor of birds

43
Q

Ammonites (Jurassic- Cretaceous)

A

Looking like an underwater snail x squid

44
Q

Ammonites (Jurassic- Cretaceous): Shells, fossilisation and mode of life

A

Siphuncle penetrates all septa and connects all chambers. It allows water or gas to pass in chambers allowing pressure to be regulated–> gives ammonite ability to move

Shells are made of aragonite, which is often not preserved. Most fossils are molds, or casts made from sediment or minerals (e.g., pyrite).

45
Q

Ammonites (Jurassic- Cretaceous): morphology

A

Shell is divided into chambers by septa, with animal living in outermost chamber

46
Q

Ammonites (Jurassic- Cretaceous): Suture lines

A

Ammonite species can be distinguished is from their ‘sutures’ - curved or intricate lines on the outer surface of the shell. Sutures occur where septa meet the shell surface

47
Q

Bryozoans

A

Ordovician - present

Mode of life:
Immobile, cemented to sea floor

48
Q

Sclereactinian Corals

A

Triassic - present

Aragonite skeleton

49
Q

Bivalves (Cambrian - present)

A

Two shells made of calcite and /or aragonite

Filter feeders

Living at lowest levels if body of water (benthic) within or on sediment

Line of symmetry is between two shells, two valves of bivalve are usually mirror images of each other

50
Q

Foraminifera

A

Cambrian - present

Microfossils

Good indicators of temperature and salinity

Single celled with shell made of calcite, aragonite or silica

Planktonic or benthic

51
Q

Radiolarians

A

Cambrian- present

Microfossils

Single celled with mineralized skeleotn of silica

Planktonic aka floating in ocean

52
Q

Relative vs absolute stratigraphy

A

Relative: eg you see rocks and can say that the oldest is at the bottom so the upper layer is younger relative to the bottom

Absolute: measuring exact age by dating rocks

53
Q

Biostratigraphy

A

uses fossils to correlate rocks and determine their relative age

54
Q

Biozone

A

The upper and lower limits of a rock based on the presence and/or abundancethe of one or more species of fossils

Zone fossils are used to define biozones

55
Q

Characteristics of a good zone fossil

A

+Worldwide geographical distribution
+Evolves quickly, so any one species has a short lifespan
+abundant
+easy to identify (through patterns, specific characteristic)
+Readily fossilised

56
Q

Good zone fossils

A

AMMONITE

Swam in the oceans so are found on many different types of marine rock

Easy to recognize because of suture patterns

57
Q

Types of Biozone

A

Total Biozone:
organisms first appearance - extinction

Acme Biozone:
biozone defined by where this organism is especially abundant

Partial Range Biozone:
Like total biozone but you’re taking into account the appearance/ disappearance of other species to define the biozone

Assemblage Biozone:
Biozone is the area where a variety of organisms are living at the same time

58
Q

Types of Biozone

A

Total Biozone:
organisms first appearance - extinction

Acme Biozone:
biozone defined by where this organism is especially abundant

Partial Range Biozone:
Like total biozone but you’re taking into account the appearance/ disappearance of other species to define the biozone

Assemblage Biozone:
Biozone is the area where a variety of organisms are living at the same time

59
Q

A biozone may not represent the same time interval everywhere that it occurs, because:

A

-A species may not have appeared and gone extinct at exactly the same time everywhere

-A species may originate in a small area, then some time later expand

-A species may go extinct in most areas, but hang on in one place

-The lack of fossils of a given species may just be because it has not been preserved, or just not yet been found

60
Q
  1. End Ordovician 443 million years ago
    (Mass Extinction)
A

Extinct species:
80% of all species, mainly marine invertebrates

Causes:
1) Global Cooling –> Burial of animals removes CO2 from atmosphere.Glaciation and lowering of sea levels affect warm shallow animals mostly
2) Global Warming–> Melting of glaciers

61
Q
  1. Late Devonian 370 million years ago
    (Mass Extinction)
A

Extinct species:
75% of marine species

Causes:
Land surface colonised by plants, greater rates of rock weathering, CO2 levels drop
GLOBAL COOLING, glaciation in Southern hemisphere

62
Q
  1. Great Dying/ Permian 251 million years ago
    (Mass Extinction)
A

Boundary between Paleozoic and Mesozoic

Extinct species:
96% of marine animals including trilobites
70% of terrestrial animals

Causes:
Volcanism –> rise in CO2 levels –> global warming –> acidification and stagnation on sea floors
+ammonia and methane in atmosphere

63
Q

4.End Triassic 201 million years ago
(Mass Extinction)

A

Extinct species:
80% of marine species including conondonts and loss of mammals that allow diversification of dinosaurs to take up left over niches

Causes:
Intense volcanic activity leading to greenhouse warming and ocean acidifcation

64
Q

5.Cretaceous- Paleogene 66 million years ago
(Mass Extinction)

A

Extinct species:
75% of species, allowing mammals and birds to diversify/ take over the niches

Causes:
Asteroid impact

65
Q

Cretaceous- Paleogene 66 million years ago
(Mass Extinction): Evidence

A

All around the world, a thin layer can be found that contains a chemical element that is more rare to Earths crust and more common in meteorites

Consists of:
-an ejecta layer: containing glass droplets thrown out by the impact
-fireball layer that contians mineral grains that have experienced high pressure eg diamonds

180km crater found buried beneath limestone in Mexico

66
Q

Cretaceous- Paleogene 66 million years ago
(Mass Extinction): Effect on global climate

A

Immediate effects:
-Sunlight blocked by rock dust and soot (from wildfires) ejected into the atmosphere. A ‘nuclear winter’.
-Photosynthesis fails
-Global cooling to sub zero temps for many years

Long term effects:
-Global warming due to the burning of vegetation releasing CO2 and CaCO3 vaporizing

67
Q

Cretaceous- Paleogene 66 million years ago
(Mass Extinction): Implications

A

Would mammals have evolved if this asteroid hadn’t hit? Because the took over the niches the dinosaurs etc left behind and evolved and diversified

Earth Science 1B (9 decks)

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