25 The History of Life on Earth Flashcards
1
Q
What is macroevolution?
A
The broad pattern of evolution above the species level.
Therefore it deals more with questions such as how did life move from the water to land.
2
Q
What is the general consensus on how life emerged from abiotic components?
A
It is believed to have happened in 4 stages:
- The abiotic (nonliving) synthesis of small organic mol- ecules, such as amino acids and nitrogenous bases
- The joining of these small molecules into macromolecules, such as proteins and nucleic acids
- The packaging of these molecules into protocells, droplets with membranes that maintained an internal chemistry different from that of their surroundings.
- The origin of self-replicating molecules that eventually made inheritance possible
3
Q
What is an example of a set of conditions where the synthesis of amino acids could occur?
A
Many were found during a stimulated volcanic eruption
4
Q
What are the basic forms of amino acids and how do they differ? (not acidic, basic etc.)
A
L Isomer and D isomer forms
Life on earth uses on the L form
5
Q
What does ‘L isomer’ refer to in terms of amino acids?
A
One of two forms (L isomer and D isomer) of amino acids
Life on earth uses only L isomer
Thus the presence of the D isomer form in meteorites shows that amino acids can be synthesised abiotically.
6
Q
What were primitive cells called?
A
Protocells
7
Q
What are protocells?
A
The first primitive cells.
They existed as vesicles that spontaneously formed from hydrophobic substances to form a basic lipid bilayer.
They had clumps of clay called ‘montmorillonite’ around which chemicals concentrated and thus the rate of reaction increased.
8
Q
What came first: RNA or DNA?
A
Probably RNA
9
Q
What is ‘montmorillonite’?
A
A soft mineral clay that was abundant when life on earn began so was likely part of the first ‘protocol.’
10
Q
What are the key sources of information about the history of life on earth?
A
- The fossil record
- Genetic analysis
11
Q
When did the first unicellular eukaryote paper?
A
1,500 mya
12
Q
What does ‘MYA’ refer to in the context of history?
A
Million years ago - therefore 1000 mya is a billion years ago
13
Q
When where plesiosaurs around n earth?
A
200 to 65.5 mya
14
Q
What is a common methods to determine the age of rocks and organic samples?
A
Radiometric dating
15
Q
What is radiometric dating?
A
A method of determining the age of something based on its concentration of isotopes.
It works on the assumption that when an organism dies it will take in no new carbon. Any radioactive carbon that remains inside will slowly decay into stable carbon.
16
Q
What it called when the age of something is determined by looking at isotopes?
A
Radiometric dating
17
Q
What is a common isotope looked at when performing radiometric dating?
A
Carbon-14 which eventually becomes carbon-12
18
Q
Some specimens are so old that they have minute amounts of carbon-12 present. How are they dated?
A
Organisms do not accumulate the radioactive uranium-238 However the rocks around them do.
Therefore by measuring the ratio of uranium-238 to U-235 in the surrounding rocks the age of the sample can be deduced.
19
Q
What is the sequence in the evolution of mammals?
A
Synapsid → Therapsid → Early cynodont → Later cynodont → Very late cynodont → Modern Mammals
20
Q
In the evolution of mammals, when did Snapsids first appear?
A
300 mya
21
Q
In the evolution of mammals, when did Therapsid first appear?
A
280 mya
22
Q
In the evolution of mammals, when did Early cynodont first appear?
A
260 mya
23
Q
In the evolution of mammals, when did Later cynodont first appear?
A
220 mya
24
Q
In the evolution of mammals, when did Very late cynodont first appear?
A
195 mya
25
In the evolution of mammals, what are synapsids?
They have multiple bones in the lower jaw and single-pointed teeth.
The jaw hinge was formed by the articular and quadrate bones. Synapsids also had an opening called the temporal fenestra behind the eye socket. Powerful cheek muscles for closing the jaws probably passed through the temporal fenestra.
Over time, this opening enlarged and moved in front of the hinge between the lower and upper jaws, thereby increasing the power
26
In the evolution of mammals, therapsids?
Therapsids had large dentary bones, long faces, and the first examples of specialized teeth, large canines. These trends continued in a group of therapsids called cynodonts.
27
In the evolution of mammals, what are Early cynodonts?
In early cynodont therapsids, the dentary was the largest bone in the lower jaw, the temporal fenestra was large and positioned forward of the jaw hinge, and teeth with several cusps first appeared.
As in earlier synapsids, the jaw had an articular-quadrate hinge.
28
In the evolution of mammals, what are Later cynodonts?
Later cynodonts had teeth with complex cusp patterns and their lower and upper jaws hinged in two locations: They retained the original articular-quadrate hinge and formed a new, second hinge between the dentary and squamosal bones.
29
In the evolution of mammals, what are Very late cynodonts
In some very late (non-mammalian) cynodonts and early mammals, the original articular-quadrate hinge was lost, leaving the dentary-squamosal hinge as the only hinge between the lower and upper jaws, as in living mammals.
The articular and quadrate bones migrated into the ear region (not shown), where they functioned in transmitting sound. In the mammal lineage, these two bones later evolved into the familiar hammer (malleus) and anvil (incus)
30
What is the ’temporal fenestra’?
An opening in the skull behind the eye socket.
Powerful muscles to close the jaw pass through this “archway"
31
In the evolution of mammals, where did the hammer (malleus) and anvil (incus) originate?
They are derived from the ‘articular-quadrate hinge'
32
What is the ‘geologic record’?
The entirety of the layers of rocks on earth and thus the entirety of Earth’s history
33
What is the geologic record divided into?
Three eons:
These are in order from oldest to most recent: Archaean, Proterozoic and Phanerozoic.
34
How long did the Archaean eon last?
4 billion years
35
How long did the Proterozoic eon last?
4 billion years
36
How long did the Phanerozoic eon last?
Half a billion years
37
What is the ‘geologic record’?
The entirety of the layers of rocks on earth and thus the entirety of Earth’s history
38
What is the geologic record divided into?
Three eons:
These are in order: Archaean, Proterozoic and Phanerozoic.
39
How long did the Archaean eon last?
4 billion years
40
How long did the Proterozoic eon last?
4 billion years
41
How long did the Phanerozoic eon last?
Half a billion years
42
What is the ‘proterozoic’ eon divided into?
The ediacaran period
Other events happened within the proterozoic but outside the Ediacaran
43
How is the Geologic record divided?
It has 3 eons.
An eon is divided into ‘eras’ which are divided into ‘periods’ which are then divided into ‘epochs'
44
What happened in the Ediacaran period?
Diverse algae and soft-bodied invertebrate animals appear
45
When was the Ediacaran period?
542 to 635 mya
46
What happened in the Archaen eon?
In order form first to most recent:
- Origin of earth
- Oldest known rocks on earth’s surface
- Oldest fossils of cells appear
- Oxygen levels in the atmosphere increase
47
What is the Phanerozoic eon divided into?
The cenozoic, mesozoic and paleozoic eras. (in order from most recent to oldest)
48
What is the Paleozoic era divided into?
The permian, carboniferous, devonian, silurian, ordovician and cambrian periods. (in order from most recent to oldest)
49
When did the earth first originate?
4,600 mya
50
When dud the first cells (prokaryotes) appear?
3,500 mya
51
When dud the first eukaryotes appear?
2,100 mya (in the proterozoic era)
52
When was the Permian period?
251-299 mya
53
When was the Carboniferous period?
299-359 mya
54
When was the Devonian period?
359 - 416 mya
55
When was the Silurian period?
416 - 444 mya
56
When was the Ordovician period?
444 - 488 mya
57
When was the Cambrian period?
488 - 542 mya
58
What happened during the Permian period?
Radiation of reptiles; origin of most present-day groups of insects; extinction of many marine and terrestrial organisms
at end of period
59
What happened during the Carboniferous period?
Extensive forests of vascular
| plants form; first seed plants appear; origin of reptiles; amphibians dominant
60
What happened during the Devonian period?
Diversification of bony fishes; first tetrapods and insects appear
61
What happened during the Silurian period?
Diversification of early vascular plants
62
What happened during the Ordovician period?
Marine algae abundant; colonization of land by diverse fungi, plants, and animals
63
What happened during the Cambrian period?
Sudden increase in diversity of many animal phyla (Cambrian explosion)
64
What is the mesozoic era of the phanerzoic era divided into?
The cretaceous, jurassic and triassic periods. (in order from most recent to oldest)
65
When was the Cretaceous period?
65.5 - 145.5 mya
66
When was the Jurassic period?
145.5 - 199.6 mya
67
When was the Triassic period?
199.6 - 251 mya
68
What happened during the cretaceous period?
Flowering plants (angiosperms) appear and diversify; many groups of organisms, including most dinosaurs, become extinct at end of period
69
What happened during the jurassic period?
Gymnosperms continue as dominant plants; dinosaurs abundant and diverse.
70
What happened during the triassic period?
Cone-bearing plants (gymnosperms) dominate landscape; dinosaurs evolve and radiate; origin of mammals
71
What is the cenozoic era of the phanerozoic eon divided into?
The Quaternary, Neogene and Paleogene periods. (in order)
72
What is the Quaternary period divided into?
The Holocene and Pleistocene epochs (in order from most recent to oldest)
73
What is the Neogene period divided into?
The pliocene and miocene epochs (in order from most recent to oldest)
74
What is the Paleogene period divided into?
The oligocene, eocene and paleocene epochs (in order from most recent to oldest)
75
When was the Holocene epoch?
Now to 0.01 mya
76
When was the Pleistocene epoch?
0.01 - 2.6 mya
77
When was the Pilocene epoch?
2.6 - 5.3 mya
78
When was the Miocene epoch?
5.3 - 23 mya
79
When was the Oligocene epoch?
23 - 33.9 mya
80
When was the Eocene epoch?
33.9 - 55.8 mya
81
When was the Palaeocene epoch?
55.8 - 65.5 mya
82
What happened during the holocene epoch?
It is now to 0.01 mya so modern stuff like the Romans
83
What happened during the pleistocene epoch?
Ice ages, the genus Homo began
84
What happened during the pliocene epoch?
Appearance of bipedal human ancestors (not in the genus Homo)
85
What happened during the miocene epoch?
Continued radiation of mammals and angiosperms; earliest direct human ancestors
86
What happened during the oligocene epoch?
Origins of many primate groups
87
What happened during the eocene epoch?
Angiosperm dominance increases; continued radiation of most present-day mammalian orders
88
What happened during the paleocene epoch?
Major radiation of mammals, birds,
| and pollinating insects
89
When was the Cenozoic era?
Now to 65.5 mya
90
When was the Paleogene period?
23 - 65.5 mya
91
When was the Paleozoic era?
251 - 542 mya
92
When was the Proterozoic era?
542 - 2500 mya
93
When was the quaternary period?
now to 2.6 mya
94
When was the Neogene period?
2.6 - 23 mya
95
When was the Paleogene period?
23 - 65.5 mya
96
In order what are some of the major events in the history of life on earth?
Photosynthesis and the Oxygen Revolution, The First Eukaryotes, Multicellularity, Cambrian Explosion and Colonisation of Land
97
When did oxygen first become widely available?
2.7 billion years ago
98
How was the oxygen on earth produced?
Largely by cyanobacteria (photosynthetic bacteria)
99
What does the ’Oxygen Revolution’ refer to?
The time 2.7 billion years ago when the levels of oxygen in the air skyrocketed.
100
How did the oxygen revolution affect the number of species on earth?
Initially it decreased them as the oxygen chemically reduced and thus harmed primitive anaerobic prokaryotes.
However others soon adapted to these conditions and the energetic advantage of being aerobic
101
In what organisms are cytoskeletons found?
Only prokaryotes
102
Do prokaryotes have cytoskeltons?
No
103
Why is the emergence of cytoskeletons in eukaryotes important?
It enables eukaryotic cells to change their shape and thereby surround and engulf other cells.
104
What is some evidence that mitochondria and endosymbiots?
- They replicate in a manner similar to prokaryotes
| - They have a single circular chromosome
105
When did the first multicellular eukaryotes appear?
About 1.2 billion years ago
106
What is the gradual movement of tectonic plates called?
Continental drift
107
What is ‘continental drift’?
The gradual movement of the tectonic plates.
This leads to the separation of Pangea
108
How many mass extinction have there been?
5 (or six if you include the modern one)
109
What is is called when the groups
| of organisms form many new species, each with unique adaptations?
Adaptive radiation
110
What is adaptive radiation?
Periods of evolutionary change in which groups of organisms form many new species
whose adaptations allow them to fill dif-
ferent ecological roles, or niches, in their
communities.
111
What are some typical situations in which adaptive radiation often occurs?
- After each of the big five mass extinctions, when survivors adapted to the vacant ecological niches.
- When an organism develops a major evolutionary advantage i.e. seeds
- Colonised regions with little competition i.e. reaches new island archipelago: one unique species develops per island
112
What are the basic forms of adaptive radiation?
‘Worldwide adaptive radiation’ and ‘regional adaptive radiation'
113
What is the fundamental difference between ‘Worldwide adaptive radiation’ and ‘regional adaptive radiation'
Worldwide is over a larger scale i.e. new species after a major catastrophe (super-volcano) or an organism with a massive advantage i.e. ability to live on land
Regional is smaller scale. For example a bird reaches a new island archipelago with little competition: becomes many species adapted
114
Alternations in which genes cause the most drastic changes and thus lead to the most profound evolutionary changes?
Genes which regulate the timing of development.
Changes in these are called ‘heterochrony'
115
What is heterochrony?
When genetic changes lead to a change in the time of developmental stages. This often leads to dramatic changes, such as a vastly different skull shape
116
What are changes to the genes that regulate the timing development called?
Heterochrony
117
What is called when sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species?
Paedomorphosis
118
What is ‘paedomorphosis’?
When a sexually mature stage of a species may retain body features that were juvenile structures in an ancestral species.
For example, most salamander species have aquatic larvae that undergo metamorphosis in becoming adults. But some species grow to adult size and become sexually mature while retaining gills and other larval features
119
What are genes that regulate development called?
Homeotic genes
120
What are homeotic genes?
Genes that regulate development (not the timing of development - changes to that is called heterchrony)
121
How can complicated structures such as the eye emerge if they don’t appear suddenly but any previous forms would be a massive waste of energy?
Actually previous versions of the eyes would not be wasteful: the simple organism with photoreceptor patches found it useful, as did the invertebrates with simple single-lens eyes.
This highlights the idea that natural selection world on the idea of ‘current utility’ in which a complex structure must have also been beneficial to all previous generations/
122
What are the basic ways that ‘current utility’ is achieved?
- A feature, such as the eye, slowly evolves with all previous steps being beneficial to the organism.
- ‘Exaption’ in which features are utilised for other purposes
123
In terms of evolution, what is it called when features are reused for different purposes?
Exaption
124
What is exaption?
When features in an organism evolve to perform different roles.
For example the jawbones of the early mammals became the malleus and incus of the ear.
