Life on the early earth Flashcards

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1
Q

How old is the earth?

A

4.5 billion years old.

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2
Q

What is data for the age of the earth derived from?

A

derived from looking at the ratios of radioactive elements - typically by using uranium-lead dating

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3
Q

What do fossil preserve?

A

Traces or remains of organisms

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4
Q

Why do the most commonly found fossils arise?

A

due to replacement of organic material after burial by minerals dissolved in water in the ground and recrystallization.

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5
Q

In exceptional circumstances fossilisation reveals…

A

…fantastic detail

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6
Q

What are microorganisms the key to?

A

the key to all life.

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7
Q

OUr perception of life tend to be…

A

anthropocentric - we notice life at our scale.

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8
Q

Why are microorganisms the key to all life?

A

they lie at the base of food chains and are essential in ensuring elements such as oxygen, carbon, and nitrogen are available to plants and animals.

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9
Q

What is life dominated by?

A

life is dominated by microorganisms

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10
Q

when was the origin of the earth?

A

origin of the earth (~ 4.5 billion years ago)

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11
Q

WHen was the origin of life?

A

origin of life (~ 3.5 billion years ago)

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12
Q

When was the origin of multicellular life?

A

Origin of multicellular life (~ 1 billion years ago)

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13
Q

When was the origin of humans?

A

200 thousand years ago

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14
Q

How does complexity change throughout the modern world?

A

increasing complexity.

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15
Q

What were key moments in evolution?

A
  1. the origin of life2. the oxygenation of the atmosphere3. the origin of eukaryotic cells4. the origin of multicellular organisms5. the ‘Cambrian explosion’6. the colonisation of the land by complex organisms
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16
Q

What did Millers experiment aim to do?

A

to recreate conditions that existed on the primordial earth

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17
Q

What was generated in Millers experiment?

A

amino acids.

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18
Q

Describe millers experiment.

A

Miller’s famous experiment used electricity to provide energy to a mixture of gases in a closed system. After incubating the mixture for a period of time he discovered that some of the building blocks of life – amino acids – had been formed.

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19
Q

What was used in Millers experiment?

A

gases - methane, hydrogen, ammonia, water vapour.energy sourceboiling watertrap to collect products

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20
Q

whats a problem of millers experiment?

A

it is now thought that the atmosphere of the earth was quite different

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21
Q

Whats a long popular theory of how life arose?

A

‘primordial soup’

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22
Q

Explain primordial soup theory.

A
  • sea acts as a trap collecting amino acids, nucleotides, and other organic molecules as they form. - these were then thought to have joined up to make macromolecules (protein and DNA) which led to life
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23
Q

WHats a problem with the primordial soup theory?

A

One problem is that the ‘soup’ was unlikely to have been concentrated enough. More of a ‘weak broth’ really…

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24
Q

Whats a alternative hypothesis more widely accepted than the primordial soup theory?

A

life arose around hydrothermal vents in the deep oceans.

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25
Q

Explain the hydrothermal vents theory of how life arose.

A

hydrothermal vents presented a far more concentrated solution of organic molecules. They also give off energy in the form of heat which is essential for life to develop. These ‘black smokers’ are found on the ocean floor now and have ecosystems that are independent of the sun

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26
Q

Describe the earliest cells.

A

the earliest cells may have been little more than ‘bags’ enabling higher concentrations of nutrients to build uphigh concentration of organic molecules enabling the construction of ‘biologically useful’ molecules

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27
Q

all current life requires…

A

…cells.

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28
Q

one possibility is that the first cells were…

A

…lipid vesicles

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29
Q

Why are lipid vesicles formed?

A

because fatty acids have one end that likes to react with water (hydrophilic) and another that likes to ‘hide’ from water (hydrophobic).This means that fatty acids will aggregate into a sphere in aqueous solution.

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30
Q

Whats the problem with simply invoking lipid vesicles to collapse and form cells?

A

The problem with simply invoking lipid vesicles to collapse and form cells is that they are unstable and… where do the phospholipids come from?

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31
Q

Whats a more recent suggestion on how lipids form cells?

A

More recently suggested that early cells were bounded by an amphiphilic protein membrane or by a combination of lipids and amino acids

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32
Q

What was early life dominated by?

A

early life on earth was dominated by the simplest organisms we know today - prokaryoteson the left are fossil prokaryotes from a rock formation over 2 billion years oldabove are three electron micrographs of prokaryotes all of these prokaryotes are types of bacteria

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33
Q

Prokaryotes are the simplest…

A

form of cells that we see living today.

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34
Q

What are the important components of the prokaryotic cell which i need to remember?

A

plasma membraneDNA in the nucleoidRibosomesCytoplasm

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35
Q

function of plasma membrane in prokaryotes?

A

(made of lipids which encloses the cell)

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36
Q

FUnction of DNA in the nucleoid in prokaryotes?

A

encodes all the information it needs to make protein

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37
Q

Function of ribosomes

A

make proteins

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38
Q

function of cytoplasm

A

where all the chemical reactions necessary for life occur

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39
Q

whats the size of prokaryotes?

A

1-10 um

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40
Q

Where are the oldest known fossils found?

A

found in a rock formation called the Apex chert

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41
Q

WHeres the apex chert?

A

australia

42
Q

What does the apex chert contain?

A

they consist of filaments of cells ‘strung’ together and date to 3.5 billion years ago

43
Q

What do the apex chert fossils closely resemble?

A

the Apex chert fossils closely resemble organisms today which are called Cyanobacteria. These bacteria photosynthesise

44
Q

What does it mean when a bacteria photosynthesises?

A

(using sunlight as an energy source to convert CO2into useful carbon compounds)

45
Q

What did analysis of the first cyanobacteria microfossils show?

A

analysis of the first cyanobacterial microfossils suggest these to be already complex – is there any evidence of older life?

46
Q

do we need a microscope to see evidence of microbial life?

A

No. You can see evidence of microbial life from a fossil stromatolite.

47
Q

How old are fossil stromatolites?

A

3 billion years old.

48
Q

What do fossil stromatolites consist of?

A

consists of many thousands of layers of individual bacteria

49
Q

Living stromatolites can be found today though they are…

A

…very uncommon

50
Q

Why do stromatolites persist in shark bay - australia?

A

they persist because they live in extremely salty conditions which nothing else can tolerate

51
Q

Many of the first organisms on earth would have originated in an atmosphere that was…

A

…devoid of oxygen

52
Q

For bacterial organisms such as cyanobacteria, oxygen is very…

A

…highly toxic

53
Q

Some of the extremely old bacteria…

A

…persist to this day – existing in environments which are free of oxygen such as mud at the bottom of stagnant ponds or the soil.

54
Q

What are bacteira termed as?

A

Anaerobes.

55
Q

How long ago did photosynthesis begin?

A

3.5 billion years ago

56
Q

How long ago did significant levels of oxygen arise in the atmosphere?

A

it took until 0.5 billion years ago to have significant levels of oxygen in the atmosphere

57
Q

What happened to most of the first oxygen produced?

A

most of the first oxygen produced reacted with dissolved iron in the oceans and was deposited as a sediment at the ocean floor.These banded-iron formations are characteristic of rock from that period

58
Q

What occurred in regards to xygen 0.5 billion years ago?

A

around 0.5 billion years ago significant amounts of oxygen build up in the earth’s atmosphere

59
Q

What does photosynthesis by cyanobacteria result in?

A

photosynthesis by cyanobacteria results in free oxygen being released into the atmosphere or dissolved in water

60
Q

Original ideas about how different species were related divided life into…

A

‘kingdoms’ – animals, plants and ‘protists’

61
Q

What does the five kingdom model and the tree of life suggest?

A

progression

62
Q

WHat does the five kingdom model split life into?

A

PlantaeFungiAnimaliaProtistaMonera

63
Q

Based on examinations of dna sequences, it is now clear that there are…

A

…three domains of life.

64
Q

When did separation between the three domains occur?

A

Very early in evolutionary history

65
Q

What are the three domains of life?

A

Bacteria, Archaea, Eukarya

66
Q

What were bacteria and archaea originally classed as in the “three domains of life” model?

A

both archaea and bacteria were originally classed as prokaryotes but they exhibit some fundamental differences

67
Q

Both of what were originally classed as prokaryotes in the three domains of life model?

A

both archaea and bacteria

68
Q

What are prokaryotes?

A

Prokaryotes are organisms whose cells lack a nucleus and other organelles. Prokaryotes are divided into two distinct groups: the bacteria and the archae.Most prokaryotes are small, single-celled organisms that have a relatively simple structure.

69
Q

What is a eukaryote?

A

Eukaryotes are organisms whose cells contain a nucleus and other membrane-bound organelles. There is a wide range of eukaryotic organisms, including all animals, plants, fungi, and protists, as well as most algae. Eukaryotes may be either single-celled or multicellular.

70
Q

Compare eukaryotic cells to prokaryotic cells.

A

eukaryotic cells are larger and more complex than prokaryote cells yet they have a similar basic structure – with one big difference.

71
Q

What are the parts of eukaryote cells that i need to know?

A
  1. plasma membrane2. DNA3. ribosomes4. cytoplasm5. organelles – e.g. mitochondria
72
Q

function of plasma membrane in eukayrotes?

A

membrane compartmentalization to allow for the formation of enclosed environments for specific metabolic processescontrols the passage of organic molecules, ions, water, and oxygen into and out of the cell

73
Q

function of DNA in eukaryotes?

A

encodes all the information it needs to make protein in a nucleus.surrounded by a membrane

74
Q

Where is dna stored in eukaryotes?

A

in a nucleus

75
Q

Where is dna stored in prokaryotes?

A

in a nucleoid.

76
Q

Examples of organelles in eukaryotes?

A

mitochondria, chloroplasts, the endoplasmic reticulum, the Golgi apparatus, and lysosomes.

77
Q

Do prokaryotes have organelles?

A

No

78
Q

What are organelles?

A

An organelle is a membrane-bound subcellular structure that has one or more specific jobs to perform in the cell, much like an organ does in the body

79
Q

What are mitochondria?

A

Mitochondria are membrane-bound organelles present in the cytoplasm of all eukaryotic cells, that produce adenosine triphosphate (ATP), the main energy molecule used by the cell.

80
Q

How are eukaryotes thought to have evolved?

A
  • eukaryotes are now thought to have evolved after an ancestral prokaryote engulfed a smaller, oxygen-breathing bacteria- the bacteria persisted and reproduced with the parent cell- the relationship benefitted both cells- the oxygen-breathing bacteria became the mitochondria- in photosynthetic eukaryotes a further endosymbiotic event occurreda photosynthetic bacteria was engulfed which became the chloroplast
81
Q

Size of single celled eukaryotes?

A

single-celled eukaryotes can be quite large – Amoebaspecies can grow up to 1mm in diameter and are thus just about visible to the naked eye

82
Q

Where are paramecium species found?

A

Paramecium species are also commonly found in freshwater –they feed by ingesting bacteria

83
Q

What is the single-celled eukaryote Giardia thought to resemble?

A

thought to resemble the ancestral eukaryote as it lacks mitochondria –however it is now known that mitochondria have been lost in this species

84
Q

Many of the single celled eukaryotes are…

A

…photosynthetic.

85
Q

Where does the photosynthetic ability of single-celled eukaryotes derive from?

A

the photosynthetic ability of these cells derives from the endosymbiosis of chloroplasts

86
Q

Multicellular plants are thought to have evolved from…

A

…single celled eukaryotes - algae

87
Q

What are some examples of single-celled eukaryotes [plant cells]?

A

Chlamydomonas reinhardtiiEuglena species

88
Q

Sinle-celled non-photosynthetic organisms similar to amoeba are likely to have given rise to…

A

…multicellular animals

89
Q

What gave rise to multicellular animals?

A

single-celled non-photosynthetic organisms are likely to have given rise to multicellular animals

90
Q

Plants, fungi, and animals are all…

A

…independently evolved multicellular organisms

91
Q

why did multicellularity evolve?

A

size… you can vastly increase how big you are and therefore can compete more successfully for food

92
Q

What is the problem for multicellular organisms?

A
  • The problem that individual single-celled organisms face is that there is a size limitation due to surface area to volume constraints- The surface area does not keep pace with increases in volume and it becomes harder for diffusion or osmosis across surfaces to take place efficiently enough
93
Q

Why (in some sense) is multicellularity almost as old as life itself?

A

cyanobacteria form colonies though these are ‘clonal’ (they derive from the same original cell)

94
Q

In Dictystellium, what is the response to starvation?

A

single celled organisms aggregate and form a ‘slug’ which migrates to a better food sourcesome differentiationoccurs during formation of the fruiting body

95
Q

How did Volvox evolve multicellularity?

A

Volvox is thought to have evolved multiceullarity by a colonial method as with Dictyostelium.

96
Q

What does Volvox resemble?

A

rather than resembling amoebae the vegetative cells closely resemble those of Chlamydomonas

97
Q

What chemical fossils were found in Oman and what did they show?

A

steroids found in sedimentary rocks in Oman which could be the remains of sponges from 635 million years ago

98
Q

How long ago did Ediacaran fauna dominate the sea?

A

600 million years ago.

99
Q

How common are ediacaran fossils and what happened to the organisms?

A

fossils are rare – all organisms seem to have been soft-bodied

100
Q

What might some ediacaran be related to?

A

some may be related to cnidarians (jellyfish) but most have no living descendants that we recognise

101
Q

WHat was the cambrian explosion a period of?

A

a period of experimentation in body plan - some survive, some go under.

102
Q

What happens when oxygenation of the atmosphere reaches significant levels?

A

oxygenation of the atmosphere reaches significant levels –animals with skeletons appear – arthropods, chordates, molluscs – fossils more abundant