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Zoology Y1 > APS11006 Principles of Evolution- Origin and Early Evolution Of Life > Flashcards

APS11006 Principles of Evolution- Origin and Early Evolution Of Life Flashcards

1
Q

Basic concepts of neo-Darwinian evolution:

A 
Reproduction
Excess (everything reproduces to excess)
Variation (Mendel's law, mutations, crossover)
Environmental/natural selection
Divergence
Ancestry
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2
Q

Mendel’s law of segregation/ independent sorting

A

Segregation: individuals possess two alleles but only one is passed to offspring by parent

Independent assortment: inheritance of one pair of genes is independent of the inheritance of the other pair

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3
Q

Divergence

A

The evolutionary process wherein a population of species diverge into two or more descendant species, resulting in once similar species becoming more dissimilar

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4
Q

What is biodiversity?

A

“Biodiversity is the variety of life, in all its manifestations.
It encompasses all forms, levels and combinations of
natural variation”

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5
Q

Why are fossil records incomplete?

A
  • Very few organisms that ever live will end up fossilised

- Entire species may not be preserved (low preservation potential, small populations or geographical area)

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6
Q

Why are fossil records biased?

A
  • Certain environments are more likely to be preserved (marine and terrestrial lowland) due to net deposition rather than net erosion
  • organisms with recalcitrant tissues more likely to be preserved (bone, tooth, shell)
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7
Q

Temporal variation

A

Frequency and magnitude of fluctuations in ecosystem structure or function

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8
Q

Examples of long term environmental change through time

A
  • Solar luminosity (sun was less bright when Earth formed)
  • Distance between the Earth and its moon (tides)
  • Continental drift and plate tectonic events
  • Changing atmosphere and climate
  • Milankovitch cycles (spin of Earth)
  • Evolving biota
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9
Q

Examples of short term and rare events through time

A
  • Large Igneous Provinces (LIPS)
  • Super eruptions
  • Meteorite impacts
  • Tsunamis
  • Mass extinctions
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10
Q

Taxonomy

A 
Kingdom
Phylum 
Class
Order
Family
Genus
Species
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11
Q

Analogous

A

Similarity due to convergent evolution (homoplasy) e.g. wing of bird and bat

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12
Q

Monophyletic group

A

Contains the latest common ancestor plus all of its descendants

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13
Q

Homologous

A

Similarity due to common ancestry e.g. wings of all birds

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14
Q

Paraphyletic group

A

Diagnosed by plesiomorphies (ancestral trait) but not including all descendants. Remains after one or more parts of a monophyletic group have been removed.

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15
Q

Polyphyletic group

A

A group in which the most recent common ancestor is assigned to some other group and not the group itself such as including birds and bats in same group

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16
Q

Brief description of cladistic analysis

A

Discovered by Hennig but was ignored at first. Create a data metric of character states for a taxa under consideration with species at top and record if present or absent. Computer analyses data and creates a cladogram and works out most parsimonious way of evolution

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17
Q

Features of prokaryotes

A

Generally 1-10 um, unicellular or colonial, made of sugars and peptides, some have flagella (made of flagellin protein), no membrane bound organelles, anaerobic or facultative aerobic, loop of DNA in cytoplasm and reproduce by binary fission. Dominantly asexual but some parasexual.

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18
Q

Features of eukaryotes

A

Generally 10-100um, mainly multicellular with tissues and organs, made of cellulose or chitin (not animals), flagella or cilia with microtubules, membrane-bound chloroplasts and mitochondria, aerobic, DNA in chromosomes in membrane-bound nucleus. Reproduce sexually by mitosis or meiosis.

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19
Q

What microscope is best for seeing prokaryotes?

A

Barely seen on light microscope due to small size, so an electron microscope is best. 50s/60s allow us to see basic structure while 80s could sequence them

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20
Q

Which are animals more closely related to: fungi or plants?

A

Fungi

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21
Q

4600 Mya:

A
  • Earth formed by gravitational accumulation of dust and larger objects
  • Mass melts due to high pressure of gravity, heavy iron and nickel migrate to centre, manganese and magnesium form the mantle, light aluminium silicate minerals and gases form crust
  • Very hot, gases lost to space
  • Moon forms
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22
Q

3750 Mya

A
  • Earth starts to cool down
  • Planets are mostly formed, more stable solar system
  • Age of the oldest rocks on Earth (Isua Supracrustal Group, Greenland)
  • Earth has cooled to extent that crust begins to solidify
  • All temperatures begin to fall, oceans and atmosphere can begin to condense
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23
Q

> 3800 Mya

A
  • Progress slowed by continued bombardment of large objects
  • Released energy is sufficient to boil off ocean and atmosphere
  • Moon is dead, no volcanic activity
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24
Q

<3800 Mya

A
  • Meteorite bombardment decreases in intensity and planet cools below threshold allowing oceans and atmosphere to condense out
  • Organic compounds begin to synthesise and accumulate
  • Volcanic outgassing gives us an idea of gases pushed into early atmosphere
  • Water vapour condenses to form oceans and H2 is lost to space
  • No oxygen
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25
Q

Earliest fossil evidence for life on Earth found from…

A

…3500 Mya

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26
Q

What is panspermia?

A

Theory that life seeded onto Earth from space i.e. on a meteorite. Not very agreed with and doesn’t solve problem of origin of life.

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27
Q

If comets contain water, why couldn’t they have been the cause of our oceans?

A
  • It would take a lot of comets!
  • Vast majority must have come from outgassing (carbon dioxide and water vapour spewed from volcanoes condensing to form part of Earth’s oceans)
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28
Q

Three approaches to solving origin of life:

A
  • Analyse living prokaryotes and attempt to reconstruct their common ancestor
  • Compare duplicated genes potentially enabling us to reach beyond ancestor and estimate some early components of genetic machinery
  • Reconstruct conditions that existed on Earth and simulate them experimentally
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29
Q

Why are prokaryotes thought to have originated before eukaryotes?

A
  • They appear earlier in the fossil record
  • They are very simpler in virtually every aspect
  • Evidence that eukaryotes evolved before prokaryotes
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30
Q

Fundamental similarities between prokaryotes and eukaryotes

A
  • Method of transmitting info in triplet code in DNA and translating to proteins through RNA
  • All amino acids are laevorotatory and in nucleic acids, sugars are dextrorotatory
  • Complex molecules form two mirror image isomers
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31
Q

Laevorotatory vs dextrorotatory

A
  • Laevo molecules rotate plane-polarised light left, and dextro right
  • When making a complex molecule, 50% are laevo and 50% are dextro
  • At some point in early biology, life began using only one type of these molecules in amino acids and nucleic acids
  • Same for both prokaryotes and eukaryotes
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32
Q

What is plane-polarised light?

A

Light that only has electromagnetic vibrations in one plane. Rotations of the plane of polarisation can be detected by a polarimeter

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33
Q

How can we look at duplicated genes to root our phylogeny?

A

Duplicated genes happen through mutation. One stays active while one is useless. By looking at duplicated genes that evolved before life did we can use these to create a root as we are reaching beyond our ancestor to find earliest components of genetic machinery.

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34
Q

What does LUCA stand for

A

Last universal common ancestor

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35
Q

Who was behind reconstructing the early Earth in experimental conditions?

A

Started by Haldane in UK in 1900s.

Miller and Urey continued research in 1953 in USA.

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36
Q

What chemicals were produced by simulating early Earth conditions?

A
  • Amino acids
  • Purines/pyrimidines including four bases of RNA
  • Sugars
  • Porphyrins, forerunners of compounds like vitamin B12 and chlorophylls
  • Complex tar-like substances that defy analysis
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37
Q

Purines vs pyrimidines

A

Purines are double ringed with 4 N atoms, while pyrimidines are single ringed with 2 N atoms. Adenine and Guanine are purines, while C, U and T are pyrimidines. A bonds to T with 2 H bonds, and G to C with 3. Purines are bigger.

38
Q

What energy sources were available for life to begin?

A
  • Sun (no oxygen, no ozone, so strong levels of UVB radiation (uninhabitable for us))
  • Radioactivity
  • Electric discharges (lightning)
  • Volcanic (hot springs, black smokers (deep ocean) etc.)
39
Q

Difference between white and black smokers

A

White smokers are alkaline (contain barium, calcium and silicon) and cooler
Black smokers omit iron sulfides which create an acidic reaction when oxidising as they release protons

40
Q

Why was the discovery of self-splicing RNA in the 1980s considered a breakthrough?

A

It began speculation on an RNA world. Before this, it was unclear whether DNA or proteins came first.

41
Q

Why were early oceans great for early life?

A
  • Full of organic dissolved matter such as iron, sulphur and carbon, creating a primordial soup (nowadays oceans are clear as life uses up organic matter)
  • RNA molecules were safe as nothing could eat them
  • Could self splice as all bases needed were dissolved in the ocean
  • Can replicate, mutations occurring
42
Q

What happened once the organic matter in the ocean was ‘used up’?

A
  • Compounds became rare
  • Molecules that were better at replicating used up the rare materials
  • This outcompeted the molecules less able to replicate
  • Natural selection
  • Believed to be how life originated
43
Q

What were the metabolic pathways taken by RNA once ocean matter was used up and was no longer a source of energy?

A
  • Chemoautotrophs, energy from oxidising inorganic substances like H2S, NH2, Fe2+, C source CO2 (bacteria do this today)
  • Chemoheterotrophs, energy and C source from consuming organic compounds
  • Photoautotrophs, energy from light, C source CO2
  • Photoheterotrophs, energy from light, C source from consuming organic material
44
Q

What did early metabolic pathways require the synthesis of?

A
  • Cytochromes (basis of oxygen metabolism)
  • Porphyrins
  • Related compounds that are the forerunners of photosynthetic pigments (the chlorophylls)
45
Q

Types of respirers

A
  • Obligate anaerobes , poisoned by O2 and live exclusively by fermentation or anaerobic respiration
  • Aerotolerant, cannot use O2 for growth but tolerate its presence and live by fermentation
  • Facultative anaerobes, use O2 if present but can live by fermentation in anaerobic environment
  • Obligate aerobes, use O2 for cellular respiration and cant live without it
46
Q

Fermentation

A

Process of sugar molecules being broken down by enzymes of microorganisms in the absence of oxygen

47
Q

Evidence for prokaryote life

A
  • Fossil stromatolites
  • Fossil microorganisms
  • Carbonaceous matter that can be identified chemically as the product of ancient life
48
Q

Fossil stromatolites

A

Dome shaped structures made up of thin concentric layers of sediment. Giant colonies of bacteria. Outer layer covered in a ‘goo’ of cyanobacteria that photosynthesises. Gets covered in sediment after which they migrate back to the outer layer. Inner layers are anaerobic bacteria.

49
Q

How do fossil microorganisms form?

A
  1. In cherts (flint, glass), very well preserved

2. Resistant cell walls (acritarchs) are preserved in siltstones, less well preserved

50
Q

How does carbonaceous matter in rocks tell us about ancient life?

A

All forms of life use RuBisCo during biological processes. RBC prefers lighter carbon isotopes (carbon 12). If a strong ratio of carbon 12 to carbon 13 is found in the rocks, it is strong evidence for life.

51
Q

What were early oxygen sinks (oxygen produced by cyanobacteria)?

A
  • Volcanic gases comprising early atmosphere readily combined (NO2, H2O, CO2, SO4)
  • Dissolved iron in oceans scavenged O2 and settled on ocean floors to form BIFs (banded iron formation)
  • Microorganisms carrying out aerobic respiration were facultative and able to switch back to anaerobic fermentation
52
Q

Why are BIFs useful to us today?

A

Huge deposits of iron. Main source of iron and steel today

53
Q

When and why did BIFs stop forming?

A

2 Bya, suggesting all iron in ocean is used up

54
Q

What are red beds and what do they show?

A

Terrestrial deposits of quartz (clear) and a layer of hematite around them (making them red) that formed after BIFs begin to stop forming. (2 Bya).
Would have only formed if there was oxygen in the atmosphere to react with iron and form hematite.

55
Q

Hematite

A

Fe2O3

56
Q

What do pyrite conglomerates tell us about oxygen in the atmosphere?

A

Found prior to 2 Bya, meaning no oxygen during that time. Stopped forming after this due to oxidisation from the atmosphere.

57
Q

Why was the formation of the ozone important?

A

Happened during the great oxidation event roughly 2.4-2 Bya when oxygen began to permanently accumulate in the atmosphere.
Ozone blocks UVB (which prevents life from forming) so life could now exist and the planet is now aerobic.

58
Q

Theories for origin of eukaryote cell

A
  • Symbiosis
  • Elaboration of cell membrane
  • Multiple symbiotic events
59
Q

History of symbiosis theory

A

Lynn Margulis (USA) discovered the theory and was originally rejected. When DNA techniques became available she gained a lot of support.

60
Q

Symbiosis theory of mitochondrial origin

A

Prokaryote host that was an anaerobe acquired an obligate aerobe purple non-sulphur bacteria.
Host was able to benefit from endosymbiont ability to detoxify oxygen.
During reproduction, both daughters of the division contain DNA.
End organism is a facultative aerobe

61
Q

Types of genomes in eukaryotes

A
  • Nuclear genome
  • Mitochondrial DNA
  • Chloroplast DNA
62
Q

Endosymbiont

A

Organism that forms a symbiotic relationship with another cell. Can be intra- or extracellular

63
Q

Symbiosis theory of chloroplast origin

A

Cells began symbiotic relationship with cyanobacteria, which allowed them to photosynthesise.

64
Q

Symbiosis theory of flagella and cilia (spirochaete bacteria) origin

A

Eukaryote cell takes on board a spirochaete in a symbiotic relationship to allow movement.
During cell division, the basal bodies line across the spindles to allow passing on to offspring.

65
Q

Symbiotic theory for mitosis origin

A

Controversial theory that centriole spindles are equivalent to tubules in cilia/flagella and derive from spirochaete bacterium.

66
Q

What is the snowball/slushball Earth?

A

Entire world is frozen, areas of volcanic activity are ‘slush’ areas and are less frozen

67
Q

How are boulder clays (glacier deposits) formed?

A

Glaciers move, picking up rocks that are ground by ice into dust. The ice then melts, leaving the rock and dust.

68
Q

Examples of extensive glaciations extending into equatorial latitudes that produce snowball/slushball Earth scenarios

A
  • 765 Mya, confined to Africa
  • 710 Mya, global
  • 600 Mya, global
  • 542 Mya, relatively small
69
Q

What bounds the boulder clays that represent the glaciation?

A
  • Bounded below by carbonates

- Bounded above by cap carbonates

70
Q

What do the carbonates below boulder clays tell us?

A
  • Have exceptionally high C-isotope values
  • Due to continental break up producing narrow seaways where life would have flourished, enhancing C burial
  • This would’ve taken CO2 out of the atmosphere, making it oxygen rich and pushing towards glaciation
71
Q

What is special about the presence of BIFs in boulder clays?

A

For the first time in 1.8 billion years iron accumulates in the oceans

72
Q

What do the cap carbonates above boulder clays tell us?

A
  • Exceptionally low C-isotope values

- Due to rapid accumulation and/or absence of organisms and/or burst of methane that ended the glaciations

73
Q

What is responsible for variation in asexually reproducing organisms?

A

Mutations

74
Q

How to almost all eukaryotes reproduce?

A

Sexually

75
Q

What is responsible for variation in sexually reproducing organisms?

A
  • Mutations
  • Independent assortment
  • Crossing over
76
Q

Crossing over

A

Exchange of DNA between two paired homologous (CODE FOR SAME GENE BUT NOT IDENTICAL) chromosomes (one from each parent (PARENT OF THE GAMETE MAKER) that occurs during the FIRST stage of meiosis (production of gametes) resulting in new combinations of alleles in the gametes.

77
Q

Problems with sexual reproduction

A
  • Binary fission is done more rapidly that sexual reproduction
  • Females become impregnated and deliver offspring
  • Losing half potential children
  • 50/50 male and female, not efficient
78
Q

When did sex evolve?

A

Probably by 1,200 Mya

79
Q

When did multicellular life evolve?

A
  • By 1,000 Mya

- Evolved several times independently in different biological groups (various protists, plants, animals and fungi)

80
Q

What was the advantage of muliticellularity?

A

Division of labour between cells

81
Q

Metazoans

A

Multi cellular animals

82
Q

Characteristics shared by metazoans

A
  • Multicellular body formed from different kinds of cells
  • Ability to manufacture the protein collagen, which sticks cells together
  • Reproductive cycle with gametes produced by meiosis
  • Nervous system comprised of neurons (except in sponges)
83
Q

Recent advances that have been important in addressing the problem of metazoan origin

A
  • New fossil finds
  • Phylogenetic analysis of anatomic and molecular data
  • Molecular clock studies
  • Molecular genetics of animal development (Evo-Devo)
84
Q

What is evo-devo?

A

The part of biology concerned with how changes in embryonic development during single generations relate to the evolutionary changes that occur between generations

85
Q

Dipoblastic

A
  • Two tissue layers
  • Most basal metazoans
  • Sponges and archaeocyathlids (extinct), jellyfish and corals
86
Q

Tripoblastic

A
  • Three tissue layers (endo-, exo- and mesoderm)
  • All other animals
  • Bilateria
87
Q

Bilateria

A
  • Bilateral body symmetry

- Two mirror images in one plane

88
Q

Basal animals

A
  • Radial symmetry

- Two equal halves in any plane

89
Q

Ediacran organisms have no mouth, gut or anus. What theories are there to how they fed?

A
  • Compartments contained unicellular photosynthetic algae (unlikely due to water depth and low light penetration)
  • Took in substances through the body wall (particulate food, dissolved organic matter, photons)
  • Chemosymbiosis (utilize sulphide oxidising bacteria)
90
Q

What have Ediacara organisms been interpreted as?

A
  • Simple ancestors of several modern phyla such as sponges, jellyfish and sea pens
  • Dipoblastic animals showing a range in variation not seen today
  • An entirely separate attempt at multicellular life that ultimately failed

Zoology Y1 (5 decks)

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