Week 1: How to grow a planet Flashcards
What are the features of life/being alive?
-growth
-respond
-reproduce
-heredity
-homeostasis
-metabolism
-cellular
What is taxonomy?
the science of naming and sorting things
organisms grouped by similarity
What is the taxonomical order?
1.Domain
2. Kingdom
3.Phylum
4.Class
5.Order
6.Family
7.Genus
8.Species
How many domains is there? How do you classify them?
3
Archea= unicellular prokaryotes with isoprene ether lipids
Bacteria= unicellular prokaryotes with fatty ester lipids
Eucarya/Eukaryotes= can be multicellular, have a cell nucleus and membrane bound organelles
How many kingdoms is there?
7
Archea, Bacteria, Protista, Chromista, Fungi, Plantae and Animalie
How do you classify Plantae?
Multicellular autotrophs with chloroplasts and cellulose cell walls.
How do you classify the kingdom of Fungi?
multicellular and unicellular heterotrophs (dont generate their own energy) with chitin cell walls
How do you classify the kingdom of Animalia/Metozoa?
multicellular heterotrophs without a cell wall
they move at least in part of the life cycle
most are bilaterians (left side, right side and a head + gut from mouth to anus)- many phyla of bilateria
What does LUCA stand for?
The Last Universal Common Ancestor
means that all life on Earth descended from a single individual cell which possessed the characteristics shared by all living organisms today.
What did LUCA look like?
DNA
RNA
Protein
Carbohydrates
Membranes, transport proteins
electron transport chains
What is central dogma?
DNA makes RNA makes PROTEIN
transcription translation
DNA= chain of nucleotides formed into double helix
Codons= combinations of 3 nucleotides code for 20 amino acids
RNA= single strand; acts as a “translator” of the DNA code
What are ribosomes?
Convert genetic code into protein sequence
Made of RNA and Protein
used to construct phylogenetic trees
What is the second law of thermodynamics?
All systems tend from a state of order to a state of disorder
Life is a highly ordered process. How can life maintain and reproduce itself?= ENERGY
What is the Urey-Miller Experiment?
experimental simulation conducted in 1953 that attempted to replicate the conditions of Earth ’s early atmosphere and oceans to test whether organic molecules could be created abiogenically, that is, formed from chemical reactions occurring between inorganic molecules thought to be present at the time
What biological molecules are important in life? What chemical elements form them?
1.C02- amino acids- protein- enzymes
2.CH4- sugars- cellulose/chitin- cell walls
3. NH3- fatty acids- phospholipids- membranes
4. SO2- nucleotides- nucleic acid- genetic material
simple chemicals can form complex structures needed for life
What is ATP?
the universal energy currency of the cell
What is chemiosmotic theory?
Peter Michell
the movement of ions across a semipermeable membrane bound structure, down their electrochemical gradient
What are reductants and oxidants?
electron donors=reductants
And electron acceptors=oxidants
Reductants are all high energy and chemically reactive
What are chemoautotrophs?
Use chemicals from the environment as reductants – Chemical Energy
e.g. hydrogen
Rely on a world out of equilibrium
reactions must overall be exothermic
What is chrorophyll?
multiple forms a-g
green/purple
absorb blue light and either red or near infrared
then light energy is turned into chemical (redox) energy in reaction centres
What are reaction centres? What do they do? What is their structure?
Structure:
-have a core which is made of two polypeptides
-where these bind together is a so-called “special pair” of chlorophylls. These are special because, when they absorb light they are liable to lose an electron.
How:
The electron is transfered through the protein to a quinone, producing an oxidised chloropyhyll (Chl+) and a reduced quinone (Q-). This electron transfer is the step where light energy gets converted into chemical energy. We call this charge separation.
What are the 2 forms of reaction centres?
Type I and Type II
Where are Type I reaction centres found?
green sulphur bacteria and in the heliobacteria
Where are Type II reaction centres found?
green non-sulphur bacteria and in purple sulphur bacteria.
What are the differences and similarities between Type I and type II reaction centres? Why are they different?
similarities:
two types have the same core structure but differ in way electrons arrive and leave
differences:
Type I, electrons are passed from the reaction centre quinone to a so-called iron-sulphur protein (Fe-S) such as ferredoxin, which is soluble.
In Type II reaction centres, the quinone itself leaves the reaction centre, carrying electrons away in the membrane
WHY:
Type I and Type II reaction centres evolved in distinct evolutionary lines - that is one ancestor photosynthetic organism separated into 2 species
it is though in two distinct bacterial lineages.
How can genes move laterally?
genes can move laterally from one species to another, without sexual reproduction occurring.
This may result from a cell breaking open, releasing DNA, and that DNA being absorbed by another species.
or It may occur in a more directed way, with direct transfer of DNA from one organism to another.
How did one group of bacteria find to have both types of reaction centres?
somewhere between 3.5 and 3 million years ago, an organism arose that had both a Type I and a Type II reaction centre through lateral gene trasnfer.
What were the implications of having both reaction centres Type I and Type II?
both reaction centres were able to work in series, with electrons for one being passed to the other ( Type II to Type I).
This combined system was able to create a bigger energy difference between the starting electron donor and the end acceptor.
The key acceptor in this system is carbon dioxide, which is reduced to form sugar.
The new electron donor which emerged was one of the most abundant molecules around - water.
These new cells evolved the ability to split water into electrons and protons, producing oxygen as a bi-product (photolysis)
What was the organism that evolved to have both reaction centres?
cyanobacterium
What are the advantages of having both reaction centres?
all organisms that have both types of centre are able to evolve oxygen and visa versa.
How do we know when cyanobacteria appeared?
3-2.4Ga
Evidence comes from geological deposits
1. stromatolites
2. distinct bands of oxidised iron and other metals in sedimentary rocks
What were the impacts of Oxygen?
-Global Cooling= As oxygen was released into the atmosphere, it stated to react with this methane, producing CO2- plunged into an ice age considered to be the first and longest major glaciation event (Huronian glaciation)
-Reactive Oxygen= When oxygen first appeared in the atmosphere, cells had not yet evolved defences against them. For organisms that have never been exposed to oxygen, so-called anaerobes, oxygen is deadly.
+Ozone= When molecular oxygen absorbs UV, the bond between the two O atoms is broken, releasing atomic oxygen, atomic oxygen is a free radical and highly reactive, but what it mostly reacts with in the atmosphere is molecular oxygen= ozone
+Oxidative Phosphorylation= cells which evolved to use their “food” more efficiently, meaning that they are able to grow bigger. Bigger cells have other advantages, notably that some cells learnt how to “eat” smaller cells.
Key moments in geological time scale of Earth?
1.4550Ma= formation of Earth
2.4527Ma= Formation of Moon
3. 4000Ma= End of the Late Heavy Bombardment of Life
4. 3200Ma= Earliest start of photosynthesis
5. 2300Ma= Atmosphere becomes oxygen rich, first Snowball Earth
6. 750-635Ma= The Snowball Earths
7. 530Ma= Cambrian explosion
8. 380Ma= first vertebrate land animals
9. 230-66Ma= non-avian dinosaurs
10. 2Ma= first hominins
Order of organisms groups formation in geological time scale?
1.Prokaryotes
2.Eukaryotes
3.Multicellular life
4.Animals
5.Land plants
6.Mammals
7.Hominins
What are the 4 Eons?
Hadean 4600-4000
Archean 4000-2500
Proterozoic 2500-540
Phanerozoic 540-today
When did complex life (animals, plants and fungi) begin to exist?
In the phanerozoic period (540-today)
What happened to oxygen levels in the proterozoic? How do we know this?
photosynthesis led to an accumulation of atmospheric O2 at Great Oxygenation Event
however modern levels were not reached until the end of Proterozoic.
EVIDENCE:
1.chemistry to try and reconstruct the levels of oxygen
2.look at geology in terms of banded iron formations
What were the Proterozoic glaciations? Name? When?
Gaskier’s glaciation
580 million years ago, (about 9 my before the appearance of large Ediacaran fossils)
Widespread glaciation deposits toward end of Proterozoic
When did large fossils turn up in geological record?
Ediacaran
Large organisms first appear in the Ediacaran fossil biota
After a long period of relative stasis, large fossils turn up in the Ediacaran deposits in Newfoundland, Australia, Russia, and UK
What are fronds?
Ediacaran fossils
-Variety of different morphologies with branching structures
-Some lay flat on sea floor surface, some attach via a holdfast
-Similar fundamental morphologies, but different sizes and shapes
-They undergo the same patterns of fractal growth
What are Rangeomorphs?
Clade of the frond taxa
Rangeomorphs are weird fractally growing fronds and are hard to characterise
-The frond taxa are fundamentally similar in their morphology and fractal growth, just differ slightly in their proportions and patterns
-They can’t be plants because the environment is too deep: no light= no photosynthesis
-unlikely to be proper animals given anatomy and asexual reproduction
-unique and weird
What are bilaterians?
Ediacaran fossils
-these taxa have different sizes and shapes but fundamental similarities in their constructions: a ‘head’, and a left side and a right side
-the symmetry is not classically bilaterian, it is ‘glide’ symmetry.
Examples: Dickinsonia and Kimberella
What were some of the Ediacaran fossils?
‘Frond’ taxa:
-similar fundamental morphology and fractal growth but different sizes and shapes with branching structures
-some lay flat on sea floor surface some attach via a holdfast
-they likely form a ‘clade’=rangeomorphs
-cant be plants as environment too deep (no light=no photosynthesis)
-unlikely to be proper animals given anatomy and asexual reproduction
“Bilaterians taxa:
-have different sizes and shapes but fundamental similarities in their construction ( a head and a left side and right side
-the symmetry was not classically bilaterian, it is ‘glide’ symmetry
Ediacaran animals?
-Dickinsonia left traces of footprints indicating it was digesting the underlying microbial mat this is consistent with osmotrophy. Also been found to composed of animal like molecules (like cholesteroids)
-Kimberella leaves mollusc style feeding grazing traces
-some Ediacaran taxa show evidence of muscle fibres=movement
-traces of tiny burrows at end of Ediacaran= possible movement
What is the evidence for possible Ediacaran animals?
Some Ediacaran organisms appear to be candidates for the first animals given their anatomy, composition, and behaviour:
-Dickinsonia leaves traces of ‘footprints’ indicating it was digesting the underlying microbial mat
(This is consistent with osmotrophy, as is their high surface area)
-Dickinsonia has also been demonstrated to be composed of animal like molecules
(Gas chromatography of organic remnants shows evidence of animal-like cholesteroids and not typically algae lipid biomarkers)
-Kimberella leaves mollusc style feeding grazing traces (suggests kimberella was an animal?)
-Some Ediacaran taxa show evidence of muscle fibres, therefore movement
-Traces of tiny burrows at the very end of the Ediacaran, possible movement
What are the possible Ediacaran Triggers? Why did large fossils appear in the fossil record during this time after long period of stasis?
1.Deglaciation:
-Gaskier’s Glaciation was about 9 my before the appearance of large Ediacaran fossils
-However there had been many previous glaciations :‘snowball earth’ so doubts
2.Oxygen:
-increasing atmospheric oxygen may have facilitated evolution of larger body sizes in the Ediacaran.
-increased tectonic activity could have led to more oxygen
-All Ediacaran organisms appear to have very high-surface area to volume ratios, important for gaseous exchange
- Carbon Excursion:
-massive Shuram Carbon Isotope Excursion occurs in the Ediacaran
What is the classification of animals as bilaterians?
-they have a left/right sides
-head and tail
-top and bottom
-gut from mouth to anus
-many phyla of bilateria
