Lecture 3- Origin of species Flashcards
How many years ago did Earth arise?
4 billion years ago
how many years did deep sea arise?
3.8/ 4.2 billion years ago
where did energy to fuel the first few replicating molecules come from?
proton gradients around alkaline hydrothermal vents- ‘Lost City’ in mid- Atlantic (where weird bacteria has been identified)
Darwin’s hypothesis of the beginning of Earth
Earth was a warm muddy pond
what brought water forming oceans in the beginning of earth
bombardments by comets and asteroids
what was the basis for reproduction before DNA
RNA
why is there no pure RNA organisms
RNA has a short life cycle of only a matter of weeks so there would be be little time for mutations
time line of the RNA world
- complex organic molecules produced by random chemistry
- RNA world
- RNP world
- LUCA (last universal common ancestor)
LUCA
last universal common ancestor ( a population of single-celled DNA organisms that lived approx 3.8 billion years ago)
what did earliest life use as enzymes
RNA so they could copy themselves
when were amino acids used
after the RNA world (formed spontaneously)
which is more fragile: DNA or RNA
RNA
how can you have a cell without DNA?
-tiny pores in rocks around vents
-lipid protobionts can reproduce and metabolise
-RNA can spontaneously reproduce within them
how old is the universe?
14 billion years old
how old is life?
3.8 billion years old
what does life need to survive?
cool temperatures, gravity, water, protection from radiation
how long did it take for multicellular organisms to appaear?
over 2 billion years
origin of oxygen
unknown
when did the great oxidation event occur
around 2.5 billion years ago
great oxidation event
high levels of oxidised rocks in the Earth’s surface
first prokaryotes
methane-producing bacteria
which algae produced oxygen
cyanobacteria (blue-green algae)
which bacteria consumed most of the oxygen
methanogenic bacteria
why do most methanogens eventually die out
due to changes in trace metals in sea
are most eukaryotes unicellular or multicellular
unicellular but some are multicellular
individual cells of eukaryotes are …. times the volume of a prokaryote
1,000,000
what is the common hypothesis for the evolution of eukaryotes
an archaebacterium engulfed a heterotrophic eubacterium, which eventually became mitochondria
-the energy provided by mitochondria allows for complex life
what is the hypothesis for the evolution of eukaryotic plants
autotrophic eubacterium engulfed by eukaryotic plant ancestor
why is the creation of eukaryotes a chance event
combination of different types of bacteria
did natural selection create eukaryotes?
no
what did natural selection act on (in the creation of eukaryotes)
individuals/ populations that were created by chance events
when was Ediacaran biota (early eukaryote)
570 My
Ediacaran life
Spriggina
- annelid worm?
- arthropod?
- 3cm long
Dickinsonia: early eukaryotes
Can reach up to 1m in length
Molecules from rock were recently shown to be animal in origin (produced cholesterol)
Rangeomorphs (early eukaryotes)
fractally branched, vaguely fern-like but lived in the dark depths. Ecology and growth patterns suggest they were animals
Erniettomorphs (early eukaryotes)
-modular or quilted
why are rangeomorphs and erniettomorphs, not plants?
-live deep in the sea
-not plants as they lived too deep therefore aren’t possible to photosynthesise
Cambrian explosion
20-30 million years ago when most of the types of animals we now see first appeared
-e.g arthropods, chordates, worms
- appearance of soft body organisms ( preservation in Burgess Shale, China, Greenland, Russia)
-not all species fir into modern taxonomies
examples of species that don’t fit in modern taxonomies
opabinia
-first reconstruction in 1972
-7cm long
physiological theories of the Cambrian explosion
dissolved oxygen levels to allow active lifestyle
geographical theories of the Cambrian explosion
new seas and new niches
geochemical theories of the Cambrian explosion
sea level changes leads to abundance of trace metals to make exoskeletons
biological theories of the Cambrian explosion
increase in zooplankton allows new predators to arise, increasing selection pressure
what do molecular phylogenies support the existence of
evolution
