The Origins of Life Flashcards
Phylogenetic Tree
- Evolutionary history of organisms
- A graphical representation of these relationships
The Origin of Life - What is Needed for Life?
- Information storage: presence of a genome that carries the info specifying a phenotype
- Compartmentalization: the ability to keep components together and distinguish itself from the environment
- Energy acquisition and utilization: metabolism, growth, behavior
- Reproduction: the ability to produce more progeny of the same type
[…] can store and transmit information, but can’t perform biological work
DNA
{…} can perform biological functions, but can’t propagate
[Proteins]
[…] can store information AND do biological work
[RNA]
Ribozymes
RNA molecules that catalyze reactions like splicing and gene expression–RNA can be both genetic material (DNA like) and a biological catalyst (protein enzymes)
[…] bind and cleave mRNS to prevent it from functioning
Ribozymes
Support for the RNA World Hypothesis
- Only known molecule that carries genetic information AND an catalyze chemical reactions
- In “modern” cells, RNA catalyzes protein synthesis
- Ribosomes are the most highly conserved component of metabolic machinery
> built on an RNA framework - Several experiments indicate RNA can evolve
HOWEVER - self-replicating RNA has not been demonstrated or discovered (except for very short RNS molecules produced in the lab)
- RNA is extremely unstable and breaks down easily (major difference as compared to DNA)
Primordial Soup - The Oparin-Haldane Model
- Assemble simple molecules into building blocks for complex polymers
- Assemble polymers that can store information and catalyze reactions
- Add membranes and an energy source to make a living organism
Miller-Urey Experiment
Demonstrated that many of the compounds necessary for life could be produced in a “pre-biotic” atmosphere
- Recreation of water cycle to synthesize ancient Earth atmosphere
Panspermia
The hypothesis that life on Earth originated from microorganisms or chemical precursors of life present in outer space and able to initiate life once reaching a suitable environment
Murchison Meteorite
- In 1969, the meteorite fell to Earth, landing in Australia
- Contained high levels of organic compounds
- Came from a parent body that had liquid water
- Estimated to be 7 BYA, much older than Earth
[…] are essential building blocks of life
[Sugars]
Sugars
- Form part of the backbone of nucleic acids
- Primary energy storage molecules
- Includes polyols very similar to glucose (a major component necessary for photosynthesis)
- Implies that early life may have been ‘seeded’ by organic compounds falling from the skies rather than starting from scratch here on Earth
Geological Time Frame
1. The universe is about […] years old
2. The solar system and Earth are about […]
3. The oldest known rocks on Earth are about […]
4. The earliest life evolved about […]
- [13.7 billion]
- [4.6 byo]
- [3.8 byo]
- [3.5 byo]
- Oldest rocks that contain any signs of lie […]
- Oldest fossils ever found controversial […]
- Five rocks older than […] still exist on Earth
> any fossils from before that are unlikely to have survived
- [~3.8 byo]
- [~3.5 byo]
- [2.5 byo]
So how can we trace back to find common ancestor?
- Know all life descended from a primordial form that used DNA to store heritable information and proteins to express that info
- Know this because all life uses DNA and proteins and in the same way
All life shares:
- The same genetic material (DNA, mRNA, tRNA)
- The same genetic code (A, C, G, T)
- The same basic process of gene expression (transcription and translation)
- The same molecular building blocks (proteins made of 20 amino acids)
The presence of ribosomes
LUCA
- Last Universal Common Ancestor
- Predates 2 billion years because of fossil evidence of cyanobacteria
However, not all genes have same evolutionary history…
… each gene (locus) has an independent history
- Recombination
Lateral (horizontal) gene transfer
The Age of Earth - A One Year Analogy
- First life appears in late March
- First marine animals debut in late October
- Dinosaur become extinct and the mammalian radiation begins on Dec 26
- The human and chimpanzee lineages diverge about thirteen hours before midnight on December 31
- Year 1 AD is about 13 seconds before midnight on December 31
Types of Rocks
- Igneous rock
- Sedimentary rock
- Metamorphic rock
Igneous rock
- created from molten material
> melting of rocks in hot, deep crust and upper mantle - formed by the crystallization (solidification of magma or lava)
Sedimentary rock
- deposition and solidification of sediments
> weathering and erosion of rocks exposed at surface - formed by the deposition, burial, and lithification
Metamorphic rock
- results from the transformation of igneous or sedimentary rock under high pressures and temperatures
> rocks under high temperatures and pressures in deep crust and upper mantle - formed by the recrystallization in solid state of new minerals
Relative Dating
- Used to arrange geological events, and the rocks they leave behind, in a sequence
> does not provide actual numerical dates for the rocks
Determining if one rock or geological event is older or younger than another, without knowing their specific ages
> sedimentary rocks do not yield absolute ages
> use correlation and index fossils
Stratigraphy
study of layered sedimentary rocks
Superposition
younger sedimentary rocks laid down on older rocks
Original Horizontality
Lave and sedimentary rock laid down horizontally; any bending or tipping occurred after deposition
Cross-cutting relationship
Intruding rocks are younger than host rocks
Inclusions
- Boulders or other fragments are older than host rock
Faunal Succession
Early fossil forms simple; more recent similar to extant taxa
Absolute Dating
- can infer actual dates
> some elements better for different ages
> also can validate ages using different elements if ages boundaries overlap - radioisotopes - isotopes that emit neutrons, protons, and electrons
- radiometric dating takes advantage of this natural phenomenon
- Often employ a half-life measurement which is time required for a quantity to reduce to half its initial value
Radiometric dating uses […]
unstable isotopes
Half Life
amount of time it takes 50% of the parent isotope to decay into the daughter isotope
Dendrochronology
biological dating with tree rings
- age determination of trees, of many types of wood, to the exact calendar year
> each ring = one year
- Applications
> paleoncology
> archaeology
> radiocarbon dating
Plate Tectonics (continental drift)
- proposed by Alfred Wegener in 1915
- very well educated from a young age and highly qualified/trained
- noticed that SE America and W Africa seemed to “fit” together like puzzle pieces
- Showed that fossils of several species were present in both Brazil and western Africa
> suggested to him that South America and Africa were in physical contact when fossilized animals and plants were alive
Divergent Plate Boundaries
the plates are moving apart
- this produces ocean floor (going on in the Atlantic)
Convergent plate boundaries
the plates are moving towards each other
- This can produce mountains ranges (Himalayas)
Transform fault boundaries
the plates are grinding past each other
- Earthquakes are common here (California)
The continents will probably come together again in the Pacific Ocean in […] million years
[~300]
Plate tectonics (continental drift)
- explains why similar organisms in similar strata are found on different continents
> this argument was used to support continental drift before oceanographic data - now we have independent data that supports plate tectonics, these biogeographical patterns really provide more support to evolutionary patterns in the fossil record
