Origins Flashcards
Atom
- The smallest particle that can exist alone or in combinations with other atoms
- The unit building block of all chemical compounds
- In a neutral atom, protons = electrons
- atomic num = num of protons
Chemical compound
- Most matter is composed of a combination of atoms
- Ex: table salt = NaCl
- These compounds result from chemical reactions during which atoms combine via shared or transferred electrons (no changes occur in the nuclei of the individual atom)
- Atoms can share electrons (covalent bond)
Nebula
Cloud of gases and space dust from which all bodies in the solar system formed
Galaxy
- Huge rotating aggregation of stars, dust, gas and debris held together by gravity
- 100 billion galaxies in universe
- 100 billion stars in each galaxy
Nebular hypothesis
- Nebula → solar system
- Gravity concentrates material at center of cloud (eventually become the sun)
- Protoplanets from the accretion of smaller particles in eddies
- Different materials condense at different temps
- Planet composition dpend on proximity to hot protosun
Eddy
- rotating/swirling feature
- current flows towards the objet that created the eddy
Birth, life, and death of stars
- Spinning solar nebula (protostar)
- Mainly composed of hydrogen (H) and helium (He)
- Heavier elements like oxygen (O) and carbon (C) formed by nuclear fusion
- Mature star
- Red giants & supernovas = dying stars
- Seeding other solar systems with heavier elements
Nuclear Fusion
- Energy-producing process that takes place continuously in sun and other stars
- In core of sun:
- temp is 10 million degrees C
- Hydrogen → helium + energy
- This energy sustains life on earth
- In core of sun:
Planet compositions
Formation of Earth
- Aggregation of particles
- Bombardment of meteors and asteroids
- Gravitational compression and heat from radioactive decay and fusion cause partial melting
- Formation of density layers / Density stratification into core, mantle, and crust
Density stratification
- Formation of density layers
- Stratification into core, mantle, and crust
- density = mass / volume
- layering of materials of different densities (higher density at the bottom)
Earth’s Internal Structure
- Layers defined by:
- Chemical composition and physical properties
How do we know the age of earth and rocks?
- Radioactive decay and dating
- Half life: how long until half has decayed
- As elements decay they turn into something [insert image decay chain]
- Carbon-14 used to measure things on a human timeline
- Uranium-335 used for dating the Earth
Origin of Earth’s Atmosphere
- Outgassing of volatile gases from within the earth during density stratification
- Contained water vapor, c02, hydrogen, lots of noxious gases like methane, hydrogen sulfide
- This early atmosphere was very different than today - very little oxygen
Origin of Earth’s Oceans
- Most of the water comes from outgassing of Earth → condensation → rain
- Some additional water comes from icy comets
- Ocean in place at ~4 billion years (compared to earth’s formation at 4.6 billion years)
Why is the ocean salty?
- Rain falls on rocks
- In contact with rainwater, rocks chemically break down, releasing elements into surface water
- Then these elements are carried by rivers into the ocean, contributing to its salinity levels
- Ocean is not getting saltier over time
- Salt settles into sea floor sediments
How did life come to be in the oceans?
- “Based on a funamentally different chemical structure than the soldi Earht”
- “Chemical phenomenon”
- “Capable of undergoing Darwinian evolution”
- “Based on molecules that transfer material and energy in complex cycles”
- Chemical composition on Earth’s crust: mainly oxygen and silicon
- Chemical composition of life: carbon and oxygen
Organic molecules
- the building blocks of life and all contain carbon
- amino acids
- carbohydrates
- Nucleic acids
- lipids
How did life evolve on Earth?
- Early hypothesis: inorganic molecules could spontaneously form organic molecules and the building blocks of life
- Result = production of organic molecules under conditions simulating early earth
- Or, an extraterrestrial source? Panspermia Hypothesis: organic molecules carries on meteorites to Earth
Morphological evidence for life
- fossils
- trace fossils
- biogenic structures
- Problem: not many suitable sedimentary rocks left, most of them destroyed through tectonic processes
Geochemical evidence for life
- Direct: molecular fossils (=biomarkers), genomic evidence
- Indirect: metabolic byproducts (like oxygen) and tracers (isotopes, trace metals)
Where did life start?
- Likely in deep sea, near hydrothermal vents or cold seeps
- Protected stable regions
- Mimics conditions on early earth
- Organic molecules → cells → advanced organisms
Procaryotes
first livign organisms, lack a nucleus, single cellular, bacteria & archea
Eucaryotes
have nucleus, single or multi cellular, animals, plants, fungi, etc
Cyanobacteria
- inventors of oxygenic photosynthesis
- Ocean phenomena
- Oldest fossils at 3.5 billion years ago
- Other types of photosynthesis before, but these were first to split water into oxygen
Phytoplankton
- the ocean’s invisible forest
- Main driver in the oxygenation of the planet
- Generate 50% of oxygen on planet
- Microscopic; both procaryotes and eucaryotes
- Diatoms, coccolithophores, dinoflagellates
- Cycling carbon and oxygen by life
- Photosynthesis, cellular respiration
Evolution of life
The effect of photosynthetic life on the atmosphere
- Photosynthesis from phytoplankton and plants
- Natural cycle created by plants is altered by humans
- The rise of atmospheric O2
The Great Oxidation event
- Photosynthesis invented a billion years before the spike
- Abundance of BIFs (Banded iron formations): red minerals (iron oxides, rust) which precipitated when the oceans became oxic
Why is there such a long lag between the beginning of
photosynthesis and the rise in atmospheric oxygen?
*in early ocean, lots of dissolved iron. oxygen produced by phytoplankton reacts with this iron
and becomes red sediment
*once dissolved iron in ocean is used up, oxygen could start accumulating in the atmosphere
More recent history of Earth’s atmospheric oxygen
low levels = extinction events
Oxygen in atmosphere leads to Ozone
Ozone is critical gas that shields the damaging UV rays from the sun
