Hudson's Portion Flashcards
When was the Big Bang and when did the Earth form?
Big Bang- 13.7 billion years ago
Earth formed 4.55 billion years ago, atmosphere was thought to be made up of helium and hydrogen.
When did the Earth cool and what else was changing during this time?
Earth cooled 4 billion years ago (.55 billion years after it formed), outer layers solidified and oceans formed. Volcanoes and other vents in the crust gave rise to a new atmosphere consisting of CO2, N2, H2S, H2O (vapour), and possibly NH3, and CH4.
How did our oceans form?
Hydrogen and oxygen was binding in the Earth’s core which eventually formed into rain clouds where it rained for thousands of years. This is where half of the Earth’s water came from, the other half came from asteroids.
What three things are all living cells made of (key molecules and macromolecules)?
DNA- stores information for the amino acid sequence of proteins
RNA- acts as the intermediary in the process of protein synthesis
Proteins- form the foundation for the structure and activities of living cells
How did life form on Earth? 1 of 4 hypothesis: Formation of nucleotides and amino acids (three hypotheses)
A- Reducing atmosphere hypothesis (Miller and Urey experiment)
B- Extra terrestrial Hypothesis
C- Deep Sea vent hypothesis (Wachtershauser 1988)
Explain the reducing atmosphere hypothesis
In a reducing environment, inorganic molecules such as water vapour, hydrogen, methane, and ammonia, can be easily reduced to form organic molecules. Boiling water was used to produce water vapour, and using a condenser to form water droplets simulated the water cycle, while electrodes simulated lightning on early earth. They found that simple organic compounds such as sugars, amino acids, and nucleotides were found in the trap
What are some features that may debunk the miller urey experiment?
Scientists believe that the atmosphere was neutral with CO, CO2, N2, and H20, because volcanic gasses contain little methane and ammonia. Also ultraviolet radiation hitting ancestral earth would destroy CH4 and NH3 rapidly. They still yielded the same results however.
Describe the extraterrestrial hypothesis for life on earth
Meteorites contain substantial amounts of organic carbon, this carbon includes amino acids and nucleic acids, may have produced a primordial soup on ancestral earth. Evidence to back this up- the Murchison meteorite which was a large meteorite, contained Amino acids and Nucleobases. Many scientists argue that most organic material would be destroyed in the intense heating and collision.
Describe the deep sea hypothesis theory to the origin of life
Water, metals, and hydrogen sulphide (H2S) exit deep sea thermal vents in excess of 300 degrees Celsius, precursors to organic molecules can be formed in the gradient between hot and cold water, ex: N2 can be reduced to NH3 in this environment, which is needed for amino acid synthesis. Nutrients were being spewed out and around these areas, life was thriving in this environment.
How did life form on Earth? 1 of 4 hypothesis: nucleotides and amino acids (monomers) become polymerized
Nucleotides and amino acids became polymerized to form DNA, RNA, and proteins. This process took place in clay or ephemeral tidal pools. Better break down- when monomers are present (amino acids or nucleotides), formation of polypeptides and nucleic acid polymers may occur on the clay surfaces without enzymes. These polymers became isolated by boundaries, developed into a protobionts (first non-living structures that evolved into cells)
What are the four characteristics of protobionts?
- Membrane (ex: lipid belayer) separated external environment from internal contents.
- Polymers inside contain information
- Polymers inside had enzymatic function
- Capable of replication (not capable of precise self replication like cells, but divide to increase in numbers).
Explain how Polymers became isolated by boundaries: Scenario 1- Coacervates
Charged polymers (proteins, carbs, or nucleic acids) spontaneously associate with each other. This happens on the inside of the polymer, which is Surrounded by a tight skin of water that is permeable to simple molecules. Depending on polymers present in cell, certain ancestral metabolic functions can proceed.
Explain how Polymers became isolated by boundaries: Scenario 2-microspheres
Hollow sphere of protein filled with water.
Explain how Polymers became isolated by boundaries: Scenario 3- Liposomes
Hollow sphere of a phospholipid bilayer filled with water. Similar to microspheres but with a Lipid outer layer. Researches have shown that clay can catalyze the formation of liposomes that grow and divide. Another thing is that if RNA is on the clay, liposomes would form and enclose some of the RNA.
Why do scientists favour RNA as the first macromolecule of protobionts (three reasons)?
RNA can perform three functions: 1- have the ability to store information 2- has the capacity for self replication 3- is capable of enzymatic activity DNA and proteins do not have all 3 of these functions.
What took place during the Hadean period (the first EON), and when did it take place?
Took place 4.6-4 billion years ago. This is when the Earth began to cool and oceans started forming.
When did the archaen period take place and what were significant features of it?
Took place 3.8- 3.5 billion years ago, protobionts gave rise to prokaryotes that lived in an environment that lacked O2. It was hypothesized that the first organisms were anaerobic heterotrophs because it was simpler for primitive cells to use organic molecules in primordial soup, than to evolve additional metabolic pathways to make organic molecules.
What is the formula for anaerobic heterotrophs metabolizing organic molecules through fermentation or methanogenesis?
C6H12O6—> 2C2H5OH (ethanol) + 2CO2 + energy (2 units)
Note: organic molecules in the primordial soup we’re made slowly so anaerobic heterotrophs would eventually exhaust this supply of organic molecules. Therefore, cells that evolved the ability to synthesize organic molecules from inorganic sources (ex: CO2) would have an advantage
What is the formula for how modern heterotrophs metabolize organic molecules by oxidation?
C6H12O6+ 6O2——> 6 H20 + 6CO2 + energy (36 units)
What is an anaerobic chemoautotroph?
An organism that obtains energy by oxidizing inorganic (ex: H2S or NH4) substances and uses CO2 as a carbon source. Energy from sunlight is not involved.
Note that these organisms along with photoautotrophs exhausted all of the H2S in the ocean.
What is an anaerobic photoautotroph?
Prokaryotes that obtain energy from sunlight to fix CO2 into organic carbon compounds.
Note that these organisms require reduced sulfur (H2S), light, and have to be in an anaerobic environment. No Oxygen is produced in this energy gaining process.
What are photoautotrophs with oxygenic photosynthesis? Why was it so successful?
Autotrophic process where CO2, water,and light produced clucks earth and oxygen. Was extremely successful because water was abundant at this point (oceans were already formed) and water became the electron donor
What was the first organism to use photosynthesis? What did this change do to the atmosphere?
Cyanobacteria bacteria in stromatolites was the first fossil organism to use this, it accumulated O2 in the atmosphere which killed off a lot of anaerobic bacteria. The ones that did survive were forced to limited areas which is why we see organisms thriving in anaerobic environments to this day.
What are stromatolites, how did they form, and when did they form?
Formed roughly 3.5- 3 billion years ago, they are rocks that are made up of a community of Cyanobacteria that create layers of CaCO3 and sediment. Form in a step by step process- dissolved calcium reacts with inorganic carbon, bicarbonate. Calcium carbonate is formed which is insoluble and precipitates onto the Cyanobacteria mat. Photosynthesis drives the reaction forward in one direction as CO2 is removed, which creates the layers.
Why are there not very many fossils of organisms before Cyanobacteria?
Organisms before Cyanobacteria are believed to lack hard structures that could be fossilized.
If Cyanobacteria became abundant over 3.5 billion years ago why did it take a billion years to build up in the atmosphere?
Banded iron formations
Explain how Banded Iron Formations work and why it took so long for the atmosphere to build up with oxygen.
Ferrous iron was plentiful in ancient oceans, entered through hot cracks and fissures in the ocean floor. Once oxygen started building up, it started oxidizing ferrous iron to ferric iron. Ferric iron is insoluble, so it would precipitate to the bottom sediments on seasonal cycles, leaving bands of iron in the sediments. As the ocean became more oxygenated, the oxygen would precipitate with ferric iron.
Why are cels so small?
Because of the surface to volume ratios, it is easier for cells that are smaller to undergo metabolic reactions because there is less distance to cross. More specifically, small cells have a greater proportion of surface area for O2 diffusion. This leads us to believe that ancestral O2 concentrations may have restricted the rate of evolution of larger organisms.
Explain the endosymbiosis theory
Endosymbiosis is the theory that a phagocytic organism engulfed an aerobic bacterial cell and over geologic time, developed a symbiotic relationship with the bacteria, that now is what is more commonly known as the mitochondria. This theory also is applied to how chloroplasts came to be in some eukaryotic cells as well (by engulfing photosynthetic bacteria). As symbionts and host became more interdependent, they have become one single organism
What is some of the evidence towards primary endosymbiosis?
The shape and size of the mitochondria and chloroplast are similar to the size of prokaryotic cells, chloroplast has two membranes, chloroplast and mitochondria has DNA different to that of the rest of the cell, and such DNA is circular and lacks histones. Lastly, mitochondria and chloroplasts reproduce through binary fission.
Explain the evidence towards secondary endosymbiosis and what it is.
Only applies to algal groups and how they obtained chloroplasts. Alga that had acquired a chloroplast via primary endosymbiosis is itself taken up by another eukaryote to become a symbiont. Small nuclei and eukaryotic-sized ribosomes are found outside the two inner most chloroplast envelopes (between 1 and 2). Note that the chloroplast in an organism that went through secondary symbiosis would have 3 membranes now. Example of an organism that is thought to have gone through this- Dinoflagellates (Protista)
When was endosymbiosis theory proposed and who proposed it?
Andreas Schimper was the first to propose it in 1883 (24 years after Darwin wrote on the “Origin of Species”) however it was neglected until the discovery of mitochondrial DNA in the 1960’s. Took 100 years for it to be mainstreamed.
What is not part of the endosymbiosis theory even though it looks like it should be?
Endosymbiosis theory does not explain the development of the endoplasmic reticulum or the nuclear envelope. The real theory behind this is that infolding from the plasma membrane resulted in these.
What are some things that all living things share in common?
Lipid bilayer that contains cell, genetic system based on DNA, messenger RNA and transfer RNA, use of ATP, the breakdown of glucose, and reliance on proteins as the major structural and catalytic molecule.
How many cell types to humans have?
411, the more complex a species the more cell types it has.
How did multicellular organisms evolve?
Two theories:
1- cells found each other and aggregated to form colonies
2- Cells remained attached after cell division
What are some advantages of being multicellular?
Become bigger to perhaps avoid predators or become a better predator. Division of labour, specialization in organism is more efficient.
What are some disadvantages of being multicellular?
Complexity of cells and ensuing specialization of species may render organisms more prone to extinction as environments change over geologic time.
What does the introduction of predation do to multicellularity?
It has been found that it dries multicellularity because they had a higher survival rate than unicellular forms.
What is the prefix/suffix zoic?
It means animal life forms. Near the end of the Proterozoic Eon, we see these types of animals to emerge, they were simple invertebrate animals.
What time period does the Phanerozoic Eon span?
Begins 543 million years ago and extends to present day
