Chapter 3 Flashcards
What does abiotic mean?
Non living
What are the seven characteristics shared by all life-forms?
- Order
- Harnesses and utilizes energy
- Reproduces
- Responds to stimuli
- Exhibits homeostasis
- Grows and develops
- Evolves
What does biotic mean?
Living
Why are viruses not considered to be true living organisms?
They display many of the properties of life, but the characteristics of life of viruses are based on its ability to infect cells.
They infect other cells and steal their organisms to survive
Ex: viruses contain nucleic acids but they lack the cellular machinery and metabolism to use that genetic information to synthesize their own proteins so they infect living cells and hijack their machinery
Why are the seven properties of life considered emergent?
They come about, or emerge, from many simpler interactions that, in themselves, do not have properties found at higher levels
Ex: the ability to harness and utilize energy is not a property of molecules or proteins or biological membranes in isolation, rather the ability emerges from the interactions of all three of these parts together
What type of earth do scientists believe life began?
They believe cells with the characteristics of life arise out of a mixture of molecules that existed on primordial earth
Why is earth so perfect for harbouring life?
- Earth developed an atmosphere that could cool the planet to a temperature life could survive on
- earth is situated in a position where heat from the sun allows for surface temperatures to be within a range that allows water to exist in a liquid state
What are all forms of life composed of?
Major macromolecules such as Nucleic acids Proteins Lipids Carbohydrates
What is the first hypothesis for the origin of life: reducing atmosphere?
Two scientists proposed that organic molecules formed the atmosphere of primordial earth and named it a reducing atmosphere because of the presence of large concentrations of molecules such as hydrogen, methane and ammonia
These molecules contain an abundance of electrons and hydrogen would have entered into reactions with eachother which led to larger and more complex organic organisms
What is the second hypothesis for the origin of life: deep-sea vents?
Suggests the origin of life fame from deep sea (hydrothermal) vents
- they release super heated nutrient-rich water and reduced molecules such as methane, ammonia and hydrogen sulfide
- today the areas around these vents support a remarkable diversity of life
What is the third hypothesis for the origin of life: Extraterrestrial Origins?
- each year more than 500 meteorites impact earth many of which are rich in organic molecules
- Murchison meteorite in Victoria Australia contained amino acids
What are monomers?
Examples
Monomers are the building blocks of polymers that are simpler and easier to synthesize
Amino acids
Nucleotides
Monosaccharides
What are polymers?
Examples
Macro molecules formed from the binding together of individual monomers
Nucleic acids
Proteins
Polysaccharides or carbs
What type of environment could have provided the necessary things for polymerization to occur?
Solid surfaces
Especially clay
What is the difference between reducing atmosphere and oxidizing atmosphere?
The oxidizing atmosphere is rich in oxygen which prevents complex, electron rich molecules from being formed
The lack of oxygen of the reducing atmosphere means it had no ozone layer
What is a protobiont?
A group of abiotically produced organic molecules that are surrounded by a membrane structure
Have formed spontaneously without energy on primordial earth
What are ribozymes?
A group of RNA catalysts that can catalyze reactions on the precursor RNA molecules that lead to their own synthesis
What are the three reasons cells that evolved the ability to use the information present in RNA to direct the synthesis of proteins turned out to be a tremendous advantage?
Also the reasons that proteins are the dominant structural and functional molecule of the modern cell
- The catalytic power of most enzymes is much greater than that of a ribozyme
- A typical cell synthesizes a huge array of different proteins
- Amino acids can interact chemically with eachother in bonding arrangements not possible between nucleotides
What are the three reasons DNA is better to store information than RNA?
- Each strand of DNA is chemically more stable and less likely to degrade
- DNA uses thymine not uracil so it can detect damaged uracil and repair it
- DNA is double stranded so if a mutation occurs on one strand it can use the complementary strand to repair it
Where is the earliest conclusive evidence of life found in? What are these?
Stromatolites
Type of layered rock that is formed when microorganisms bind particles of sediment together, forming thin sheets
What are heterotrophs?
Organisms that obtain carbon from organic molecules
Humans are heterotrophs
What are autotrophs?
Organisms that obtain carbon from the environment in an inorganic form (CO2)
Plants are autotrophs
What is the earliest type of photosynthesis?
Anoxygenic photosynthesis
Uses hydrogen sulfide and ferrous iron as electron donors for the light reactions of photosynthesis
How were ancient stromatolites formed?
Cyanobacteria
Photosynthetic bacteria
What is oxygenic photosynthesis?
Photosynthesis that relies on the oxidation of water as the source of electrons
Cyanobacteria uses this
Why was oxygenic photosynthesis huge on the evolution of life?
It gave the organism using it the ability to grow anywhere it could get sunlight
What is panspermia?
The name given to the hypothesis that very simple forms of life are present in outer space and that these may have seeded early earth
What is an extremophile?
General term given to an organism that is found growing in environments that are lethal to most other organisms
What are the three domains that all present day organisms can be placed into? Where do they all connect?
Archaea
Bacteria
Eukarya
They connect at the last universal common ancestor (LUCA)
What are the seven common attributes all life forms share?
- Cells made of lipid molecules brought together by bilateral
- A genetic system based on DNA
- A system of Info transfer DNA to RnA to protein
- A system of protein assembly from amino acids
- Reliance on proteins
- Use of ATP as chemical energy
- Breakdown of glucose by glycolysis to produce ATP
What are the six lines of evidence that support the theory of endosymbiosis?
- Morphology- form or shape of mitochondria and chloroplasts is similar to that of bacteria and archaea
- Reproduction- can’t synthesize M or C
- Genetic information- M and C contain their own DNA
- Transcription and translation- both M and C compete these cycles
- Electron transport- both have electron transport chains
- Sequence analysis- sequencing of RNA that makes of ribosomes of C and M
What is the model of endosymbiosis?
States that the prokaryotic ancestors of modern mitochondria and chloroplasts were engulfed by larger prokaryotic cells
What is genome?
The complete complement of an organisms genetic material
Where was the endomembrane system derived from?
The plasma membrane
Pockets of the plasma membrane may have extended inward and surrounded the nuclear region
