Exam 1 Flashcards
What is the major reason we think life will be found elsewhere?
Statistics, the total number of possible exoplanets
Describe the likely first life (not LUCA)
single-celled prokaryotes based on RNA
Why do we want to find life as a global entity?
much less likely to be a contamination event
Vernadsky
geology and biology are fundamentally indistinguishable, the line between living and non-living is not very clear
Lovelock - Gaia hypothesis
once life is established, it would respond to the changing environment to ensure that it continues
living, self-regulating, homeostatic system
Miller and Urey
mimicked conditions on early Earth with electrodes and inorganic compounds
solution became cloudy with organic molecules, including amino acids
What is the predominant form of life on Earth?
prokaryotes
What would a methane-based solvent change about life?
may be based on silicon instead of carbon
What would a non-water solvent change about life?
upside-down lipid bilayer (hydrophobic exterior)
Why would life need constant habitats?
to maintain life
Why would life need variable habitats?
resources are not depleted, waste products do not build up, produces natural selection
What is the “life as a process” defn of life?
something that consumes energy to maintain its organization (lower entropy, build biomass)
What is the textbook defn of life?
a self-sustaining bounded local environment in disequilibrium with its environment
Why does life require “some” fidelity?
fidelity is required so life can continue and make more cells, mistakes are required to produce variety for evolution to act upon
Defn of metabolism
the sum of all the chemical reactions that occur within the cell
Describe anabolism
consuming energy to build things up
Describe catabolism. How is the way life performs this process different than non-life?
releasing energy by breaking things down, life can use a number of steps to control the release of energy and reduce the amount of energy wasted
Describe autopoiesis
self-creation powered by the controlled consumption of energy; the process of making more biomass
What are the two life-specific parts of reproduction?
start with raw materials and use anabolic reactions to form monomers, polymers, and a cell
have an evolutionary history
What is the unique chemistry of life on Earth?
nitrogen, carbon, oxygen, hydrogen, sulfur, phosphorus
Earth’s crust is mainly silicon
Types of life - Darwin life
emphasis on the capacity for organisms to adapt to their environment and change through time
Types of life - Haldane life
emphasis on metabolism and maintenance, if organisms are decreasing entropy and processing the chemical reactions that make up life
Types of life - Carl Woese life
he used the r16s (small subunit rRNA) gene to develop the phylogeny of life that moved us from 5 kingdoms to 3 domains
Types of life - synthetic life
wetware; taking living cells and genetically modifying them
Types of life - virtual life
software; AI or life contained within the machine
Types of life - mechanical life
hardware; life that cannot build new versions of itself from raw materials
Types of life - Paul Davies “dark life”
life that does not rely on sunlight for energy and instead uses chemicals such as hydrogen sulfide or ferrous iron
Origin of life - Panspermia
Francis/Crick, life came from elsewhere, does not explain where that life came from
Origin of life - Primordial Soup
dilute solutions on earths surface where life could use lightning or UV radiation from the sun as energy and the water and simple organic molecules brought by asteroids; requires cycles of freezing or desiccation
Origin of life - Deep Sea Vents
hydrogen sulfide and other inorganic compounds that can serve as sources of energy; would also be hard to concentrate reactants and retain products; iron/sulfur chimney structures as catalysts
Thermal beginning of life
thermophiles are at the root of the tree of life; may indicate support for deep sea vents or just that thermophiles are the most likely to survive the early bombardment of Earth
8 steps for life (list)
source of energy, polymerization, formation of a membrane, info-polymers, RNA, DNA, statistically re-occurring of effective and efficient metabolites, proteins
What are some compounds found on early Earth? What sort of atmosphere did we have?
hydrogen, nitrogen, carbon dioxide, ammonia, cyanide, formaldehyde, hydrogen sulfide
reducing atmosphere
How much energy does the reaction of hydrogen and oxygen yield?
237.14kJ
What are the three ways ATP can be produced?
electron acceptor chains, substrate level phosphorylation, electron pair bifurcation
Describe LUCA
contains DNA and proteins; proto-cell with a cell membrane; small size
Age of universe
14 BYA
First elements
hydrogen and helium, combine for nuclear fusion in protostars
Formation of earth
4.46 BYA, heavy elements closer to sun, lighter elements further away
Age of first life, description
3.5-3.8 BYA, bacterial mats / stromatolites found in Australia
Age of anoxic photosynthesis, description
3.4 BYA, used hydrogen sulfide before water
Age of rock evidence for the release of oxygen
2.3-2.4 BYA, oxygen reacted with ferrous iron to make banded iron formations, allowed for aerobic respiration and multicellular life
Age of first cyanobacteria
2.7 BYA
Age of red/brown algae
1.2 BYA
Why has increased complexity favored?
movement and increased specialization
Evolutionary significance of stable environments
stabilizing selection with fewer extreme phenotypes, low diversity
Evolutionary significance of changing environments
preference for extreme phenotypes, causes speciation and high diversity
Meaning of inclusive fitness
the heredity of genes is the most important; even if you die, close relative may survive and pass on your genes
Minimum temperature, adaptations
-10/-15*C, increased branched fatty acids and cholesterol in membranes
Maximum temperature, adaptations
121*C, disulfide protein bonds, lipid monolayer and/or ether bonds, reverse gyrase
Minimum pH, adaptations
below 0, use electrons from ferrous iron to balance protons in the environment
Maximum pH, adaptations
around 11, use sodium pumps for ATP production
Essay ? - Nelson Conrad 1999, three categories of life
physicists - use light/heat, chemists - use chemical energy, biologists - use other organisms
Essay ? - Mariscal and Doolittle 2018, defining life
all defns of life suck, choose what you like best
Essay ? - Jeffares et al 1998, RNA world
DNA - double stranded, deoxyribose sugars, thymine
Proteins - shorter reaction times, more functional groups, precise tertiary structure, small substrates
Essay ? - Darwin’s pond
favor hydrolysis, cycles of desiccation or freezing
Essay ? - Upper temperature limit
121*C, disulfide bonds, lipid monolayer and/or ether bonds, reverse gyrase
