9.1 The Origins of Life on Earth Flashcards
What had to happen for simple prokaryotes to form?
Earth had to cool enough for liquid water to exist
What is Primary Abiogenesis?
life came from non-living matter
Primary Abiogenesis
-Oparin & Haldane (1920s)
-Life came from non-living matter
-Life arose spontaneously once organic molecules were made
-Organic molecules (with CHO) can combine to create LIFE!
Which organic molecules can combine to create life?
-Carbohydrates
-Lipids
-Proteins
-Nucleic acids(DNA + RNA)
What was the Urey Miller experiment?
-Simulated life on early Earth
-Created organic molecules from inorganic molecules
-Mimics ancient earth’s water cycle
-Proves that life came from non-living matter (inorganic molecules)
-Others have replicated this experiment many times
What theory does the results of the Urey Miller experiment support?
This results of this experiment support the Theory of Primary Abiogenesis
Where did life begin?
-Planet cooled enough for liquid water
-Land surface likely too hot for life to exist there
-Likely started in deep sea hydrothermal vents
-Likely chemoautotrophic
-Likely similar to modern day extremophiles or archaebacteria in deep sea vents
Chemoautotroph definition
organisms that obtain their energy from a chemical reaction
How can we tell that life existed around 3.5 billion years ago?
fossils
Stromatolites
-Earliest known fossils
-Dome shaped accumulations of bacteria
-Built up over very long period of time
-Likely first photosynthetic organisms to exist in the anaerobic environment
What are stromatolites comprised of?
a mound built up of layers of cyanobacteria and trapped sediment, found in Precambrian rocks
How did oxygen change the world?
-The oldest photosynthetic prokaryotes lived 3.5 billion years ago
-Likely evolved from chemoautotrophs
-As photosynthetic organisms became more common, more oxygen was released into the atmosphere
-when oxygen came out, there was a mass extinction→ species couldn’t adapt to new environ.
What are obligate anaerobes, and how did having more oxygen in the atmosphere impact them?
obligate anaerobes- don’t need oxygen → oxygen kills them
-more oxygen in the atmosphere caused mass extinction of obligate anaerobes
What did more oxygen in the atmosphere lead to?
-led to adaptation & created aerobic organisms
-cellular respiration then developed
-prokaryotes were now aerobic! (i.e. could function/live in the presence of oxygen
What was a crucial step in the development of more complex organisms?
more oxygen in the atmosphere
Why were aerobic organisms “selected” by the environment over anaerobic organisms?
evolution selects aerobic organisms bc they were more successful and fit than anaerobic organisms
What is the theory used to explain the origin of eukaryotes?
Endosymbiosis Theory:
-Ancestral proto-eukaryote engulfed aerobic prokaryote
-Symbiotic relationship established
-Allowed for creation of mitochondria
-Chloroplast evolved same way
What did the ancestral prokaryote look like?
had DNA, cytoplasm and a plasma membrane
How did the endoplasmic reticulum evolve?
plasma membrane infolded
What did the infolding of the plasma membrane lead to?
-endoplasmic reticulum
-nucleus
-nuclear envelope
cell with nucleus and endomembrane system
How did mitochondria evolve?
ancestral prokaryote engulfed aerobic heterotrophic prokaryote
- evolved into a mitochondrion
What did the ancestral prokaryote with mitochondria evolve into?
ancestral heterotrophic eukaryote
How did chloroplasts evolve?
ancestral prokaryote engulfed photosynthetic prokaryote
-evolved into chloroplast
What did the ancestral prokaryote with chloroplasts evolve into?
ancestral photosynthetic eukaryote
How did sexual reproduction contribute to evolution over the years?
-Allowed for genetic recombination
-Variation allows for evolution
-The environment selects those variations that allow individuals to survive & reproduce
-Unicellular organisms evolved into multicellular organisms over hundreds of millions of years
What is a geologic time scale?
Chart that organizes Earth’s history into blocks of time
What are the three eras marked by major fossil record changes?
-Paleozoic (old)
-Mesozoic (middle)
-Cenozoic (recent)
Eras are divided into ____
periods
Periods are divided into _______
epochs
What are the boundaries between eras and some periods marked by?
widespread extinctions
Paleozoic Era events
-Sudden increase in diversity of many animal phyla (Cambrian explosion)
-Marine algae abundant; colonization of land by fungi, plants, and animals
-Diversification of early vascular plants
-Diversification of bony fishes; first tetrapods
and insects
-Extensive forests of vascular plants; first seed
plants; origin of reptiles; amphibians dominant
-Diversification of reptiles; origin of most present-day groups of insects; extinction of many marine and terrestrial organisms at end of period
periods in the paleozoic era
-cambrian
-ordovician
-silurian
-devonian
-carboniferous
-permian
Mesozoic Era events
-Cone-bearing plants (gymnosperms) dominate landscape; origin and diversification of dinosaurs;
origin of mammals
-Gymnosperms continue as dominant plants;
dinosaurs abundant and diverse
-Flowering plants (angiosperms) appear; many groups of organisms, including most dinosaurs, become extinct at end of period
Which era and period did many marine and terrestrial organisms go extinct?
Paleozoic (era), Permian (period)
Which era and period were dinosaurs abundant and diverse?
Mesozoic (era), Jurassic (period)
Which era and period did dinosaurs become extinct?
Mesozoic (era), Cretaceous (period)
Cenozoic Era events
-Major diversification of mammals, birds,
and pollinating insects
-Angiosperm dominance increases; continued
diversification of most present-day mammalian orders
-Origins of many primate groups, including apes
-Continued diversification of mammals and
angiosperms; apelike ancestors of humans appear
-Origin of genus Homo
-Ice ages; humans appear
-Historical time
periods in the mesozoic era
-triassic
-jurassic
-cretaceous
periods in the cenozoic era
-paleogene
-neogene
name of the current geological epoch
holocene
in which era, period and epoch did apes originate in?
cenozoic; paleogene; oligocene
in which era, period and epoch did apelike ancestors of humans appear?
cenozoic; neogene; miocene
in which era, period and epoch had the origin of genus Homo?
cenozoic; neogene; pliocene
in which era, period and epoch was there an ice age and humans appeared?
cenozoic; neogene; pleistocene
what’s currently happening in the holocene epoch?
-the climate has seen some warming and cooling, including the Little Ice Age
-large mammals have gone extinct
-humans have possibly caused the Holocene extinction event and added to global warming
Continental Drift and Macroevolution
-Plates shift on hot mantle
-Same fossils on South America and Africa—fit like puzzle pieces
-Explains why Australia split early–> was isolated: has marsupials
-won’t find any marsupials anywhere else bc it’s
been isolated for so long
Pangea
-250mya; one giant land mass
-Reduced shoreline
-Drained shallow seas, little marine life and fossils
-More competition between organisms in one land mass
What did the break up of Pangea allow for?
convergent evolution since it led to the formation of continents
Mass extinctions
-Long periods of stability followed by mass extinctions are common in Earth’s history
-Allows for adaptive radiation of organisms that survive
-(ex. rise of the mammals following extinction of
dinosaurs)
-Five mass extinctions in Earth’s history
What do mass extinctions allow for?
Allows for adaptive radiation of organisms that survive
-ex. rise of the mammals following extinction of
dinosaurs
What may be one cause of the extinction of
many land plants and animals in North America?
the cause may be the impact of a meteorite 65 million years ago near the Yucatan Peninsula in Mexico
Summarize the Miller-Urey experiment
-an experiment that simulated conditions on early Earth
-Miller placed gases in a flask to represent Earth’s ancient atmosphere
-used electric sparks to represent lightning as an
energy source
-the experiment produced a variety of small organic molecules that are essential to life, including amino acids — the building blocks
of proteins.
Why was this experiment important to
the primary abiogenesis theory?
The Miller-Urey experiment provided the first evidence that organic molecules needed for life could be formed from inorganic components
Why was the development of membrane-bound
organelles beneficial to the cell?
Membrane-bound organelles allowed the cell
to carry out more complex chemical reactions in separate compartments
Describe the endosymbiotic theory
-According to the endosymbiotic theory, mitochondria evolved from small aerobic prokaryotes that lived inside larger eukaryotic cells.
-An ancestral eukaryote may have ingested
some of these prokaryotes for food.
-Instead of being digested, these prokaryotes continued to live inside the larger eukaryote
-aerobic heterotrophic prokaryote evolved into mitochondria
-photosynthetic prokaryote evolved into chloroplasts
Why is sexual reproduction important for
evolution?
-sexual reproduction allows for more genetic
variation in the population
-variation is the raw material for natural
selection
-the environment selects those variations that allow individuals to survive and reproduce, and those organisms evolve and increase in population
What are the three main geological eras in
Earth’s history?
-paleozoic
-mesozoic
-cenozoic
What marks the change of eras in general?
-major change in the forms of life
-widespread extinctions
What are the distinguishing features of each era?
Paleozoic
-increase in diversity of animal phyla
-diversification of plants, bony fishes, reptiles
-extinction of many marine and terrestrial
organisms
Mesozoic
-dinosaurs
-gymnosperms (dominant plants)
-flowering plants appear
-extinction of dinosaurs
Cenozoic
-mammals, birds, pollinating insects
-primates + apes
-apelike ancestors of humans
-origin of genus homo
-ice ages
-*humans appear
What biological evidence is there that Pangaea
once existed?
-diversity of marsupial mammals in Australia
-both marsupial and placental mammals lived in Pangaea
-the Australian land mass split off early in the break-up of Pangaea and remained isolated
-the few placental mammals that lived there became extinct
How did continental drift lead to
macroevolution?
-it explains why the plants and animals of Australia are so different from those in the rest of the
world.
-after Australia became an isolated land mass, the
organisms living there would have evolved independently of those living on other continents.
-this could lead to speciation
continental drift could lead to macroevolution because it can cause the origin of different
species, the extinction of species, and the evolution of major new features of living things, such as wings or flowers
Which location(s) might contain organisms
that resemble the first living creatures on
Earth? Explain.
since the first organisms were chemoautotrophs, it would be locations where they could survive
-e.g. bottom of the ocean(deep sea vents) or in acidic hot springs
Describe the four-stage hypothesis on how life arose on Earth
(1) small organic molecules, such as amino acids, formed from simpler molecules present in the environment
(2) these small molecules joined together into larger ones, such as proteins and nucleic acids
(3) molecules that could copy themselves
provided a basis for the inheritance of molecular information
(4) these various organic molecules became packaged within membranes and separated from their surroundings, formed pre-cells
What evidence is there that mitochondria
and chloroplasts evolved from self-sustaining
prokaryotes?
endosymbiotic theory
-Bacteria, a prokaryote, has circular DNA, as do mitochondria and chloroplasts
-This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote
Cyanobacteria are believed to resemble some of the earlier autotrophs that existed on Earth. What cellular features do you think helped species succeed on early Earth? Explain why
chloroplasts (later evolved- energy)
mitochondria (energy)
Give an example of how the evolution of species
changed the atmosphere
The first photosynthetic prokaryotes evolved in the absence of oxygen. Over time, they became common and started to increase the oxygen concentration in the atmosphere
How do you think human activity today
can affect the composition of gases in the
atmosphere?
Burning fossil fuels, releasing chemicals into the atmosphere, reducing the amount of forest cover, and the rapid expansion of farming, development, and industrial activities are releasing carbon dioxide into the atmosphere and changing the balance of the climate system
The endosymbiotic theory explains how
eukaryotic cells may have evolved. Which
do you think evolved first: autotrophic
eukaryotes or heterotrophic eukaryotes?
Explain your reasoning
-heterotrophs because they eat other plants or animals for energy and nutrients
-autotrophs could have later evolved
How can the mass extinction of one group
of organisms, such as the dinosaurs, lead to
diversification of other species?
-a lot of competitors and predators of mammals disappeared, meaning that a great deal of the pressure limiting what mammals could do ecologically was removed
-less predators, the prey can freely reproduce and increase in population
what events occurred in the precambrian era?
-Origin of Earth
-Oldest known rocks on Earth’s surface
-Oldest fossils of cells (prokaryotes)
-Concentration of atmospheric oxygen begins to increase
-Oldest fossils of eukaryotic cells
-Diverse algae and soft-bodied invertebrate animals
Which gas was not present in Earth’s atmosphere when the first living cells originated?
a) ammonia
b) oxygen
c) carbon
b) oxygen
Even though we think of oxygen as being a vital gas for most forms of life, oxygen in the atmosphere of the early Earth was rare, if it existed at all. Ammonia, carbon dioxide, and hydrogen, carbon monoxide, nitrogen, and water vapour were the primary gases at that time.
In which era did the Cambrian explosion, which resulted in a sudden increase in diversity of many animal phyla, occur?
paleozoic
What event is most closely associated with the formation of Pangaea near the end of the Paleozoic era, 250 million years ago?
permian extinction
At the end of the Cretaceous period, about 65 million years ago, many species became extinct including all the dinosaurs. Many environmental changes occurred during that time, but which event most likely dealt the final blow to the dinosaurs?
meteor strike
The oldest known insect resembled this springtail.
It likely fed on the tips of sporophytes and may have had wings. To which period did this ancient insect belong?
devonian
