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Name the 4 criteria necessary for the first cells on Earth
Explain/know what each means
The synthesis of small organic molecules (has carbon and hydrogen)
Macromolecules made from the smaller molecules (amino acids, nitrogenous bases)
Molecules packaged into membrane-containing droplets = protocells
Self-replicating molecules which allowed for inheritance (RNA)
Which gas was ABSENT in early Earth’s atmosphere?
What did it acc mean?
Oxygen
There was no free oxygen, only in compounds
What compounds were produced in the Miller Urey Experiment?
Amino Acids
What is Chemosynthesis?
The ability to create energy/food through chemical means, rather than sunlight.
What do Chemosynthetic organisms in deep-sea thermal vents use to obtain energy?
Chemical reactions with the chemicals obtained from Earth itself.
What molecule is thought to be the first genetic material used by cells and why?
Ribozymes, as they can catalyze many different reactions including their own, and were made up of RNA.
Give three reasons fossils may not be found.
The organism may not have existed for a long period of time
The organism may not have been abundant or widespread
The organism was made of mostly soft stuff/tissue that did not fossilize
What are strata in reference to fossils?
Layers of sedimentary rock where fossils can be found
Briefly identify what follows most extinction events
Adaptive radiation through an alteration of ecological communities and available niches. This causes millions of years to go toward recovering the planet and its biodiversity, including evolution.
How old is the earth?
4.6 Billion years
When were the first prokaryotic fossils discovered? (make sure you know what prokaryote cells are)
3.5 BYA
When did oxygen appear on the planet?
2.7 BYA
When did the first eukaryote cells appear
2.1 BYA
What are eukaryotic cells?
Cells that have membrane organelles and more complex structures
What process resulted in the production of oxygen gas on the earth?
Evidence?
Photosynthesis by cyanobacteria
Oxygen levels on the planet increased after the evolution of cyanobacteria and other eukaryotic cells containing chloroplasts.
Describe the endosymbiotic theory and identify the organelles that are associated with this theory.
Mitochondria and plastids were originally smaller organisms that lived within larger host cells. The cells for some reason were not digested by the larger cell, only injected, leading to a cooperation where the smaller organisms would supply power and the larger cell would provide shelter.
What are factors that have led to extinction?
Changes to an environment and other major events. Volcanism, global warming, reduced temperature gradients, oceanic anoxia, asteroid impacts, etc.
What are two possibilities of how life started on earth? What is evidence for each of these?
RNA World; RNA was stable and able to replicate fast. It could also create enzymes to catalyze its own reactions. RNA could’ve provided a blueprint for the eventual creation of DNA.
Terrestrial origins of organic compounds, brought by celestial objects through collision with the Earth. Various meteorites were found to contain organic material(amino acids and nitrogen bases)
Describe Heterochrony
A change in developmental timing, a mechanism of evolutionary change.
An evolutionary change in the rate or timing of developmental events
Changes when genes turn on or off
What can heterochrony impact?
It can have a significant impact on body shape
The contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates
Describe Paedomorphism
The delaying or slowing of the physiological, or somatic, development of an organism, usually in animals.
Infantile characteristics from an ancestral species in an adult
What are Homeotic genes and give an example of a homeotic gene.
A group of genes that control the pattern of body formation during the early embryonic development of organisms. An example in flies, are those that have feet in place of mouths or any other switched part.
Homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged
Master regulatory genes for turning on other genes(determine location and organization of body)
What is an Exaptation?
A trait, feature, or structure that’s function changes during evolution
What was Earth’s early atmosphere like?
Likely contained water vapor and chemical released by volcanic eruptions
Nitrogen, nitrogen oxides, carbon dioxide, methane, ammonia, hydrogen, hydrogen sulfide
NO OXYGEN
What were all the chemicals in early Earth’s atmosphere (generally)?
Inorganic
What did A.I. Oparin and J.B.S. Haldane hypothesize?
That early Earth’s atmosphere was a reducing environment
What did Stanley Miller and Harold Urey do?
They tested Oparin and Haldane’s hypothesis by showing that the abiotic synthesis of organic molecules in a reducing atmosphere is possible
They were able to replicate the early world
Produced amino acids
What is a reducing environment
An atmospheric condition in which oxidation is prevented by removal of oxygen and other oxidizing gases or vapours
No free oxygen (dissolved or as a gas)
Giving electrons = reduced charge
What was energy in early Earth?
Lighting and UV radiation
What new hypothesis was formed from the reducing atmosphere hypothesis?
That rather than forming in the atmosphere, the first organic molecules may have been synthesized near volcanoes or deep-sea vents
Pockets of reducing areas; not the whole atmosphere
What did the Miller-Urey experiments teach us?
That organic molecules have formed with various possible atmospheres
How were RNA monomers produced?
They were produced spontaneously from simple molecules (nucleic acids)
When do small organic molecules polymerize?
When they’re concentrated on hot sand, clay, or rock
What two key properties of life may have appeared together?
Replication and metabolism
What are protocells?
Fluid-filled vesicles with a membrane-like structure
What can lipids and other organic molecules form in water?
They can spontaneously form vesicles with a lipid bilayer
What do vesicles exhibit?
Simple reproduction and metabolism. They also maintain an internal chemical environment.
Why was RNA most likely the first genetic material?
Ribozymes(RNA molecules), have been found to catalyze many different reactions as well as their own.
They can also make complementary copies of short stretches of RNA
True or False: DNA could of been a template for RNA
False, it’s vice-versa
What vesicles would have had RNA capable of replication?
Protocells
When did the first living organisms appear?
3.5 BYA
When did oxygen first arise?
2.7 BYA
How did oxygen get abundant on the planet?
Cyanobacteria use light energy for photosynthesis, allowing them to harness carbon to make food, releasing oxygen in the process
Null Hypothesis (H0)
The implied hypothesis
Null = nothing
This hypothesis states that there is no differences between groups or no relationships between variables.
A presumption go status quo or no change
Alternative Hypothesis (Ha)
AKA: The claim
States what you expect the data to show, based on your research on the topic
Answer to research question
What does the fossil record reveal?
Changes in the history of life on Earth
What is the richest source of fossils
Strata
What are these terms in relation to the fossil record?
Mineralized
Organic
Incomplete record
Mineralized = hard body structures
Organic = rare in fossils, but found in amber, frozen, tar pits
Incomplete record = many organisms not preserved, fossils destroyed, or not yet found
What are stromatolites and what’s there significance?
They are iron deposits that have layers that were photosynthesizing, pumping oxygen into the ocean
Oldest fossils
Rocks formed by the accumulation of sedimentary layers on bacterial mats
3.5 BYA
What kinds of species is the fossil record biased in favor of?
Ones that:
Existed for a long time
Were abundant and widespread
Had hard parts (easy to fossilize)
What’s the difference between relative dating and radiometric/numerical dating?
Relative dating uses sedimentary strata and what is found AROUND a fossil to relatively date the fossil
Relies on index fossils
Absolute dating uses radioisotopes and the amount remaining to measure the amount of time that has passed
How does dating using radioisotopes work?
Parent isotopes decay into daughter isotopes over time
What’s a half-life?
What’s the half-life of carbon-14?
The time it takes for half the parent isotope to decay
5730 years
What are index fossils?
Fossils that are found during a relatively short period of time
If something is found near it, it’s obvious what the time period is, because there’s only one option
What usually happens before and after major events?
Adaptive radiation, major extinction
Major boundaries between geological divisions correspond to what?
Extinction events in the fossil record
Major Events During Each Era: Precambrian
Microscopic fossils (stromatolites)
Photosynthesis, atmospheric O2
Eukaryotes (endosymbiont theory)
Major Events During Each Era: Paleozoic
Cambrian Explosion
Plants invade land, many animals appear
Permian Extinction (-96% species)
Major Events During Each Era: Mesozoic
“Age of Reptiles”, dinosaur, plants
Formation of Pangaea supercontinent
Cretaceous Extinction – asteroid off Mexico’s coast
Major Events During Each Era: Cenozoic
Primates
Order Key Events in Life’s History
3.5 BYA = First single-celled prokaryotes
2.7 BYA = Oxygen accumulation in atmosphere
2.1 BYA = First single-celled eukaryotes
1.2 BYA = First multicellular eukaryotes
535-525 MYA = Cambrian Explosion
500 MYA = Colonization of land by fungi, plants, and animals
200,000 = Humans
What were the sole inhabitants of Earth from 3.5-2.1 BYA?
Prokaryotes
Was most atmospheric oxygen(O2) of organic origin?
Yes
What was the oxygen revolution
From 2.7-2.3 BYA
O2 began to accumulate in the atmosphere
Caused the death of many prokaryote groups because they were “obligate anaerobes“
Other prokaryotes adapted using cellular respiration to harvest energy
What did Eukaryotic cells have 2.1 BYA?
A nuclear envelope, endoplasmic reticulum, cytoskeleton
Endosymbiotic Theory
Proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells
What’s an endosymbiont?
A cell that lives within a host cell
How did the prokaryotic ancestors of mitochondria and plastids gain entry to the host cell?
How did they form a union
As undigested prey or internal parasites
The mitochondria/plastid were able to use oxygen effectively, so they provided energy for the host cell and the host provided shelter
Serial endosymbiosis
Supposes that mitochondria evolved before plastids through a sequence of endosymbiotic events
Endosymbiotic Theory
Mitochondria & plastids (chloroplasts) formed from small prokaryotes living in larger cells
What is evidence of the endosymbiont theory?
Replication by binary fission..similar to prokaryotes
Single, circular DNA (no histones)
Have their own ribosomes to make proteins, and ribosomes are more similar to prokaryotes
Enzymes similar to living prokaryotes
Two membranes, Inner membranes are similar to plasma membranes of prokaryotes
What did the evolution of eukaryotic cells allow?
A greater range of unicellular forms
How did unicellular forms diversify/specialize?
The cells started to live in colonies and eventually those cells took on different roles → rise of multi-cellular organisms!
The Cambrian Explosion
The sudden appearance of fossils resembling modern animal phyla in the Cambrian period (535 to 525 million years ago)
Provides the first evidence of predator-prey interactions
True or False: Plants and fungi today do not form mutually beneficial associations and dod not likely colonize land together
FALSE
Plants and fungi today form mutually beneficial associations and likely colonized land together
What is a tetrapod?
4-legged organism with a backbone
What are the most widespread and diverse land animals?
Arthropods and tetrapods
What did tetrapods evolve from? When?
Lobe-finned fishes around 365 million years ago
What are lobe-finned fish?
Fish with fleshy tissue that goes into their fins
What does the rise and fall of groups depend on?
Speciation and extinction rates within the group
Theory of Plate Tectonics
Continental Drift
Earth’s crust is composed of moving plates floating on Earth’s mantle
Tectonic plates move slowly through the process of continental drift
Oceanic and continental plates can collide, separate, or slide past each other
Interactions between plates cause the formation of mountains and islands, and earthquakes
What were the consequences of Pangea?
A deepening of ocean basins
A reduction in shallow water habitat
A colder and drier climate inland
What are the effects of continental drift on living organisms?
A continent’s climate can change as it moves north or south
Separation of land masses can lead to allopatric speciation
Geographic barriers
True or False: The distribution of fossils and living groups reflects the historic movement of continents
True
Paleogeography
The study of the movement of plates across the face of the Earth
What happens are mid-ocean ridges?
Where plates meet
Sea floor spreading
Subduction
Supercontinent Cycle
Continents breaking apart and coming together
Are most species that have ever lives still alive?
No, most are now extinct
What can extinction be caused by?
Changes to a species’ environment
What is mass extinction the result of?
Disruptive global environmental changes
In each of the five mass extinctions, how much of Earth’s species became extinct?
More than 50%
What are some factors of extinction
Intense volcanism in what is now Siberia
Global warming resulting from the emission of large amounts of CO2 from the volcanoes
Reduced temperature gradient from equator to poles
Oceanic anoxia from reduced mixing of ocean waters
What does the presence of iridium in sedimentary rocks suggest?
A meteorite impact about 65 million years ago
Dust clouds caused by the impact would have blocked sunlight and disturbed global climate
The Chicxulub crater off the coast of Mexico is evidence of a meteorite that dates to the same time
Adaptive Radiation
What is it
Many new species arise from a single common ancestor
The evolution of diversely adapted species from a common ancestor
When does adaptive radiation occur?
A few organisms make way to new, distant areas (allopatric speciation)
Environmental change → extinctions → open up new niches for survivors
Organisms colonize new environments with little competition
What’s a famous showcase of adaptive radiation?
The Hawaiian Islands
What did the disappearance of dinosaurs (except birds) allow for?
The expansion of mammals in diversity and size
What does adaptive radiation follow?
Mass extinctions
The evolution of novel characteristics
The colonization of new regions
Is a Sixth Mass Extinction Under Way?
Yes, a human-caused mass extinction; unless dramatic action is taken