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Origins of Life (Chp. 23-24)
Terms in this set (76)
In what type of rock are fossils found?
Rock formed from sand and mud that once settled on the bottom of seas, lakes, and marshes
The Fossil Record
The sequence in which fossils appear in the layers of sedimentary rock that constitute Earth's surface
Why is The Fossil Record incomplete?
It favors organisms that existed for a long time, were relatively abundant, and had shells or hard bony skeletons
Uses the order of rock strata to determine the relative age of fossils
-The oldest fossils are deposited in the lower strata
Geological time scale
Sequence of species
Age using half lives of radiometric isotopes
Uses the decay of radioactive isotopes to determine the age of the rocks or fossils
Based on the rate of decay, or half-life of the isotope
Unstable atom that decay into more stable atoms as time goes on
Time it takes for half of a radioactive isotope to decay
Geologic Time Scale
Putting together and looking at life on Earth by chapters
Large chunk of time
What are the three groups of tetrapods?
Cite three ways of distinguishing mammal fossils from the other two groups of tetrapods.
-One long jaw bone
-3 bones in inner ear
The super continent
The movement of Earth's continents on great plates that float on the hot, underlying mantle
Plates move a few centimeters each year. Big things happen when the plates collide (mountains)
Loss of large numbers of species in a short period
Have resulted from global environmental changes that have caused the rate of extinction to increase dramatically
What causes the Permian mass extinction?
The continents coming together (Pangea collision)
This lead to major methane release
What are adaptive radiations?
Periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological niches
When does adaptive radiation occur?
-After mass extinctions
-After major evolutionary innovations
When was Earth formed?
4.6 billion years ago
When did life on Earth emerge?
3.8 billion years ago
When did oxygen begin to accumulate in Earth's atmosphere as a result of photosynthesis?
2.7 billion years ago
When did eukaryotes appear on Earth?
2.1 billion years ago
When did multicellular eukaryotes evolve?
1.2 billion years ago
When did the colonization of land occur?
500 million years ago
The current theory of the origin of life suggests a sequence of four main stages. What are they?
1. Abiotic (nonliving) synthesis of small organic molecules/monomers
2. The joining of these small molecules into macromolecules (Polymer Formation)
3. The packaging of these molecules into protocells
4. The origin of self-replicating molecules that made inheritance possible
Oparin and Haldane
Hypothesized that the early atmosphere could have formed organic compounds from which life arose
Hypothesized that the early atmosphere was a reducing environment. This means electrons were being added. Lots of molecules present were able to donate molecules, not steal. Oxygen steals electrons.
What was the early atmosphere made of?
water vapor, nitrogen, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide.
Energy could've come from UV radiation and/or lightning
What was the early atmosphere lacking?
It is a byproduct of photosynthesis and we don't think that photosynthesis was present yet.
Miller and Urey
Tested Oparin and Haldane's hypothesis and produced a variety of amino acids
Their experiments show that the abiotic synthesis of organic molecules is possible under various assumptions about the composition of the early atmosphere
In the Miller and Urey experiments, what was collected in the sample for chemical analysis? What was concluded from the results of this experiment?
First evidence of an organic compound forming spontaneously with no living things on Earth
What are protocells? What properties of life do they demonstrate?
The first theoretical cell-like structure
Would have covering to separate interior from exterior and abilities to resemble a living thing
RNAs that act as a catalyst
Explain the evidence for an early "RNA world".
RNA requires way less to work
We have built RNA nucleotides under abiotic conditions
It is hypothesized that self-replicating RNA, not DNA, was the first genetic material
Proposes that mitochondria and plastids (chloroplasts) were formerly small prokaryotes that began living with larger cells
What is the evidence for the endosymbiotic hypothesis?
-Both organelles have enzymes and transport systems homologous to those found in the plasma membranes of living prokaryotes
-Both replicate by a splitting process similar to prokaryotes
-Both contain a single, circular DNA molecule, not associated with histone proteins
-Both have their own ribosomes, which can translate their DNA into proteins
What are the three domains?
Genomes of prokaryotes vs eukaryotes
Do prokaryotes have a plasma membrane?
Where is the genome located in a prokaryote?
What three shapes of prokaryotes are most common?
1. Coccus (sphere)
2. Bacillus (rod)
3. Spirillum (spiral)
What is the composition of the typical bacterial cell wall?
What is peptidoglycan?
A network of modified sugars cross linked by polypeptides
What material comprises the cell wall of plants?
What material comprises the cell wall of fungi?
What material comprises the cell wall of arcahaeans?
Lack peptidoglycan but contain proteins and carbohydrates
Bacteria have simpler walls with a large amount of peptidoglycan
Bacteria have less peptidoglycan and an outer membrane that can be toxic
-The kind that can cause problems!!!!
What is a bacterial capsule? What function can it serve?
Sticky layer of polysaccharide or protein that can help cell adherence and/or evasion of a host's immune system
Used for sticking and protection
*Gram negatives often have this feature
What is pili used for?
Sticky and conjugation
What structure makes movement of bacteria possible?
Hairlike appendages that help cells adhere to other cells or to a substrate (like pili)
Appendage that facilitates conjugation
How do prokaryotes reproduce?
Through an asexual process called binary fission
-Prokaryotes have short generation times
Small, circular, self-replicating pieces of DNA
Many prokaryotes are capable of directional movement. What is this called?
Go towards a stimulus
When prokaryotic cells take up and incorporate foreign DNA from the surrounding environment
The movement of genes between prokaryotic cells by bacteriophages
A process by which genetic material is transferred directly between prokaryotic cells
DNA transfer is one way
Doesn't create offspring, is just an exchange of genes
Usually a plasmid is what is being exchanged
Do bacteria and archaea have a nuclear envelope?
What are the different types of archaea?
Either tolerate or require a highly saline environment
Thrive in very hot environments
Strict anaerobes that produce methane as a waste product
-Live inside other creatures (ex: cow stomachs)
Break down dead organisms and waste products thereby unlocking supplies of carbon, nitrogen, and other elements
An ecological relationship in which two species link in close contract with each other
The larger organism in the symbiotic relationship
The smaller organism in the symbiotic relationship
An ecological relationship interaction between two species in which both benefit
An ecological relationship in which one species benefits while the other is not harmed or helped in any significant way
An interaction in which a parasite eats the cells contents, tissues, or body fluids of its host
Parasites that cause disease
Cannot grow without oxygen because they need oxygen for cellular respiration
Poisoned by oxygen
Many live exclusively by fermentation
Use oxygen if it is available but also carry out fermentation
The process of changing free nitrogen into a usable form of nitrogen
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