LIFE 121 CH 24
Terms in this set (105)
Our planet first formed _____ years ago
The origin of life on earth dates back to fossils that are _____ years old
What are prokaryotes?
informal term for single-celled organisms in domains Bacteria and Archaea
Eukaryotes appeared _____ years ago
What are the four stages that chemical and physical processes could have produced simple cells?
1. Abiotic synthesis of small organic molecules
2. Joining of these small molecules into macromolecules
3. Packaging of these molecules into protocells
4. Origin of self-replicating molecules that eventually made inheritance possible
What does reducing mean?
What does oxidizing mean?
All organisms must be able to carry out what?
reproduction and energy processing (metabolism)
What are vesicles?
fluid filled compartments enclosed by a membrane like structure
The first genetic material was most likely _______, not _______
RNA, not DNA
What are RNA catalysts called?
Unlike double-stranded DNA, which takes the form of a uniform helix, single-stranded RNA molecules...
assume variety of specific three-dimensional shapes mandated by their nucleotide sequences
Many of the oldest fossils are of ___________________
What are stromatolites?
layered rocks that form from activities of certain prokaryotes
The earliest stromatolites date back to _____ years ago
3.5 billion years ago
By _____ years ago, stromatolites with two distinctly different morphologies had appeared
3.1 billion years ago
By _____ years ago, stromatolites occurred in salty lakes as well as marine environments
2.8 billion years ago
What organism is one of the most important group of photosynthetic organisms alive today?
Most prokaryotes are unicellular/multicellular?
unicellular, although the cells of some species remain attached to each other after cell division
What is the typical diameter of prokaryotes?
What are the most common shapes of prokaryotes?
spherical, rod shaped, spiral
What is a key feature of nearly all prokaryotic cells?
the cell wall
What does the cell wall do?
maintains cell shape, protects cell, prevents it from bursting in hypotonic environment
In a hypertonic environment, most prokaryotes....
lose water and shrink away from their wall (plasmolyze)
Why can salt be used to preserve foods?
it causes food-spoiling prokaryotes to lose water, preventing them from rapidly multiplying
How do the cell walls of prokaryotes differ in structure from those of eukaryotes?
Prokaryote cell walls have peptidoglycan, eukaryotic cell walls have cellulose or chitin
What is peptidoglycan?
polymer composed of modified sugars cross-linked by short polypeptides
The walls in gram-positive bacteria have...
simple walls composed of thick layer of peptidoglycan
The walls in gram-negative bacteria have....
-less peptidoglycan and are structurally more complex
-outer membrane that contains lipopolysaccharides
The lipid portions of the lipopolysaccharides in the walls of many gram-negative bacteria are...
toxic, causing fever or shock
Which are more resistant to antibiotics, gram-negative or gram positive bacteria?
gram-negative, because outer membrane impedes entry of drugs
The cell wall of many prokaryotes is surrounded by a....
sticky layer of polysaccharide or protein, called a capsule if it's dense and well defined or a slime layer if it is not well organized
What are endospores?
When do endospores develop?
when they lack water or essential nutrients
What are fimbriae?
What are pili?
appendages that pull two cells together prior to DNA transfer from one cell to the other
What is taxis?
directed movement toward or away from a stimulus
How do prokaryotic flagella differ from eukaryotic flagella?
they're one tenth width and are not covered by an extension of plasma membrane, molecular composition, mechanism of propulsion
What is an exaptation?
process in which structures originally adapted for one purpose take on new functions through descent with modification
What shape are prokaryotic chromosomes?
What shape are eukaryotic chromosomes?
Who lacks a nucleus, prokaryotes or eukaryotes?
Where are prokaryotes chromosome located?
nuclei, region of cytoplasm not enclosed by a membrane
What are plansmids?
rings of independently replicating DNA molecules
What are phototrophs?
organisms that obtain energy from light
What are chemotrophs?
organisms that obtain energy from chemicals
What are autotrophs?
organisms that need only CO2 or related compounds as carbon source
What are heterotrophs?
require at least one organic nutrient to make other organic compounds
What are obligate aerobes?
must use O2 for cellular respiration and can't grow without it
What are obligate anaerobes?
poisoned by O2
What is anaerobic respiration?
substances other than O2 accept electrons at the downhill end of electron transport chains
What are facultative anaerobes?
use O2 if it's present but can also carry out fermentation or anaerobic respiration in anaerobic environment
What element is essential for the production of amino acids and nuclei acids in all organisms?
What is nitrogen fixation?
when atmospheric nitrogen is converted to ammonia
What do heterocyst carry out?
carry out only nitrogen fixation
What are biofilms?
surface coating colonies
What is binary fission?
a single prokaryotic cell divides into 2 cells, which then divide into 4,8,16, and so on
What are three key features in the biology of prokaryotic species?
1. they are small
2. they reproduce by binary fission
3. they often have short generation times
What are the three factors that give rise to high levels of genetic diversity in prokaryotes?
1. rapid reproduction
3. genetic recombination
What is genetic recombination?
the combining of DNA from two sources
What three mechanisms bring together prokaryotic DNA from different individuals (different cells)?
transformation, transduction, conjugation
What is horizontal gene transfer?
when the movement of genes from one organism to another by different species
In transformation, what happens?
the genotype and possibly phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings
In transduction, what happens?
phages carry prokaryotic genes from one host cell to another
In conjugation, what happens?
DNA is transferred between two prokaryotic cells (usually of same species) that are temporarily joined
What does the F factor do?
gives the ability to form pili and donate DNA during conjugation
The F factor can exist as either a ______ or ________
plasmid or as a segment of DNA within bacterial chromosome
The F factor in its plasmid form is called _________
the F plasmid
Cells containing the F plasmid, designated F+ cells, function as what?
DNA donors during conjugation
Cells lacking the F facto, designated F-, function as what?
DNA recipients during conjugation
What is a recombinant cell?
its chromosome contains DNA derived from two different cells
What are R plasmids?
plasmids that carry resistance genes
What are the two lineages that prokaryotes have evolved in?
bacteria and archaea
What are extremophiles?
lovers of extreme conditions
What are extreme halophiles?
live in highly saline environments
What are extreme thermophiles?
thrive in very hot environments
What is symbiosis?
ecological relationship in which two species live in close contact with each other
In a symbiotic relationship, the larger organisms is known as the ______ and the smaller is known as the ________
What is mutualism?
an ecological interaction between two species in which both benefit
What is commensalism?
ecological relationship in which one species benefits while the other isn't harmed or helped
What is parasitism?
interaction in which parasite eats cell contents, tissues, or body fluids of its host
Do parasites kill their host?
they harm but usually don't kill their host, at least not immediately
Parasites that cause diseases are known as _________________
All the pathogenic prokaryotes known to date are ___________
What are exotoxins?
proteins secreted by certain bacteria and other organisms
What are endotoxins?
lipopolysaccharide components of outer membrane of gram-negative bacteria
In contrast to exotoxins, endotoxins are released when?
only when bacteria die and their cell walls break down
What is bioremediation?
use of organisms to remove pollutants from soil, air, or water
Which of the following steps has not yet been accomplished by scientists studying the origin of life?
a. synthesis of small RNA polymers by ribozymes
b. abiotic synthesis of polypeptides
c. formation of molecular aggregates with selectively permeable membranes
d. formation of protocells that use DNA to direct polymerization of amino acids
a. more than 2.8 billion years old have not been discovered
b. formed around deep-sea vents
c. resemble structures formed by bacterial communities that are found today in some shallow marine bays
d. provide evidence that photosynthesis was occuring in the oceans by 2.5 billion years ago
Genetic variation in bacterial populations cannot result from
a. light as an energy source and methane as a carbon source
b. light as an energy source and CO2 as a carbon source
c. H2S as an energy source and CO2 as a carbon source
d. CO2 as both an energy source and a carbon source
Which of the following statements is not true?
a. archaea and bacteria have different membrane lipids
b. the cell walls of archaea lack peptidoglycan
c. only bacteria have histones associated with DNA
d. only some archaea use CO2 to oxidize H2, releasing methane
Bacteria participate in many ecological interactions. Which of the following bacterial roles typically does not involve symbiosis?
a. living as commensalists on the skin of humans
b. providing bioluminescence in fish
c. digesting food as mutualists in animal intestines
d. decomposing dead organisms and organic wastes
Plantlike photosynthesis that releases O2 occurs in
d. chemoautotrophic bacteria
What are the subgroups of proteobacteria?
alpha, beta, gamma, delta, epsilon
Proteobacteria include what
photoautotrophs, chemoautotophs, heterotrophs
Where can chlamydias survive?
only within animal cells
Are chlamydias gram negative/positive?
What is unusual about chlamydias gram negative walls?
they lack peptidoglycan
Are spirochetes gram negative/positive?
Are spirochetes free livingo r parasites?
many are free living, but others are parasites
Are cyanobacteria gram negative/positive?
Are cyanobacteria photoautotrophs?
yes, they're the only prokaryotes with plantlike, oxygen generating photosynthesis
Most species in this subgroup are pathogenic to humans or other animals, which subgroup is this?
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