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172 Cards in this Set
- Front
- Back
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define stromatolites
from the Greek stroma, bed, and lithos rock |
rocklike structures, composed of many layers of bacteria and sediment dating from 3.5 billion years ago
fossil record indicates that lawns of prokaryotes covered every wet, sunlit surface on the planet |
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who first released oxygen in the air
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thick mats of photosynthetic prokaryotes that dominated a shoreline
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when and how did planet earth form
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4.6 billion years ago as a cold world
-heat generated by meteorites, radioactive decay, and compaction by gravity thawed EArth -turned it into molten mass that sorted into lays of varying densities -most nickel and iron sunk to center forming a core -less dense material became concentrated in mantle surrounding core -least dense settled on surface |
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first atmospehere was probably composed of mostly what gas?
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hot hydrogen gas
h2 and since gravity was not strong enough to hold such small molecules, h2 excaped into space |
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volcanones and other vents beleched waht gases?
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carbon dioxide, co2
nitrogen, n2 hydrogen sulfide h2s water vapor 239 methane ch4 ammonia nh3 |
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the first seas were created by---
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torrential rains that began when planet had cooled enough for water vapor in the atrmopshere to condnse
lightnihg, volcanic activity, and uv radiation was much more intense |
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fossil evidence indicates the presence of primitive cellular organisms within a few hundred million years after earth's crust solidified
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early organisms were primitive prokaryotes and the fossil record supports this idea
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photosyntheic prokaryotes lived 3.5 billion years ago is strong support for life in a simpler form was unable to make own food
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photosynthesis is not a simple metaolic process, so other organisms must have existed as early as 3.9 billion years ago
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many people thought that life came from nonliving matter. but what did experiments prove?
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relatively large organisms cannot arise spontaneously from nonliving matter
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who confirmed that all life arised by reproduction of preexisting life?
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louis pasteur
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what two important properties define life?
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agggregates of molecules w/ a particular arrangement that made simple metabolism and self replication possible
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lbecause iving organisms consist of polymers froemed from small organic molecules (monomers)---
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synthesis and accumulation of small organic molecules must have been the earliest chemical stage preceding the origin of life
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where did these organic molecules come from?
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some scientists propose that metorites and coments seeded Earth with organic molecules
but the prevailing opininon is that most of hte first organic molecules arose form inorganic materials on teh early planet |
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the first cells were preceded by the abiotic formation of small ____________ molecules, which joined to form _____________.
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organic
polymers |
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What did Stanley Miller do?
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he was the first t o show that amino acides and other orrganic molecules could have been generated on a lifeless earth
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why doesn't present day condditions on eartth not allow the spontaneous synthesis of organic compounds?
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the earth's atmosphere is rich in o2 which is corrosive
it's a strong oxidizing agent that tends to disrupt chemical bonds by extracting electrons from them. |
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before the early prokaryotes added o92 to the air, what was th atmophere like?
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it had a reducing (electron adding) atmosphere instead of an oxidizing one.
it oculd have caused simple molcules to combine, forming more complex ones. |
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but doens't construction of complex molecules from simple ones require energy?
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there was abundant energy sources in the early enviroment of the earth.
-uv radition reach Earth's surface w/ greater intensity since now we have an ozone layer (03 which screens those uv rays out) |
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discuss how miller went about his exp
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-a flask of warm water represented the primeval sea
-the atmopshere consited of water vapor, h2, ch4, and nh3 -electrodes discharged sparks into the gas mixture to mimc lightning -below the spark chamber, a glass jacket called a condenser surrounded the apparatus -filled with cold water, the condenser coeled and condencsed the water vapor in the gas mixture, causingn "rain" along with any dissolved compounds to fall back into the miniature sea -as material circulated through the apparatus, the solution in the flask changed color |
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what did miller find in this solution?
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a variety of orgnic compounds, inc some amino acides that make up the proteins of organisms
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how might have the first polymers have formed?
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hot rocks or clay
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after small organic molecles formed, teh second major chemical step before life arose was what?
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polymerization, the formation of organic polymers from monomers
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the polymers of lif eare synthesized how?
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dehydration reactions that release a water molecule for each monomer added to the chain
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in the living cell what catalzyes these dehydration reactions?
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specific enzymes
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how can polymerization occur in lab situations w/o enzymes?
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when dilute solutions of organic monoers are dripped onto hot sand, clay, or rock. the heat vaporizes the water in the solutions and concentrates the monomers on the underlying usbstance.
-some of the monomers then spontaneously bond together in chains, forming polymers |
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who succeeding in making polypeptides
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sidney fox
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raindrops or waves may have spashed dilute solutions of organic monomers onto fresh lava or hot rocks, then what occured?
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it rinsed polypeptides and other polymer sback into the sea
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clay surfaces may ahve been important as polymerization sites
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cool clay surfaces concentrate amino acides and other organic monomers from dilute solutions bc the monomers bind to electrically charged sites on the clay particles.
binding sites could have brought monomers close together |
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what atoms does caly contain that can act as catalysts?
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metal atoms: iron and zinc
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b4 enzymes existed, clays with metal atoms might have catalyzed the ________________ reactions that joined organic monomers, forming ______________.
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deydydration
polymers |
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the first genetic materail and enzymes may have been
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RNA
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the formation of polymefrs on early EARth set teh stage for the orgin of early forms of life. but which polyers were most important?
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an essential difference between life and nonlife is replication. nucleic acids are the biological polymers that replicate and store genetic info, they were most likely the essential first polymers.
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describe today's cells
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they store genetic info as dna, transcribe the info into rna, then translate rna messages into specific enzymes and other protiens
dna -> rna -> protiens |
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one hypoteisis is that the first genes were shrot strands of RNA that replicated themselves w/o the assistance of proteins, perhaps on clay surfaces.
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lab experiemnts suppor thtis idea
-short molecules can assemble spontaneously from nucleotide monomers in the absence of enzymes -when RNA is added to a solution containing a supply of RNA monomers, new RNA moelcules complementary to parts of the strating RNA sometimes assemble |
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scenario on early EArth of formation of RNA
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1. RNA monomers -nucleotides- spontaneously join, forming the first small "genes"
2. then an RNA chain complementary to one of these genes assemble if the new chain serves as a template for another round of RNA assembly, the result is a replica of the original gene |
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who succeeding in making polypeptides
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sidney fox
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raindrops or waves may have spashed dilute solutions of organic monomers onto fresh lava or hot rocks, then what occured?
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it rinsed polypeptides and other polymer sback into the sea
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clay surfaces may ahve been important as polymerization sites
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cool clay surfaces concentrate amino acides and other organic monomers from dilute solutions bc the monomers bind to electrically charged sites on the clay particles.
binding sites could have brought monomers close together |
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what atoms does caly contain that can act as catalysts?
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metal atoms: iron and zinc
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b4 enzymes existed, clays with metal atoms might have catalyzed the ________________ reactions that joined organic monomers, forming ______________.
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deydydration
polymers |
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the first genetic materail and enzymes may have been
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RNA
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the formation of polymefrs on early EARth set teh stage for the orgin of early forms of life. but which polyers were most important?
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an essential difference between life and nonlife is replication. nucleic acids are the biological polymers that replicate and store genetic info, they were most likely the essential first polymers.
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describe today's cells
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they store genetic info as dna, transcribe the info into rna, then translate rna messages into specific enzymes and other protiens
dna -> rna -> protiens |
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one hypoteisis is that the first genes were shrot strands of RNA that replicated themselves w/o the assistance of proteins, perhaps on clay surfaces.
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lab experiemnts suppor thtis idea
-short molecules can assemble spontaneously from nucleotide monomers in the absence of enzymes -when RNA is added to a solution containing a supply of RNA monomers, new RNA moelcules complementary to parts of the strating RNA sometimes assemble |
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scenario on early EArth of formation of RNA
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1. RNA monomers -nucleotides- spontaneously join, forming the first small "genes"
2. then an RNA chain complementary to one of these genes assemble if the new chain serves as a template for another round of RNA assembly, the result is a replica of the original gene |
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thisi RNA replication process might have been aided by RNA molecules that acted as catalysts. what are they called?
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ribozymes
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define ribozymes
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RNAs that can carry out a number of enzyme like catalytic functions
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define RNA world
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hypothetical period in the evolution of life when RNA served as rudimentary genes and the sole catalytic moleces
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the earliest form of molecular cooperation may have involved what?
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a primitive form of translation of simple RNA genes into polypeptides, tranlation that did nto use ribsomes or tRNA
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define protobiont
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isolation of a colelction of abiotically created molecules within a membrane
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how did protobionts form?
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spontanteously from abiotically produced organic compounds
-in the same way that small membrnae bounded droplets can dorm when lipoids are added to water -spheres are NOT alive,but display properties of living cells -slectiveley permeable memrane-like surface, can grow by absorbing molecules frmo their surroundings, divide when they reach a certain size, and swell or shrink osmotically when placed in solution sof different salt concentrations |
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protobionts could have come closer to eveolign in a Darwininan sense
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-cell link entities on early EArth might have contained some self replicating RNA molecules and RNA polypeptide co-ops
-naturaly selection would have begun to shape the properties of these protobionts -those that grew and replciated moe efficiently than others would have increased in number, passing their abilities on to subsequent generations |
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protobionts would have developed the ability to replicate and carry out esseentail chemical reactions- a primitive metabolism
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with thier assosicatons of moelcues now enclosed by membranes
-during this long beriod, protobionts would have developed into complex metabolic machines containing DNA and capable of efficietnly using a variety of raw materials for the environment |
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the earliest form of molecular cooperation may have involved what?
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a primitive form of translation of simple RNA genes into polypeptides, tranlation that did nto use ribsomes or tRNA
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define protobiont
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isolation of a colelction of abiotically created molecules within a membrane
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how did protobionts form?
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spontanteously from abiotically produced organic compounds
-in the same way that small membrnae bounded droplets can dorm when lipoids are added to water -spheres are NOT alive,but display properties of living cells -slectiveley permeable memrane-like surface, can grow by absorbing molecules frmo their surroundings, divide when they reach a certain size, and swell or shrink osmotically when placed in solution sof different salt concentrations |
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protobionts could have come closer to eveolign in a Darwininan sense
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-cell link entities on early EArth might have contained some self replicating RNA molecules and RNA polypeptide co-ops
-naturaly selection would have begun to shape the properties of these protobionts -those that grew and replciated moe efficiently than others would have increased in number, passing their abilities on to subsequent generations |
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protobionts would have developed the ability to replicate and carry out esseentail chemical reactions- a primitive metabolism
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with thier assosicatons of moelcues now enclosed by membranes
-during this long beriod, protobionts would have developed into complex metabolic machines containing DNA and capable of efficietnly using a variety of raw materials for the environment |
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what did hte early protobionts rely on?
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molecules present in the primitive soup of organi molecules surrounding them
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early protobionts were replaced by what?
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organisms that could produce their own needeed compounds
-used sunlight or energy rich molecules in the environmentn for energy -the diversification of these autotrophs encouraged hte emergence of organisms that could live on products the autotrophs excreted or on the autotrophs themselves |
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atomsphereic oxygen began to appear 2.7 years ago bc of waht?
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prokaryotic photosynthesis
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why was the enclosure of molecular cooperatives by membranes a key requirement for th eprocess of natural selcetion?
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segreation within membrane enclosed comparments allowed selection for the self replecating molecular systems that grew the fastest and passed their successful properties to the next generation
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why are prokaryotes so successful?
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they thrive in habitats too cold,ktoo hot, too salty, too acidic, or too alkaline for any eukaryote
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biologists are discovering that these organisms have an astonishing genetic diversity
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ex: comparing ribosomal RNA reveals that two strains of hte bacterial species E coli are genetically more diff than a human and a platypus
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define pathogens
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disease causing agents
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bacteria are mare beneficial
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we have bacteria in our intestines that provide us with important vitamins
bacteria in our mouth to help prevent harmful fungi from growing there prokaryotes decompose dead organisms they return vital chemical elements to the enviromnmen t that can be used by plants, which in turn feed animals |
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what would happen if prokaryotic decomopsers were to disappear?
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the chemical cycles that sustain life would halt, and all forms of eukaryotic life woudl be doomed
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why might two strains of e coli b e geentically more different than a human and a platypus?
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bacteria have been evolving and accumulating differences for billions of years; placental mammals and egg laying mammals diverge nly about 200 millino years ago
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what are two main branches of prokaryotic evoluation
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bacteria and archaea
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define peptidoglycan
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a polymer of sugars cross linked by short polypeptides
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differences between bacteria and archaea: rRNA sequences
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B: some unique to bacteria
A: soem unique to archaea; some match eukaryotic ones |
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differences between bacteria and archaea: RNA polymerase
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B: one kind; mall and simple
A: sevearl kinds; complex; similar toeukaryotic ones |
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differences between bacteria and archaea: introns
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B: absent
A: present in some genes |
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differences between bacteria and archaea: antibiotic sensitivity
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B: growth inhibited
a: growth not inhibited |
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differences between bacteria and archaea: peptidoglycan in cell wall
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B: present
A: absent |
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differences between bacteria and archaea: membrane lipids
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B: carbon chaisn unbranced
A: soem carbon chains branced |
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differences between bacteria and archaea: histones assosicated w/ DNA
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B. absent
a: present |
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define cocci
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spherical prokaryotic cells
occur in chains or clusters |
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define bacilli
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rod shaped prokaryotes
occur singly but some in pairs or chains |
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curved or spiral shaped cells
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comma shaped: VIBRIOS
helical shape and short: SPIRILLA helical shape and long: SPIROCHETES |
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what does the cell wall do?
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it mainstains cell shpae, provides physical protetion, and prevents the cell form bursing in a hypotonic envirionment.
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what heppsn in hypertonic environments?
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most prokaryotes lose weater and shrink away form their wall. severe water loss inhibits reproduction, whcih expains why salt can be used to preserve ceratin foods
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the cell walls of bacteria fall into two general tiypes which scienetist can identify with a tenchinque called what?
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gram stain
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describe gram positive bacteria?
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they have simpler walls with a relatively think layer of peptidoglycan.
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describe gram negative walls
(more threatening) |
they have less peptidoglycan and are more complex, with an outer membrane that contains lipids bonded to carbs which are often toxic. the membrane also protecrts them against th ebody's defenses and impededs the entry of antibiotic drugs.
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the effectiveness of many antibiotics is due to what?
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their inhibitiion of cross linking in the peptidoglycan cell wall.
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the cell wall of many prokaryotes is covered by waht?
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a capsule, a sticky layer of polysacchariddes or protein
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what does the capsule do?
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it enables prokaryotes to adhere to their substrate or to other individuals in a colony
and they also sheild pathogenic prokaryotews from attacks by their host's immune system |
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define pili
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hairlike apendages
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what can pili do?
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stick to their substrate or other seurfaces
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many bacteria are equipped with what kind of locomotion?
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flagella, enabling them to move about
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in response to chemical or physcial signals in their environment, prokaryotes can move twoard nutrietss or other membrers of their species or away from a toxic substance
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flagella may be scattered over the entire cell surface or concentrated at one or both ends of the cell
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how is the flagellum different in struture from eukaryotic cells?
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its a naked protein structure that lacks microtubules. it is attached to the cell surface by a system of rotating rings anchored in the plasma membrane and cell wall
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how do prokaryotes reproduce?
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divide by binary fission, a single cell becomes 2 cells, which ten become 4, 8, 16 and so on
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how long does it take for prokaryotes to reproduce?
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1-3 hours, some 20 min
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what would happen if reproduction continued unchecked, and explain why this can't happen
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prokaryotic reproduction would give rise to a colony outweiging Earth in three days
in reality, prokaryotic reproduction is limited, cells evetually exhuast their nutrient supply, poison themselves with metabolic watstes, or are consumed by other organisms |
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who are prokaryotes competition?
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microorganisms which produce antibiotic chemicals that slow prokaryotic reproduction
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define endospore
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think, protective coat, dehydrates and becomes dormant. it can survive all sorts of trauma, inc extreme heat or cold. when the endospore receives cues that the environmental conditions have improved, it absorbs water and resumes groth
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why do mi robiologists autoclave lab instruments and glassware rather than simply boiling them?
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to kil bacterial endospores, which can survive boiling water.
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when classifying diversese organisms, biologists use the phrase mode of unturtion to describe how an organism obtains two man reasources, waht are they?
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carbon for synthesizing organic compounds
energy |
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define autotrophs
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self feeders, making own organic coompounds from inorganic sources
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hwo do dutotrophs obstain tiehr carbon atoms and energy?
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carbon atoms from co2
energy from sunlight or inorganic chemicals |
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autotrophs that harness sunlight for energy and use co2 for carbon do so by photosytheiss; what are these autotrophs called?
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pohtoautotrophs
energy source: sunlight carbon source co2 |
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autotrophic organisms atht obtain enrgy form inorganic chemicals insteaed of sunlight are called what?
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chemoautotrophs
energy source: inorganic chemcials carob source: co2 |
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define heterotrophs
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feeders that obtain their carbon atoms from organic compounds
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define photoheterotrophs
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energy source: sunlight
carbon source: organic compounds |
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define chemoheterotrophs
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energy source: organic compounds
carbon source: organic compounds |
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prokaryotes once were thought of as single celled individualists but now---
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biologists recognized that cyanobacterium has genes for photosynthesis and for nitrogen fixation
but bc the o2 produced by photosynthesis inactivates nitrogen fixing enzymes, one cell cannot carry out both processes |
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define biofilms
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surface caoting coloines
in some prokaryotes metabolic cooperation occurs in biofilms |
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describe these biofilms
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cells in a coly secrete signaling moelcules that recruit nearby cells. once the colon yccoems large, the cells prouce proteins that adhere them to the substrate and to each other. channels in the bifilm allow nutrients to reach cells in the interior and wastes to be expelled
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explain why a filament of Anabaena can be described as one of life's most self sufficientn organisms
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that filament procudes its food by photosynthesis and has specialized cellsthat supply it w/ the nitrogen needed for protein synthesis.
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define extreme halophiles
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archaea thrive in very salty places
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define thermophiles
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a crop of archae that trhrive in very hot water or deep ocean vents
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define methanogens
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they live in anaerobic environments and give off methane as a waste product
inhabit digestive tracts of animals |
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though archae are seen as extremophiles they cactually
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live in more moderate environments, like oceans
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define proteobacteria
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clade of gramnegative bacteria
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define chlamydia
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a group of bacteria that includes a parasite that cuases a common sexually transmitted disease
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define spirochete
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a group of helical bacteria that spiral through environment by means of rotating, internal filaments. notorious pathogens, syphilis and lyme disease
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define gram positive bacteria
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bacteria with a cell wall that is structurally less complex and contains more peptidoglycan than that of gram negative bacteria. less toxic than gram negative bacteria
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define cyanobacteria
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only prokaryotes w/ plant like, oxygen gernating photosynthesis
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which group of baceria use h2s as an electron source in its photosynthetic production of organic molecules
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sulfer bacteria of the subgroup gamma protebacteria
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define exotoxins
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secreted by bacterial cells and include some posions
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define endotoxins
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components of th eouter membrane of gram negative bacteria. they induce the same symptoms: fever, aches, and drop in blood pressure.
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lyme disease
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a debilitating human disease caused by teh abcterium Borrelia burgdorferi; characterized at first by red rash at the site of a tick bite and if not treated, by heart disae, arthritis, and nervouse disorders
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contranst exotoxins w/ endotoxins
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exotoxins: poisons secreted by pathogenic bacteria
endotoxins: compontents of the cell walls of phathogenic bacteria |
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why is bacillus anthracis an effective bioweapon
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it is easy to obtain, easy to grow in teh lab, and forms potentially deadly endospores that resist destruction and can be easily dispersed.
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prokaryotes help recycle chemicals and clean up environment
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cyanobacteria
-contribute to aquatic food cains -release oxygen -convert nitrogen to nitrogen compounds that plants can take up and use |
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porkayrotes decompose organic wastes and dead organisms to inorgani chemicals
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if it were nto for htem, carbon, nitrogen, and other elements essential to life would be locked in the organic molecules of cropses and waste products
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define bioremediation
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the use of organims to clean up pollution
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eukaryotic cells arose through which two processes?
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membrane infolding and endosymbiosis
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define membrane infolding
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the eukaryotic cell's endomembrane system, all the membrane enclosed organelles except mitochondria and chloroplasts- evolved form infward folds pof the plasma membrane of a prokaryotic cell
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define symbiosis
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a closer association between organism of two r more speciesk
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the ancestors of mitochonderia may have been heterotrophic prokaryotes that were aboe to use o2 and relase large amounts of energy from organic molecules by cellular respration
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an acestral host cell may have ingested some of these aerobic cells and pakaged them in a vacuole. some of th cell smight have remained alive and coninuted to perform repstion in the host cell
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photosyntheic prokaryotes acestral to chloropasts may have come ot live inside a larger host cell
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mitochondira envolved first since apll eukaryotes have mitochondira but only some have chloroplasts
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how is this symbiosis beneficial
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the engulfed cel3ls may have grown dependent on the host cell for molecules and oinorganic ions needed to carry out biochemical activites. the host cell may have derived increaseing proportions of its ATP and organic molcules form th eengulfed ce3lls
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how are present day mitochondria and chloropasts similar to prokaryotic cells?
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both types of organelles contain small amoutns of DNA, RNA, nad ribosomes, all of which resemble their ocunterparts in prokaryotes more than those in eukaryotes.
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chrlorplast and mitochondria transcaribe and tralste their DNA into polypeptides, contributing to some of their own enzymes.
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they also replicate their own DNA and reproduce by a process similar to the binary fission of prokayotes
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define protists
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a diverse collection of mostly unicellular eukaryotes
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define algae
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protists that synthesize their food by photosynthesis
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definen protozoans
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heterotrophic, eating bacteria and othe rprotists.
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protists are found where?
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usually moist environments
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as eukaryotes, protistsa re more complicated than any prokaryotes
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htier cells have a membrane-enclosed nucleus w/ multiple chromosomes
and other organells the flagella and cilia of protistan cells have a 9 + 2 pattern of microtubules |
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what are characteristics of diplomonads
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have two nuclei and multiple flagella
their fmodified mitochondria have no DNA or electron transport chain anaerobic common one is found in the intestions of mammls, picked up by drinking water contaminated w/ feces conatin the parasite |
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characteristics of euglenozons
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clade tha tincludes hterotrophs, photosynthetic autotrohps, and pathogenic parasites
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how do the nutritional modes of diplomonads and euglenozoans differ?
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d: anaerobic heterotrophs
e: all types of nutritial modes |
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characteristics of alveolates
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sacs (alveoli) beneath the plasma membrane and include dinoflagellates, apicomplexans, and ciliates
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what does the alveoli do?
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help stablize the cell surafce or regulate water and ion content
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dinoflagellates
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common componets of marine and freswater phytoplankton
-reside iwithin coral animals, providing much of the food for coral reef communities others are heterotrophic -eadch species has a characteristtic shape reinforced by plates made of cellulose RED TIDE |
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apicomplexans
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prarasites of animals
infectious cell of these parasites contains a complex of organells specilized for penetrating host cells causes maliria, feeding and destroying red blood cells |
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ciliates
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large, varied gropu of aleolates, named for their use of cilia to move and feed
freeliving two types of nuclei: a singlek, large macronucleus, which controls everyday activies and muliple tiny micronuclei, which function in sexual reproduction |
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stramenopiles are named for
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their hairy flagella and include water molds, idatoms, and brown algae
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define water molds
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fungus-like protist that decompose dead plants and animas in freshesater habitats
-they grow on the skin or gills of fish |
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define diatoms
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unicellular, photostynthetic algae with a unique, glassy cell wall containing SILICA, the mineral used to make glass
-cell wall consists of two halves that fit together like the bottom and lid of a shoe box -both freshwater and marine environments are rich in diatoms, and th eorganic molecules these microscopic algae produce are a key source of food in all aquatic environments |
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diatoms store their food reserves in waht form?
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form of an oil, which provides buoyancy, keeping diatoms floating nearr the survace in teh snlight.
massoive accumulations make up thick sediments known as DIATOMACEOUS EARTH, which is mined for use as both a filterin gmedium and a gridnding and polishing agent |
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define brown algae
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largest and most complex algae
-multicellular and marine -seaweeds sometimes used in soups red alga are used to war sushi |
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define kelp
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underwater bed of bwon algae
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which strameopiles are not photosyntheic
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water moles and downy mildews
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amoebozons
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have pseudopodia (lobe shaped) and include amoebas and slime molds
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amoebas move and feed by means of
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pseudopodia which are temporary extension of the cell
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define plasmodial slmie mold
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yello, brancing growth
portists that are common where there is moist, decaying organic matter NOT multicellular |
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define plasmodim
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conatian many nuclei within one mass of cytoplasm undivided by plasma membranes
it extends pseudopodia through soil and rotting logs, engulfing food by phagocytosis as it grows |
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what happens when food and water are in short supply, the plasmodium
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stops growing and differentiates into reproductive structures that produce spores which relase haploiecells that fuse to form a zygote
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cellular slime olds
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exists as solitary amoeboid cells.
-small, dark rods around the ameoboid cells are BACTERIA; the bateria inside th cells are being digested in food vaculouses |
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what happens when the food is in short supply, the amoeboid cells
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swarm toegether, forming a slug-like aggregate that wanders around
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contranst the plasmodium of a plsmodial slime mole with teh slug-like stage of a cellular slime molde
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a plasmodium is not multicellular, but is one cytoplasmic mass with many nuclei; the slug-like sgae of a cellular slime mole consists of many cells
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secondary endosymbiosis of red alga led to
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alveolates and stramenopiles
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red algae
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their red color comes form an accessory pigment that masks the green of chlorophyll
-soft bodied, some have cell walls, encrused with hard, choalky deposits encrused species are common on croral reefs and their hard parts are imporant in reef building |
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green alagae
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named for their grass green chloroplasts
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alternation of genreatiosn
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multicellular diploid form algernates with amulticellular haploid form.
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gameotophyes
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multicellular haploid forms
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sprophyte
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diploid gernation that features a multicellular diploid form
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what ere teh probable origins of hte chloropasts of green, red, and brown algae
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a cyanobacterial endosymbiont in both green and red algae, a red algal
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