Life 121 Exam 2

when was the earth formed?

4\.6 billion years ago

what was earth like 4.6 billion years ago?

hot and not conducive to life

what was the sequence of events for the origin of earth?

* abiotic synthesis of small organic molecules
* formation of macromolecules
* packaging of molecules into protocells
* origin of self-replicating molecules

what element did earth’s early atmosphere not contain?

free O2

where were the first polymers produced?

on hot sand, clay, and rock surfaces

what is the iron-sulfur world theory?

the early life may have formed on iron sulfide minerals near deep sea hydrothermal vents

what are protocells?

a precursor of cells that require a localized environment separate from the surroundings where reproduction and energy processing occurs

what is a micelle protocell?

a monolayer protocell

what is a vesicle protocell?

a bilayer protocell

what are some characteristics of protocells?

* simple, imprecise reproduction
* exhibit some properties associated with life
* absorb particles
* simple metabolism
* excitability

where did protocells get rna from?

montmorillonite clay particles from the environment

what is the purpose of catalytic rna?

* acts as enzymes
* make copies of rna

rna can be…

* genetic material
* biological catalyst
* self-replicating

t/f prokaryotes were the first organisms to inhabit earth

true

when did prokaryotes emerge?

3\.5 - 3.8 billion years ago

about how long after prokaryotes did eukaryotes emerge?

1\.5 billion years after

which two domains include prokaryotes?

* bacteria
* archaea

what are some characteristics that bacteria share with eukaryotes?

* plasma membranes
* ribosomes
* common metabolic pathways
* dna replication, transcription and translation

what are some characteristics of bacteria that are different from eukarya?

* divide by binary fission
* genetic material organized differently (no nucleus)
* lack membrane enclosed organelles

t/f most prokaryotes are small and single celled

true

what are the shapes of prokaryotes?

* coccus


* rod
* spiral

what are the two types of bacterial cell walls in prokaryotes?

gram positive and gram negative

what do gram positive bacterial cell walls have?

a uniformly dense cell wall consisting primarily of peptidoglycan

what do gram negative bacterial cell walls have?

a very thin peptidoglycan layer and an outer membrane

what is the purpose of the capsule in prokaryotic cells?

* adhere to surfaces
* virulence factor

what is the purpose of the fimbriae in prokaryotic cells?

* adhere to substrates
* colony formation

what is the purpose of pilus in a prokaryotic cell?

allows for transfer of genetic material from one bacterium to another during conjugation

what is taxis in prokaryotes?

movement towards or away from a stimulus

what is the purpose of the flagellum in prokaryotes?

enables movement

what are the parts of the flagellum?

* filament
* hook
* motor

how is dna organized in prokaryotes?

in the nucleoid with circular chromosomes and plasmids

what are plasmids?

independently replicating dna molecules with few genes

what are the characteristics of the endospore in prokaryotes?

* found in some G+ bacteria
* resistant cell
* response to stress (lack of nutrients)
* contains genetic material
* resistant to heat, desiccation, freezing

what do prokaryotes use to reproduce?

binary fission

t/f prokaryotes have short generation times

true

what are the sources of genetic variation in prokaryotes?

* mutation
* genetic recombination
* horizontal gene transfer

what are the types of genetic recombination?

* transformation
* transduction
* conjugation

what is transformation?

* uptake of foreign dna from surroundings

what is tranduction?

phages carry dna from one cell to another cell

what is conjugation?

dna transferred from donor to recipient cell through pilus

what is the f factor in conjugation?

piece of dna that allows pili formation

t/f the f+ condition is transferable

true

what is an hfr cell and what does it do?

* high frequency of recombination cell
* a donor that allows the recipient cell to remain f- after recombination

what are r plasmids?

genes that code for enzymes that disrupt antibiotic efficacy

what are virulence plasmids?

cause of going from non pathogenic to pathogenic

what is hortizontal gene transfer?

genes are transferred between bacteria of same species or even different species

t/f gene transfer does not complicate phylogenetic relationships

false

what is the difference between aerobic and anaerobic respiration?

aerobic respiration uses oxygen as the final electron acceptor and anaerobic respiration does not

what is a facultative anaerobe?

an organism that can do either aerobic or anaerobic respiration

what are autotrophs?

can make their own CO2

what are heterotrophs?

have to take in CO2 from an outside source

what are photoautotrophs?

organisms that use light energy to produce organic compounds

what are the energy sources for prokaryotic nutrition?

* light
* chemicals

what is nitrogen fixation?

fixing of inert N2 into ammonia and other molecules

what is the purpose of denitrifiers?

use nitrate as an electron acceptor

what are heterocysts?

serve as nitrogen fixation sites when fixed nitrogen is limited

what is biofilm?

a sticky gel-like matrix that allows microbes to form communities

what cell type has a nuclear envelope?

eukarya

what cell type has membrane enclosed organelles?

eukarya

what cell type has peptidoglycan in cell wall?

bacteria

what cell types have circular chromosomes?

bacteria and archaea

what cell types have plasmids?

bacteria and archaea

what cell types have 70S ribosomes?

bacteria and archaea

what cell type has 80S ribosomes?

eukarya

what cell type can grow in temps above 100 degrees celcius?

archaea

what kinds of habitats do archaea live in?

extreme habitats and ocean depths

what are the four groups of archaea?

* korarchaeotes
* euryarchaeotes
* crenarchaeotes
* nanoarchaeotes

what are crenarchaeotes?

live in hot or acidic places

* thermophiles
* acidophiles

what are euryarchaeotes?

* halophiles
* salty environments, pink carotenoid pigments
* methanogens
* produce 80 - 90 of CH4 entering atomosphere

what are korarchaeotes?

found in hot springs in yellowstone

what are nanoarchaeotes?

parasites of crenarchaeotes that are found in hydrothermal vents and hot springs

what are the 5 types of bacteria?

* proteobacteria
* chlamydias
* spirochetes
* cyanobacteria
* gram-positive bacteria

what are the types of proteobacteria?

* alpha
* beta
* gamma
* delta
* epsilon

what are chlamydias?

* very small bacteria
* parasites
* G-, cocci

what are spirochetes?

* G-, motile, spiral shaped
* parasites
* free-living

what are gram positive bacteria?

very diverse subgroup of bacteria that have a dense peptidoglygan layer

what are cyanobacteria?

photosynthetic bacteria

what are some key organelles of eukaryotes?

* membrane-enclosed structures with specialized functions
* golgi apparatus
* endoplasmic reticulum
* mitochondrion
* chloroplast

what is the purpose of the golgi apparatus?

synthesis and secretion of cell products

what is the purpose of the endoplasmic reticulum?

membrane synthesis, metabolism

what is the purpose of the mitochondrion?

cellular respiration, ATP production

what is the purpose of the chloroplast?

photosynthetic organelle

what is an endosymbiont?

a cell that lives within another cell

t/f in eukaryotes, energy metabolism is largely the product of endosymbiosis

true

what is the endosymbiotic theory

a theory that suggests that mitochondria and chloroplasts in today’s eukaryotic cells were once separate prokaryotes

what is some evidence for the endosymbiotic theory?

* inner membranes have enzymes and transport systems homologous to prokaryote membranes
* mitochondria and chloroplasts have two membranes
* they have circular dna and ribosomes
* the grow and independently divide via binary fission

what are protists?

small, mostly unicellular eukaryotes

t/f protists are found in all 4 subgroups of eukaryotes

true

what did multicellularity result from?

changes in how existing genes are used

multicellularity arose in what eukaryotic lineages?

algae, plants, fungi and animals

from what did multicellularity arise in animals?

choanoflagellates

what are the 4 subgroups of eukaryotes?

* excavata
* SAR clade
* archaeplastida
* unikonta

what are the 3 types of excavata and what are its characteristics?

originally based on cytoskeletal morphology, modified mitochondria, marine, freshwater, and terrestrial

* diplomonads
* parabasalids
* euglenozoans

What are the subgroups of the SAR clade?

* stramenopiles
* alveolates
* rhizarians

what are stramenopiles and what are the types?

“hairy” flagellum, autotrophs and heterotrophs

* diatoms (unicellular)
* brown algae (all multicellular, largest and most complex algae)

what are the types of alveolates?

* dinoflagellates
* apicomplexans
* ciliates

what are characteristics and subgroups of rhizarians?

have amoebas

* forams
* cercozoans

what are the two subgroups of uniknonta?

* amoebozoans
* opisthokonts

what are the subgroups of opisthokonts?

* nucleariids
* fungi
* choanoflagellates
* animals

what are the subgroups of amoebozoans?

* gymnamoebas
* slime molds