Prokaryotes Are Classified As Belonging To Two Different Domains. What Are The Domains?

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Prokaryotes are classified as belonging to two different domains. What are the domains?


The two domains to which Prokaryotes belong are the Bacteria and Archaea domains.

Prokaryotes, which include bacteria and archaea, may be found almost everywhere – in every ecosystem, on every surface of our homes, and even within our bodies! Some live in extreme environments unsuitable for other animals, such as hot vents on the seafloor.

Prokaryotes can be difficult to discover, identify, and categorize since they are all around us. The prokaryotic species that we recognize today constitute only a tiny percentage of the total number of prokaryotic species thought to exist.

To discuss the search for prokaryotic species, we must first understand what they are. It may appear to be a simple question, but it’s a complicated and even contentious issue for a microbiologist.

Most scientists define a species as a group of organisms that can breed and produce fertile offspring, but this definition does not apply to prokaryotes. This definition makes sense for reproducing sexually, but it doesn’t work so well for things like bacteria. Bacteria make copies of themselves by reproducing asexually; they do not interbreed.

Bacteria and archaea are classified scientifically according to similarities in form, physiology, and genetics. Many organisms have traditional Linnean taxonomic categories such as genus and species. The issue of whether prokaryotes should be classified into species is still a point of contention among experts. The correct “species concept” for these creatures is yet to be determined.


Bacteria and Archaea
Prokaryotes are classified as belonging to two different domains. What are the domains?
Most recent ancestor of eukaryotes?
Archaea is more closely related to eukaryotes than bacteria because eukarya and archaea share dna
eukarya arose from archaes
differences between bacteria and archaea
archaea has several kingdoms and no known human parasites. known for living in extreme habitats which has to do with the bonding in their phospho lipids. archaea is mostly salt tolerant and heat tolerant
bacteria the domain live in more moderate habitats and are mostly known for their diseases
how do prokaryotes primarily reproduce?
binary fission (form of asexual reproduction) in which the daughter cells are identical to the parent cell
horizontal growth transfer
not necessarily a form of reproduction bc not creating a new individual. DNA transferred from one individual to the next and it only occurs in unicellular organisms (bacteria and archaea)
purpose of dormant stage
during dormancy, the prokaryote survives extreme conditions to grow and reproduce later
bacteria is able to survive harsh conditions as dormant akinetes or endospores
thick walled dormant cells specialized for survival produced by bacteria
A thick-walled protective spore that forms inside a bacterial cell and resists harsh conditions. it is a tough protein coat around the DNA and cytoplasm and they are released when the enclosing cell dies
Photo autotrophs
Use light as energy source and carbon dioxide gas as their carbon source
Chemo autotrophs
Use other compounds as their energy source and use carbon dioxide gas as their carbon source
Photo heterotrophs
obtain energy from sunlight but get their carbon atoms from organic compounds
Chemo heterotrophs
take in organic molecules for both energy and a supply of carbon
as source of atp
obligate aerobes
require O2 for cellular respiration
facultative aerobes
can live with or without oxygen
they can use oxygen in aerobic respiration or get energy from anaerobic fermentation or use chemical rxns to obtain energy
can use 02 or not depending on its availability
obligate anaerobes
organisms that cannot live where molecular oxygen is present
aerotolerant anaerobes
do not utilize oxygen but can survive and grow in its presence
these organisms obtain their energy by fermentation or anaerobic respiration
why might symbioses between bacteria and other organisms be common?
they might be common because they benefit noth organisms involved (mutualism)
many mutualistic bacteria live in symbioses with 2 or more other bacterial species that supply eachother with nutrients
bacteria are involved win many mutually beneficial symbiosis- provide eukaryotes with minerals
are bacteria normally harmful to us?
they are not usually harmful since they are an essential part of the human microbiome/biota
they promote absorption of nutrients and are involved with our immune system
however some bacteria are harmful because parasitic microbes causes disease symptoms.
what distinguishes prokaryotes vs eukaryotes
prokaryotes have no internal membrane
eukaryotes are more closely related to archaea
bacteria are ester bonded phospholipids whilst eukaryotes are have ether bonded phospholipids
there is a similarity between eukarya and archeaa in their lipid structure but eukaryotes has more internal membrane
When did prokaryotes appear?
3.5 billion years ago
found in almost every habitat
A eukaryotic organism that cannot be classified as an animal, plant, or fungus.
They are mostly unicellular and primarily found in moist habitats
3 major groups of protists
1)Algae – plant like protists
2) Protozoa- animal like protists
3) fungus like protists- absorptive nutrition (absorb molecules)
Habitats of protists
found in damp or aquatic environments such as decaying leaves, damp soil, ponds, streams, and oceans
Mobility of Protists
Some just float and have no wasy of swimming. other have structures allowing them to move
1) flagella- flagellates can swim using flagella which can also be used to bring in food
2) cilia- smaller and more numerous and can support larger organism bc all cilia moving at once
3) pseudopod- amobeoid movement
extension of cytoplasm into pseudopod aka false foot. they move toward food source and the rest of the cytoplasm follows after them. (protist cells that move by pseudopod are describes as ameoboid)
4) snail like movement- glide along surfaces by secreting slime
Nutrition of Protists
Protists can be photo autotrophs and chemo heterotrophs
protists that combine photosynthesis and heterotrophic nutrition. use both autotrophy and heterotrophy to obtain nutrients
Heterotrophic protists that feed by ingesting particles. They rely on particle feedinf (ciliate) and uptake small nutrients from the environment like fungus does which provides them with energu and carbon building blocks
heterotrophs that rely on uptake of small organic molecules
in paramecium it extrudes filaments with a pointy tip to deter other protists
largely inhibit things attempting to eat protists. a defense mechanism of protists to protect them from other protists and fish.
Reproduction for protists
1) asexual reproduction- protists undergo binary fission
2) some protists have sexual reproduction in which their gametes are haploid and the zygote is diploid
ecological roles of fungi
Decomposition, Nutrient Recycling, Mutualistic Partnerships, Food Source, Parasites, Predators
Decomposers- they break down organic animal and plant matter. without fungi working as decomposers, plants would take forever to break down because of the molecule lignin.
Fungi also recycles nutrients
Fungi pathogens also cause many plant diseases
fungi have mutualisms normall w plants and plants benefit from their association with hyphae because the hyphae is connected to plants roots which increases the surface area for water absorption
mycorrhizal fungi
a type of fungi that are found in association with plant roots and may improve delivery of minerals to the plant, while being supplied with organic nutrients
represent symbiotic relationships between a fungus and a photosynthetic partner (usually algae) and provides sugar and oxygen
lichens evolved independently mutliple times
Fungi- unique cell wall chemistry and body form
fungal cell walls made of chitin a polysaccharide. most fungi have distinctive body known as mycellium which is composed of hyphae (microscopic filaments)
in what supergroup are fungi?
most recent ancestor of fungi?
ancestral organism diverged from common ancestor with animals
traits fungi share w animals
sexual reproduction
can be chemo heterotrophs just like animals meaning their carbon source comes from organic compunds and energy from other compounds
How do hyphae grow?
by elongation of the tip. mycellia grow at their edges as hyphae extend thru their tips thru indigested substrate
water enters fungal hyphae by means of osmosis and swells the hyphal tip which produces force necessaru for tip extension
Fungi asexual reproduction
– Releasing spores that are adapted to travel through air and water
– breaking off a hyphae
Fungi reproduce asexually by means of asexual spores
the asexual spores are known as conidia- produces at the hyphal tips
when land on favorable substrate, the conidia (asexual spores) germinate into a new mycellium
fungi sexual reproduction
fungal sexual reproduction is unique becuase it includes the function of the hyphal branches as gametes and the development of fruiting bodies.
fungal hyphae occurs in multimating types that differ biochemically
during sexual reproductiona hyphal branch of mycellium fuses with hyphal branch of different mycellium

the union of the cytoplasms of two parent mycelia

for many fungi, haploid gamete nuclei remain seperate for a long time after plasmogamy occurs. gamete nuclei divide at each cell division producing mycellium that is dikaryotic or heterokaytoic

Fusion of two haploid nuclei to form a diploid nucleus. Occurs in many fungi, and in animals and plants during fertilization of gametes
Referring to a fungal mycelium with two haploid nuclei per cell, one from each parent.
A fungal life cycle stage that contains two genetically different nuclei in the same cell.
fruiting bodies of fungi
fungi produce diverse types of fruiting bodies that foster spore dispersal by wind, water, or animals. some edible others have defensive toxins/ hallucinogens
what is an animal
Eukaryotic, multicellular heterotrophs that lack cell walls
-can move at at least one point in their life
chemo heterotroph
generally more specialized structures and sensory abilities
lack cell walls
3 themes apparent in evolution of animals
1) greater mobility
2) greater cephilization
3) greater specialization of body parts
A group of similar cells that perform the same function.
the inner germ layer that develops into the lining of the digestive and respiratory systems
Outer layer of skin
the middle layer of an embryo in early development, between the endoderm and ectoderm.
options in animals
1) no tissue layers
)2 tissue layers (dipoblastic)
3) triploblastic0 3 tissue layers
No symmetry
radial symmetry
Symmetry about a central axis.
bilateral symmetry
Body plan in which only a single, imaginary line can divide the body into two equal halves.
a fluid-filled space
an organism with a “true” body cavity, meaning one who’s cavity is completely lined with mesoderm
animals (roundworms) have a functional body cavity NOT fully lined with mesoderm. false coelom
no body cavity
protostome development
In animals, a developmental mode distinguished by the development of the mouth from the blastopore; often also characterized by spiral cleavage and by the body cavity forming when solid masses of mesoderm split.
Animals in which the blastopore becomes the anus during early embryonic development. radial cleavage
echinoderms and chordata
the division of the body of an organism into a series of similar parts
no true tissues
phylum porifera
loosely organized
asexual and sexual reproduction
Cnidaria and Ctenophora
radial symmetry
have true tissue
the cnetophora have a complete digestive track while cnidara have a one way digestive track
refers to animals in the taxa who either develop a lophophore ( a feeding device) or go through the trochophore larva stage
lopophorata (bryozoa and brachiopoda)
and annelida
specialized structure that rings the mouth and functions in suspension feeding in
distinct larval stage
aceolomate- no body cavity
but they are tripoblastic. they have no specialized organs
protonephridia- waste diffuses out
Phylum of worms with a crown of cilia surrounding the mouth
wheel like crown of cillia
pseudoceolomate. it is triploblastic but not a full body cavity
complete digestive track
(snails, clams, squids, octopuses) have a soft body that in many species is protected by a hard shell
true body cavity
ceolom pretty small
3 main body part: foot, mantle( covers visceral mass) and the visceral mass aka the internal organs
closed circulatoru system
segmented worms
cephilization- brain like structures
known for segmentation
inhabitat all habitats
tough callogen cuticle
large number of parasitic species
most abundant group of animals on earth
first group of animals to invade land
deal w temp changes via exoskeleton
varying body segments
circulatory system
radially symmetrical marine invertebrates including e.g. starfish and sea urchins and sea cucumbers
deuterostome development
filter feeders
known for special type of radial symmetry 5 parts
no cephilization
larvae- have bilateral symmetry
The phylum of the animal kingdom that includes vertebrates.
a part of the supergroup archaeplastida
includes green plants and land plants
all have chlorophyll- green pigment
most recent ancestor of plants
complex streptophyte algae: shares these 3 characteristics w plants:
1) plasmodesmata
2)plant specific features of cell division
3)sexual reproduction
channels through cell walls that connect the cytoplasms of adjacent cells
challenges of being on land
obtaining and transporting water
moving sperm and egg with out water
protection from drying out
uptaking nutrients whether dissolves or as a gas
alternation of generations
the alternation between the haploid gametophyte and the diploid sporophyte in a plant’s life cycle. one generation creates spores (diploid) and the other generation creates gametes (haploid)
Haploid, or gamete-producing, phase of an organism
The stage in the life cycle of a plant in which the plant produces spores.
advantages of alternation of generations
alternation of generations means there are diploid and haploid adults
the advantage is that there are more spores more multicellular sporophytes compared to just 1 zygote
Land plants
divides into two categories: vascular and non vascular
vascular can be further subdivided into seed/ seedless
those with seed can be gymniosperm or angiosperm
nonvascular plants
have embryo, gametangia, and sporangia.
-500 mya
small and resitricted to small habitats
reliant on water , small
reproduction requires water
lack true roots, stems, leaves
A reproductive organ that houses and protects the gametes of a plant
multicellular organs that produce spores
female gametangia and a gametangia is a reproductive organ that houses gamete of plant
zygote protected in archegonium and embryo nurtured in archegonium
male gametangia
seedless vascular plants
Plants that have vascular tissue but reproduce by spores (ferns, club mosses, and horsetails)
2 phyla (lycohpytes and pteridophytes)
1) water conducting tissue- vascular tissue
2) sporophyte dominant to gametophyte
3) cuticle- waxy covering on leaves to prevent drying out
4) true stem. leave, roots
5) stomata- pores on surface can be opened/ closed to prevent dessication and let carbon dioxide in- regulates gas exchange
seed plants
gymnosperms and angiosperms
1) woody tissue which provide structure
2) seeds- zygote, food, protective coating
3) ovule- structure that develops into seed
4) pollen carries sperm
gymniosperm= naked seed
no fruit
ex: ginkos, conifers
flowering plants
3 main innovation
1) flowers- specialized reproductive structures to attract pollinators and more pollen and female part of other flowers
not reliant upon chance, more efficient than wind pollination
2) fruits- develop after fertilization from aprts of the flower, attract animals and disperse seeds
3) endosperm-nutritive tissue in seed
another name for a seed leaf
An angiosperm that has only one seed leaf.
two cotyledons- two seed leaf
4 things plants need to survive
1) Light needed for photosynthesis
2) carbon dioxide gas for photosynthesis and to build plant
co2 gas taken up thru stomata, a limiting nutrient
3) water- involved in sev chem rxns (metabolism and photosynth)
pushes up against cell wall and gives plant rigidity
water is the transport medium for things such as dissolved minerals and sugar
4) minerals- dissolved in water and taken up by roots. mg central moelcule in chlorophyll
ca- involved in cell signalling and K regualtes cell water content
nutrients in topsoil most abundant in nutrients coming from erosion, decomposition, fertilizer, etc
plants use nitrogen in soil to make proteins but need fixed version
converts n2 gas into fixed form of nitrogen
soil bacteria that fix nitrogen after becoming established inside root nodules of legumes
rhizobia coexists in root nodules and are fed in exchange for nitrogen fixing
carnivorous plants
gets nitrogen from insects
have enzymes to digest insects
mostly getting minerals
live in sunny. moist habitat w water but shitty soil
parasitic plants
4500 species
grow into or onto another plants
putting roots in host plant to meet their needs

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