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Biology library
Course: Biology library > Unit 36
Lesson 1: Crash Course: Biology- Why carbon is everywhere
- Water - Liquid awesome
- Biological molecules - You are what you eat
- Eukaryopolis - The city of animal cells
- In da club - Membranes & transport
- Plant cells
- ATP & respiration
- Photosynthesis
- Heredity
- DNA, hot pockets, & the longest word ever
- Mitosis: Splitting up is complicated
- Meiosis: Where the sex starts
- Natural Selection
- Speciation: Of ligers & men
- Animal development: We're just tubes
- Evolutionary development: Chicken teeth
- Population genetics: When Darwin met Mendel
- Taxonomy: Life's filing system
- Evolution: It's a Thing
- Comparative anatomy: What makes us animals
- Simple animals: Sponges, jellies, & octopuses
- Complex animals: Annelids & arthropods
- Chordates
- Animal behavior
- The nervous system
- Circulatory & respiratory systems
- The digestive system
- The excretory system: From your heart to the toilet
- The skeletal system: It's ALIVE!
- Big Guns: The Muscular System
- Your immune system: Natural born killer
- Great glands - Your endocrine system
- The reproductive system: How gonads go
- Old & Odd: Archaea, Bacteria & Protists
- The sex lives of nonvascular plants
- Vascular plants = Winning!
- The plants & the bees: Plant reproduction
- Fungi: Death Becomes Them
- Ecology - Rules for living on earth
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Old & Odd: Archaea, Bacteria & Protists
Hank veers away from human anatomy to teach us about the (mostly) single-celled organisms that make up two of the three taxonomic domains of life, and one of the four kingdoms: Archaea, Bacteria, and Protists. They are by far the most abundant organisms on Earth, and are our oldest, oddest relatives. Created by EcoGeek.
Want to join the conversation?
- I'm wondering about the concept of Archaea fossils. What is leftover in single celled organism after fossilization? In multicellular organisms the bones remain, which while composed of cells, has a lot of calcium which allows us to dig them up. What would an archaea fossil be like?(24 votes)
- If Archae such as thermophiles were relocated to a much milder environment, will they survive?(14 votes)
- Some of them can only survive under anaerobic conditions, that means they would die in presence of oxygen. Also many thermophiles feed on substances which you can only find in their hot environment, so they would also probably starve.(13 votes)
- Why does it take so long for things to evolve?(8 votes)
- Evolution takes so long because it is an unguided natural process with no goal in "mind" acting on countless variations and situations. It involves no planning whatsoever.(9 votes)
- what is a micro organism(3 votes)
- A micro-organism is a living thing that cannot be seen with the naked human eye.
Micro organisms have the same character traits as any living thing, namely cellular structure, exchanging gases, growth, response to stimuli, reproduction and converting some form of energy to an energy their 'bodies' can use in order to survive.
Keep in mind that a micro-organism doesn't necessarily have to be a unicellular organism.
Hope this helps!(15 votes)
- Is Horizontal Gene Transfer basically Bacterial Conjugation?(4 votes)
- Bacterial conjugation is one type of horizontal gene transfer. I believe that bacterial transformation and transduction are also types of horizontal gene transfer in bacteria.(7 votes)
- Slime molds: Are they "fungi-like" (they look like a fungus) or "animal-like (they are amoeboid) ? I have seen them classified both ways. Would like a definitive answer.(3 votes)
- Slime moulds are now generally considered as protists!(5 votes)
- What are hydrothermal vents?(4 votes)
- A hydrothermal vent is a vent in the planet's surface that spews out water which has been warmed by the planet's interior.(2 votes)
- What is the name of the pigment that red algae possess?(3 votes)
- The red color comes from the pigments phycoerythrin and phycocyanin(2 votes)
- At, the screen says "the four kingdoms", but aren't all organisms now classified into six: archaebacteria, eubacteria, plantae, animalia, fungi, and protista? I know that cladistics is a quickly changing science, but how did this change come about? 1:55(3 votes)
- there have been various types of kingdom classifications. alex talks about five kingdom classification while laura is talking about six kingdom classification. 6 kingdom one is more recent. but we now accept the three domain system, different domains contain different kingdoms. its given in video description.
the classification system is still evolving and will continue to evolve for many more years.(2 votes)
- Another question: If evolution is an unguided process, then how do they decide to do certain things? Is it just what they need to survive? And why are there so many variations?(2 votes)
- The mutations and variations are completely random. It's the environment that 'selects' which mutations/variations survive (i.e., which ones are beneficial). When you see the word 'select', don't think that it means the environment has a conscience or free will - the whole process requires zero guidance. A hot environment is going to 'select' for genes that allow an organism to cope with the heat. This organism will survive and pass its genes on where others may not.(3 votes)
Video transcript
- We've spent the past few months talking about animals
here on Crash Course, specifically human animals because, well because humans, we love
talking about ourselves, and also because animals
are just really interesting. But it's high time that we talked about the
rest of the living world. Because I hate to break it to you, but most of the alive things on Earth are single celled organisms. And by most of the alive things, I mean that these organisms make up two of the three taxonomic
domains of all life plus one of the four kingdoms. I'm talking about archaea,
bacteria, and protists. With the exception of a few protists, they're all unicellular and they are by far the most abundant and diverse organisms on Earth. Maybe more importantly, they lay claim to the world's oldest and
earliest living lineages, dating back to the very first twinkle of life on this planet. So by understanding these three groups, we begin to truly
understand life on Earth, its origins and how everything
that came after them, including us, came to be. What's more, because their
heritage is so ancient, these organisms often
take weird, cool forms that don't look like life
as we think about it, and they do amazing things. Some not only live but
thrive in environments that would kill you, me,
and everything we hold dear, and others make their living
by invading organisms, including us, and causing disease. Then there are those that do the opposite, making life possible by fixing
nitrogen from the atmosphere, helping animals digest food. Members of these groups have
names like sailor's eyeballs and dog vomit slime mold, and they can take the shape of rods, blobs, corkscrews, or coils. Kinda like the doddering,
eccentric relatives you're forced to spend some
holiday with once a year, the archaea, bacteria, and
protists are our oldest, oddest relatives, and it's
about time you got to know them. There's no denying it. Every multicellular
organism on this planet, whether it be a mushroom or a vampire bat, evolved from a single celled organism. And while some of these
single celled organisms evolved to populate the world
as rhinos and strangler figs, others found happiness in
the unicellular lifestyle, and they haven't changed much
in the past few billion years. Today, nearly all unicellular
organisms are either archaea, bacteria, or protists. Protists, you'll recall,
are eukaryotic organisms that make up the kingdom Protista
under the domain Eukarya. Bacteria and archaea, meanwhile, are their own prokaryotic domains. And I hope you haven't forgotten this. The big difference between
prokaryotes and eukaryotes is that eukaryotic organisms, including you and the plants and fungi, animals that you know,
have cells with a nucleus that hold their genetic information, while prokaryotic cells
don't have a nucleus or any organelles to speak of. These two groups do have some
important things in common, like having plasma membranes
that are filled with cytoplasm and ribosomes that contain
RNA and synthesize proteins. And they both have DNA that
carries the instructions for operating the cell. But eukaryotic DNA comes in strands in the form of chromosomes,
while prokaryotic DNA is found in rings called plasmids. So again, and this time with feeling, protists are mostly single
celled eukaryotic organisms. Archaea and bacteria are single celled prokaryotic organisms. The word prokaryote actually
means before the nucleus, which is a clue that prokaryotes
are an older form of life. And we literally cannot find
anything older than archaea. The first archaea fossils date back to 3.5 billion years ago. I'm talking just a billion
years after the Earth formed and was still bombarded
by comets and meteors, not to mention fried by UV radiation. But in the midst of all that, archaea were just chillaxing. Earth's climate has
calmed down since then, so today, archaea are found
in some of the world's most extreme environments, in
underwater hydrothermal vents, in oil wells, in volcanic hot springs, even acidic mine drainage. Archaea were probably the
earliest living things, and their adaptability is
probably what allowed them to take root in Earth's early
kinda groddy environment. One key group of the
archaea are the methanogens. These guys prefer more
moderate environments like mud, swamps, and your intestines, but they derive energy from
hydrogen gas and carbon dioxide, which is pretty cool, and they emit methane
as their waste product. Methanogens, methane generators. We know that waste as swamp gas
and also other kinds of gas. The other groups are extremophiles,
which not only tolerate but prefer really wicked surroundings. The most famous of these
are the thermophiles, which live in temperatures
that would melt your face off. I'm being serious, Pyrolobus fumarii, a species of archaea
discovered in the late 1990s in a hydrothermal vent, live at temperatures
around 113 degrees Celsius, not Fahrenheit, Celsius, significantly above the
boiling point of water. Most organisms can't take heat like that because it causes their DNA to unwind and their proteins to denature
or permanently change shape, but thermophiles have evolved adaptations that keep them stable at these
screaming hot temperatures. There are also halophiles or salt lovers, which live in places like the Dead Sea or the Great Salt Lake and
probably Daniel Tosh's mouth. Most halophiles breathe
oxygen and are heterotrophic, but there are some bizarro outliers, like species that use
sunlight to make energy but not like plants do. They have light harvesting
pigments in their membranes that react with light and enable the cell to make ATP for energy. I know, it's crazy. But despite their alien
sounding ways of life, archaea really aren't all that different from bacteria, which are also prokaryotes. In fact, archaea and bacteria
were classified together for much of the 20th century. It was only when scientists realized that they had some important
genetic differences, like in the sequence
of their ribosomal DNA and the make up of their RNA, that they were separated into two domains. Bacteria are nearly as ancient as archaea. Fossils show that they were widespread about 1.5 billion years ago, but there's evidence
that they've been around for more than three billion years. Today they make up the vast
majority of prokaryotes on Earth and they're super slick when
it comes to adapting quickly. Many bacteria are parasitic. Think your strep throat,
your staph infection, anything you've ever
taken an antibiotic for. But bacteria can fend off antibiotics and the ninjas in your immune system by garbling up their DNA from
one generation to another. They can randomly turn genes on and off, creating unique genetic combination as its population multiplies, keeping its host's immune system and drug makers on their toes. Like archaea, bacteria
don't reproduce sexually, but bacteria have devised a way to pass their genetic
material to their buddies, a little trick called
horizontal gene transfer. For example, you've heard of
antibiotic resistance, right? Well, horizontal gene
transfer is one reason for it. A strand of bacteria that
has genetic resistance to an antibiotic can pass some of its DNA and that drug resistance
to another strand, which is why we're always
in kind of an arms race with the bacteria of the world. And of course, bacteria
are incredibly diverse, with too many phyla to
name, more than two dozen. But one way of classifying them is by their different
kinds of cell membranes, which react differently
to a staining technique scientists use called Gram staining. Gram positive bacteria
have thick cell membranes, and they're a huge group that includes species that live individually, like staphylococcus and streptococcus, as well as some colonial
bacteria that are responsible for diseases like leprosy and tuberculosis. And there are lots of
Gram negative bacteria too which have thinner membranes. The biggest group here
are the proteobacteria named after Proteus because
they take so many forms. These include bacteria that
make our lives possible by converting nitrogen in the atmosphere to compounds available to plants as well as others that cause
stuff like food poisoning and Legionnaires' disease. Cyanobacteria meanwhile
are the only prokaryotes that use photosynthesis
to make their food, and they're some of the
most important members of aquatic food webs,
providing microscopic forage for all kinds of freshwater
and marine ecosystems. Spirochetes are the
corkscrew-shaped bacteria that you've no doubt heard of. Most are harmless but a
couple of parasitic species are the culprits behind illnesses like Lyme disease and syphilis. And speaking of sexually
transmitted diseases, the last major group of
bacteria worth mentioning are chlamydias which
are strictly parasitic and live only in animal cells. They're scumbags obviously and are the leading infectious cause of blindness in the world as well as that eponymous
infection of the urethra that makes me kinda want to cross my legs just thinking about it. So archaea have managed to make a nice multibillion year living
by surviving in weird, out of the way places, and bacteria have developed
ways to pass their DNA without sexual reproduction. But you know who's a hot freaking mess? Protists. Evolutionarily, they're
the youngest of the three, having evolved from bacteria
around 1.7 billion years ago, and in a lot of ways,
they're more sophisticated. For starters, they're eukaryotic, but also, some are multicellular and a few kinds can
even reproduce sexually. But their domain is a big crap circus because some protists seem
to be more closely related to plants or animals or
fungi than other protists. So scientists tend to talk about them based on what else they resemble. There are protozoa which
are kinda animal-like, algae which are kinda plant-like, and fungus-like ones
including the tastefully named slime molds. The one thing all these have in common is they need to live somewhere wet, in a bog or in your body
or in a snowbank, wherever. Protozoa are actually really cool because they're like tiny animals. Like us, they're heterotrophs, so they have to eat other
stuff in order to live. And because they need to eat, they've got mouth parts or at least mouth part sorts of things, and they can move around
by using all kinds of really cool structures. Some have flagella that look like tails to propel them through the water, or cilia, little hairlike
structures that work like oars, and some move around with a kind of blobby, amoeba-like motion. I say amoeba-like because the
protozoans that move this way are amoebas. And speaking of amoebas, some
protozoans are parasitic. You've probably heard
of amoebic dysentery. That's caused by amoebas. Malaria is caused by this little guy, a protozoan called Plasmodium vivax, while African sleeping
sickness is caused by Trypanosoma brucei, this guy here. Moving on to the plant-like
protists, which are algae. All algae photosynthesize like plants even though they're not plants because they use different
kinds of chlorophyll molecules. Some are unicellular like tiny diatoms which have a hard shell made of silica. The amazing thing about
single celled algae is that they can get really honking huge. For example, ladies and gentlemen, cast your gaze upon the sailor's eyeball, thought to be the biggest
single celled organism on the planet, also known as bubble algae. It lives on the sea
floor in tropical oceans and can grow up to five
centimeters across. How is that thing one cell? Anyway, you already know
multicellular types of algae, a.k.a. seaweed. They're closely related to land plants as you can tell by looking at them. And they're generally grouped into red, green, and brown varieties, although these all have their
unicellular forms as well. The green algae are probably
what gave rise to land plants about 475 million years ago. They're the most abundant and diverse, and they have chloroplasts
very much like land plants. So they can only live in shallow water because they need a lot of sunlight. Red algae is able to
live at greater depths and has an extra pigment
in it called phycoerythrin, which gives its chlorophyll
a boost in deeper waters. And brown algae is what
most of the seaweed you see in the ocean is, kelp is an example. They're the largest and most complex of the multicellular algae. Finally, we have our fungus-like protists, which include the delightful slime molds. They absorb nutrients
from their environment and produce fruiting bodies like fungi. But even though they
look like piles of barf, they can actually move
around like an amoeba and eat bacteria by phagocytosis. Slime molds can be pretty easy to spot because they're often brightly colored like this charming species
which, in all seriousness, is known as dog vomit slime mold. You heard me, these organisms
are so freaking screwed up that scientists couldn't
think of a better name for it than dog vomit slime mold. Like I said, they're old,
they're odd, get used to it.