Science is the poetry of Nature.

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Posts tagged "life"


Prokaryotes vs Eukaryotes

We know how to tell if something is alive or not, but if a bacterium and a dog are both living organisms, then what differentiates them? There are actually two distinct types of living beings, prokaryotes and eukaryotes, each made up of specialised prokaryotic and eukaryotic cells. In the three phylums of life—bacteria, archaea, and eukarya—prokaryotes cover the first two, and eukaryotes cover eukarya. You can probably already guess which groups a bacterium and a dog belong to, but let’s find out why.

All cells (i.e., both prokaryotes and eukaryotes) contain four common structures:

  1. A plasma membrane, which is a “barrier” that separates the cell from the outside world, like how your skin prevents your organs from falling out.
  2. The cytoplasm, which is the jelly-like substance that takes up the spaces inside the cell that aren’t already occupied by organelles.
  3. Nucleic acids, the genetic material, which tell the cell how to operate and reproduce.
  4. Ribosomes, where protein synthesis takes place according to the information contained in the genetic material. Proteins are organic compounds essential to living organisms, and they’ll be explored in more detail in a later article.

But there are also fundamental differences between living cells. Prokaryotic organisms as a whole are much smaller than eukaryotes, because they’re just made up of single cells, while eukaryotic organisms are made up of many specialised cells. The size of individual cells is different, too: prokaryotes are about 1-10 µm (micrometres) in diameter, while eukaryotes are 10-100 µm. If you want to get your head around the scale of things, go nuts with this interactive page.

Prokaryotes also lack a nuclear compartment and other membrane-bound organelles (which are like little organs within cells, each performing specific functions), so their genetic material and basic functioning processes happen out in the open, in the cytoplasm. This allows for less specialisation, so prokaryotes turn out to be pretty simple cells.

(Image source)

They reproduce asexually by binary fission, meaning that each cell splits in two to create a copy of itself. This gives rise to less diversity, but there is some scope for something called “horizontal gene exchange”: directly exchanging genetic information between the same generation, as opposed to passing genetic information onto the next generation. See illicit bacterial sex tape here.

Eukaryotes, on the other hand, have a range of organelles designed to perform specialised functions, such as the mitochondria, which creates the cell’s energy, the chloroplast, which converts light energy to chemical energy in plants, and the Golgi body, which modifies and processes proteins. This “compartmentalisation” allows for greater complexity—different compartments can have different functions even if they conflict, because they’re sealed off from each other.

Eukaryotes divide and reproduce by mitosis (the division of cells for tissue growth) and meiosis (the division of sex cells), and what results is two parents passing their genetic information onto the next generation. This creates the opportunity for more diversity, though it’s a longer process—some prokaryotes can divide and create a new organism in 20 minutes flat, while in humans it’s just a tad longer than that.

So what’s the difference between a bacterium and a dog? You can probably answer that yourself: bacteria are prokaryotic organisms and dogs are eukaryotic.

Further resources: Comparison table and Khan Academy video

When I look up at the night sky, and I know that yes we are part of this universe, we are in this universe, but perhaps more important than both of those facts is that the universe is in us.
Neil deGrasse Tyson (via lanadelpizzaqueen)

(via afro-dominicano)


What is life?

This is the first article in an introductory biology series I’ll be writing over the next 4-6 weeks, starting from scratch and covering approximately final year high school/first semester university biology. My revision has begun, so buckle up: your learning is about to begin too.

The question of what is life? is as simple as it’s going to get, but also the most complex. Life is a weird, multi-faceted, conditional thing, and sometimes it’s hard to draw a line between what’s alive and what’s not. If I showed you a diamond, a virus, a fungus, a volcano, a dog, and a bacterium, how would you know which ones are living organisms?

There are a few key components of life, usually abbreviated to the acronym HOMER:

  1. Homeostasis: This is the regulation of internal conditions, like keeping pH and temperature constant. Polar bears, for example, help regulate their internal temperature with their thick coats.
  2. Organisation: Living things are built from complex assemblage of molecules, the smallest units of which are called cells.
  3. Metabolism: This is the transformation of energy for an organism’s use—for example, humans convert chemical energy from our food into energy that our cells can use to perform vital functions.
  4. Evolution: This is technically optional, because some living organisms don’t really evolve, but most are able to slowly change the genetic information passed down over generations, giving rise to diversity.
  5. Reproduction: Living organisms are able to pass on hereditary information into offspring.

Thinking about these five properties, let’s reconsider the list. A diamond and a volcano don’t tick any of our boxes and so are definitely not alive. A dog and a fungus are definitely alive. But the last two are more difficult to consider. What’s the difference between a bacterium and a virus? Well, we have to know a little bit more about them. Viruses are so harmful because they function by injecting their genetic material into a host, taking over the reproductive system in order to make more copes of themselves. They therefore don’t have their own reproductive system, since they have to hijack someone else’s—so they’re not alive.

Bacteria, on the other hand, tick all our boxes. We’ll find out a little more about them in the next article.

Further resources:First Life"  - David Attenborough documentary


We’ll Find Alien Life in This Lifetime, Scientists Tell Congress

Humans have long wondered whether we are alone in the universe. According to scientists working with the Search for Extraterrestrial Intelligence (SETI) Institute, the question may be answered in the near future.

Image 1: SETI uses the Arecibo’s 305-meter telescope — the largest in the world — to scan the sky for signals from alien civilizations all year round. Credit: Arecibo Observatory/NSF

Image 2: Kepler-186f, the first Earth-size planet orbiting in the habitable zone of its star, is just one of the many potentially habitable planets in a galaxy teeming with satellites. Credit: NASA Ames/SETI Institute/JPL-Caltech

"It’s unproven whether there is any life beyond Earth," Seth Shostak, senior astronomer at the SETI Institute, said at a House Committee on Science, Space and Technology hearing Wednesday (May 21). “I think that situation is going to change within everyone’s lifetime in this room.”

Scientists search for life beyond Earth using three different methods, Shostak said.

The first method involves the search for microbial extraterrestrials or their remains. Investigations include robotic missions to Mars, such as Curiosity and Opportunity, which are currently searching for signs that the Red Planet could once have hosted potentially habitable environments.

Local habitable worlds?

But Mars isn’t the only target in the solar system. In fact, Shostak said there are "at least half a dozen other worlds" in Earth’s neighborhood that have the potential to be habitable. Icy moons such as Jupiter’s Europa and Ganymede hide subsurface oceans, while Saturn’s largest moon, Titan, contains lakes of liquid methane, all of which could make the moons appealing homes for life.

A second technique involves examining the atmospheres of planets in orbit around other stars for traces of oxygen or methane or other gases that could be produced by biological processes. As an observed planet passes between Earth and its sun, a thick enough atmosphere has the potential to be detected.

Shostak said both of these methods could yield results in the next two decades.

The third plan involves searching not just for life, but also for intelligent life — a project that SETI pioneers. By scouring the universe for signals in a variety of spectrums, SETI hopes to find intentional or accidental broadcasts from extraterrestrial civilizations.

Determining the success rate of such a program is difficult, but Shostak said that the best estimates suggest that a reasonable chance of success would come after examining a few million star systems. So far, SETI has examined less than 1 percent of those star systems. However, Shostak expects that number to increase as technology advances.

"Given predicted advances in technology, looking at a few million star systems can be done in the next 20 years," he said.

"Teeming with … life"

NASA’s Kepler telescope has revealed that planets are abundant in the galaxy. Each of the 4 billion stars in our galaxy has an average of 1.6 planets in orbit around it, with one out of five of those planets are likely to be “Earth cousins.” That means there are tens of billions of potentially habitable planets in the Milky Way alone.

"If this is the only planet on which not only life, but intelligent life, has arisen, that would be very unusual," Shostak said.

On Earth, life arose in the first billion years of the planet’s 4.5-billion-year history. Its rapid origination suggests that it could arise quickly elsewhere as well, which could result in a profusion of life on planets across the galaxy.

"I suspect that the universe is teeming with microbial life," Dan Werthimer, director of the SETI Research Center at the University of California, Berkeley, told the committee.

How much of that life might be intelligent is another question altogether.

On one hand, although life arose early in Earth’s existence, complex — and then intelligent — life took much longer to develop.

"This place has been carpeted with life, and almost all that time, it required a microscope to see it," Shostak said.

However, Werthimer noted that intelligent life evolved in several species on Earth. He suggested that some planets evolve selective pressures that guide evolution toward different characteristics. On one planet, it may be most beneficial for life to be fast, while on others, it might need to be strong to survive.

"I think there are going to be some planets in the universe where it’s advantageous to be smart," Werthimer said.

Hunting for intelligence

Werthimer outlined several of the programs SETI utilizes in its search for intelligent life. The most well known of these is its use of the largest telescope in the world, the 1,000-foot (305 meters) Arecibo Observatory in Puerto Rico. Although most astronomers would feel lucky to obtain a day of observations with the instrument, scientists at SETI have figured out how to “piggyback” their research onto other observations, allowing for virtually continuous observation of the universe.

It requires a significant amount of computing power to churn through the resulting data in search of signals. In 1999, SETI@home was released to allow members of the public to put their computer to work when it might otherwise be idle. Today, 8.4 million users in 226 countries have the program running as a screensaver.

"Together, the volunteers have created the most powerful supercomputer on the planet," Werthimer said.

When asked about potential safety issues with downloading the program, Werthimer said, "In my opinion, SETI@home is one of the safest things you can install on the computer." He pointed to the millions of users who have put it through its paces over the last 15 years. On top of that, the program is open source, which means that anyone can examine it for viruses or potential problems in the code.

In the next few months, SETI will launch its Panchromatic SETI program, using six telescopes to scour the skies for signals in a variety of wavelengths, including radio, optical and infrared.

"This will be an extremely comprehensive search," Werthimer said.

Another program seeks to eavesdrop on potential communications between two bodies in an alien solar system. Just as NASA sends signals to the Curiosity rover on Mars, or would need to communicate with a future outpost on another body in the solar system, alien civilizations may be in the process of exploring or colonizing their own neighborhood. By using information from Kepler, SETI scientists can observe when two planets line up in another system and attempt to eavesdrop on potential signals.

By relying on a multitude of technologies in the search for advanced alien civilizations, SETI hopes to increase its odds of finding intelligent life beyond the solar system. Programs continue to evolve alongside technology, as SETI attempts to put a new one in play each year.

"I think the best strategy is a multiple-[pronged] strategy," Werthimer said. "We should be looking for all kinds of different signals and not put all of our eggs in one basket."

Shostak agreed, and noted that dated technology, such as radio signals, may not necessarily be obsolete.

"One shouldn’t discount a technology just because it’s been around awhile," he said. "We use the wheel every day."

If scientists were to discover a signal that might potentially stem from an alien civilization, the news would spread fairly rapidly. SETI might ask observers at another observatory to verify the data before officially announcing it, but such news would never stay under wraps for long.

"The public has the idea that the government has a secret plan for what we would do if we picked up a signal," Shostak said.

But he said he’s received no calls or clandestine visits for the false alarms SETI has already observed.

In fact, Shostak said the news will spread before it can be fully verified.

"There will be false alarms," he said.

But what about the funding? Read the full story at LiveScience

(via afro-dominicano)


Ganymede May Harbor ‘Club Sandwich’ of Oceans and Ice

The largest moon in our solar system, a companion to Jupiter named Ganymede, might have ice and oceans stacked up in several layers like a club sandwich, according to new NASA-funded research that models the moon’s makeup.

Previously, the moon was thought to harbor a thick ocean sandwiched between just two layers of ice, one on top and one on bottom.

"Ganymede’s ocean might be organized like a Dagwood sandwich," said Steve Vance of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., explaining the moon’s resemblance to the "Blondie" cartoon character’s multi-tiered sandwiches. The study, led by Vance, provides new theoretical evidence for the team’s "club sandwich" model, first proposed last year. The research appears in the journal Planetary and Space Science.

Continue Reading

What to think of these stars without any doubt similar to our sun, destined like the sun to keep alive an enormous quantity of creatures of every kind?
Angelo Secchi 1870 - “Le Soleil” (via kenobi-wan-obi)


Organic Farms Harbor Diversity

On average, organic farms support 34 percent more plant, insect and animal species than conventional farms, say Oxford Univ. scientists. Researchers looked at data going back 30 years and found that this effect has remained stable over time and shows no signs of decreasing.

“Our study has shown that organic farming, as an alternative to conventional farming, can yield significant long-term benefits for biodiversity,” says Sean Tuck of Oxford Univ.’s Department of Plant Sciences, lead author of the study. “Organic methods could go some way towards halting the continued loss of diversity in industrialized nations.”

Read more:

(via afro-dominicano)


The Evolution of Life

In its 4540 million (4.54 billion) years circling the sun, Earth has provided a home for life that has become more and more complex. [The timeline can be seen here in more detail.

  • for the last 3600 million years, simple cells (prokaryotes);
  • for the last 3400 million years, photosynthetic cyanobacteria
  • for the last 2000 million years, complex cells (eukaryotes);
  • for the last 1000 million years, multicellular life;
  • for the last 600 million years, simple animals;
  • for the last 550 million years, bilaterians,
    animals with a 
    front end and a back end,
    as well as an upside and a downside;
  • for the last 500 million years, fish and proto-amphibians;
  • for the last 475 million years, land plants;
  • for the last 400 million years, insects and plants with seeds;
  • for the last 360 million years, amphibians;
  • for the last 300 million years, reptiles;
  • for the last 200 million years, mammals;
  • for the last 150 million years, birds;
  • for the last 130 million years, flowers;
  • for the last 60 million years, the primates,
  • for the last 20 million years, the family Hominidae (great apes);
  • for the last 2.5 million years, the genus Homo (human predecessors);
  • for the last 200,000 years, anatomically modern humans.

Image retrieved here [source unknown]


Finding alien worlds on Earth

Have you ever wondered which places on Earth most resemble other planets? For some of us, imagining the landscape of other worlds might just be for fun, but scientists and engineers wonder about what the otherworldly places on Earth can tell us about neighbours like the Moon and Mars.

Working in the most unusual places on Earth can help us to prepare for human flights, robotic missions and the search for life beyond our own planet. These ‘analogues’ are chosen because they are similar in one way or another to particular planetary environments. They can be used for technical tests and research before the effort and expense of a launch into space.

The most hostile environments on Earth are home to unusual life forms. By studying these ‘extremophiles’ that can cope with extreme heat, cold, pressure or radiation on Earth, astrobiologists can consider whether certain environments in space might be home to similar tiny creatures. Needing unspoiled land, often without vegetation, means that astrobiologists and geologists often find themselves in very remote places.

Past research for ESA includes expeditions to Svalbard in conjunction with NASA. The teams visiting this remote island far to the north of Norway included geologists, biologists and engineers, and their tests included some of the instruments now working on Mars aboard the Curiosity rover.

Sites like the Atacama Desert, recently used to test a sampling rover for ESA’s ExoMars mission, are valuable. Trials can find out what sort of terrain a rover can cross, what kind of slopes it can go up and down, and whether it can sample the surface.

"We examined what kind of interesting areas there are on Mars and the Moon, and how to find something similar on Earth," says Oliver Angerer, Human Exploration Science Coordinator for ESA.

"For example, if you want to study lava tubes on Mars, what is the nearest equivalent on Earth? Depending on your mission requirements, you can choose Iceland, Hawaii or Tenerife."

And what about a Mars or Moon analogue as a holiday destination?

"There are a lot of places in this catalogue that I would like to visit," says Oliver. "So far, I haven’t been to the Dry Valleys in Antarctica, which is an amazing area for field activities. It’s the closest you can get to being on another planet while staying on Earth."

Image credit: ESA

Vaccine Refusals Fueled California’s Whooping Cough Epidemic : Shots - Health News : NPR

When the whooping cough vaccine was invented in the 1940s, doctors thought they had finally licked the illness, which is especially dangerous for babies. But then it came roaring back.

In 2010, a whooping cough outbreak in California sickened 9,120 people, more than in any year since 1947. Ten infants died; babies are too young to be vaccinated.

Public health officials suspected that the increased numbers of parents who refused to vaccinate their children played a role, but they couldn’t be sure.

(via callipygianology)


Influenza Virus | kat m research

This negative-stained transmission electron micrograph (TEM) depicts the ultrastructural details of an influenza virus particle, or “virion”. A member of the taxonomic family Orthomyxoviridae, the influenza virus is a single-stranded RNA organism


Hours after death, we can still bring people back

Resuscitation specialist Sam Parnia believes we can bring many more people back to life after they die – it’s just a matter of training and equipment

Are the people you resuscitate after cardiac arrest really dead? Isn’t the definition of death that it is irreversible?
A cardiac arrest is the same as death. It’s just semantics. After a gunshot wound, if the person haemorrhages sufficiently, then the heart stops beating and they die. The social perception of death is that you have reached a point from which you can never come back, but medically speaking, death is a biological process. For millennia we have considered someone dead when their heart stops beating.

People often confuse the terms cardiac arrest and heart attack. Clearly, they’re very different.
A heart attack happens when a clot blocks a blood vessel to the heart. The portion of the heart muscle that was supplied blood and oxygen by that vessel will then die. That’s why most people with a heart attack don’t die.

What is the biggest problem in bringing someone back to life?
Reversing death before the person has too much cell damage. People die under many different circumstances and under the watch of many different medical specialists. No single speciality is charged with taking and implementing all the latest advances and technology in resuscitation.

How long after they die can someone still be resuscitated?
People have been resuscitated four or five hours after death – after basically lying there as a corpse. Once we die the cells in the body undergo their own process of death. After eight hours it’s impossible to bring the brain cells back.

What is the best way to bring people back?
The ideal system – and they do this a lot in South-East Asia, Japan and South Korea – is called ECPR. The E stands for extra corporeal membrane oxygenation (ECMO). It’s a system in which you take blood from a person who has had a cardiac arrest, and circulate it through a membrane oxygenator, which supplies oxygen and removes carbon dioxide. Then you pump the blood back into circulation around the body. Using ECMO, they have brought people back five to seven hours after they died. ECMO is not routinely available in the US and UK, though.

So, when I go into cardiac arrest, ideally what steps do I want my doctors to take?
First, we start the patient on a machine that provides chest compressions and breathing. Then we attach the patient to a monitor that tells us the quality of oxygen that’s getting into the brain.

If we do the chest compressions and breathing and give the right drugs and we still can’t get the oxygen levels to normal, then we go to ECMO. This system can restore normal oxygen levels in the brain and deliver the right amount of oxygen to all the organs to minimise injury.

At the same time you also cool the patient. This slows the rate of metabolic activity in the brain cells to halt the process of cell death while you go and fix the underlying problem.

How do you cool the body?
It used to be ice packs. Today a whole industry has grown up around this, and there are two methods. One is to stick large gel pads onto the torso and the legs. These are attached to a machine that regulates temperature. When the body reaches the right temperature, it keeps it there for 24 hours. The other way is to put a catheter into the groin or neck, and cool the blood down as it passes by the catheter.

Cooling benefits the heart and all the tissues, but we focus on the brain. There are also new methods in which people are cooled through the nose. You put tubes in the nostrils and inject cold vapour to cool the brain down selectively before the rest of the body.

If I had a cardiac arrest today, what are the chances I would get all of that?
Almost zero.

Why isn’t this type of care routine?
Cardiac arrest is the only medical condition that will affect every single one of us eventually, unfortunately. What’s frightening is that the way we are managed depends on where we are and who is involved. Even in the same hospital, shift to shift, you will get a different level of care. There is no external regulation, so it’s left to individuals.

There is disagreement over the interpretation of near death experiences (NDEs) – such as seeing a tunnel or a bright light. When a person dies, when do these experiences shut off?
One of the last things to fall into the realm of science has been the study of death. And now we have pushed back the boundary of death. In order to ensure that patients come back to life and don’t have brain damage, we have to study the processes that go on after they die. Whether we like it or not, we have gone into the “afterlife” or whatever you want to call it.

For people who have NDEs, they are very real. Most are convinced that what they saw is a glimpse of what it’s like when we die. Most come back and have no fear of death, and are transformed in a positive way – becoming more altruistic. As a scientific community we have tried to explain these away, but we haven’t been successful.

So how can a doctor, or any person of science, deal with such otherworldly experiences?
We have to accept that these experiences occur, that they are real to the people who have them, in the same way that if a patient has depression you would never say, “I know that you are feeling depressed but that is just an illusion. I’m the doctor. I’m going to tell you what your feelings really mean.” But with NDEs, we do this all the time: “I know you think you saw this, but you really didn’t.”

Aren’t NDEs just hallucinations?
We know from clinical tests that the brain doesn’t function after death, therefore you can’t even hallucinate. It’s ridiculous to say that NDE people are hallucinating because you have to have a functioning brain. If I take a person in cardiac arrest and inject them with LSD, I guarantee you they will not hallucinate.

For your study of out of body experiences (OBEs), you placed images in hospital rooms on high shelves only someone floating near the ceiling could see. So far, two patients have had OBEs, but neither in a room with a shelf…
That’s right. We had 25 hospitals that had an average of 500 beds working on the study. To put a shelf above every single bed, we would have to put up 12,500 shelves. That was completely unmanageable. We selected areas where cardiac arrest patients are frequently treated but even with that, at least half of those who had cardiac arrests and survived were in areas without shelves.

Are you continuing the experiment?
Yes. It’s part of an overall package to improve resuscitation to the brain. We are trying not to forget during resuscitation that there’s a human being in there.

In your book, you imply that death might be pleasant. Why do you think that?
The question is, what happens to human consciousness – the thing that makes me into who I am – when my heart stops beating and I die? From our external view, it looks like it simply disappears. But it sort of hibernates, in the same way as it does when you are given a general anaesthetic. And it comes back. I don’t believe that your consciousness is annihilated when you reach the point of death. How far does it continue? I don’t know. But I do know that at least in the period of time in which we can bring people back to life that entity of the human mind has not been annihilated.

What does this mean?
Those people who have pleasant experiences after death suggest that we should not be afraid of the process. It means there is no reason to fear death.

(Image: Martin Adolfsson)

Microscopic Life Captured in a Plankton Net

The photo above shows a sample of water teeming with microscopic life.

The sample was collected in a plankton net suspended into an incoming tide for 20 minutes from a bridge over an inlet near Brunswick, Maine. It was later photographed in a lab at the Southern Maine Community College. Several diatoms (aquatic, photosynthetic plants) can be identified here.

The round, cathedral window like structure is a stepanodiscus and the connected, rectangular tubes are tabellaria. Diatoms are at the bottom of the food chain, meaning that nearly all life depends upon these creatures. They produce as much as 50 percent of the Earth’s oxygen. — Paula Ursoy and John Stetson

Life Confirmed in Buried Antarctic Lake

Blobs and smears of microbial life growing in clear plastic disks are confirmation of a community living in a lake buried beneath the Antarctic ice, scientists studying the lake have said.

Water retrieved from subglacial Lake Whillans contains about 1,000 bacteria per milliliter (about a fifth of a teaspoon) of lake water, biologist John Priscu of Montana State University told Nature News. Petri dishes swiped with samples of the lake water are already growing colonies of microbes at a good rate, Nature News reported.

Lake Whillans is 2,625 feet (800 meters) below the West Antarctic Ice Sheet. After breaking through the ice on Jan. 28, researchers are returning to the United States with 8 gallons (30 liters) of lake water and eight sediment cores from the lake bottom. These samples will be tested for signs of microbial life, which could shed light on the types of extreme life that is able to thrive in such harsh environments.

Now, I don’t want to get people too excited but just imagine what the results could imply for a future mission to the Galilean satellite, Europa.