Monday, January 26, 2015
Friday, January 23, 2015
Thursday, January 22, 2015
Science and plants
http://www.saps.org.uk/
http://www.saps.org.uk/secondary/teaching-resources/299-measuring-stomatal-density
http://www.saps.org.uk/secondary/teaching-resources/784-microscopy-specialised-cells-in-african-violets
http://www.saps.org.uk/secondary/teaching-resources/235-student-sheet-23-photosynthesis-using-algae-wrapped-in-jelly-balls
http://www.saps.org.uk/secondary/teaching-resources/299-measuring-stomatal-density
http://www.saps.org.uk/secondary/teaching-resources/784-microscopy-specialised-cells-in-african-violets
http://www.saps.org.uk/secondary/teaching-resources/235-student-sheet-23-photosynthesis-using-algae-wrapped-in-jelly-balls
Monday, January 19, 2015
Lettuce seeds germination
(..)La siguiente clave importante en la comprensión de la respuesta de las plantas a las proporciones relativas de luz y oscuridad la aportó el trabajo de los investigadores de la Estación de Beltsville, en Maryland, perteneciente al U.S.D.A. La clave se encontró en el informe de un estudio previo realizado con semillas de lechuga (Lactuca sativa).
|
Las semillas de lechuga germinan
solamente si se han expuesto a la luz. Muchas semillas pequeñas
tienen este requerimiento, ya que necesitan germinar en un suelo seco y cerca de la superficie
para que las plántulas aseguren su emergencia.
| |
|
Los primeros
investigadores, al estudiar los requerimientos de luz para que las
semillas de lechuga germinaran, demostraron que la luz roja estimulaba
la germinación, y que la luz de una longitud de onda ligeramente
superior (rojo lejano) la inhibía aún de forma más efectiva que la
ausencia total de iluminación.
|
Effect of the light:
http://es.slideshare.net/KarinaPz/informe4morfo
http://www.euita.upv.es/varios/biologia/Temas/tema_15.htm
Effect of metals:
https://www.wwoa.org/public-education/lettuce-seed-bioassay.php
Effect of chemicals:
https://www.google.es/url?sa=t&rct=j&q=toxicology%20experiment%3A%20seed%20bioassay&source=web&cd=1&ved=0CCQQFjAA&url=https%3A%2F%2Fwww.toxicology.org%2FISOT%2FRC%2FNLSOT%2Fdocs%2FSeedBioassay.pdf&ei=n1i9VP_SGMS0UY61grAI&usg=AFQjCNHU7IrvKTOYioJidaPFZRl6oemIcA&sig2=SGTMpS5pAjHDQlqJuxZqIQ&bvm=bv.83829542,d.d24
Wednesday, January 14, 2015
Investigating Nettle Stings
Stinging
nettles have developed stinging cells as an adaptation to deter herbivores from
eating them. The plants contain long, thin, hollow hairs that cover the
majority of the stem and the underside of the leaves. These hairs contain
stinging chemicals.
Stinging hairs on a nettle leaf
Equipment
·
gloves
·
microscope
·
slides
·
plastic cover slips (small pieces of clear
plastic such as acetate can be used if plastic cover slips are not available)
·
Universal Indicator solution
·
Universal Indicator paper
·
nettle leaves
·
dock leaves
Method
1.
Look at a piece of a nettle leaf under the microscope – you should be
able to see the stings as hollow hairs containing a colourless liquid.
2.
Put a drop of Universal Indicator solution onto the piece of nettle
leaf on the slide and lay another slide on top.
3.
Press the slides together to break open some of the stings.
4.
You should see a pink colour developing around the spines after you press
down on the top slide. What does this tell you about the liquid inside the
spines?
5.
Take a fresh piece of nettle leaf and place it with the underside
against a piece of damp Universal Indicator paper.
6.
Place a plastic cover slip on the leaf and press down to break some of
the stings.
7.
You should see yellow spots on the paper where stings broke open. What
does this tell you about the liquid inside the stings?
A piece of damp universal indicator
paper that has been pressed against a nettle leaf. Yellow spots show where acid
has been released from the stings.
From
these experiments we can see that the stings contain acid.
Tuesday, January 13, 2015
The Endosymbiotic Theory
A theory on the Origins of Eukaryotic Cells: Mitochondria and
Chloroplasts
http://www.biology.iupui.edu/biocourses/N100/2k2endosymb.html
The Endosymbiotic Theory was first proposed by former Boston University Biologist Lynn Margulis in the 1960's and officially in her 1981 book "Symbiosis in Cell Evolution". Although now accepted as a well-supported theory, both she and the theory were ridiculed by mainstream biologists for a number of years. Thanks to her persistance, and the large volumes of data that support this hypothesis gathered by her and many other scientists over the last 30 years, biology can now offer a plausible explanation for the evolution of eukaryotes. [Quote]
Dr. Margulis was doing reserarch on the origin of eukaryotic cells. She looked at all the data about prokaryotes, eukaryotes, and organelles. She proposed that the similarities between prokaryotes and organelles, together with their appearance in the fossil record, could best be explained by "endo-symbiosis".
Her hypothesis originally proposed that:
The result = a cell with a double-membrane bound organelle. The inner lipid bilayer would have been the bacterial cell's plasma membrane, and the ouler lipid bilayer came from the cell that engulfed it.
http://www.biology.iupui.edu/biocourses/N100/2k2endosymb.html
The Endosymbiotic Theory was first proposed by former Boston University Biologist Lynn Margulis in the 1960's and officially in her 1981 book "Symbiosis in Cell Evolution". Although now accepted as a well-supported theory, both she and the theory were ridiculed by mainstream biologists for a number of years. Thanks to her persistance, and the large volumes of data that support this hypothesis gathered by her and many other scientists over the last 30 years, biology can now offer a plausible explanation for the evolution of eukaryotes. [Quote]
Dr. Margulis was doing reserarch on the origin of eukaryotic cells. She looked at all the data about prokaryotes, eukaryotes, and organelles. She proposed that the similarities between prokaryotes and organelles, together with their appearance in the fossil record, could best be explained by "endo-symbiosis".
Her hypothesis originally proposed that:
- mitochondria are the result of endocytosis of aerobic bacteria
- chloroplasts are the result of endocytosis of photosynthetic bacteria
- in both cases by large anaerobic bacteria who would not otherwise be able to exist in an aerobic environment.
- this arrangement became a mutually beneficial relationship for both cells (symbiotic).
Each would have performed mutually benefiting functions from their symbiotic relationship. The aerobic bacteria would have handled the toxic oxygen for the anaerobic bacteria, and the anaerobic bacteria would ingested food and protected the aerobic "symbiote"..
The result = a cell with a double-membrane bound organelle. The inner lipid bilayer would have been the bacterial cell's plasma membrane, and the ouler lipid bilayer came from the cell that engulfed it.
Survival of the Sneakiest by the Understanding Evolution team
| Survival
of the fittest" means that the strong succeed, and the weak fail,
right? Well, often that's how it's portrayed, but the real story is a
bit trickier. Let's take a closer look at what the crickets do...
|
 |
|
|
Discussion questions
|
Monday, January 12, 2015
Social Skills: Kids vs. Apes
http://www.pbs.org/wgbh/nova/evolution/social-skills.html
We humans are exceptionally good at manipulating our environment, but what makes us so successful compared with other primates? Our intelligence? Our opposable thumbs? A clever experiment conducted in Africa and Europe suggests another answer: our social skills.
On a warm afternoon in Cambridge, Massachusetts, a few dozen kids and
adults have found refuge on a shaded playground. Victoria Wobber, an
anthropologist from just down the road at Harvard University, stands off
to the side.
"There are a number of kids playing on slides," she says, watching all the activity. "There are kids playing with sand castles."
The scene is so familiar that it's hardly remarkable. And yet, Wobber is here to point out something fundamental about who we are as human beings, and who we grow up to become.
"Look at the boy using a shovel to get the sand into that container," she says.
The kids on this playground, even the ones who are too young to speak, are already little engineers, using tools to build structures out of sand. But where does this ability to understand our environment—and then manipulate it so successfully—come from? And why are our closest primate relatives unable to do it as well as we can? In other words, what sets us apart?
Wobber teamed up with scientists in Germany to study the kids, and she went to Africa to study the apes: 25 chimps, and 17 pygmy chimps, also called bonobos.
To study bonobos, Wobber visited a wildlife sanctuary in the Democratic Republic of Congo. In one experiment, which she videotaped, you can see her inside a tiled room. A metal grill separates her from a three-year-old male bonobo named Kubulu.
Wobber holds up two pieces of pipe. The pipes are designed so one can attach to the other. She tries to put them together three times, and she fails on purpose each time. Kubulu watches the pipes intently.
The point of this experiment is to see whether Kubulu understands the goal of the experimenter (i.e., to connect the pipes) by doing it himself. In the video, Wobber hands the tubes over to Kubulu.
Rather than putting the pipes together, he plays with them. Kubulu pops one in his mouth, climbs the wall, leaps down, jumps on top of the pipes, and then pushes them across the floor.
"And so that's typically what most chimps and bonobos did," Wobber explains. "They said, 'Great! You've given me a great toy. Thank you, I'll go play with this.' Rather than, well, here the goal was to put the two ends of the tubes together."
Wobber has a second video, this one recorded at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, which shows the other half of the experiment.
In the video, a three-year-old German boy sits across a table from a woman. Just like in the experiment from Africa, the woman tries to put the two pipes together three times, and fails. No words are spoken.
Wobber explains what's happening. "The kid here is really watching very carefully what [the experimenter is] doing," Wobber says. "But you can see he's looking at her face as a source of her intentions—what she is doing with these strange pipes."
The woman then slides the tubes across the table to the boy. Within a few seconds, he successfully inserts one tube into the other. As soon as he is done, he looks up at her face for approval—to see how he did.
Over the course of the study, not all the kids were successful at this
task, and not all the apes failed. But, in general, the kids got it and
the apes did not, in this and about a dozen other experiments, including
ones involving tangible rewards for succeeding (balloons for the kids,
bananas for the apes).
"I think the study's critical finding is that human children are very sensitive to the goals of another [person]," says Amanda Seed, a psychologist at the University of St. Andrews in Scotland who studies the evolution of human behavior. She calls the new research groundbreaking.
This is something that we're not seeing in the young chimpanzees and bonobos. The chimpanzees and bonobos focused on the objects, and on the enjoyment of the objects," she says. "The child is focused on the experimenter—and on pleasing the experimenter."
Consider the experiment involving the pipe. In general, the chimpanzees and bonobos tossed it around and jumped on it. That is how they learn about their environment; they build an understanding of the world by themselves, from scratch, working out how to use tools and solve problems through trial and error.
But the children in this experiment were constantly watching people. Amanda Seed says kids learn a lot from others, even without language. Children look into the eyes and faces of adults to understand what those adults intend to do. She says these subtle cues provide humans with a rich source of information about our world and give us an advantage over chimps and bonobos.
Seed does raise some concerns about this study. For instance, it was always a human experimenter doing the demonstrating. "The challenge for the chimpanzees and bonobos is that much greater," she says. "They have to read through the behavior of another species to appreciate the goals that that species is trying to perform."
But Seed says this new study adds to a growing body of evidence that our primate cousins are not as focused as we are on the actions and intentions of others. She says the new research provides an elegant demonstration that our ability to manipulate our physical environment, a hallmark of what it means to be human, comes in part from our social skills.
Wobber looks over at a boy in a blue-and-white striped shirt. He is about two years old.
"He's pointing out something for his mom there," she says, as if providing color commentary. The boy picks up a rag. "[He's] trying to show that to his little friend over there in the bathing suit."
The boy's mom picks her son up and moves him to a different part of the playground, where he soon finds a new toy. Rather than playing with it by himself, he holds it up, shows it to his mom, and then, looks into her eyes.
We humans are exceptionally good at manipulating our environment, but what makes us so successful compared with other primates? Our intelligence? Our opposable thumbs? A clever experiment conducted in Africa and Europe suggests another answer: our social skills.
Listen to the story.
To see what sets humans apart, anthropologist Victoria Wobber challenges young apes and children to do the same tasks.
"There are a number of kids playing on slides," she says, watching all the activity. "There are kids playing with sand castles."
The scene is so familiar that it's hardly remarkable. And yet, Wobber is here to point out something fundamental about who we are as human beings, and who we grow up to become.
"Look at the boy using a shovel to get the sand into that container," she says.
The kids on this playground, even the ones who are too young to speak, are already little engineers, using tools to build structures out of sand. But where does this ability to understand our environment—and then manipulate it so successfully—come from? And why are our closest primate relatives unable to do it as well as we can? In other words, what sets us apart?
An elegant experiment
Wobber came up with a way to unravel these questions as part of her Ph.D. work at Harvard University. She decided to challenge little kids and little apes of the same age, between two and four years old, with the same simple tasks.Wobber teamed up with scientists in Germany to study the kids, and she went to Africa to study the apes: 25 chimps, and 17 pygmy chimps, also called bonobos.
To study bonobos, Wobber visited a wildlife sanctuary in the Democratic Republic of Congo. In one experiment, which she videotaped, you can see her inside a tiled room. A metal grill separates her from a three-year-old male bonobo named Kubulu.
Wobber holds up two pieces of pipe. The pipes are designed so one can attach to the other. She tries to put them together three times, and she fails on purpose each time. Kubulu watches the pipes intently.
The point of this experiment is to see whether Kubulu understands the goal of the experimenter (i.e., to connect the pipes) by doing it himself. In the video, Wobber hands the tubes over to Kubulu.
Rather than putting the pipes together, he plays with them. Kubulu pops one in his mouth, climbs the wall, leaps down, jumps on top of the pipes, and then pushes them across the floor.
"And so that's typically what most chimps and bonobos did," Wobber explains. "They said, 'Great! You've given me a great toy. Thank you, I'll go play with this.' Rather than, well, here the goal was to put the two ends of the tubes together."
Wobber has a second video, this one recorded at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, which shows the other half of the experiment.
In the video, a three-year-old German boy sits across a table from a woman. Just like in the experiment from Africa, the woman tries to put the two pipes together three times, and fails. No words are spoken.
Wobber explains what's happening. "The kid here is really watching very carefully what [the experimenter is] doing," Wobber says. "But you can see he's looking at her face as a source of her intentions—what she is doing with these strange pipes."
The woman then slides the tubes across the table to the boy. Within a few seconds, he successfully inserts one tube into the other. As soon as he is done, he looks up at her face for approval—to see how he did.
Reading intentions
So what do the results mean?"I think the study's critical finding is that human children are very sensitive to the goals of another [person]," says Amanda Seed, a psychologist at the University of St. Andrews in Scotland who studies the evolution of human behavior. She calls the new research groundbreaking.
"The child is focused on the experimenter—and on pleasing the experimenter.""This is something that we're not seeing in the young chimpanzees and bonobos. The chimpanzees and bonobos focused on the objects, and on the enjoyment of the objects," she says. "The child is focused on the experimenter—and on pleasing the experimenter."
This is something that we're not seeing in the young chimpanzees and bonobos. The chimpanzees and bonobos focused on the objects, and on the enjoyment of the objects," she says. "The child is focused on the experimenter—and on pleasing the experimenter."
Consider the experiment involving the pipe. In general, the chimpanzees and bonobos tossed it around and jumped on it. That is how they learn about their environment; they build an understanding of the world by themselves, from scratch, working out how to use tools and solve problems through trial and error.
But the children in this experiment were constantly watching people. Amanda Seed says kids learn a lot from others, even without language. Children look into the eyes and faces of adults to understand what those adults intend to do. She says these subtle cues provide humans with a rich source of information about our world and give us an advantage over chimps and bonobos.
Seed does raise some concerns about this study. For instance, it was always a human experimenter doing the demonstrating. "The challenge for the chimpanzees and bonobos is that much greater," she says. "They have to read through the behavior of another species to appreciate the goals that that species is trying to perform."
But Seed says this new study adds to a growing body of evidence that our primate cousins are not as focused as we are on the actions and intentions of others. She says the new research provides an elegant demonstration that our ability to manipulate our physical environment, a hallmark of what it means to be human, comes in part from our social skills.
A new view of the playground
Back at the playground in Cambridge, there is a lot more going on here when viewed through the lens of Victoria Wobber's study. The kids are not just playing on slides and in the sand. They are watching others closely, and learning from them.Wobber looks over at a boy in a blue-and-white striped shirt. He is about two years old.
"He's pointing out something for his mom there," she says, as if providing color commentary. The boy picks up a rag. "[He's] trying to show that to his little friend over there in the bathing suit."
The boy's mom picks her son up and moves him to a different part of the playground, where he soon finds a new toy. Rather than playing with it by himself, he holds it up, shows it to his mom, and then, looks into her eyes.
Sunday, January 11, 2015
A planet full of life. The origin of life.
What is Life?
For scientists there is not a unique concept for life but there are some common characteristics that allow us to distinguish the most essential of this phenomenon.
Life is a system that uses an environment for reproduction and perpetuation of species.
The chemical basis of Life: Immediate Principles
http://www.youtube.com/watch?v=PYH63o10iTE
Immediate principles are biomolecules that are part of living beings. They consist of about 70 chemical elements that are also called bioelements.
Bioelements can be classified into:
• Primary or essential (CHONPS). Constitute 96% by mass of living matter. They are the key components of the water and organic biomolecules.
• Secondary. Are less abundant (approximately 4 %) but play an essential role in the physiology of living being. Are calcium (Ca), magnesium (Mg), sodium (Na), potassium (K) and chlorine (Cl).
• Tertiary. They are part of living being in a small proportion (0.1%), but they are essential for life as they are involved in many biological processes. Examples: iodine (I), iron (Fe), manganese (Mn), cobalt (Co), selenium (Se), fluoride (F), copper (Cu) , etc.
Biomolecules, in turn, can be divided into two groups:
INORGANIC: water and mineral salts.
ORGANIC: carbohydrates, lipids, proteins and nucleic acids, made up of chains of carbon and hydrogen and they can be found exclusively in living beings
Redi's experiment.
Francesco Redi, an Italian physician, performed an experiment in 1668 in which he placed four glasses in which respectively put a piece of snake, fish, eels and a piece of beef. Then prepared another four glasses with the same materials and left open, while the first ones remained sealed. Soon some flies were attracted by food left in open vessels and went to eat and lay eggs; after a period of time, in this series of vessels began to appear some larvae. This is not verified, however, in closed vessels, even after several months. Therefore, Redi concluded that the larvae (maggots) were originated because of flies and not by spontaneous generation.
http://www.youtube.com/watch?v=WNByRghR6sw&list=PLPPRUDh1AoDoc3C7vRZRiYFrbmAzEQQjK
Some people objected to Redi saying in closed vessels had lacked air circulation (which, they said, lay the "vital principle") and that had prevented spontaneous generation. Redi made a second experiment, this time the experiment vessels were not sealed, but only coated gauze. The air, therefore, could circulate. The result was identical to the previous experiment, because the gauze obviously prevented insect access to the vessels and subsequent deposition of eggs and therefore not given birth larvae.
With these simple experiences, Redi showed that putrefying flesh was developed by a larvae action and not by a meat processing, as was claimed by supporters of spontaneous generation.
For scientists there is not a unique concept for life but there are some common characteristics that allow us to distinguish the most essential of this phenomenon.
Life is a system that uses an environment for reproduction and perpetuation of species.
The chemical basis of Life: Immediate Principles
http://www.youtube.com/watch?v=PYH63o10iTE
Immediate principles are biomolecules that are part of living beings. They consist of about 70 chemical elements that are also called bioelements.
Bioelements can be classified into:
• Primary or essential (CHONPS). Constitute 96% by mass of living matter. They are the key components of the water and organic biomolecules.
• Secondary. Are less abundant (approximately 4 %) but play an essential role in the physiology of living being. Are calcium (Ca), magnesium (Mg), sodium (Na), potassium (K) and chlorine (Cl).
• Tertiary. They are part of living being in a small proportion (0.1%), but they are essential for life as they are involved in many biological processes. Examples: iodine (I), iron (Fe), manganese (Mn), cobalt (Co), selenium (Se), fluoride (F), copper (Cu) , etc.
Biomolecules, in turn, can be divided into two groups:
INORGANIC: water and mineral salts.
ORGANIC: carbohydrates, lipids, proteins and nucleic acids, made up of chains of carbon and hydrogen and they can be found exclusively in living beings
Origin of Life
First Theories about the Origin of Life
Creationism
This
is a philosophical doctrin which considers that from the beginning, man
has sought explanation of the origin of life. The first cultures linked
this to the presence of an omnipotent being (God), although this
hypothesis is not scientific by not testing any observable fact that can
verify it, however, creationism have survived to this day.
Spontaneous generation
Experiments conducted between the XVII and XVIII centuries eventually banish this idea. Here is the most important experiment:Redi's experiment.
Francesco Redi, an Italian physician, performed an experiment in 1668 in which he placed four glasses in which respectively put a piece of snake, fish, eels and a piece of beef. Then prepared another four glasses with the same materials and left open, while the first ones remained sealed. Soon some flies were attracted by food left in open vessels and went to eat and lay eggs; after a period of time, in this series of vessels began to appear some larvae. This is not verified, however, in closed vessels, even after several months. Therefore, Redi concluded that the larvae (maggots) were originated because of flies and not by spontaneous generation.
http://www.youtube.com/watch?v=WNByRghR6sw&list=PLPPRUDh1AoDoc3C7vRZRiYFrbmAzEQQjK
Some people objected to Redi saying in closed vessels had lacked air circulation (which, they said, lay the "vital principle") and that had prevented spontaneous generation. Redi made a second experiment, this time the experiment vessels were not sealed, but only coated gauze. The air, therefore, could circulate. The result was identical to the previous experiment, because the gauze obviously prevented insect access to the vessels and subsequent deposition of eggs and therefore not given birth larvae.
With these simple experiences, Redi showed that putrefying flesh was developed by a larvae action and not by a meat processing, as was claimed by supporters of spontaneous generation.
How could life have begun?
Some people think it was carried to Earth from another planet. But that just
puts back the problem of how life began to that other planet. It is simplest to
assume that life began on Earth. Indeed, the Earth has the right conditions for
life to exist. It is at just the right distance from the Sun for water to be a liquid, and its orbit is almost
circular. This is probably unusual among planets round other stars, so it seems
sensible to assume Earth was the place where life began.
Meterorites&Life: http://www.pbs.org/exploringspace/meteorites/murchison/page8.html
Modern theories about the Origin of Life
Prebiotic Synthesis: The Origin of Life upon Alexander Oparin
Oparin postulated that 4,000 million years ago, about the time the Earth´s crust cooled, small molecules of atmospheric gases (H2O, methane [CH4 ] and ammonia [NH3]) resulted in a organic molecule called prebiotic, thanks to the energy provided primarily by ultraviolet radiation from the Sun and the constant shock of storms. These prebiotic molecules, more complex, would become amino acids (protein constituent of elements) and nucleic acids. According to Oparin, these first molecules would be trapped in shallow pools formed in the early ocean coastline, forming a prebiotic soup. Afterwards these simple compounds forming polymers were grouped into forming more complex organic molecules. At some point, somewhere a molecule capable of replicating itself would appear and lead the formation and appearance of the first cell.
Meterorites&Life: http://www.pbs.org/exploringspace/meteorites/murchison/page8.html
Modern theories about the Origin of Life
Prebiotic Synthesis: The Origin of Life upon Alexander Oparin
Oparin postulated that 4,000 million years ago, about the time the Earth´s crust cooled, small molecules of atmospheric gases (H2O, methane [CH4 ] and ammonia [NH3]) resulted in a organic molecule called prebiotic, thanks to the energy provided primarily by ultraviolet radiation from the Sun and the constant shock of storms. These prebiotic molecules, more complex, would become amino acids (protein constituent of elements) and nucleic acids. According to Oparin, these first molecules would be trapped in shallow pools formed in the early ocean coastline, forming a prebiotic soup. Afterwards these simple compounds forming polymers were grouped into forming more complex organic molecules. At some point, somewhere a molecule capable of replicating itself would appear and lead the formation and appearance of the first cell.
Origin of life required organizing atoms
into larger and larger molecules
We start with some of the commonest atoms in the Universe: hydrogen, oxygen, nitrogen and carbon. These
were assembled into smaller molecules, amino acids
and bases, which were eventually built into large
molecules such as proteins and nucleic
acids.
These molecules were certainly present in
the atmosphere released by the volcanoes of the young
Earth.
This atmosphere probably contained
molecules such as methane, ammonia, carbon
dioxide and water, but
not oxygen molecules.
http://www.youtube.com/watch?v=mF9U5x6Nxnw
They were washed down to Earth in the rain. There they were joined together to make nucleic acids and proteins, perhaps by being heated on the slopes of volcanoes, or on the ocean floor where hot rock rises from the Earth’s mantle.
The Miller experiment:
Experiments show that energy such as lightning
can create amino
acids and bases out of
these simpler molecules.http://www.youtube.com/watch?v=mF9U5x6Nxnw
They were washed down to Earth in the rain. There they were joined together to make nucleic acids and proteins, perhaps by being heated on the slopes of volcanoes, or on the ocean floor where hot rock rises from the Earth’s mantle.
It is not clear when life began. We guess
that it was soon after the meteorite era ended, about
4 billion years ago. All traces of early life on Earth have long since been
wiped out. One reason for exploring other planets is the hope that they will
show us life at an early stage of formation.
Could life exist on other planets? Our
Milky Way Galaxy contains 200 billion stars. If even a small percentage of them
have Earth-like planets, then our galaxy could contain many Earth-like planets.
Some of them, perhaps, are at just the right distance from their star to be
warmed to lukewarm temperatures where the water could be in liquid form and
perhaps life could flourish once it had begun. Of these, some must have
circular orbits (like the Earth) rather than the more common oval (elliptical)
orbit.
But since we do not know how life began, we
cannot say how probable it is that it could begin on these other planets.How life began is another of the great unanswered questions .
Creation of life on Earth
Some scientists are trying to create
artificial or synthetic life on Earth. In 2010 the J Craig Venter Institute created synthetic DNA
which they inserted into a bacterium. However this is still a long way from
creating a complete cell from simple chemicals.
And even if they managed to create life in
a laboratory, scientists would still be a long way off explaining how life
began, when only nature’s laboratory existed.
Reproduction
Once life had appeared it spread. If it had not spread it would quickly have been damaged
and died out.
http://www.youtube.com/watch?v=dKubyIRiN84 
Genes were able to
reproduce because of the way they were made.
 
Then new genes were built up on each half.
In this way two exact copies of the
original gene were made
Because of the way the bases fitted
together, they both carried exactly the same information as the original gene.
So these two genes carried the information for exactly the same protein. Life
could continue as before.
This is called reproduction. Life
reproduced and spread.
Mutation
Life not only reproduced and spread,
it also changed. We will see many changes as we follow the story of life. How did
these changes happen?
We normally think of mistakes and accidents
as bad. But sometimes they are good. Our own mistakes give us the chance to
learn, to discover something new. So it was with life.
A base of one nucleic acid could be changed into another base. These mistakes are called
mutations. They could be caused by sunlight, by
harmful chemicals or by radioactive atoms in the Earth.
The two genes which grew upon these two
halves were different from each other. They carried information
for different proteins.
Evolution
The world was a test bed where nature could
try out the mistakes caused by mutations. The new protein which had been made by accident was given a chance to prove itself.
In most cases it was useless, or even harmful, and the life which carried it
died.
But in a few cases it was useful, and it
helped life. It may, for example, have made it grow slightly quicker than other
life. After thousands of years other forms of life died out and were replaced
by this new form. This process is called evolution by natural selection. By
adding together lots of little changes life could slowly evolve into entirely
new forms. Notice that evolution depended upon the death of less successful
types of life. Death was the price that life paid for progress.
The life we see around us has evolved after
many small accidental mutations in genes over billions of years.
Charles Darwin and the Tree of Life - David Attenborough
23-6-14
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Thursday, January 8, 2015
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