I just posted a new YouTube video on the Darwin Channel in which Darwin explains the symbiogenetic origin of complex cells using sushi as a visual example. The direct link is here.
Another useful video is one that I posted a long time ago and it has gotten buried under dozens of others. It is called "Darwin eats a hamburger" and it ties several crucial themes in biology together: nutrition (the dangers of eating too much fat), global warming (raising cattle releases a lot of greenhouse gas), and evolution (why we crave fat). In this video, Emma Darwin also speaks from behind the camera. The direct link is here.
Showing posts with label symbiogenesis. Show all posts
Showing posts with label symbiogenesis. Show all posts
Wednesday, September 5, 2012
Thursday, June 7, 2012
Evotour, part four. The Purisima Hills
From
Paso Robles (see previous entry) I headed south to Lompoc, which is known mainly as an agricultural
center with vast fields of broccoli, artichokes, and flowers; and as the city
closest to Vandenberg Air Force Base. My parents and I briefly lived there over
thirty years ago. Every afternoon, a strong sea breeze blows in, bringing mist
and fog. One time I saw it blowing a refrigerator box down the street. Not
every part of coastal California is a tropical wonderland.
My
main purpose was to visit the Purisima Hills, north of the city. Although just
a few square kilometers in extent, perhaps the largest diatomite deposit in the
world is found here. I made a Darwin video there, in which Darwin had been
reading Hemingway’s Hills Like White Elephants, and had been expecting to learn
something about the hills, but instead it was just about a man and a woman in a
bar. But the Purisima Hills are really white, because they consist almost
entirely of the shells of dead diatoms that accumulated over hundreds of
thousands of years starting about five million years ago. I have not posted the video yet.
The
reason this place is of great interest to science educators is that it
represents absolute proof that geological deposits could not have been produced
by a Flood of Noah. These are not flood deposits. They formed from dead diatoms
that accumulated undisturbed in a shallow sea, without the intermixture of very
much sand, silt, and clay. Mineral deposits are found nearby, but the diatomite
deposits are nearly pure. And they represent more diatoms than could exist at
any one time in one place. There is no way a Flood could have produced this,
unless God decided to filter out all the diatoms and slop them down in one
place, for reasons that are unknown and certainly not found in the Bible. Of course,
creationists think that God scooched all the large mammals into some places,
all the dinosaurs into other places, to make it look like they lived at
different times, just to play with our minds today. But diatoms? What kind of
God would play with our minds by scooping billions of diatoms and slapping them
down in one location, which ultimately became Lompoc, California? Diatoms float
because they produce oil. The diatomite deposits also contain petroleum, which
is in this case the transformed product of diatom oil. That’s why there are no
side roads on which I could retreat to make my video away from highway noises:
all side roads are blocked and posted with serious oil-company no-trespassing
signs.
Also
at this location is a small population of bishop pines (Pinus muricata). Like Torrey pines near San Diego, the bishop
pines grow and produce mature cones, but the cones do not open and release
seeds unless a fire burns them. Then the burned forest is immediately replaced
by a solid growth of small pines. There was a fire in the Purisima hills about
1964, and another in 1995. These pines (like Torrey pines, Monterey pines, and
digger pines) are not only adapted to inevitable fires but capitalize on them.
Not
only is the fire cycle an interesting adaptation, but also the pines represent
an example of evolutionary radiation. Different species of pines have evolved
in different locations in the coastal California hills: Monterey pines south of
San Francisco, bishop pines south of them, digger pines throughout the coastal
hills, and Torrey pines near San Diego. In addition, the Purisima population of
bishop pines are genetically distinct from the main population, which is found
over a hundred kilometers north of the Purisima Hills. Speciation at work.
The
Santa Ynez Valley, adjacent to the Purisima Hills, is also famous for having
the world’s largest species of lichen, Ramalina
menziesii. The strong winds bring moisture and minerals to these
impressively long lichens that hang from the branches of the Quercus agrifolia coast live oaks.
Lichens themselves are a wonderful example of symbiosis, and of symbiogenesis,
which are major forces in evolution.
Thursday, January 26, 2012
In Memory of Lynn Margulis
This essay will also be posted on my website at www.stanleyrice.com.
One of the greatest evolutionary scientists, Lynn Margulis, died last November 22. In this essay I would like to reflect on her contributions to our understanding of the world. Not just of a narrow aspect of science, but the whole world.
Lynn was a child prodigy who began her university studies at age 14. In graduate school, she studied genetics, and married her fellow graduate student, Carl Sagan (who was as creative and large a thinker as she). She was not content to just learn what others said about genetics. She wanted to understand why some traits were inherited only through the mother’s side. These traits appeared to be passed on not through the chromosomes in the nucleus but through the mitochondria, which are tiny energy factories inside of most cells. Some plant traits appeared to be passed on through chloroplasts, the tiny green photosynthesis factories in many plant cells. This meant that mitochondria and chloroplasts had, and used, their own DNA. She wondered why they had that DNA. When she read about the work of some Russian scientists in the early twentieth century, she had her answer. Mitochondria and chloroplasts started off as bacteria, which moved into and took up residence inside of larger cells that already had nuclei. They did not consume the larger cell, nor did it consume them. Instead they formed a permanent partnership, which has been going on for billions of years. Mitochondria and chloroplasts began, she said, by symbiosis—cells living together. The result was the genesis of a new, complex kind of cell. She called this process symbiogenesis.
When Lynn Sagan (later Margulis) wrote her paper, it was rejected fifteen times. She was persistent. Finally it was published. At first her ideas were scorned. But in less than a decade, most biologists were convinced that she was right. When I went to hear her speak, while I was a sophomore at the University of California, Santa Barbara (it was the first scientific seminar I ever attended), she was well received, even though the professor who introduced her made some off-color jokes. At the time, I was a creationist, and I thought that there were only two alternatives to the origin of a complex cell: either gradual evolution, or sudden creation. Lynn Margulis presented a third alternative. Her view was entirely evolutionary, of course; but the host cell and the bacteria had evolved, separately and gradually, then suddenly merged together.
Today Margulis’s view of the origin of mitochondria and chloroplasts is a textbook standard. Scientists are working on an even more amazing example of symbiogenesis: many believe that the nucleus itself is the evolutionary descendant of a bacterium that moved into a larger cell that did not yet have a nucleus. I suspect that this idea would have been too wild even for Lynn in the early days.
In her final years, Lynn was looking for evidence that cilia and “flagella” of complex cells (such as paramecia) were the evolutionary descendants of spirochete bacteria. She had some good circumstantial evidence, but never did find proof.
She was also the principal biological champion of the “Gaia” view of the Earth, a view first proposed by atmospheric scientists James Lovelock. All of the organisms of the Earth form a single network of life. The Earth is therefore not just the home of life, but is alive. Not every component of the Earth is alive, of course; but neither is every component of a cell. A cell has living components, such as mitochondria, and nonliving components, such as water. But nobody would say that a cell is not alive. By the same reasoning, the Earth is alive.
Lynn was pugnacious. She was not afraid of a good scientific debate. And she was not afraid to be wrong. Clearly she was wrong in her assertion that HIV is not an infectious virus. But if she had never taken the risk of being wrong, would she ever have had the insights that changed modern biology?
I had a chance to talk with Lynn Margulis in 2004, as I was preparing my Encyclopedia of Evolution. She was 66 years old at the time, and could have retired comfortably and with renown. But she was still fighting for recognition of yet more of her insights. I mispronounced her name, and she corrected me: the emphasis is on the first syllable, Margulis. She said I would only be allowed to make that mistake once. I didn’t make it again. She enjoyed what I had written in my encyclopedia but was not afraid to point out what she considered errors. When I dedicated Life of Earth to her last year, she left me a phone message saying that the dedication brought tears of happiness to her eyes. She bought copies and left them for students to read at the University of Massachusetts, where she worked. I am glad to have brought a little joy and appreciation into the life of this great scientist.
We can carry on Lynn’s legacy if we continue to think big about the world. When Lynn started, most scientists were trying to decompose the big picture down into component parts. But now, many scientists consider that the interactions of those components are the most important thing. An entire research institute, the Santa Fe Institute, is devoted to understanding complex interactions and emergent properties. Geneticists now know that humans and mice have about the same number of genes, and most of them are the same genes; the big difference between a mouse and a human is not the genes but the interactions among the genes. I like to think that Lynn contributed greatly to this important change in the scientific view of the world.
Announcement: I just posted a new YouTube video on www.youtube.com/StanEvolve. It will be up soon. Darwin comments on…Newt Gingrich?
Also, please send comments about what you would like to discuss, and thanks for the comments received.
One of the greatest evolutionary scientists, Lynn Margulis, died last November 22. In this essay I would like to reflect on her contributions to our understanding of the world. Not just of a narrow aspect of science, but the whole world.
Lynn was a child prodigy who began her university studies at age 14. In graduate school, she studied genetics, and married her fellow graduate student, Carl Sagan (who was as creative and large a thinker as she). She was not content to just learn what others said about genetics. She wanted to understand why some traits were inherited only through the mother’s side. These traits appeared to be passed on not through the chromosomes in the nucleus but through the mitochondria, which are tiny energy factories inside of most cells. Some plant traits appeared to be passed on through chloroplasts, the tiny green photosynthesis factories in many plant cells. This meant that mitochondria and chloroplasts had, and used, their own DNA. She wondered why they had that DNA. When she read about the work of some Russian scientists in the early twentieth century, she had her answer. Mitochondria and chloroplasts started off as bacteria, which moved into and took up residence inside of larger cells that already had nuclei. They did not consume the larger cell, nor did it consume them. Instead they formed a permanent partnership, which has been going on for billions of years. Mitochondria and chloroplasts began, she said, by symbiosis—cells living together. The result was the genesis of a new, complex kind of cell. She called this process symbiogenesis.
When Lynn Sagan (later Margulis) wrote her paper, it was rejected fifteen times. She was persistent. Finally it was published. At first her ideas were scorned. But in less than a decade, most biologists were convinced that she was right. When I went to hear her speak, while I was a sophomore at the University of California, Santa Barbara (it was the first scientific seminar I ever attended), she was well received, even though the professor who introduced her made some off-color jokes. At the time, I was a creationist, and I thought that there were only two alternatives to the origin of a complex cell: either gradual evolution, or sudden creation. Lynn Margulis presented a third alternative. Her view was entirely evolutionary, of course; but the host cell and the bacteria had evolved, separately and gradually, then suddenly merged together.
Today Margulis’s view of the origin of mitochondria and chloroplasts is a textbook standard. Scientists are working on an even more amazing example of symbiogenesis: many believe that the nucleus itself is the evolutionary descendant of a bacterium that moved into a larger cell that did not yet have a nucleus. I suspect that this idea would have been too wild even for Lynn in the early days.
In her final years, Lynn was looking for evidence that cilia and “flagella” of complex cells (such as paramecia) were the evolutionary descendants of spirochete bacteria. She had some good circumstantial evidence, but never did find proof.
She was also the principal biological champion of the “Gaia” view of the Earth, a view first proposed by atmospheric scientists James Lovelock. All of the organisms of the Earth form a single network of life. The Earth is therefore not just the home of life, but is alive. Not every component of the Earth is alive, of course; but neither is every component of a cell. A cell has living components, such as mitochondria, and nonliving components, such as water. But nobody would say that a cell is not alive. By the same reasoning, the Earth is alive.
Lynn was pugnacious. She was not afraid of a good scientific debate. And she was not afraid to be wrong. Clearly she was wrong in her assertion that HIV is not an infectious virus. But if she had never taken the risk of being wrong, would she ever have had the insights that changed modern biology?
I had a chance to talk with Lynn Margulis in 2004, as I was preparing my Encyclopedia of Evolution. She was 66 years old at the time, and could have retired comfortably and with renown. But she was still fighting for recognition of yet more of her insights. I mispronounced her name, and she corrected me: the emphasis is on the first syllable, Margulis. She said I would only be allowed to make that mistake once. I didn’t make it again. She enjoyed what I had written in my encyclopedia but was not afraid to point out what she considered errors. When I dedicated Life of Earth to her last year, she left me a phone message saying that the dedication brought tears of happiness to her eyes. She bought copies and left them for students to read at the University of Massachusetts, where she worked. I am glad to have brought a little joy and appreciation into the life of this great scientist.
We can carry on Lynn’s legacy if we continue to think big about the world. When Lynn started, most scientists were trying to decompose the big picture down into component parts. But now, many scientists consider that the interactions of those components are the most important thing. An entire research institute, the Santa Fe Institute, is devoted to understanding complex interactions and emergent properties. Geneticists now know that humans and mice have about the same number of genes, and most of them are the same genes; the big difference between a mouse and a human is not the genes but the interactions among the genes. I like to think that Lynn contributed greatly to this important change in the scientific view of the world.
Announcement: I just posted a new YouTube video on www.youtube.com/StanEvolve. It will be up soon. Darwin comments on…Newt Gingrich?
Also, please send comments about what you would like to discuss, and thanks for the comments received.
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