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Mechanical gears in Nature

26 Mar

The Issus is a plant-hopping insect living in gardens all across Europe (Fig.1). Now, scientists found they have in their legs gear mechanisms previously thought to be man-made and used on every bicycle and car gear-box. Their discoverers from the University of Cambridge said that this is the “first observation of mechanical gearing in a biological structure”, and published their findings in the journal Science.

As it is clearly seen on Fig.2, the gear teeth on the opposing hind-legs lock together. The legs move within 30 microsecond of each other, securing complete synchronicity in leg movement, otherwise would result in “yaw rotation” and putting the insect spinning out of control.
It is hard to understand how random mutation could provide the Issus with a so complex and perfect mechanism, but the authors said: “These gears are not designed; they are evolved – representing high-speed and precision machinery evolved for synchronisation in the animal world.”  It is worth to mention that the mechanistic gears are only found in the insect’s juvenile – or ‘nymph’ – stages; they are lost in adulthood. The authors apparently suggest that the risk of breaking one tooth on the gear due to systematic use (entropy!) may be the reason why nature prefers another solution.

 

Fig. 1 – The Issus. Image credit: Cambridge University.

 

Fig. 2 - Gears inside the Issus. Image credit: Cambridge University

Fig. 2 – Gears inside the Issus. Image credit: Cambridge University

REF.
{1} – Site Cambridge University

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The Origin of Death

11 Nov

Each continent, each culture, gave its own interpretation of this common fate of human existence. Numerous myths are heard all over the globe, but the main question remains within us: why and how Nature “invented” death, instead of other form of existence? Because apparently other possible paths were open.

One man who studied these matters was the American scientist George Wald, who won the Nobel Prize of Physiology and Medicine in 1967, a reward for his studies about the pigments in the retina, see his Nobel Lecture entitled “The Molecular Basis of Visual Excitation“.

Wald become a prominent social and political activist, and in a talk given at the MIT, he deplore: “Our government has become preoccupied with death, with the business of killing and being killed” . In a world unfortunately at the hands of the Military-Industrial Complex, seeking obsessively to generate wars around the globe in order to maintain its huge profits, Wald gave in 1970 a famous speech “The Origin of Death”, to which we refer in this text, since at the very end this talk is a lesson about life… Numerous other important individualities around the planet also did so, denouncing the situation, among them the ex-President Dwight Eisenhower (listen here), but the most hard denunciation was the one made by «the Major General [Smedley Butler] in the U.S. Marine Corps, an outspoken critic of U.S. military adventurism, and at the time of his death the most decorated Marine in U.S. history» {FN1}. Quoting again Wikipedia «In his 1935 book War is a Racket, he described the workings of the military-industrial complex and, after retiring from service, became a popular speaker at meetings organized by veterans, pacifists and church groups in the 1930s. In 1934, he became involved in a controversy known as the Business Plot, when he told a congressional committee that a group of wealthy industrialists were planning a military coup to overthrow Franklin D. Roosevelt. The purported plotters wanted Butler to lead a mass of armed veterans in a march on Washington and then become a dictator. Butler never met with any of the principals, and the individuals supposedly involved all denied the existence of a plot. The media ridiculed the allegations. Biographer Hans Schmidt portrays him as the victim of a small-time trickster». And it is a kind of surprise to find in Smedley Butler, the most decorated Marine in US history, the one who just asked: In the war, who pays the bills? who makes the profits?…

Hence, I try to follow here the reasoning of George Wald [1].

When death appeared in the evolution timeline, it seemed indeed a rather late evolution mechanism in the evolution.

George Wald. Image credit: elijahwald.com

But what is a cell, what are the main parts? Let us watch the next video (made in 1981 and interestingly we feel the passion that scientific knowledge woke in our societies at that time…)

Ricin is a naturally occurring protein that is among the most potent toxin from the vegetal world. Botulinum and tetanus toxins are more deadly and there is not known antidote. One milligram can kill  an adult…For example, during the Cold War, Georgi Markov, the Bulgarian writer that fled from Bulgaria and was working at the BBC as a journalist, was hit by an umbrella with a modified tip, prepared to inject a small amount of ricin into Markov’s leg; Markov died three days later. Ricin is extracted from the castor-oil plant (Ricinus communis), a tropical plant, and its lethal effect are known since 1888 (most countries banned its use under the Geneva Protocol).

The reason for this resides into one’s of ricin’s two polypeptide chains, in fact, one enzyme that inactivate ribosomes. Ribosomes assemble amino acids into proteins, and when cells are unable to reproduce them, they die very quickly. A cell is the smallest unity of life that can survive and reproduce by itself, possessing its information encoded in DNA, and provided it can access sources of energy and raw materials. What it is called the emergent property of life is a result of a collective of molecules organized in the form of a cell. All the molecules of life (as we know it now) are formed with carbon atoms; the function of organic molecules in biological systems (complex carbohydrates and lipids, proteins, and nucleic acid) start with their structure. The importance of carbon is based on the kind of bond (i.e. versatile bond): each carbon atom can bind to other 4 atoms through covalent bonds (i.e., in a covalent bond, two atoms share a pair of electrons).

In order to better grasp the scientific basis of life, I collect some resumed notes with important concepts down here (a task to be continued…):

George Wald was among the first scientist to ask himself: why cells start to die? Because in Nature cells have four ways to reproduce, without dying. The first is fission. One cell divides in two, and at the end we have two organisms when at the very beginning we just have one. That’s why Wald argue bacteria do not age, are immortal.

But occasionally, single-celled organism can do conjugation:this means the temporary union of two single cells with at least one of them receiving genetic material from the other, transferred the DNA from one cell to the other through a thin tube, called the pilus. This is the bacterial equivalent of sexual reproduction.

Endomixis is another possible process that cells have in order to reborn. “In endomixis the macronucleus in a Paramecium disintegrates, the micronucleus  divides, one of those new micronuclei grows up to a new macronucleus and you  have a brand new Paramecium.” (see next video).

Next, see an amoeba eating (this animal eats everything) two paramecia. Amazing! the paramecia seem possess by fear, just like us when cornered by a predator, like us supposed to be at another level of development…

Some elementary form of life that exists since the beginning of life on earth are the dinoflagellates, a kind of algae invisible to the bare eye, but that are present in all kind of ponds.

They seem to have a kind of primitive eye, and with their flagellum they are fast swimmers. Even some of them even possess a delicate cellulosic armature. In the next video you can see a dinoflagellate “stunned” by a passing paramecium…It is an amazing reaction at a such micro-level…We find everywhere primitive forms of life, strange forms of life, that persisted in our planet for millions of years, but it is unlikely that we may find among these forms of life, the primitive being, the original one. dinoflagellates, despite the magnesium that take part of their composition, we cannot easily say if they are plants or animals. In their classification, they are in fact a kind of algae, but they are fast swimmers, showing a great number of different forms, some of them with a cellulosic armature.

In nature, life takes advantage of any phenomena, and the next video illustrates this statement, showing the amazing bioluminescence produced by dinoflagellates.

The fourth process that nature invented for reproduction is syngamy. In this process, two cells fuse to make one. Or, in more technical language, it is the fusion of two haploid gametic nuclei to form the diploid nucleus of the zygote.

Hydra reproduces by budding, that is, a bud grows and separates from the main body, starting a new hydra. This small animal living in fresh water was recently discovered that it might be an antibacterial agent since we can extract from it a substance called hydramacine-1, strong enough to kill the klebsiella oxytoca, responsible for nasomiacales infections {FN2}.

Some animals have a fate that is shocking to us: they die immediately after reproduction! That is the case of the salmon…

Lamprey is another specie with daunting habits…

The lamprey begins its life as a wormlike larva, with no eyes, buried in the mud or sand of a swift-flowing stream. It stays that way for perhaps two or three years. Then it goes through a first metamorphosis, in the course of which, among other things, it acquires eyes. With that it gets itself out from the mud and sand and starts migrating downstream, usually to the sea, where it grows up. At sexual maturity it goes through a second metamorphosis. There are a lot of changes, but one of the most striking is a complete disintegration of the digestive system. That animal will never eat again; it loses its entire apparatus for consumming food. Then it starts its journey upstream [1].

It is difficult not to be touched by emotion when seeing a mature cell ending with programmed cell death…We may recall here Shakespeare, in Measure for measure (1603)

If I must die
I will encounter darkness as a bride,
And hug it in mine arms.

Well, everything around us seems to point to the inevitability of death, but George Wald finally argue that, at the very end, the germplasma is the entity that permanently survives, in the dynamic process of life…and death. The germ-plasm theory,  was advanced by the 19th-century biologist August Weismann, and defends that the germ plasm, i.e. the hereditary material, it is what is passed from generation to generation. And this idea, which is the basis of the modern understanding of the process of physical inheritance, is what Wald, at the end of his survey, concludes to be the essence of our eternity.

If the germ plasm wants to swim in the ocean, it makes itself a fish; if the
germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to
Harvard, it makes itself a man. The strangest thing of all is that the germ
plasm that we carry around within us has done all those things.[1]

Well, what we are doing here in this planet we don’t have a clue (although we can justify our existence on faith), but this can be a question of time, needing progress on our level of consciousness, both as individuals connected in a weird net with other beings and the cosmos…[see also Ref. [4]].

To finalize this post, let us do our homage to life with music, listening the oldest song ever written in our world. I agree with the great German philosopher, Friedrich Nietche, when he says: “Without music, life would be a mistake.”  ―    Friedrich Nietzsche,    Twilight of the Idols

REFERENCES:

[1] George Wald, The Origin of Death

[2] Microscopic Worlds

[3] Biology: concepts and applications, by Cecie Starr, Christine A. Evers, Lisa Starr (Cengage Learning, Belmont CA, 2011) [This is a very good book explaining the fundamental concepts of biology]

[4] The Uniqueness of the individual, by Peter Medawar

[5] Friedrich Nietzsche, Twilight of the Idols (or listen here)

FOOTNOTES:

{FN1} Quote here Wikipedia.

{FN2} See “New class of antibiotics”

SITES:

{1} Class notes Ciliata

{2} The Virtual Museum of Bacteria

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