February 7, 2010

Life Ascending - by Nick Lane.

Life Ascending - by Nick Lane.

[From the viewpoint of biochemist about 10 great inventions of evolution; they are the origin of life, DNA, Photosynthesis, The Complex Cell, Sex, Movement, Sight, Hot Blood, Consciousness,& Death. Interesting, but easier to folks from that background]

This is a redox reaction in which electrons are transfered from a donor (hydrogen) to an acceptor (oxygen) which wants them a lot more to form water, a thermodynamically stable product. All redox reactions involve electrons transfer from a donor to an acceptor and remarkably all life, from bacteria to man, relies on electron transfer. of one sort or another for its energy. As the Nobel Laureate Albert Sznet-Gyorgy put ir, " Life is nothing but an electron looking for a place to rest".

There are 3 billion letters (base pairs) in the human genome. every-time a cell divides, it replicates all of its DNA - a process that takes place in a matter of hours. The human body is a monster of 15 million million cells , each one harboring its own faithful copy of the same DNA.  To form your body from a single egg cell, your DNA helices were prised apart to act as a template 15 million million times. Each letter is copied with a precision bordering on the miraculous , recreating the order of copied with a precision with an error rate of about one letter in 1,000 million. 

Each generation is different from the last, not only becase our genes are stirred by sex, but also becasue we all carry new mutations. Sex is most peculiar randomizer of successful genes known.an infamous, albeit mostly hamrless organization known as 'Nobel sperm bank' fell into exactly that trap. Most of us sense that teh magic of sex (as a form of reproduction) lies in exactly this ability to generate variation, to pull a unique being from a hat every time. 

Oxygen is the key to planetary life. Oxygen does not just rescue a planet's life; it energizes all life and makes it big. Bacteria can do perfectly well without oxygen; they have an unparalleled skill at electrochemistry, they are able to react to react together virtually all molecules to glean a little energy. Photosynthesis and respiration are equal and opposite processes. In a nutshell, photosynthesis makes organic molecules from two simple molecules, carbon dioxide and water, using sunlight to provide the energy needed. Respiration does exactly the opposite. When we burn organic molecules(food) we release carbon dioxide and water back into air; and the energy released is what powers our lives. All our energy is a beam of sunlight set free from its captive state in food.

There is about 550 times Oxygen than carbon dioxide in the atmosphere. However even though atmosphere oxygen levels have not changed much at all, rising temperature lowers the solubility of oxygen in water. 

Hot blood is all about metabolic rate, all about the pace of life. However hot-blooded animals are not necessarily any hotter than cold-blooded animals, for most reptiles are adept at absorbing energy of the sun, warning their core body temperature up to levels similar to mammals and birds. But cold-blooded animals don't maintain such high temperature at night, and hot-blooded animals (humans & birds) are inactive at night too, but their hot-blood level is still the same throughout the whole life. Col-dblooded animals save energy by not keeping the same hot-temparature at night.

The main drawback wth cold-blooded animals is stamina. Lizards can match mammals easily for speed or muscle power and indeed over short distances outpaces them; but they exhaust quickly. Grab a lizard and it will disappear in a flash, streaking to the nearest cover as fast as they eyes can see. But then it rests, often for hours, recuperating painfully slowly from the exertion. The problem is that reptiles are not built for comfort, but for speed. The difference is written into the structure of muscle. Three key components in muscle: muscle fibers, capillaries, and mitochondria. In essence the muscle fibers contract to generate force, the blood capillaries supply oxygen and remove waste, while the mitochondria burn up food with oxygen to provide the energy needed for contraction. Train to be sprinter and you will develop bulky 'fast-twitch' muscles with lots of power but littel stamina. Train to be a long-distance runner and you'll shift the other way. That is why Nepalese, East Africans and Andean Indian have a good many traits in common - traits that lend themselves to life at high altitude - whereas lowlanders are heavier and bulkier.

The maximal metabolic rate is defined as the amount of oxygen consumed at full rate when we can push ourselves no further. It depends on many things, including fitness and genes. The maximal metabolic rate depends ultimately on the rate of oxygen consumption by the end-users, the mitochondria in the muscles. The faster they consume oxygen, the faster they maximal metabolic rate. But even a cursory refelction makes it plain that many factors must be involved, all of them iterrelated. it will depend on the number of mitochondria, the number of capillaries supplying them, the blood pressure, the sizt and structure of the heart, the number of red blood cells, the precise molecular structure of the oxygen-transporting pigment(haemoglobin), the the diaphragm and so on. 

According to a quietly significant paper that slipped into a quietly obscure journal, 'Ecology Letter' in 2008, the vegetarians may have a lot more to be smug than they credit. If we weren't vegitarians or rather their ancestral herbivores, we may never have evolved hot blood and fast pace of life that goes with it. We need to eat proteins to ensure that we get enough nitrogen in our diet which is i=needed for making fresh portiens for ourselves as well as DNA, both rich in nitrogen. Eat meat for proteins and if you are a vegetarians, make sure you eat plenty of nuts, seeds and pulses. 

Eye changed over these millions of years; the early humans eyes no wherr near to the present eyes of humans, The succession of steps needed to evolve an eye according to Dan-Eric Nelson and Susanne Pelger with an approximate number of generations for each change. Assumeing each change is one year, the full progression requires somewhat less than half-a-million years.

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