Chapter 1.a

December 2, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

MAN, ONE OF THE EVOLVING SPECIES

Let’s have a look around us; let’s observe the environment, with all the fantastic animals that flanked us in the wonderful journey of life and then let’s try to understand the role of man in the complex carousel of nature.
To succeed, we need to have a basic knowledge on the concept of biological species and on the theory of evolution, then stop and reflect with a deeper knowledge on the nature of human beings.

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1.a.1 – What do we mean with species?

December 3, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

leone

What do we mean with species?

The term species is synonymous with variety, gender, type, but in biology has taken a precise and technical meaning of fundamental importance to become one of the basic concepts of modern biology.
Men see living around them so many varieties of animals and it can be observed that these animals generate cubs of their own kind by mating with their own kind; horses generate other horses, dogs other dogs, etc.., just as men generate other men. The plants, animals and men who die are therefore replaced by the new born, generation after generation, in an endless cycle that, like the cycle of seasons, is repeated always equal to itself, forming an extremely stable picture.
Every form of life appears therefore as a manifestation of the many and immutable laws of nature, which form a smooth and reassuring context; bear with patience every winter knowing that then inevitably spring comes, as after the night a new day will come, after a thunderstorm, the calm will return etc.. and the repetition of the events thus infuses security to the extent that allows to provide that the hardships sooner or later certainly will end and good things will return.
Likewise, you can observe that mixed mating (between different kinds) will not take place or do not generate children; anyway, considering the domestic varieties, sometimes this happens: If we look at the many breeds of dogs, we can in fact note how these have the opportunity to cross; two groups of dogs of different races, placed in the same pen, form mixed couples that generate puppies with mixed physical characteristics. Once grown, these puppies also form couples, mating both among themselves and with the original groups and, after several generations, the peculiar characters of a race will also present in the other descendants and vice versa, there will be no more two groups distinguishable for their appearance but one group born from the merger of the first two; by farming chickens and pigeons instead, this won’t happen. The same phenomenon happens even in a forest or in another natural environment, in the presence of different varieties with the possibility of intercrosses in reproduction.
If we call “races” the varieties with the possibility of intercrosses and we call the other “species”, we can therefore say that in the same environment cannot coexist for long time two or more different races because the same tend to combine giving rise to a single genre. In a single natural environment therefore we can only find different species, which differ from the races for their inability to interbreed, regardless of the appearance of their physical characteristics; this is a general rule by definition, valid for all species of animals we see around us; they are separated from the point of view of reproduction and are kept separated by nature and therefore it is not just a question of appearance or a simple human convention.
The stable repetitiveness of species, both for animals and plants, is possible thanks to a reproductive isolation, which is the reason why biology bases the concept of species on the reproductive capacity. Giving therefore the name “horse” to a given reference animal, will also be horses all the animals that can inbreed with it (or who appear like it, even though of the same sex) to generate other horses, able in turn to repeat the cycle of reproduction. Are excluded all other animals, including donkeys that can generate with horses only sterile offspring.
Still using the example of the many breeds of dogs, it is often possible to find some of them with enormous physical differences, but to continue on existing in a distinct manner, they must be kept separate, otherwise they would intercross. The existence in nature of different races of the same species is therefore due to the fact that these races live in different regions, separated by a long distance, by a mountain range or by the sea, as well as domestic races are kept separate in different farms or by a simple fence.
Since the concept of species is linked to stability, immutability in succession of generations, one can understand the difficulty, even in the absence of religious dogmas, to accept the idea that the various forms of life can change over time.

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FURTHER INFO
   BREED,   SPECIES

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1.a.2 – Is an evolution of species possible over time?

December 4, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

giraffa

Is an evolution of species possible over time?

The modern theory of evolution says that with the elapse of many thousands years, living species can change and give rise to new species; this means that this theory denies that species are fixed and immutable as it appears in everyday life. These changes are anyway  so slow to be perceptible only in a few millennia and then, in similar time intervals, the species can almost always be regarded as fixed and immutable as they appear in everyday life. The immutability of species is therefore a valid but relative concept, as its validity is limited to some centuries or millennia, i.e. periods that exceed the lives of dozens of subsequent generations of men, who will not perceive these changes, neither from experience inherited by forefathers or by direct experience.
The generation of a new species occurs when, among the many changes that happen over time, there is one that impels the intercross with the original species.
The current theory of evolution has its basis on two pillars, two phenomena both necessary for the evolution of species: natural selection and genetic mutation.

 

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FURTHER INFO
   EVOLUTION

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1.a.3 – What is the role of natural selection in the evolution of species?

December 5, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

mimetico

What is the role of natural selection in the evolution of species?

To understand the concept of natural selection we should start by noting that, like human beings, specimens of an animal species have many individual characteristics and therefore are not perfectly equal to one another. The elements in common are distinctive of species, others are peculiar to the individual (for example, among equines, white coat with black stripes characterizes the species of zebras, but two zebras can be distinguished for the different height, different strength, difference in quality of teeth etc.).. Another fundamental and easily observed phenomenon is that some of the individual features can be inherited.
The variability of individual characteristics and their inheritance are objective facts always exploited by farmers to select particularly valuable breeds of livestock. Specimens with distinctive features considered positive are isolated from others and made inbreed between them; those cubs who inherit the desired qualities will remain in the group while the others  will be sent away. This way, the positive characteristics will be increasingly common in the group and, after a number of generations, the distinctive elements of a few individuals shall have become common features of the whole group, now become a variety of their particular species.
The animals in their environment form a sort of natural breeding in which each individual has numerous special features that can be transmitted to the offspring. Some quality of individual animal can, in a special environment, increase the survival of his offspring, compared to their own kind; these characters, generation after generation, will inevitably spread in the population and become common to the entire population itself, forming a new variety. This phenomenon is called natural selection.
It is important to note that, to spread the distinctive elements of an individual, it is not necessary that all the others are either eliminated or being prevented from reproducing: just their reproduction has less success, i.e., there will be a minor number of offspring able to reproduce. In nature the role of breeder is done by the environment, since they are the characteristics of the same to determine the probability of reproductive success. This is exactly the same for plants and fungi.

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FURTHER INFO
   NATURAL SELECTION

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1.a.4 – How mutations happen in the evolution of species?

December 6, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

dna

How mutations happen in the evolution of species?

The individual characteristics are inherited through the genes, chemical entities present in the cells, including those intended for the reproduction of the body. To the total number of genes, also called genetic heritage, correspond all the individual inheritable physical characteristics.
The genes are linked to one another in a long chain forming  the DNA molecule. This molecule has the ability to replicate, thus duplicating the genes as well. It is possible, although it is a rare phenomenon, that a mistake occurs in that duplication and this leads to the modification of a gene. Mutations can be also caused by physical or chemical agents as external radiation, viruses and other things that are called mutagen. The alteration of a gene is called mutation and may result in the emergence of a new individual feature.
The structure of an organism is a very complicated architecture in which an arbitrary change of a gene can have the most disparate effects; it will be disastrous if compromises the functioning of a gene that plays a strategic and fundamental role (like genetic diseases), while the effects will be less deleterious if the mutated gene has a more marginal role, up to the case when no harmful effect is there, as it may be the case of the emergence of a new nuance of eye color. The genetic characteristics of an organism are enormously numerous as well as the possible mutations, including those harmless. These mutations, just because harmless, will not be eliminated by natural selection and therefore roll over time giving rise to great variability of individual characters (almond eyes, protruding cheekbones, receding chin, taurine neck etc.). The greater the variety is, the greater will be the chance that some feature is useful in the event of an environmental change (for example, the color of the skin, hair and eye for men who have colonized the northern regions of the planet).
It should be noted that mutations play a key role in the evolution of species as natural selection provide the material to work on. Without mutations, natural selection tends only to standardize the most of existing genetic heritage without further changes. On the other hand, we can say that without selection even natural mutations alone could not lead to the phenomenon of  evolution of species, but only to an increase in individual genetic variability with new purely random combinations.

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FURTHER INFO
   DNA,   GENE,  MUTATION,  RADIATION,  VIRUS

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Selezione naturale e MutazioniABSTRACTS
   n. 1 – NATURAL SELECTION AND MUTATIONS

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1.a.5 – How a new species appears?

December 7, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

pinguino

How a new species appears?

When in evolution appears a mutation that prevents the possibility of crossing with the original species, it is passed a point of no return, a point after which there can be no longer the genetic mixing. This reproductive isolation, leads to the formation of a new species: it is not due to physical or geographical barriers but it is physiological, is part for the intrinsic nature of the species.
This can happen in many ways, for example, two people of the  same species, separated in different regions, can develop mutations that lead to the creation of two separate races. Then if the race of the first region develops a ritual of courtship incompatible with the other members of the second region, these latter will always be discarded in case of encounter. Another case occurs when the two races develop a physical shape too different; think of the difference in size between a St. Bernard dog and a Chihuahua dog that makes mating mechanically impossible.
The most important case is however the one due to genetic causes, that is when the accumulation of several mutations makes the fusion of DNA of two individuals increasingly difficult, until the total incompatibility is reached, causing sterility of the offspring or its failure to develop.

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1.a.6 – Is there a kinship among all species?

December 8, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

GORILLA RID  Fotolia_5005909_XSIs there a kinship among all species?

When a species is divided in two or more species, we can say that the new forms appeared descend from the first as the children are descended from their parents. This way it is highlighted a kind of kinship between species which, as human beings, may arise from each other, have a common ancestor, belonging to a very large family and form dynasties with also very complicated genealogical trees. Generally, the more distant the relationship is, the greater are the physical differences that appear, as a result of the sum of many mutations; with a reverse reasoning, as more are similarities, the closer we expect the kinship to be. With this criterion, it is easy to establish that a gorilla is a closer relative of man than it is of a horse and that this, in turn, has a closer kinship with man than with a hawk.
All this shows that man is not derived from present monkeys as well as a given individual is not derived from a cousin; the human  species and that of gorillas, today coexisting, result from an ancestor of both species as well as two cousins descended by a pair of grandparents in common.

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1.a.7 – The adaptation is subject to environmental context?

December 9, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

falco

The adaptation is subject to environmental context?

For adaptation we mean the sum of changes that a species undergoes because of natural selection in a given environment.  Natural selection favors the mutations that promote the survival of future generations, who consequently will be better fit to live in that environment. A classic example of adaptation is the development of a thick, warm fur in a region having very cold climate, or the development of long fast legs to escape predators.
Adaptation is always related to a certain environment because this determines the chances of survival and therefore the natural selection. However, a positive change in a certain context may also prove to be useful in other circumstances: for example hands, that the first monkeys used to cling to branches and to collect fruits, were then used by men to build instruments of all kinds, to write and to drive a car; another example is the stratum of fat, developed to deal with periods of famine and then became a protection against the cold for animals of polar regions. In these cases, we talk about pre-adaptation, as if they were an early adaptation, but in fact these are fortunate combinations which are anyway of great importance for the evolution, because increase the chances of adaptation to new environments, as well as to meet new needs and exploit new resources. In general, the evolution progresses by small steps but cannot create from scratch the new organs: it can only modify the existing ones, which therefore constitute a pre-adaptation, that is a basis for future developments.
In any stable environment, which does not change over time, positive mutations would sum up to exhaust all possibilities; over time, the appearance of new positive changes would increasingly become less likely and the different species would  find themselves in a sort of state of equilibrium given by the maximum adaptation to their environment.
The evolution is slow, gradual, but not uniform; often presents a variable speed precisely because of stability or instability of the environment. A situation of perfect stability is also very unlikely, in fact every mutation of any species is actually a small or large environmental change and thus the evolution will not stop ever, even without considering geological and climatic changes.

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1.a.8 – Progress and development: two terms to be distinguished?

December 10, 2009 — Riccardo Sabellotti - Giacinto Sabellotti

treno

Progress and development: two terms to be distinguished?

With the term progress it is generally meant an improvement, namely a change that brings some benefits: in fact we speak of economic, technological progress etc…
If we talk instead of evolution, it refers to a gradual change over time, not necessarily beneficial, for example the evolution of a disease, a storm, the phases of the moon.
Since the biological evolution is a gradual change that involves always some benefit for the survival of the species (or the offspring) such as a greater capacity to provide food, to protect the offspring, to escape predators, we may ask why it is defined evolution and not biological progress.
The main reason is that natural selection favors those changes that offer an immediate advantage in the environment in which the species lives, but often these changes are valid only in that environment, for example, it is good to develop a thick fur in a very cold climate, but if it warms, the same fur will become a problem. The biological progress is therefore related to a given environment, limited to this and is more precisely defined as adaptation, while the biological evolution never stops and is indeed stimulated by environmental changes.
To a continuous evolution does not match then a continuous progress, so it is good not to confuse the two concepts.

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THE POINTS OF VIEW
lente_ingrandimento SOCIAL PROGRESS
Progresso ed evoluzione

ABSTRACTS
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n. 2 – PROGRESS AND EVOLUTION 

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