معلومات قصير موضوع انجليزي بحث تقرير بالانجليزي باللغة
الانجليزية انشاء
موضوع عن الحيوانات الاليفة وانواعها
اين تعيش ماذا ياكل مدة حياتها اسماء صغارها
تعبير عن الجمل بالانجليزي تعبير كتابي عن وصف حيوان اليف
عبارات قصيره للاطفال
information about
paragraph معنى برزنتيشن معلومات بسيطه
اسم نطق كلمة معنى كلمة برجراف حيوان
مفترس لاحم عاشب اليف متوحش وحيش الغابة موسوعة عالم الحيوانات برمائي كل شيئ عن تزاوج
انواع الانجليزي الشائعة معنى كلمة بالانجليزي
اختصارات
معلومات عن الحيوانات بالانجليزي موضوع عن الحيوانات الاليفة
بالانجليزي دورة حياتها
تغذية الحيوانات والحشرات على ماذا تتغذى كيف تتغذى الموسوعة
تتذوق الطعام تصنيف
فوائد الجنس للصف الرابع للصف السابع الاول الثاني الثالث
الخامس السادس الثامن التاسع كتابة ذكر اضرار معلومات طائر انواع تربية قصة صفات حديقة الحيوانات
حيوانات المزرعة لرياض الأطفال براعم لائحة اسماء الحيوانات
العاشبة اللاحمة حيوانات تاكل النباتات مختلطة التغذية تتغذى
The evolution of animal species in nature
Evolution is by definition the change that things
undergo over time. For the animals that are now found on the globe, they are
the survivors of natural evolutions determined by the natural selection that
has eliminated the less adapted species.
The evolution of an animal will allow a race to
survive or simply disappear. A striking example of evolution is the giraffe,
which thanks to its long neck, can eat higher vegetation in the branches, which
allowed its species to survive.
Natural selection makes it possible to eliminate weak
individuals, but also weak animals that are diminished. However, some mutations
will help the individual survive better, and possibly move on to the next
generations.
The observation of fossils and the different kinds of
animals that form the same family, has allowed to detect certain species that
are the product of evolutions of other older animals.
A fairly easy example of the action of evolution, but
at a faster rate, is the crossing of purebred dogs. According to the usefulness
of the dog, crossbreeds were made which had the characteristics that one wanted
to obtain for the animal to produce. So, dogs of small or big size, long-haired
or short, aggressive or affectionate ... After several generations of crosses,
one ended up obtaining a new breed of dog. It is an evolution forced by the
man, by selecting the individuals of the crossing, to obtain a new animal. The
same thing is done for cattle, cats ...
The natural evolution of animals is simply dictated by
changes in environment, food, temperature, and accidental mutations of the
breed. So it's a very slow natural process. The creation of a new animal breed
can take thousands of years, but decimating one can be done in a few seasons.
Endangered animal breeds are a good example of breeding, even if the cause is
man, they simply can not survive their changing environment.
DNA has also helped to better understand the evolution
of animal and plant breeds, by making it possible to better identify members of
the same genus. It often happened that some specimens were joined to a family,
by physical traits, to then see that the DNA pointed to a different race.
Evolution is also observable more rapidly in the case
of bacteria and microbes. Seasonal flu is a mutation of the previous one, which
is quite different for the immune system to develop a new antibody. In the case
of more developed animals, the change is slower and usually occurs from one
organ to another.
The use of an organ that is necessary for the survival
of a breed determines its persistence, because a mutation that diminishes this
function puts the individual at greater risk. If this organ improves, it is
possible that it helps this individual to survive, and that his descendants
bear this new character. If the improvement is strong enough, the modified
organ can save more mutant individuals and eventually become dominant for this
breed.
The organ that is no longer truly used can atrophy
without risking the life of the animal, and thus become another viable
mutation. With time and many generations, it is possible that the organ
disappears completely, to give a new breed.
Natural selection will therefore determine the
evolution of a race, eliminating weak individuals who lose abilities, and
retaining only those individuals who survive or have positive mutations. It is
according to this theory that the evolution would have started with the
unicellular ones, to then give the microorganisms, the fishes, the amphibians,
the reptiles ... until the complex animals of today.
Animal evolution is therefore more likely to improve
animal species, since negative mutations are usually less viable in nature.
Even if the evolution tends to improve a species, a dominant character that
does not help, but does not harm, can take place in the evolution of a species.
It is simply a physical trait that does not result in harmful or positive
consequences on the evolution and wildlife of the animal.
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