Life in the broadest sense, is defined as the condition of the body, which shows an increase due to metabolism, reproduction and adaptation to the environment. These characteristics distinguish living organisms from inanimate objects.
The cell is the basic unit of life, and the body must consist of at least one cell to qualify as a living being.
The cells of all living organisms contain deoxyribonucleic acid (DNA), which contains genetic instructions for the development and functioning of life forms. These substances allow a living organism to grow and multiply.
DNA was first discovered in 1869 by Swiss physician Friedrich Miescher who noticed clusters of microscopic substance in the pus on the dressing over the wound. This substance was later identified as DNA.
The virus does not quite fit the definition of all life, and, according to the scientific definition, is not living in the technical sense. It consists only of DNA and ribonucleic acid (RNA) strands surrounded by a protein coat which do not require a host cell to metabolize nutrients and regenerated. When the virus is outside the host cell, it is dormant and is nothing more than a static organic particles.
Scientists believe that the age of the Earth about 4, 5 billion years, and the first forms of life began to emerge about 3, 7 billion years ago.
Scientists believe that amino acids and nucleic acids directly involved in the creation of the first forms of life on Earth, but the question of how nucleic acids could arise from nonliving matter still can not answer. Actually, as there is no definitive answer as a whole about the origin of life on Earth.
Throughout history, dominated by two main theories of the origin of life on Earth: 1. abiogenesis theory, which is now discredited, believes that life happened spontaneously from decaying organic matter. 2. The theory of biogenesis, on the other hand, argues that the new life comes from already existing forms of life.
The oldest living things on Earth, according to scientists, are single-celled prokaryotes, now known as bacteria. Researchers have found fossils of prokaryotes, age about 3, 5 billion years.
The emergence of life on Earth relief was likely to 430 million years ago. The first plant is a single-celled organisms that are distantly related to algae.
The first reptiles appeared 300 million years ago, and modern mammals began his story about 75 million years ago.
Scientists believe that the Earth will be more 7, 5 billion years before the sun becomes a red giant star, and is likely to destroy the planet. Earth may cease to exist long before that date because of multiple releases of radioactive substances from the surface of the sun.
Monkey appeared on Earth about 35 million years ago, and the first humans evolved from apes about 10 million years ago. Modern man Homo Sapiens species exist on Earth only 100 000 years.
Living organisms are divided into two major subtypes: prokaryotes and eukaryotes. Eukaryotes, which include all humans have cellular structure with the core and genetic information of the membrane, while not prokaryotic cells contain nuclei.
To date, all known living organisms were identified and scientifically classified according to the taxonomy of the Swedish scientist Carl Linnaeus. In 1758, published "The System of Nature", Linnaeus divided and qualified variety of living organisms to the assessment scale: kingdom, phylum, class, order, family, genus and species.
Scientists estimate that between five and 100 million unique species of plants and animals are now living on Earth. However, only about two million of these species has not yet been identified.
Insects number about 950 000 species from two million identified in the world.
There are about 300 000 different species of plants, which currently grow on our planet.
Mammals make up only 5416 species of the total number of identified animals on the planet Earth.
The theory of evolution, which explains how living things change over time through natural selection, was first published by Charles Darwin in 1859. Many scientists now point to this natural phenomenon as the cause of great biological diversity of the Earth.
Worldwide are currently living a little more than 6, 7 billion people. The population of men is slightly higher than women (approximately in the ratio of 3.41 billion to 3.37).
According to the Central Intelligence Agency, the average life expectancy of a person in the US is 78, 11 years.
During the XX century, the average life expectancy in the United States increased by more than 30 years. Officials attributed most of these achievements to advances in health care and timely awareness.
According to the 2008 report, the average life expectancy in the world is 66.26 years.
An old man, according to the documented, was a Frenchwoman Jeanne Calment, who lived 122 years and 164 days. Alive today - 114-year-old Gertrude Baines of the United States.
The average life expectancy in the world ranges from a maximum 84.36 years to a minimum of 31.88 years (African state of Swaziland). Experts explain the low life expectancy in many African countries, the rapid spread of HIV / AIDS.