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MECHANISMS OF HEREDITY

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 The cells of the body are constantly dividing to replace damaged cells. Before a cell divides to create new cells, a process known as mitosis, or to form ovules or spermatozoa, a process called meiosis, the DNA included in each cell needs to copy, or replicate, itself. This process is possible because the DNA strands can open and separate. Each of the two strands of the original DNA serves as a model for a new strand. In this chapter, we will also tell you how human beings vary in height, weight, skin colour, eyes and other physical characteristics despite belonging to the same species. The secret is in the genes. Chemical Processes Although it is assumed today that all life-forms are connected to the presence of oxygen, life began on Earth more than three billion years ago in the form of micro-organisms. They determined, and still determine today, the biological processes on Earth. Science seeks to explain the origin of life as a series of chemical reactions that occurred by chan...
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CULTURE

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       АIthough questions remain about how culture originated, it is almost impossible to determine which things of the human world are natural and which are not. Scientists of many disciplines are trying to answer these questions from the evidence of prehistoric life found by paleontologists. The subspecies of mammals to which man belongs, Homo sapiens sapiens, appeared in Africa some 150,000 years ago, disseminated through the entire Old World some 30,000 years ago (date that the oldest signs of art were found) and colonized America 11,000 years ago; but the first traces of agriculture, industry, population centres and control over nature date from barely the last 10,000 years. Some believe that the definitive leap towards culture was achieved through the acquisition of a creative language capable of expressing ideas and sentiments more advanced than the  simple communication of Homo erectus.The First Artists  Cave paintings, like those of the caves of Al...
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FIRST HUMAN 2

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 Able Hunters Descendants of Homo heidelbergensis, the Neanderthals were the first inhabitants of Europe, western Asia and northern Africa. Diverse genetic studies have tried to determine whether it is a subspecies of Homo sapiens or a separate species. According to fossil evidence, Neanderthals were the first humans to adapt to the extreme climate of the glacial era, to carry out funerals and to care for sick individuals. With a brain capacity larger than that of present-day humans, Neanderthals were able to develop tools in the style of the Mousterian culture. The cause of their extinction is still under debate.                 Homo neanderthalensis                                                                                  ...
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FIRST HUMANS

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        The Australopithecus were the first humanlike creatures who could walk in an upright posture with their hands free, as indicated by the fossils found in Tanzania and Ethiopia. It is believed that climatic changes, nutritional adaptations and energy storage for movement contributed to bipedalism. In any case, their short legs and long arms are seen as indications that they were only occasional walkers. Their cranium was very different from ours, and their brain was the size of a chimpanzee's.         There is no proof that they used stone tools. Perhaps they made simple tools with sticks, but they lacked the intelligence to make more sophisticated utensils. Adaptation to the Environment         The climatic changes that occurred during the Miocene probably transformed the tropical rainforest into savannah. Various species of hominins left their habitats in the trees and went down to the grasslands in search of food....
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HUMAN EVOLUTION

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  Homo sapiens, the name that scientifically designates our species, is the result of a long evolutionary process that began in Africa during the Pliocene Epoch. Very few fossils have been found, and there are no clear clues about what caused the amazing development of the culture. some believe that a change in the brain or vocal apparatus permitted the emergence of a complex language. Other theories hypothesize that a change in the architecture of the human mind allowed Homo sapiens to use imagination. what is certain is that hunting and gathering was a way of life for 10,000 years until people formed settlements after the ice age and cities began to emerge.   PRIMATES DEVELOP         Perhaps motivated by climatic change, some five million years ago the species of primates that inhabited the African rain forest subdivided, making room for the appearance of the hominines, our first bipedal ancestors. from that time onwards, the scientific community has trie...
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THE INTRODUCTION

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                                                                  The human body is arguably the most complex organism that exists on this planet. made up of more that 100000 billion cells, each with its own unique identity, the human anatomy is a fabulously synchronized and integrated living machine that can perform a remarkable range of activities and functions.            A human being consists of a single structure, but this one entity is made up of billions of smaller structures of four major kinds. these are cells, tissues, organ and systems.         Cells have long been recognized as a simplest unit of living matter that can maintain life and reproduce themselves. the term cell was first applied by Robert Hooke, a 17th century English scientist , who compared the inter...
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