Theory of Evolution The Definition of Biological Evolution Biological evolution is the process through which the characteristics of organisms change over successive generations, by means of genetic variation and natural selection. It is most commonly referred to as changes in gene frequencies in populations.
Fossil record Scientists combine several well-tested techniques to find out the ages of fossils. The most important are Relative Dating, in which fossils and layers of rock are placed in order from older to younger, and Radiometric Dating, which allows the actual ages of certain types of rock to be calculated. If we begin at the present and examine older and older layers of rock, we will come to a level where no fossils of humans are present. If we continue backwards in time, we will successively come to levels where no fossils of flowering plants are present, no birds, no mammals, no reptiles, no fourfooted vertebrates, no land plants, no fishes, no shells, and no animals. Though the fossil record does not include every plant and animal that ever lived, it provides substantial evidence for the common descent of life via evolution. The fossil record is a remarkable gift for the study of nature. Darwin's theory of evolution says that each new organism is subtly different from its parents, and these differences can sometimes help the offspring or impede it. There are two main methods determining a fossil's age, relative dating and absolute dating. Relative dating is used to determine a fossil's approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is a method that tells us the actual age (in years) of an object by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it. There are many absolute dating
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methods. Nearly all of these methods make use of radioactive elements that occur naturally in various types of minerals and organic matter.
Natural Selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time. Charles Darwin popularized the term, natural selection; he compared it with artificial selection or selective breeding. The process whereby organisms better adapted to their environment tend to survive and produce more offspring. The theory of its action was first fully put forward by Charles Darwin, and it is now regarded, as be the main process that brings about evolution. Natural selection changes the genetic makeup of a population by favoring some genotypes over others. It does so through the differential reproduction of those genotypes. For example, when the industrial revolution came into place in 1890 most moths were grey and blended well with the grey bark on the trees. As time went on, the trees got soot on them and the black moths survived while birds ate the grey moths. The majority of moths now were black. In 1895 they started to clean up the pollution in the air and then the peppered white moths started to come back because the sut in the air had lowered and in 1956 the black moth population from 1890 started to be rare around England because of less pollution in the air.
Speciation Speciation is when new types of species are created over time due to various factors such as geography, physical traits, anatomy features or behavioral factors. It can happen on a microevolution and macroevolution level. Microevolution is when we see species changes for small groups in a relatively short amount of time. For example, Italian lizards on a Croatian island became not only insect eaters but also plants eaters in a period of 30 years or so. Macroevolution is the same but on a large scale.
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The environmental factors that come with speciation is that say when 2 flies are finding food and a storm comes along, the storm picks up the food and brings those 2 flies to a different environment than their original one. Then they adapt to their new environment. There is already another species of flies in that environment so they are used to it. Then another storm rolls through and they finally get to go back to the other environment and all the flies have to adapt to the environment again.
How we Know that Evolutionary theory is accurate Many scientists and philosophers of science have described evolution as fact and theory, a phrase, which was used as the title of an article by paleontologist Stephen Jay Gould in 1981. He describes fact in science as meaning data, not absolute certainty, but a scientific theory that is a wellsubstantiated explanation of such facts. The facts of evolution come from observational evidence of current processes, from imperfections in organisms recording historical common descent, and from transitions in the fossil record.
Human Evolution Human evolution is the lengthy process of change by which people originated from apelike ancestors. Scientific evidence shows that the physical and behavioral traits shared by all people originated from apelike ancestors and evolved over a period of approximately six million years. One of the earliest defining human traits, bipedalism -- the ability to walk on two legs -- evolved over 4 million years ago. Other important human characteristics -- such as a large and complex brain, the ability to make and use tools, and the capacity for language -- developed more recently. Many advanced traits -- including complex symbolic expression, art, and elaborate cultural diversity -- emerged mainly during the past 100,000 years. Humans are primates. Physical and genetic similarities show that the modern human species, Homo sapiens, has a very close relationship to another group of primate species, the apes. Humans and the great apes (large apes) of Africa -- chimpanzees (including bonobos, or so-called “pygmy chimpanzees�) and gorillas -- share a common ancestor that lived between 8 and 6 million years ago. Humans first evolved in Africa, and much of human evolution occurred on that continent. The fossils of early humans who lived between 6 and 2 million years ago come entirely from Africa. Jahvia Peters
Most scientists currently recognize some 15 to 20 different species of early humans. Scientists do not all agree, however, about how these species are related or which ones simply died out. Many early human species -certainly the majority of them – left no living descendants. Scientists also debate over how to identify and classify
species of early humans, and about what factors influenced the evolution and extinction of each species. Early humans first migrated out of Africa into Asia probably between 2 million and 1.8 million years ago. They entered Europe somewhat later, between 1.5 million and 1 million years. Species of modern humans populated many parts of the world much later. For instance, people first came to Australia probably within the past 60,000 years and to the Americas within the past 30,000 years or so. The beginnings of agriculture and the rise of the first civilizations occurred within the past 12,000 years. particular
Jahvia Peters