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UNIT 2: THE ORIGIN OF LIFE AND EVOLUTION Caracteristics of Life 1. 2. 3. 4. 5. 6. 7. Cellular organisation Reproduction Growth and Developement Energy Response to the Environment Regulation Evolutionary adaptation http://study.com/academy/lesson/the-defining-characteristics-of-living-organisms.html Activity 1: Make your own quotation about life or living organisms 1. THE ORIGIN OF LIFE The Origin of Life Timeline http://exploringorigins.org/timeline.html http://www.daniellaberge.com/history/timeline1.htm The Oparin Hypothesis Among the explanations for the origin of life we can mention the theory of the prebiotic chemical evolution. This theory was stated at the beginning of the 1920s by the biochemist Alexander Oparin, and it said that the organic molecules appeared on Earth thanks to the inorganic compounds that evolved into the most primitive forms of life. inorganic molecules (H2, CH4, NH3…) organic molecules (aminoacids, sugars, nucleic acids…) This hypothesis suggested the existence of a primitive atmosphere without oxygen, but with other gases such as methane, ammonia or molecular hydrogen, along with steam, a huge amount of energy related to the volcanic activity and strong electric storms. The absence of the ozone layer also promoted a huge amount of ultraviolet radiation. That atmosphere favored chemical reactions among gases and the formation of organic molecules, that were accumulated in the primitive oceans creating what we call the primordial soup. Stanley Miller´s experiment •Stanley Miller´s experiment reinforced the hypothesis of the change of inorganic molecules into simple organic molecules. •In 1953 Miller simulated the conditions of Oparin’s primitive atmosphere in the laboratory and, by using electrodes that generated electric shocks, he found out that amino acids, sugars and some precursors of nucleic acids appeared. https://www.youtube.com/w atch?v=iahBQolXQH8 We don’t know how fast or slow has been the development of those chemical reactions, but we have found evidence of life with an age of 3,500 million years. 2. EVOLUTION It is the change in biological organisms over successive generations. 2.1.-Theories about evolution AGAINST IN FAVOUR FIXISM (Until XIX century) Linneo LAMARCKISM (1809) Lamarck CATASTROPHISM (1822) Cuvier DARWINISM (1859) A. Wallace and C. Darwin CREATIONISM (1859) BALDWIN EFFECT (1896) Baldwin NEODARWINISM (1930-1940) T. Dobzhansky PUNCTUATED EQUILIBRIUM (1972) S.J. Gould Lamarck In 1801, a French naturalist named Jean Baptiste Pierre Antoine de Monet, Chevalier de Lamarck proposed a theory of evolution. We know now that Lamarck´s theory of evolution is incorrect, but it is interesting from the point of view of the history of science. Lamarck stated that when environments changed, organisms had to change their behavior to survive. If they began to use an organ more than they had in the past, it would increase in its lifetime. For example, if a giraffe stretched its neck for the highest leaves of a tree its neck would become longer. Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations. Meanwhile organs that organisms stopped using would shrink. Incorrect theory of Lamarck Darwin´s theory of evolution Nowadays, it is thought that the different ways of life are related to each other, and that they come from a common ancestor called LUCA (Last Universal Common Ancestor). The main idea of Darwin´s Evolution Theory has to do with the concepts of variability and natural selection. CHARLES DARWIN Alfred Wallace and Charles Darwin observed some morphological variations in some species that they saw during their journeys around the World. The conclusion was related to the existence of a common ancestor which suffered changes that lead to the appearance of new species. The responsible for that process was the natural selection. ALFRED WALLACE The naturalists were aware of the morphological variability among the individuals of the same species. However, Darwin and Wallace realized that some individuals were better adapted to some environmental conditions because they had some specific morphological features. The conclusion to that fact was that the Earth wasn´t static and that the environmental conditions have changed through time. The adaptation is the clue to the biological evolution. The organisms that are better adapted have more possibilities to survive and to reproduce. This is called natural selection. Those organisms transmit some of their features to their descendants so that the individuals that own those characteristics dominate the biological community. Neodarwinism Nowadays, it is known that the morphological changes depend on changes produced in the DNA by mutations and recombination during the sexual reproduction. Knowledge of DNA + Darwinism = Neodarwinism The key of Darwin´s natural selection is that there is variability in a community. Using our knowledge of DNA to explain the variability of species is called Neodarwinism. Variability is due to the mutations and to the recombination of genes in sexual reproduction. Neodarwinism explains the variability in a community. Natural selection will make the better adapted members of the community survive and spread their genes. Punctuated equilibrium It is difficult to understand the idea of the evolution as a gradual process. An important part of the scientific community defend that there is not enough evidence in the fossil register to talk about a gradual process. In fact, the paleontological evidence shows that the evolution is not a gradual process but a process produced by sudden changes. Punctuated equilibrium The theory of the punctuated equilibrium stated by the scientist Stephen Jay Gould, defends that the mechanisms of evolution are not gradual. What´s more, they are accelerated during the periods of important changes. 2.2.-Scientific Evidence of Evolution Paleontological Fossil record Evidence Molecular Biological Genomics Proteomics Homologies vestigial structures LUCA Paleontological: Fossil record • Taken together, fossils can be used to construct a fossil record, which is a timeline of fossils reaching back through history. • Several factors must be taken into account when constructing such a record. The strata of rock in which fossils are found give us clues about their relative ages and the environments in which an animal or plant lived. • Similarly, new technological techniques such as radioactive carbon dating help determine the absolute ages of fossils. Biological: Homologies Evolutionary theory predicts that related organisms will share similarities that are derived from common ancestors. Similar characteristics due to relatedness are known as homologies. Homologies can be revealed by comparing the anatomies of different living things. Homologous organs Homologous organs have the same structure but different function.They prove the existence of a common ancestor. Analogous organs These are organs that have the same function but different structures. The species that show analogous structures are not related (adaptations) Vestigial organs These are structures found in an organism with little or no known function. Such structures are thought to be remnants of a structure that at one time had a function in an ancestral species. For example, both whales and snakes have vestigial pelvic and leg bones, left over from ancestral species that walked. Molecular Molecular evidence for evolution includes similarities at the gene, protein, chromosomal, and genome levels. Proteomics Biologists have found that the more closely related two species are, the greater the similarity in amino acid sequences of their proteins. Such comparisons allow scientists to deduce evolutionary relationships between various organisms. Genomics Since DNA molecules are highly conserved and passed from one generation to the next, base sequence pattern should indicate evolutionary relationships. Via the process of DNA hybridization, scientists can accurately determine the degree of relatedness between various groups of species. Matches in base sequence between species indicate a high degree of relatedness. For example, in the figure on the right you can see that more matches are made between a human and a chimp than between a human and a chicken. This indicates that the human and the chimp shared a more recent common ancestor than the human and the chicken and are closely related Phylogenetic trees All life on earth shares a common ancestor. This common ancestor of life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Evolution means that we're all distant cousins. How to build a phylogenetic tree https://kozmopolitaydinlar.wordpress.com/201 2/09/20/evidence-for-evolution/ 3. FROM THE HOMINIDS TO THE HOMO SAPIENS Features as a very developed brain, the ability to make instruments, the use of language or the lengthening of the learning period (childhood) characterise the human being. We can also mention that we have a very specific way to walk (bipedalism) and opposable thumbs in our hands. These two features could be useful for carrying objects and for manipulating tools. Africa seems to be the home of hominisation. The majority of the ancient hominid fossils were found in the Rift Valley, near the Red Sea. However, in 2002 there were found the most ancient remains related to the hominids. They have an age of 6 to 7 million years and they were found in Chad (Central Africa), far away from the most known fossils. Some fossils of Autralopithecus were found in Kenia, Ethiopia and Tanzania. Lucy was the famous female Autralopithecus afarensis that was found in Kenia and whose skeleton is highly represented by several hundred pieces of bone. It seems that the hominids followed different evolutionary tracks from 3 to 1.5 million years ago, and it is generally accepted that the Autralopithecus afarensis was the only common ancestor. One of these tracks was the Homo group, whose eldest ancestor dated back to 2.3 million years ago. It was discovered in 1996 in Ethiopia and it was associated with some carved tools. It seems that the first humans were part of the Homo habilis species (from 2.3 to 1.8 million years ago) and of the Homo ergaster (from 1.9 to 1.3 million years ago). Homo ergaster was considered as a different hominid. Their height and the size of their brains were higher than the ones of their predecessors. They were also good at making tools and they are thought to be the ones who abandoned Africa, giving rise to the Homo erectus. In Europe, the oldest human remains date from 780,000 years ago. They were found in Burgos, in Sierra de Atapuerca, and they were classified as Homo antecessor. They were part of the evolutionary track that led to the Homo neardenthalensis. That track would have also led to the Homo sapiens, 100,000 years ago. Homo sapiens and Homo neardenthalensis coexisted for thousands of years. The last Homo neardenthalensis lived in the South of the Iberian peninsula, 28,000 years ago. Nowadays, there is a controversy about the geographical origin of the Homo sapiens. In 1987, there were some genetic analyses that pointed that all the current races come from the African ancestor, that could have lived from 200,000 to 130,000 million years ago.