VIEWS: 8 PAGES: 92 POSTED ON: 11/29/2011
Evolution Evolution The Universe formed 13.7 GYA as a product of the “Big Bang”. • The Solar system formed 4.6 GYA Our Sun is a Star • Its life span is approximately 10 billion years…. Our star has 5 billion years left. Jean Baptiste Lamarck • Published his Theory of Evolution in 1809. • Proposed that Life changed from simple to complex over time. According to Lamarck Fossils were the remains of past life forms. Lamarck’s Mechanisms 1. Use and Disuse Body parts used to survive become larger and stronger. Body parts not used to survive deteriorate. Lamarck’s Mechanisms 2. Acquired Characteristics Modifications acquired by use/disuse were passed on to offspring. Lamarck’s Mechanisms 3. Natural Transformation of Species ….species change with every generation. Problems with Lamarck’s Theory • No knowledge of genetics. • Acquired traits are not transmitted offspring. To Lamarck’s Credits • Did suggest correctly the role of fossils in evolution. • Did suggest that adaptation to the environment is a primary product of evolution. James Hutton (geologist) Gradualism - 1795 • Gradualism is the idea that changes to the Earth’s surface is the cumulative product of a slow, but continuous processes. Result • Changes on the earth were gradual, not catastrophic. Charles Lyell Uniformitarianism • Incorporated Hutton’s gradualism into a theory called Uniformitarianism. Uniformitarianism • Geological processes have operated at the same rate over the Earth’s history. Result • The Earth must be VERY old. (much older than 6000 years of the fixed species concept). • Idea that slow and subtle processes, such as volcanoes, erosions and earthquakes can cause substantial change to the Earth’s surface. Thomas Malthus 1798 and 1826 • Malthus's idea of man's "struggle for existence" had an influence on Darwin's theory of evolution….. This struggle for existence of all creatures provides the catalyst by which Natural Selection produces the "survival of the fittest“. Origin Theories Before Darwin • The prevailing worldview, before Darwin’s ideas took hold, was that the earth was very young, species did not change, and the intricate features we now call adaptations were designed by a Creator. This worldview had held for about 2,000 years, since the time of Aristotle. Charles Darwin (1809–1882) was the most influential contributor to our current ideas about evolution. His book, On The Origin of Species, written in 1859, described evidence for changes in species over time and presented a mechanism, natural selection, for how these changes occurred. Darwin - 1859 • Publication of "The Origin of Species” “The Origin of Species” • Documented the occurrence of evolution. • Suggested that the mechanism for evolution was Natural Selection. Comment • Darwin is best remembered for the theory because of his overwhelming evidence. Voyage of the Beagle In 1831, Charles Darwin began a 5-year voyage around the world as a naturalist on the HMS Beagle. What he saw on that trip had a tremendous influence on his ideas about the natural world. In particular, he saw the organisms on the Galapagos Islands as examples of descent with modification, which was Darwin’s term for evolution. Darwin's had two evolutionary ideas...........they were "descent with modification" and "modification by natural selection"..... explain both and give an example both. Descent with Modification Evolution is defined as descent with modification from a common ancestor. Evolution only occurs when there is a change in gene frequency within a population over time. These genetic differences are heritable and can be passed on to the next generation. The central ideas of evolution are that life has a history—it has changed over time—and that different species share common ancestors. • On the next slide, you can explore how evolutionary change and evolutionary relationships are represented in “family trees,” and how these trees are constructed. You will also find a timeline of evolutionary history and information on some specific events in the history of life: human evolution and the origin of life. Natural Selection Natural selection is one of the basic mechanisms of evolution. Darwin’s idea of evolution by natural selection is relatively simple but often misunderstood…. It is composed of 4 ideas: 1.) variation in traits, 2.) differential reproduction, 3.) heredity, and 4.) the end result. To find out how “Natural Selection” works, imagine a population of beetles: 1. There is variation in traits. For example, some beetles are green and some are brown. 2. There is differential reproduction. Since the environment can’t support unlimited population growth, not all individuals get to reproduce to their full potential. In this example, green beetles tend to get eaten by birds and survive to reproduce less often than brown beetles do. 3. There is heredity. The surviving brown beetles have brown baby beetles because this trait has a genetic basis. 4. End result The more advantageous trait, brown coloration, which allows the beetle to have more offspring, becomes more common in the population. If this process continues, eventually, all individuals in the population will be brown. If you have variation, differential reproduction, and heredity, you will have evolution by natural selection. Evidences of Evolution 1. Fossils 2. Biogeography 3. Homologous and Analogous Structures 4. Vestigial Structures 5. Biochemical Similarities Fossils are the remains or traces of once living organisms. Molds are fossils which formed Casts are fossils which are from an impression of the shape formed when sediments fill or tracks of an organism. in the cavity left by decomposing organisms. Fossils can be used to 1. Show the course of natural selection… how organisms change overtime. 2. Fossils can tell us a great deal about an organism’s surroundings and the conditions under which it lived. 3. Certain parts of certain fossils can tell us about growth, injury, disease, form, function, activities, and instincts. Preserved Bones Bones can tell us a great deal about the area where the muscle attaches to the bone and leaves marks that indicate size, shape, and functions of these varied organs. An example of this kind of fossilization is petrified wood. Amber is fossilized resin of a coniferous tree. Fossils that are preserved in amber give us information about the anatomy of that organism; since the organisms that are preserved in amber, mostly insects, are usually preserved intact without any disintegration of organs, muscles, and coloring. • The cavities and the channels in skulls give us an idea of intelligence, behavior, and their principle features. Dating of Fossils • The two methods of Dating fossils are: • 1. “Relative” Dating And • 2. “Absolute” Dating Relative Dating Using the Law of Superposition (successive layers of rock were deposited one on top the other) scientists can estimate the “Relative” age of a fossil. Fossils are approximately the same age as the layer they are found in. The younger fossils are found closer to the surface, the older fossils are found in the deeper layers. Grand Canyon 250 million years old 255 million years old 260 million years old 265 million years old 285 million years old Absolute, or Numerical Dating using Radioactive Isotopes to determine the age of a sample. To Determine the Age of the Earth Scientists use Radiochronometry (The use of radioactive isotopes to determine the age of rocks) Radioactive isotopes: are atoms with too many, or, not enough neutrons to stabilize their nucleus…. As a result the nucleus “decays”. Atomic Structure • Atoms have Atomic numbers and Atomic masses (amu) • Atoms can be identified by their atomic numbers • If you change the number of protons in the nucleus, you change the atom. • Atomic number of Hydrogen : 1 • Atomic number of Helium: 2 • Atomic number of Gold : 79 • Atomic number of Lead: 82 • Atomic number of Uranium: 92 • Atomic number of Plutonium: 94 Types of Radioactive Decay Alpha Radiation, Alpha Particles are composed of 2 protons and 2 neutrons…. a He nuclei • Beta Radiation, Beta particles are high energy electrons • Gamma Radiation, Gamma rays are high energy photons Parent Element Daughter Element Half-life • 238 U 206 Pb: 4.51 Gyr • 235 U 207 Pb: 710 Myr • 87 Rb 87 Sr: 50 Gyr • 40 K 40 Ar: 1.30 Gyr Earth’s oldest rock Rock solidified 4.3 billion years ago How Carbon-14 Dating Works • Carbon-14 dating is a way of determining the age of certain fossils up to about 50,000 years old. It is used in dating things such as bone, cloth, wood and plant fibers. Carbon-14 dating can only be used to date fossils which were once alive. How Carbon-14 is Made Cosmic rays enter the earth's atmosphere in large numbers every day. For example, every person is hit by about half a million cosmic rays every hour. It is not uncommon for a cosmic ray to collide with an atom in the atmosphere, creating a secondary cosmic ray in the form of an energetic neutron, and for these energetic neutrons to collide with nitrogen atoms. When the neutron collides, a nitrogen-14 (seven protons, seven neutrons) atom turns into a carbon-14 atom (six protons, eight neutrons) and a hydrogen atom (one proton, zero neutrons). Carbon-14 is radioactive, with a half-life of about 5,730 years. Carbon-14 in Living Things • The carbon-14 atoms that cosmic rays create combine with oxygen to form carbon dioxide, which plants absorb naturally and incorporate into plant fibers by photosynthesis. Animals and people eat plants and take in carbon-14 as well. The ratio of normal carbon (carbon-12) to carbon-14 in the air and in all living things at any given time is nearly constant. Maybe one in a trillion carbon atoms are carbon-14. The carbon-14 atoms are always decaying, but they are being replaced by new carbon-14 atoms at a constant rate. At this moment, your body has a certain percentage of carbon-14 atoms in it, and all living plants and animals have the same percentage. Dating a Fossil • As soon as a living organism dies, it stops taking in new carbon. The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced. The carbon-14 decays with its half-life of 5,730 years, while the amount of carbon-12 remains constant in the sample. By looking at the ratio of carbon-12 to carbon-14 in the sample and comparing it to the ratio in a living organism, it is possible to determine the age of a formerly living thing fairly precisely. • Because the half-life of carbon-14 is 5,730 years, it is only reliable for dating objects up to about 60,000 years old. However, the principle of carbon-14 dating applies to other isotopes as well. Potassium-40 is another radioactive element naturally found in your body and has a half-life of 1.3 billion years. Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years). Biogeography Biogeography is the study of the distribution of fossils and living organisms. The distribution of fossils indicate the continents were once part of a single super-continent known as Pangea • Changes to the Crust of the Earth Edge-on View of Crust Continent Sea Floor 6 miles 25 miles Convection Currents Plate Tectonics Theory that the Earth’s Crust is Broken into moving Plates. Some of the Major Plates Convection currents in the Mantle are responsible for moving the various plates. The Edges of the Plates are areas of Intense Geologic Activity, such as Earthquakes, Volcanoes an Mountain Building. Transform Zone: one Plate slips by an adjacent Plate San Andreas Fault North American Plate Pacific Plate San Andreas Fault Approximately 1 million years from now the “Bay-Bridge” series (baseball) will be between San Francisco and Los Angeles. “Homologous” Structures and "Analogous" Structures Homologous Structures in Animals Homologous Structures are body parts which resemble one another in different species because they have evolved form a common ancestor. Homologous structures may look different because the anatomy is modified to live in different environments. Analogous Structures in Animals BAT BIRD Analogy of bat & bird wings • Analogous structures are body parts that resemble one another in different species, not because they have evolved form a common ancestor, but because they evolved as adaptations to their environment. Wings of bat and wings of a bird are analogous because they are both adaptations for flying. The fins of a whale and the fins of a shark are also analogous because they are both adaptations for swimming. “Vestigial Structures” are functionless structures that were once functional in ancestral species. This is a skeletal view of what would be the pelvic region of a boa - a large snake. Snakes obviously do not have legs, yet these boas have the vestigial remnants of both pelvic girdles and limbs, complete with a rudimentary claw. • In the illustration above, the coccyx or "tail-bone" of a human is shown. It is a much-shortened version of the tail present in most mammals. The tail is also equipped with vestigial muscles and nerves, yet it is short, rigid, contained completely within the body in most people, and completely non-functional! Other examples of such structures in humans include the appendix, wisdom teeth, and the muscles to used move the ears. In the case of the appendix and wisdom teeth, the structures are not only non-functional, but they have the potential for serious infection or even death. Biochemical (macromolecule) Similarities and Molecular Evolution • For evolutionists the revolution in DNA technology has been a major advance. The reason is scientists can determine the nucleotide and amino acid sequences of DNA and proteins form different species. Closely related species share a higher percentage of sequences than species distantly related. • More than 98% of the DNA sequences in humans and chimpanzees are identical…..did we evolve from chimpanzees?...of course not….if we did there would no longer be chimpanzees…….however, there is strong evidence that we share a common ancestor. What is a Species? A species is often defined as a group of individuals that actually or potentially interbreed in nature. For example, these happy face spiders look different, but since they can interbreed, they are considered the same species: Theridion grallator. Speciation Speciation is a lineage-splitting event that produces two or more separate species. Imagine that you are looking at a tip of the tree of life that constitutes a species of fruit fly. Move down the phylogeny to where your fruit fly twig is connected to the rest of the tree. That branching point, and every other branching point on the tree, is a speciation event. At that point genetic changes resulted in two separate fruit fly lineages, where previously there had just been one lineage. The branching points on this partial Drosophila phylogeny represent long past speciation events. Adaptive Radiation • An adaptive radiation generally means an event in which a lineage rapidly diversifies, with the newly formed lineages evolving different adaptations. Different factors may trigger adaptive radiations, but each is a response to an opportunity. These include: The evolution of a key adaptation A key adaptation usually means an adaptation that allows the organism to evolve to exploit a new niche or resource. A key adaptation may open up many new niches to an organism and provide the opportunity for an adaptive radiation. For example, beetle radiations may have been triggered by adaptations for feeding on flowering plants. Release from competition/vacated niches: Lineages that invade islands may give rise to adaptive radiations because the invaders are free from competition with other species. On the mainland, other species may fill all the possible ecological niches, making it impossible for a lineage to split into new forms and diversify. On an island, however, these niches may be empty. Extinctions can also empty ecological niches and make an adaptive radiation possible. For example, open niches vacated by dinosaur extinctions may have allowed mammals to radiate into these positions in the terrestrial food web. Specialization: Specialization may subdivide a single niche into many new niches. For example, cichlid fishes have diversified in East African lakes into more than 600 species. This diversification may have been possible because different fish lineages evolved to take advantage of different foods (including insects, algae, mollusks, small fish, large fish, other fishes’ scales, and even other fishes’ eyes!). Genetic Drift • Changes in the gene pool of a small population by chance. By Chance Convergent Evolution Even though fish are not at all closely related to whales and dolphins, they look very similar. Both groups have pairs of fins, a tailfin and a streamlined form. Since these characteristics are extremely successful for animals living in the water, these groups evolved along the similar lines. This is known as convergent evolution - i.e. similar characteristics evolving as the result of living in similar environmental circumstances. Wings are another example of convergent evolution; they can be found in birds, bats and insects, and these animals are not at all closely related! Divergent Evolution Divergent Evolution occurs when one species evolves into two (or more) species, which continue to change over time and become less and less alike. Coevolution Coevolution is the evolution of one species in response to new adaptations that appear in another species. • Pollination of many of flowers occurs as a result of the coevolution of finely-tuned traits between flowers and their pollinators. Yucca tree flowers have coevolved with moths who roll the pollen into balls and carry it to another Yucca tree deposit it on the stigma. Pollination of many of flowers occurs as a result of the coevolution of finely-tuned traits between flowers and their pollinators. Red, tubular flowers have coevolved with hummingbirds who have long beaks and are attracted to red. By studying inherited species' characteristics and other historical evidence, we can reconstruct evolutionary relationships and represent them on a "family tree," called a phylogeny.
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