Transcript Evolution
Evolution Changes in types of organisms over a period of time Fossils • A fossil is some remnant of an organism that proves its existence Imprints of bacteria, leaves or footprints Insects, pollen, or flower parts in amber Tools or pottery shards Bones of organisms in sedimentary rock Cave drawings Amber, sap from ancient trees, hardens and encases soft-bodies Cave drawings Determining fossil age • Relative dating • Oldest fossils are in the deepest sedimentary rock layers • Younger layers hold newer, more complex fossils • Absolute dating • Can be used to determine a precise age in years • Use the decay rate of radio-isotopes like carbon 14 • The oldest known fossils are approximately 3 billion years old • Half Life = time it takes for half of a radioactive element to decay. • Radioactive Decay = isotope breaking down into another substance. Radioisotope Half-life Polonium-215 0.0018 seconds Bismuth-212 60.5 seconds Sodium-24 15 hours Iodine-131 8.07 days Cobalt-60 Radium-226 Uranium-238 5.26 years 1600 years 4.5 billion years Comparative studies •Researchers use comparative studies to establish evolutionary relationships between organisms Comparative anatomy • Comparing specific body structures • Analogous structures have a similar function but the structure is different – Ex the wing of an insect and the wing of a bird • Homologous structures are similar in structure but may have different functions – Ex) human hand, cat paw, whale flipper, bat wing • Vestigial structures are reduced in size and have no known function • They resemble structures in other organisms – Ex) the human appendix or the pelvis bone in a whale Comparative embryology • The comparison of embryonic development • Early development is similar in many species • The closer the relationship between species the more similar is development Comparative cytology • Observing similarities in cell structures • All cells have some common organelles that perform identical functions Comparative Biochemistry • Similarities involving proteins, enzymes and nucleic acids –All organisms share genetic codes • Transcription and translation –All organisms carry on cell respiration in the same way –All autotrophs carry on photosynthesis in the same way Theories of Evolution J.B. Lamarck Use and disuse Organisms can change their body structure over the course of a lifetime ATROPHY – structure decreases in mass with disuse HYPERTROPHY – structure increases in mass with use • Lamarck believed that ACQUIRED TRAITS could then be passed to the offspring – Example) the neck of the giraffe August Weissman • Disproved Lamarck’s theory of use and disuse – He cut off the tails of mice then mated them – All of the offspring had long tails – This experiment was repeated for 22 generations – All of the mice were born with long tails! Charles Darwin • Theory of Natural Selection • Darwin served as a geologist, botanist, zoologist, and general man of science aboard the H.M.S. Beagle from 18311836 Darwin • Overproduction – organisms produce more offspring than can possibly survive • Struggle for existence – there are only limited resources available –Not all offspring will survive • Natural selection – those organisms with advantages in a given environment are most likely to survive and reproduce –Those who survive and reproduce are the FITTEST • Variation – offspring tend to be different from their parents and each other • Speciation – after many generations are involved in natural selection – A population may be so different from the original population that it can be classified as a different species – SPECIES = organisms who can mate and produce fertile offspring DNA analysis has confirmed that a bear shot in the Canadian Arctic last month is a halfpolar bear, half-grizzly hybrid. While the two bear species have interbred in zoos, this is the first evidence of a wild polar bear-grizzly offspring. Wildlife officials seized the bear after noticing its white fur was interspersed with brown patches. It also had long claws, a concave facial profile, and a humped back, which are characteristic of a grizzly. Now the genetic tests have confirmed that the hybrid's father was a grizzly and its mother was a polar bear. Speciation •Involves isolation –Anything which prevents two groups within a species from interbreeding Geographic isolation • A population is divided by a natural barrier – Mountains – Deserts – Body of water – Landslide cause by an earthquake – But genetic changes are necessary to complete the process Reproductive isolation • Differing selection pressures on the new environments can complete the differentiation of the new species. Microevolution •Small, gradual changes which are detectable within a few generations • Industrial Melanism – changes in the colors of a population as a result of human industrial activity Macroevolution • Long term changes that make a new species General patterns for evolution • Divergent evolution – different groups evolve from one ancestor • Convergent evolution – two or more different groups evolve so that they resemble one another strongly • Adaptive radiation – organisms spread into new environments and become adapted through natural selection Adaptations • an anatomical structure, physiological process or behavioral trait of an organism that has evolved over a period of time by the process of natural selection – it increases the expected long-term reproductive success of the organism • Organisms that are adapted to their environment are able to: – obtain air, water, food and nutrients – cope with physical conditions such as temperature, light and heat – defend themselves from their natural enemies – reproduce – respond to changes around them • Camouflage and mimicry are adaptations some animals use as protection from predators. • An animal that uses camouflage looks like things in its environment. It might look like a leaf, a twig, or a rock. • Animals that use mimicry use colors and markings to look like another animal. –Example) the Monarch Butterfly and the Viceroy Heterotroph Hypothesis • 1920-30s • Formulated by a small group of scientists • Suggests a probable sequence in which organisms appeared • Life on Earth began about 3.5 billion years ago. • The atmosphere was very different from what it is today. • The early Earth atmosphere contained mostly hydrogen, water, ammonia, and methane. • There was very little oxygen • There were abundant energy sources for chemical reactions to occur –Heat –UV radiation –Electrical activity Primordial soup • Gases in the atmosphere reacted with each other to form simple organic molecules –Example ) Amino acids, nucleotides Atoms combined to form molecules Amino acids were formed Stanley Miller • Miller built an apparatus to test these ideas in 1953 – A mixture of gases thought to resemble the Earth’s primitive atmosphere was passed through an electric spark • After one week the contents were analyzed • Miller found that it contained organic molecules –Urea –Amino acids –Lactic acid –Acetic acid • The Heterotroph Hypothesis SUGGESTS – The first organisms were anaerobic •No O2 was available in Earth’s primitive atmosphere • The first organisms used the organic molecules in the water for food • They released CO2 as a waste product • These organisms were ANAEROBIC HETEROTROPHS • Organisms that were able to use the CO2 evolved next • These organisms were ANAEROBIC AUTOTROPHS (have chloroplast) – They used the CO2 for photosynthesis – O2 was released as a waste product • Organisms that were able to use O2 evolved next • These were AEROBIC AUTOTROPHS and AEROBIC HETEROTROPHS Rate of Evolution •Gradualism = occurs slowly and continuously over time •Punctuated equilibrium = evolution can occur quickly