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THEORY OF EVOLUTION Chapter 16 Idea of Evolution ◦ Charles Darwin (1809-1882) ◦ English naturalist ◦ Took a trip around the world on a ship called H.M.S. Beagle ◦ Mostly fascinated with the Galapagos Islands ◦ Best known for his theory of evolution by natural selection Darwin’s Journey ◦ Began in 1831 ◦ Sailed on a ship called the H.M.S. Beagle ◦ Five year voyage sailing around the coast of South America and Australia Observations Aboard the Beagle ◦ Darwin collected 68 species of beetles ◦ Wrote about the different characteristics of habitats and species that live there ◦ Species vary globally ◦ There are similar organisms around that world with similar ecological habitats ◦ Ex: Rhea birds in S. America and ostriches in Africa Observation Aboard the Beagle ◦ Species vary locally ◦ Related animals species often occupy different habitats within a local area ◦ Ex: Tortoise shell shape among Galapagos Islands Observation Aboard the Beagle ◦ Species vary over time ◦ Some fossils of extinct animals were similar to living species ◦ Ex: Armadillo fossils compared to modern day armadillos Darwin’s Findings ◦ Galapagos Islands ◦ Groups of animals vary from island to island ◦ Ex: tortoises and finches on each island resemble each other but differ in the shape and function of their shells and beaks ◦ Darwin believed these unique animals all came from a common ancestor and they changed/adapted to their environment Idea of Evolution ◦ Evolution ◦ Development of new types of organisms over time ◦ Heritable change in the characteristics within a population from one generation to the next http://ed.ted.com/lessons/myths-and-misconceptions-about-evolution-alex-gendler Ideas of Darwin’s Time ◦ Scientists thought all species were permanent and unchanging ◦ The Earth was believed to only be a few thousand (not billions) of years old ◦ During Darwin’s time, new research was being done to figure out the geology of the Earth Ideas that Influenced Darwin ◦ James Hutton was a geologist in 1700’s ◦ Made connections between mountains, valleys, and layers of rock ◦ Believed the Earth was older than thousands of years -- a time so old for the human mind to image ◦ The Earth changes very slowly and some layers can accumulate as the environment is changing Ideas that Influenced Darwin ◦ Charles Lyell was a English geologist that believed the Earth’s surface continues to change ◦ He explained that past processes that occurred are still occurring now ◦ Ex: Volcanoes erupted in the past and still today ◦ Published a great work called Principles of Geology in 1830 that built on the work of Hutton ◦ Darwin read this book while on his journey around the world Ideas that Influenced Darwin ◦ Jean-Baptiste Lamarck ◦ French naturalist that supported the idea that populations of organisms change over time Ideas that Influenced Darwin ◦ Proposed two hypotheses: Called Theory of Acquired Traits ◦ Organisms could change during their lifetime by using or not using selected parts of the body ◦ Individuals could pass these acquired traits on to their offspring ◦ Ex: Giraffes could lengthen their neck by stretching over a period of time to get the height they needed to eat and survive and then pass the longer neck trait to their offspring Ideas that Influenced Darwin ◦ Thomas Malthus was an English economist in the 1790s ◦ Reasoned that if the human population grew continuously, there would not be enough resources for everyone ◦ His reasoning explained why plants and animals produced more a high amount of offspring since a portion will not survive due to environmental factors ◦ Ex: Maple tree produces thousands of seeds each summer ◦ Ex: Oysters produce millions of eggs each year with the understanding that only a fraction will survive Darwin’s Ideas ◦ Around the same time Darwin and Wallace formed theory to explain evolution ◦ Darwin was able to publish his book first called On the Origin of Species in 1858 ◦ Book explained how evolution occurs by means of natural selection Free in iBooks! Artificial Selection ◦ Darwin studied animal breeders ◦ Farmers would select to breed only trees with the largest fruit, or the cows that produce the most milk ◦ Darwin called this process artificial selection ◦ Nature provides the variations, and humans select hose they find to be useful and allow them to breed and pass on traits to offspring http://www.youtube.com/watch?v=AJNK3FwtZFg Evolution by Natural Selection ◦ Mechanism from descent with modification ◦ 1. Struggle for Existence ◦ Organisms produce more offspring than can survive ◦ Ex: dogs give birth to a litter of puppies, while only a majority survive ◦ 2. Variation and Adaptation ◦ Traits vary within a species and their environment called adaptations ◦ These adaptations help increase ability to survive ◦ Ex: Mimicry with coral snake and scarlet snake Natural Selection (cont’d) ◦ 3. Survival of the Fittest ◦ Organisms best adapted for an environment will survive best and reproduce ◦ The ability for an organism to reproduce and pass on adaptations http://www.youtube.com/watch?v=t-LTWFnGmeg ◦ 4. Natural Selection ◦ Process by which organisms with variations most suited to their local environment survive and leave more offspring ◦ Organisms choose their mate based on desired traits ◦ Ex: beetles that are not eaten because of their color, will reproduce https://www.youtube.com/watch?v=7NQUqR_YpsA Types of Natural Selection Directional Selection ◦ An extreme phenotype becomes the favorable adaptation ◦ Occurs when the environment changes or species migrate ◦ The new environment favors the extreme conditions ◦ Ex: Long neck of giraffes Types of Natural Selection Stabilizing Selection ◦ Occurs when the average phenotype is the favorable adaptation ◦ Extreme phenotypes are unfavorable ◦ Most common type of natural selection Types of Natural Selection Disruptive Selection ◦ Very rare ◦ The average phenotype is unfavorable while the two extreme phenotypes are favorable ◦ Creates two subpopulations Common Descent ◦ Idea that every species must have descended by reproduction from preexisting species that arrange over time ◦ Ex: finch beaks at Galapagos ◦ All species – living and extinct – are descended from ancient common ancestors Transitional Species ◦ Organisms with features that are between hypothesized ancestors https://www.youtube.com/watch?v=XGHxjgrZ1X0 https://www.youtube.com/watch?v=o5Z4mPQBjqA Age of the Earth & Fossils ◦ Noted that fossils of extinct animals resembled living species ◦ Relative Age ◦ Age compared to other fossils in order of old to young ◦ Absolute Age ◦ Using radioactive dating to get actual number age Age of the Earth and Fossils ◦ Age of the Earth ◦ Geologists are certain based on evidence via radioactive dating to indicate the Earth is about 4.5 billion years old ◦ Fossils ◦ Remains of an organism that died long ago ◦ Many fossils form a series that can trace back to an ancient extinct ancestor ◦ Superposition ◦ Idea that strata form in layers where the layers closest to the top are the younger than below Anatomy and Embryology ◦ Anatomy: study of the body ◦ Embryology: study of development ◦ Homologous structures ◦ Anatomical structures that originated from the same common ancestor ◦ Ex: bones in arms of humans, penguins, alligator and bat ◦ Related structure but function may differ Anatomy and Embryology ◦ Analogous Structures ◦ When structures have similar function, but did not develop the same way ◦ Ex: wings of bat vs. bird ◦ Vestigial Structures ◦ Organs that no longer serve a function in an organism ◦ Ex: human tail bone, appendix Anatomy and Embryology ◦ Embryology ◦ Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor ◦ Many animals look similar during development and produce homologous tissue Genetics and Molecular Biology ◦ At the molecular level, the genetic code and homologous molecules provide evidence of common descent Phylogeny ◦ Relationships among groups of organisms ◦ Can make a “tree” of animals evolved ◦ Trunk of the tree would represent species that are closely related ◦ Branches represent a separate population or lineage Evolution in Action ◦ Biologists tested the hypothesis by comparing DNA from the various species ◦ DNA evidence supported hypothesis 2 that each lizard evolved independently on each island ◦ Convergent Evolution ◦ Process by which different species evolve similar traits ◦ Ex: twig-dwelling species came from different ancestors but evolved similar adaptations to their environment Divergence & Radiation ◦ Divergence evolution ◦ Process by which the descendants of a single ancestor diversify into species that each fit different parts of the environment ◦ Ex: All breeds of dog share a common ancestor with wolves Divergence & Radiation ◦ Adaptive Radiation ◦ Pattern of diversity when a new population in a new environment undergoes divergent evolution https://www.youtube.com/watch?v=Fl4iCDYYot8 Coevolution ◦ Evolution is on-going and many species may evolve together ◦ When two or more species have evolved adaptations to each other’s influence ◦ Ex: ◦ Predator/Prey Interactions ◦ Introduction of new species ◦ Creating antibiotics https://www.youtube.com/watch?v=nZyuqS-Kb7k