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Units 8 : Evolution Explaining how species change over time and the great extent of different species on Earth A. Theory of Evolution Explains how changes in a species occur over time ________________ sails around the world on the HMS Beagle Make a historical stop over in the ____________________ 1. Observations on the Galapagos Islands a) Islands have very different _______________________ b) Diversity of life hundreds of plant and animal species so ___________ to their environment c) _______ organisms in ________ parts of the world living in similar habitats were often very __________ from each other d) Some living organisms resembled _______________. Some fossils very different, Some living organisms very different 2. Publishes: The Origin of Species by Means of Natural Selection Darwin explains evolution as a ____________________ 3. Theory of Natural Selection a) ___________________ - Within a population more offspring are produced than can survive - There is variation among the offspring - Darwin could not explain the variation Where does variation come from? b) ______________________ - The number of organisms in a population tends to stay constant generation after generation - At some level there has to be _________ among the individuals of a population for ______, ____, _______, _________ - ________________ – compete for limited resources c) ______________________ - Those organisms best adapted to the environment are more likely to survive - __________ = any inherited characteristic that increases an organism’s chance of survival Structural, Behavioral, Chemical d) _________________ - The organisms with the _____________ survive and pass their adaptations on to their offspring - How are adaptations passed on? e) ________________ - After generations adaptations accumulate in the offspring as such that the offspring creates a new species - Species = a group of organisms that can interbreed and have viable offspring How did the Giraffe get its long neck? Overproduction Variation Competition Survival of the Fittest Reproduction Speciation How did the Giraffe get its long neck? 4. Artificial Selection = ____________________ Choosing specific traits in the hope the offspring will have a combination of the traits. Done for thousands of years by humans 5. Competing idea of Evolution Lamarck’s Theory of Evolution selective __________ of traits led to the change in a species over time This theory has been ___________! Don’t mess this up! Lamarck’s theory is based on the idea that evolution is based on need. ______________ to do with evolution. Millions of species have gone extinct because they needed a new adaptation! B. Evidence for Evolution How do we know that Darwin is correct? 1. ___________________ - Theory that Earth formed 4.6 billion years ago - Radioactive dating of rocks on Earth - 4.0 billion years ago – Earth begins to cool Water Vapor condenses and it Rains Oceans = Primordial Soup - 3.5 billion years ago – first signs of life simple single celled organisms ______________________ Heterotroph Hypothesis – 1st organisms on Earth were anaerobic heterotrophs autotrophs aerobic heterotrophs - 2.0 billion years ago – first signs of single celled eukaryotes - 250 million years ago – age of dinosaurs - 200,000 years ago – first signs of modern humans 2. ________________ Fossil = organismal remains that have been mineralized Bones, imprints, amber Generally: a) the deeper the layer the ______ the layer so organisms found in deep layers tend to be older b) Older organisms tend to be ______________ c) Upper / newer layers show more _________________ that have a connection to the older structure shows change d) more _______ of organisms tend to show up in the newer layers 3. Comparative biology a) Anatomy 1. ___________________ – on the outside the structures may look different and perform very different functions, but on the inside the structures are built ________________. Evidence that the organisms came from a _____________ and adapted to different environments= _______________ 2. ___________________ perform the same function but built __________________. Evidence that organisms of different origins ________ to _____________ = ____________________ 3. _______________________ body structure that is reduced in the living organism but __ ________________________________ of the organism the structure had some significance and importance. Evidence that the organism is now ___________________________ b) _______________________ the more closely related organisms are the _____________ ______________________________. Shows the organisms had a common ancestor. c) ___________________ The more similar the chemical make up of the organisms the more closely related they are. Compare ____________: Human - Chimp – 98.2% Human - Gorilla – 97.7% Human - Orangutan – 96.3% 4. Geographic Distribution of Species biological diversity results from the descendants of a local species migrating and adapting to new environments C. Mechanisms of Evolution Populations evolve not the individual organism Natural Selection acts upon the phenotypic expression of a gene in the life time of an individual organism new features do not evolve in a life time new adaptations result from mutations and sexual reproduction Gradualism Darwin’s idea of evolution Slow steady process over millions Supported by the fossil record ex: Giraffe, Elephants Punctuated Equilibrium Evolution occurs in rapid bursts with long ofperiods years of stability in between Drastic environmental changes occur that cause extinction or rapid change in species ex: bacteria resistance, peppered moth Genetic Drift - because populations don’t always remain stable - gene frequencies are changing = evolution is happening! 1. Stabilizing Selection – evolution that favors the average individual reduces variation 2. Directional Selection – evolution that favors either of the extreme forms 3. Disruptive Selection – evolution that favors both of the extreme forms evolution of new species