J Lecture 1 - Evolution

J Lecture 1 - Evolution - Evolution, Biodiversity and the...

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Unformatted text preview: Evolution, Biodiversity and the Environment Steve Johnson sjohnson@bio.umass.edu Readings: all reading will be posted on the course website and are REQUIRED! What is Evolution? Evolution: change over time Biological Evolution: change in the genetic composition of populations of organisms over the course of generations When did it all start? Formation of the Earth 5 4.5 billion years ago Spinning clouds of gas and dust collapse to form stars and planets. The Origin of Life - 3.8 billion years ago Evidence: carbon that had been processed by an organism Primitive earth had an atmosphere of hydrogen, methane, ammonia, water and CO2 - uninhabitable to life as we know it. Lots of carbon (carbon is common in our universe). Unstable atmosphere, lightning and volcanoes. Life started in "primordial soup" (hot organic-rich water) Experimental Evidence Experiments show that amino acids (the building blocks of life) can form in the conditions of the primitive atmosphere. History of Life: first cells 3.5 - 3.8 billion years ago Fossilized algae 19th Century Biology - Darwin and Wallace 1858 - On the Tendency of 1859 - On the Origin of Species Varieties to Depart Indefinitely from the Original Type (unpublished manuscript sent to Darwin) Darwin and Wallace - important experiences Wallace Darwin and Wallace - important experiences Wallace Darwin What Darwin saw in the Galapagos Concept - 1. Descent with Modification Species are descended from other species and descendents are slightly different from their ancestors. The descendent finch species have different beak shapes compared to the ancestor (middle). Concept - 2. Common Ancestry These organisms share many traits because they share a common ancestry. Concept - 3. Natural Selection Escape ability (gene) Mate-finding ability (gene) Food-finding ability (gene) Nest-finding ability (gene) Natural Selection: greater reproductive success arising from (genetically determined) characteristics that confer an advantage in a particular environment Charles Darwin, shortly after returning from his around-the-world voyage on the Beagle Three things must be present for evolution by Natural Selection to occur... 1:Variation Variation Variation 2: Heredity 3: Differences in reproductive success Heredity, and sexual reproduction create more variation! Early Evidence of Evolution Archaeopteryx Peppered Moth of early industrialized England Peppered Moth of pastoral country side But how are traits inherited? The Genetics Connection - Mendel 18 1865 - Treatises on Plant Hybrids An Augustinian monk, Mendel demonstrated that characteristics are inherited by conducting cross-breeding experiments with garden peas. He said that inheritance was due to factors - what we now know are genes. The Modern Synthesis - 1900's 1. Characteristics are inherited as genes (pieces of DNA). 2. Recognizes mechanisms of evolution in addition to natural selection (mutation, random genetic drift, migration, etc.). DNA molecule - Watson and Crick, 1953 Natural Selection increased reproductive success arising from genetically-controlled characteristics that confer an advantage in a particular environment Mutation random changes in DNA that alter existing genes Genetic drift - changes in the genetic composition of a population due to random events Migration - changes in the genetic composition of a population due to movement of individuals The Modern Synthesis - 1900's Darwin/Wallace Concept of Speciation time Species A Species B time Species C barrier time Synthetic Concept of Speciation Population B time Species B Species A time Species A time Species A Suggests that new species result from isolation and the accumulation of small genetic changes. Recognizes that evolution is not directional - there is no "goal" to evolution Evidence of Evolution: genetic change in populations over time wild mustard All of these vegetables are descendants of the wild mustard plant. Humans selectively bred wild mustard plants to get the different vegetables. The genetic make-up of each kind of plant is different. Evidence of Evolution: transitional forms Modern Whale pelvis Evidence of Evolution: patterns of genetic similarity among organisms In many instances, the same genes control the development of body segments. Evidence of Evolution: Pesticide Resistance Bacteria are becoming increasingly resistant to antibiotics Sarah Huber Andrew Hendry Geospiza fortis Why are there so many kinds of organisms? Why are there similarities among groups of organisms? Why is it that within a group we typically see variations on a theme? "Nothing in biology makes sense except in the light of evolution." -Theodosius Dobzhansky, 1973 "The more complex aspects of biology tend to make a lot more sense when considered from an evolutionary perspective." -Steve Johnson, about 10 seconds ago ...
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This note was uploaded on 05/18/2008 for the course BIO 105 taught by Professor Adler,irschick,podos during the Fall '08 term at UMass (Amherst).

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