14 03 2011 19 48 00 LECTURE 8 Species A set of individuals that are closely related by descent from a common ancestor and ordinarily can reproduce with each other but not with members of any other species Same species are capable of but morphologically look very different Some plants look the same but due to polyploidy more than the diploid number of chromosomes they can not interbreed Morphological species concept Based on their morphological features shape size body parts Biological species concept A group of interbreeding populations Offspring are fertile Evolutionary species concept A group of individuals with a common evolutionary lineage Carolus Linnaeus Swedish scientist Carl von Linne doctor and botanist Born in 1707 Called the Father of Systematic Botony Established modern system of nomenclature Used risqu language for his time o Classifying plants by their flowers he compared flower parts to human sexuality stamens were husbands many and the pistil was the wife the flower was the bed o Many were shocked His binomial system of nomenclature in which the genus and species names are Classified 12 000 plants and animals Published Systema Naturae in 1753 and many of the names he first proposed are still used in use today Evolution A genetic change in a population of organisms that occurs over time often adapting to an environment or way of life Evolutionary changes must be genetically inherited not acquired Creationism was the main belief all organisms were specially created unchanging Jean Baptiste Lamarck 1744 1829 French naturalist Proposed a theory that organisms were driven by some inner force toward greater complexity Thought that organisms could pass on traits to their offspring that they acquired during their lives Lamarckism proposed in 1809 Lamarckism Holds that traits acquired or diminished during the lifetime of an organism can be passed to its offspring Based his theory on two observations thought to be true in his day o use it or lose it individuals lose characteristics they do not require and develop those which are useful o inheritance of acquired traits individuals inherit the acquired traits of their ancestors theory was later disproved Charles Darwin 1809 1882 Born in England studied medicine theology Takes a 5 year trip around the world as a naturalist on the HMS Beagle Observes plant and animal species in Galapagos Islands Australia NZ egc Observed island animals are similar to mainland animal species descended but they show differences due to the conditions on their island Came home married cousin worked for 16 years analyzing his data Published the most influential text of all times On the Origin of Species by means of Natural Selection in November 24 1859 Controversy The Origin of Species caused great arguments between scientists and philosophers both noting the theories and failures and strengths Darwin s Revolutionary thoughts Darwin thought of organisms not as constant unchanging or specially created beings Could not believe that organisms today appeared as they have always appeared Changed biological thought forever with the concept of Natural Selection Natural Selection Has four premises inheritable 1 Variation members of a population have individual differences that are Natural selection won t work in a population of clones A key to variation is sexual reproduction 2 Overproduction natural populations reproduce geometrically Producing much more offspring than will survive 3 Competition individuals compete for the same limited resources Darwin called it Struggle for existence 4 Survival to reproduce only those individuals that are better suited to the environment survive and reproduce survival of the fittest fit individuals pass on to a proportion of their offspring the advantageous characteristics works on the individual phenotype which in turn changes the population gene pool time long periods of time must be available in order to change to a completely different species changes are slow offspring that inherit the advantageous traits are selected for o their changes of survival are greater o may live to reproductive age o may pass on those desirable attributes to future generations those that do not inherit these favorable genes are not likely to survive reproduce gradually the species evolves changes as more individuals carry these traits over time enough changes lead to a new species Artificial Selection selective breeding as practiced by humans on domesticated plants and animals Rates of Evolution Two interpretations about the pace speed of evolution based on the fossil record 1 Gradualism a traditional view Evolution occurs as a slow and steady accumulation of changes in organism Darwinian evolution Not much evidence 2 Punctualed Equilibrium Evolution proceeds with periods of inactivity followed by periods of very rapid evolution Gould and Eldridge model Fossil record supports this view Long periods of stasis no change in species followed by rapid change However fossil record is evidence only of Morphology structure while evolution encompasses morphology ecology biochemistry and behavioral changes There may be stasis in morphology while there is still active evolutionary changes going on LECTURE 9 Three types of Natural Selection Directional Selection o One trait at the extreme of the range is favored over individuals with the average or opposite extreme of the trait Stabilizing Selection Disruptive Selection o The average trait is favored over the extreme traits o The extreme traits are favored over individuals with the average trait Evidence in support of evolution Evidence of evolution can be found in extant organisms living organisms o Comparative anatomy Homologous organs organs similar in form in different organisms due to a common evolutionary origin share the same common origin but may have different functions Analogous organs organs that have similar look and or functions in different organisms but do not share a common evolutionary origin In some plants stems may look and function like leaves but they have different origins Similar function of tendrils climbing but different origin leaf vs stem Convergent evolution the process by which unrelated organisms in a similar environment evolve similar adaptive structures and physiol Vestigial organs organs or parts of organs that are non functional and degenerate An organ loses its function no selective advantage to have it but no selective pressure to get rid of it ex Wisdom teeth o