BCOR 12 1st Edition Lecture 2 Outline of Last Lecture I Major Themes in Biology II Chapter 22 Descent with Modification Outline of Current Lecture I Evidence for Evolution II Evolution Process and a pattern III Darwin s Main Observations and inferences IV Important Points about Natural Selection Current Lecture Fossils are evidence of evolution o Ex Beluga whale bones were found in the swamps of Charlotte VT the landlocked state of New England Artificial Selection selective breeding of domesticated plants and animals by humans Increases the frequency of traits in the animals and plants desired by HUMANS Desired traits are usually not beneficial to an animals in its natural habitat Ex A Dalmatian doesn t have coloring like that of a wolf to hide and survive in the wilderness and therefore would be spotted by its prey quickly Lamark was one of the very first scientists to propose a mechanism for evolutionary change He is known for his hypothesis being incorrect Lamark s Theory of Evolution 1 Use and disuse parts of the body being used often and extensively by the organisms will grow longer during the lifetime to benefit the organsim s survival a Ex A giraffe has a very long neck to be able to reach the leaves to eat Lamark s hypothesis says the giraffe s neck stretched DURING the period of it s lifetime 2 Inheritance of acquired characteristics a Ex Characteristics the long neck of the giraffe were acquired DURING the lifetime of the organism Lamark thought that the DNA inheritance changed during the organism s lifetime which we now know is indeed incorrect These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Charles Darwin was the first scientist to demonstrate a mechanism of evolution with evidence During his travels overseas Darwin came up with this question as he saw a great variety in species that were widely similar Could a new species arise by the gradual accumulation of adaptations to different environments Adaptation inherited characteristics of an organisms that enhances its survival and reproduction in a particular environment they are born with the adaptation they do not acquire it during their lifetime Darwin came up with this question based on his observations at the Galapagos Islands and on the South American mainland Observations Plants and animals found on the islands were very similar yet distinctively different to those on the mainland There was variation among organisms from island to island tortoises are a great example Variation differences between members of the same species Variation drives natural selection Ex Sailor s could spot the different between tortoise to tortoise on the islands MUTATIONS are the molecular source of variation They are the ONLY way to get a allele in the DNA code Gene expression expressing DNA as proteins DNA RNA Proteins Genotype phenotype Evolution by Natural Selection Natural Selection the process where organisms inherit certain characteristics that make them much more likely to survive and reproduce and pass on these chosen characteristics than those with other less favorable characteristics Ex Peppered moths are characteristically white with black spots however in the 19 th century industrialization and coal fires made towns rather sooty and black making the white moths more visible to predators that the black moths This caused the black moths to survive and reproduce much more often than that of the white moths This caused the numbers of black moths to rise Survival of the fittest doesn t count in natural selection Reproduction is what counts What counts is Fitness the measure of how many offspring are produced and how many of these offspring reproduce themselves Darwin made 3 major observations during his travels 1 Within a population there is a great variety in traits a Ex Not all humans look the same We can be of different skin colors height weight eye color etc 2 Traits are inherited from parents to offspring a This is through DNA 3 Species often produce more offspring that the environment can support Due to lack of food and other resources many offspring do not survive Darwin made two inferences based on these observations 1 Individuals who had inherited traits that infer a high survival and reproduction in a given environment will leave more offsprings 2 This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable trains in the population over generations In other words those who have the favorable traits to survive will produce offspring with the traits to survive and the favorable traits will later become the norm of the population over the years Natural Selection Main Ideas from Charles Darwin s book Origin of the Species 1 Descent with modification explains life s unity and diversity 2 Natural selection brings about the match between organisms and their environment Important points about Natural Selection 1 Natural selection is an editing mechanism not a creative force 2 Natural selection favors traits that increase fitness in the current local environment In other words Natural selection edits out the unfavorable traits so that the favorable traits that best suit the population to survive in their environment at that current time will pass on to further generations The favorable traits are bound to change over time as the environment changes