Unit III Evolution Population Genetics 1 What is the biological meaning of the term evolution Contrast microevolution with macroevolution Evolution Species change over time New species arise by the modification of earlier species o Descent with modification Evolution changes in the frequencies of alleles in a population Not goal oriented Microevolution Macroevolution disputed can be observed today the evolution of an entirely new species disputed has not occurred recently the gradual evolution of traits within a population of a species over time not 2 Describe explain how each of the following serves as evidence that evolution could be a means by which life s diversity arose artificial selection comparative anatomy paleontology and comparative embryology Artificial Selection breeding by humans New species are created from a common ancestor via selective Comparative Anatomy The anatomy of different organisms could be similar because they descended from a common ancestor Ex Mammals have the same bones in the same relative positions in their forelimbs which suggests that mammals evolved from a common ancestor who had this basic forelimb groundplan o Forelimbs later evolved different functions in different 1 groups of mammals 2 Paleontology Paleontology The study of fossils The pattern of fossils in rock strata layers suggests that organisms have changed evolved over time Fossil organisms in close more recent layers are similar but still different Fossil organisms in farther apart layers are less similar New species appear in upper layers that didn t exist in lower layers Many species in older lower layers don t exist today extinct Comparative Embryology Early embryos of different vertebrates share many general features von Baer s Law As development proceeds similarity persists only among more closely related vertebrates Ex Reptile human early embryos are similar but pig and human later embryos still look similar whereas those of reptiles do not 2 lizard turtle pig human 3 3 How can molecular biology provide evidence for evolution Provide two examples Protein DNA sequence comparisons o The more recently two species shared a common ancestor the more similar their proteins DNA o Ex Humans and monkeys share 95 of their genetic content and shared a common ancestor more recently than humans mice 87 4 Distinguish between homologous analogous and vestigial structures providing at least one example of each Homologous Structures Structures that share similarities because of common ancestry o Look similar but many have evolved for different functions Analogous Structures Structures that have a similar function but not 4 because of common ancestry 5 o Ex Wings of birds and wings of insects Vestigial Structures Remnants of once functional ancestral structures o o Ex Hindlimbs of whales snakes Ex Human appendix tail bone goose bumps 6 5 What did Darwin find intriguing about the finches on the Galapagos Islands Explain why how the Galapagos finches might have helped Darwin formulate his hypothesis of evolution by natural selection Darwin noticed that the species of finch that lived close together appeared similar and species living in the same kind of habitat but in different locations did not The most notable difference was the size shape of their beaks He concluded that while they had descended from a common ancestor o on the mainland new species of finch had arisen through adaptive radiation Adaptive Radiation When members of an ancestral species radiate move into new environments and eventually become several new species each adapted to a particular lifestyle Genetic variability within species made finches with certain beaks more suited to their environment and the type of food available o o Ex Thin sharp beaks were ideal for consuming insects Ex Short powerful beaks were ideal for crushing seeds The offspring of finches whose beaks were more adapted to facilitating the consumption of the food available were more fit and survived and produced more offspring than those whose beaks had not adapted passing on the genes for the modified beaks o This is an example of natural selection because in the competition for resources those who were better equipped to feed won The finches who lived on different islands could not interbreed so they eventually became distinct species 7 6 Describe the process by which populations evolve via natural selection Why is it said that genetic variation is a prerequisite is required for evolution by natural selection Darwin s Model of Natural Selection Within a population more offspring are produced than can survive to reproduce genetic This leads to competition for resources and a struggle for existence Variation exists in all organisms and much of this variation is heritable o Some of this variation affects an individual s ability to survive and reproduce o Who survives to reproduce is not random The fittest individuals produce more offspring and contribute more of their genes to the next generation This results in a change in the gene composition from one generation to the next with favorable adaptive characteristics accumulating over time o This change in the gene composition of a population over time is evolution in its most basic form Genetic variation is required for evolution by natural selection because if all organisms had the same genes and as result were completely similar none of the organisms would be better suited for their environment than the others As result they wouldn t have a reproductive advantage and their genes wouldn t be selected for in the population All members of the population should survive and reproduce equally well Hardy Weinberg equilibrium 7 Lamarck thought that evolution was the best explanation for life s diversity as did Darwin How did Darwin s view differ from Lamarck s 8 Lamarck Said that species evolve by gradually changing to adapt to their environment o Right idea wrong mechanisms Use and Disuse 9 o If used body parts become stronger if not they deteriorate and eventually disappear Inheritance of acquired characteristics o Traits that an individual acquires in its lifetime not born with it by responding to their environment can be passed onto their offspring Ex Giraffes used to have short necks but as they reached for the leaves in the trees they stretched their necks and their offspring inherited the genes for longer necks Genetic variation within a population leads to some individuals having a greater chance at surviving
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