Chapter 15 - Principles of Evolution PDF

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Chapter 15 - Principles of Evolution Thursday, October 12, 2017 2:39 PM

15.1 Hos Did Evolutionary Thought Develop  Evolution: change overtime in the characteristics of a population o Population: consists of all the individuals of one species in a particular area  Modern biology is based on our understanding that life has evolved Early Biological thought Did not Include the Concept of Evolution  Pre-Darwinian science held that all organisms were created simultaneously by God and that each distinct life-form remained permanently fixed and unchanging from the moment of creation (over time) o Plato - each object on Earth is merely a temporary reflection of its divinely inspired "ideal form" o Aristotle - categorized all organisms into a linear hierarchy - "Ladder of Nature Exploring New Lands Revealed a Staggering Diversity of Life  After observing and collecting data, naturalists were surprised by the number of species, or different types of organisms, was much greater than anyone expected  Some naturalists began taking note of fascinating patterns o Each geographic area has its own set of species o Some of the species in a given location closely resembles one another, yet differed in some characteristics o The differences between the species of different geographic areas and the existence of clusters of similar species within area seemed inconsistent with the idea that species were fixed and unchanging A Few Scientists Speculated that life had Evolved  French naturalist George Louis Leclerc suggested that the original creation provided a relatively small number of founding species, after which some might wave "improved" or "degenerated" o Species changed over time through natural process Fossil Discoveries Showed that Life has Changed Overtime  During excavations for roads…, rock fragments that resembled parts of living organisms appeared  Fossils: the preserved remains or traces of organisms that had died long ago o Bones, wood, sells, impressions in mud that have been converted into stone  Major events in the evolution of life can be observed in the fossil record  Fossil discoveries inform us about evolution  How to become a fossil o Tree leaf falls o Tree falls o Flooding brings in sand and mud o Drying of layers  Some pioneers realized that the distribution of fossil in rocks is significant  William Smith realized that certain fossils were always found in the same layer of rock  Also, the organization of fossils and rock layers was consistent across different areas  Fossil remains showed remarkable progression o Resemblance but different  Many of the fossils were from plant or animal species that had gone extinct: no members of the species still lived on earth

o Extant: still living  Different types of organisms had lived at different times in the past Some Scientists Devised Nonrevolutionary Explanations for Fossils  George Cuvier advanced the idea of catastrophism to account for extinct species while preserving the notion of a single creation by God  Cuvier hypothesized that a vast supply of animals were originally created and some dies and fossilized in rocks while others survived Geology Provided Evidence that Earth is Exceedingly Old  Lyell considered the forces of wing, water and volcanoes and concluded that there was no need to invoke catastrophes to explain the findings of geology o Evidence of ordinary, natural process occurring over time o Uniformitarianism Some Pre-Darwinian Biologists Proposed Mechanisms for Evolution  Lamarck published a book in which he hypothesized that organisms are evolved through the inheritance of acquired characteristics, a process in which the bodies of living organisms are modified through the use or disuse of parts, and these modifications are inherited by their offspring o This happens because organisms poses an innate drive for perfection  NOT correct - acquired characteristics are not passed down or inherited Darwin and Wallace Proposed a Mechanism of Evolution  Both studies species that differed in only a few features  Darwin published book "On the Origin of Species by Means of Natural Selection" - attracted attention to new ideas about evolution o Decent with modification and natural selection 15.2 How Does Natural Selection Work?  Darwin and Wallace proposed that life's huge variety arose by a process of descent with modification, in which individuals in each generation differ slightly from the members of the preceding generation - accumulate over time  Evolution = o Process by which modern organisms descend with modification o Theory that organisms evolve from common ancestor o A change overtime in the characteristics of a population o A change in genetic make-up of a population overtime Darwin and Wallace's Theory Rests on 4 Postulates about Population  Postulate 1: individual members of a population differ from one another in many respects o Ex: people differ in eye, skin, and hair color  Postulate 2: at least some of the differences among members of a population are due to the characteristics that may be passes down from parent to offspring (Selective breeding) o Offspring generally resemble their parents (BUT traits acquired by parents aren't passed down)  Postulate 3: in each generation, some individuals in a population survive and reproduce successfully but others don't o More organisms must be born than survive long enough to reproduce o Organisms produce far more offspring than are required to merely replace the parents o Even among offspring that do survive many fail to reproduce, produce few offspring, or produce less-vigorous offspring (which fail to reproduce in the future)

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Postulate 4: the fate of individuals is not determined entirely by chance or luck. Instead, an individual's likelihood of survival and reproduction depends on its characteristics. Individuals with advantageous characteristics survive longest and leave the most offspring - natural selection o Reproductive success depends on individual's characteristics (who wants to mate with who) o Fitness: relative reproductive success of one variant in a given environment o Adaptations: traits that increase individual fitness in an environment  Darwin and Wallace understood that is all 4 postulates were true, populations would inevitably change overtime  The characteristics of the population will change slightly with each generation o Process of natural selection Natural Selection Modifies Populations Overtime  Observation and experiment suggest that the 4 postulates are sound  Natural selection acts on individuals, but the influence of natural selection on fates of individuals has consequences for the population  A population evolves not an individual  Favorable heritable traits tend to get passed on 15.3 How do we Know that Evolution has Occurred?  Evolution is an accepted scientific theory  Scientific theory: a general explanation of important natural phenomena, developed through extensive/reproducible observations)  Key evidence for evolution are fossils, comparative anatomy, embryology, biochemistry, and genetics Fossils Provide Evidence of Evolutionary Change Over Time  Series of fossils from ancient organisms, intermediate organisms, and modern day organisms  Fossil series suggest that new species evolved from, and replaces previous species Comparative Anatomy Gives Evidence of Descent with Modification  Comparing the bodies of organisms of different species can reveal similarities that can be explained only by shared ancestry and differences that could result only by descent from a common ancestor o Different species are connected by a common evolutionary heritage Homologous Structures Provide Evidence of Common Ancestry  A body structure may be modified by evolution to serve different functions in different species o Internal anatomy looks the same - external anatomy changes - function changes o Shows that traits derived from a common ancestor  Homologous structures: have the same evolutionary origin despite any differences in current function or appearance Vestigial Structures are Inherited from Ancestors  Vestigial structure: no longer preforms the function for which it evolved in a species' ancestors, often serve no function at all o Homologous structures that are used by other vertebrates o "evolutionary baggage"  Animals/humans survive despite having vestigial structures because they do not constitute a survival-reducing burden over time Some Anatomical Similarities Result from Evolution in Similar Environments

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Comparative anatomy has demonstrated the shared ancestry of life by identifying homologous structures that were inherited by common ancestors, but also that anatomical similarities do not stem from common ancestry  Convergent evolution: when natural selection causes non-homologous structures that serve similar functions to resemble one another o Similarity arose from parallel modification of two different, non-homologous structures  Sometimes there is roughly similar appearance because the similarity is superficial  Analogous structures: outwardly similar but non-homologous superficial structures o Typically very different in internal anatomy because the parts are not derived from common ancestral structures Embryological Similarity Suggests Common Ancestry  Vertebrates are so different as adults but so similar at the early stage of development because they all descent from the same ancestors o Then when reached adult life genes are either expressed or not Modern Biochemical and Genetic Analyses Reveal Relatedness Among Diverse Organisms  Biochemical similarities among organisms provide the most striking evidence of their evolutionary relatedness  Structures and molecules can be homologous  Tool to reveal molecular homologies - DNA sequencing o Able to see nucleotides  Some biochemical similarities are so fundamental that they extend to all living cells o All cells have DNA as the carrier of genetic information o All cells have RNA, ribosomes, and approximately the same genetic code to translate that genetic information into proteins o All cells use roughly the same set of 20 amino acids to build proteins o All cells use ATP as a cellular energy carrier  The most plausible explanation for such a widespread sharing of complex and specific biochemical traits is that the traits are homologous o All of today's organisms inherited them 15.4 What is the Evidence that Populations Evolve by Natural Selection?  Artificial selection: the breeding of domestic plants/animals to produce specific desirable features o Produces a spectrum of living organisms  Connection between artificial and natural selection Evolution by Natural Selection Occurs Today  Scientific observation and experimentation  There is no reason to believe that evolutionary change is limited to the past  If inherited variation and competition exist, so does evolution by natural selection  Natural selection has silenced calling crickets  Natural selection can lead to herbicide and pesticide resistance  Natural selection can change coloration of guppies  Experiments can demonstrate natural selection o Lizards on islands - shorter legs o Animals best fit to survive will have adaptations inherited Selection acts on Random Variation to Favor Traits that Work Best in Particular Environments  2 important points underlie the evolutionary changes: o The variations on which natural selection works are produced by a change mutation

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Mutations produce beneficial traits that are passed on spontaneously Natural selection favors organisms that are best adapted to a particular environment  Natural selection favors what's "best" for the environment...