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Evolution Vocabulary Endosymbiotic Theory Evolution Convergent Evolution Coevolution Punctuated Equilibrium Descendant Ancestor Fossil Homogolous Sturcture Vestigial Structure Analogous Structure Embryology Biogeography Hominid Candidate Fossils ORIGINS OF LIFE Theories of the Origin of Life Abiogenesis Primordial soup Endosymbiotic theory Hydrothermal vents Panspermia Abiogenesis = "non biological origins“: hypothetical generation of life from non-living matter. Spontaneous generation Primordial Soup Famous Miller-Urey experiment (1953) suggested that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form. Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen. Endosymbiosis Deep-Sea Vents The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents These vents spew key hydrogenrich molecules. Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems. Panspermia = life did not begin on Earth at all, but was brought here from elsewhere in space Rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally. Key Concept Evidence of common ancestry among species comes from many sources. Evidence for evolution came from several sources. Fossils provide evidence of evolution. Fossils in older layers are more primitive than those in the upper layers. Paleontology provides evidence to support evolution. The study of geography provides evidence of evolution. Island species most closely resemble nearest mainland species Populations can show variation from one island to another Embryology provides evidence of evolution. Identical larvae, different adult body forms Similar embryos, diverse organisms The study of anatomy provides evidence of evolution. Homologous structures are similar in structure but different in function. Homologous structures are evidence of a common ancestor. Human hand Mole foot Bat wing The study of anatomy provides evidence of evolution. Analogous structures have a similar function. Human hand Mole foot Analogous structures are NOT evidence of a common ancestor. Fly wing Bat wing Structural patterns are clues to the history of a species • Vestigial structures are remnants of organs or structures that had a function in an early ancestor. • Ostrich wings are examples of vestigial structures. Molecular & genetic evidence support fossil & anatomical evidence Two closely-related organisms will have similar DNA sequences. Humans share a common ancestor with other primates. Primates are mammals with flexible hands and feet, forward-looking eyes and enlarged brains. Anthropoids are humanlike primates. So why are humans so advanced? BRAINSTORM with a shoulder partner about what makes us more advanced than other primates and organisms So why are humans so advanced? Bipedal means walking on two legs. – – – foraging carrying infants and food using tools HUGE brains! Language Use of tools NATURAL SELECTION Or, how did we get here…. Natural Selection Natural selection is a mechanism by which individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals. • • • Heritability is the ability of a trait to be passed down. There is a struggle for survival due to overpopulation and limited resources. Darwin proposed that adaptations arose over many generations. Natural selection explains how evolution can occur. • There are four main principles to the theory of natural selection. – variation – overproduction – adaptation – descent with modification ADAPTATION DESCENT VARIATION OVERPRODUCTION with MODIFICATION Variation 1. Reproduction occurs with variation This variation is heritable (traits inherited from parents) Variation Variation is a difference in a physical trait. Galápagos tortoises that live in areas with tall plants have long necks and legs. Galápagos finches that live in areas with hard-shelled nuts have strong beaks. Overproduction 2. Overproduction of offspring (too many babies!) There is competition among living things More are born or hatched or whatever, than survive and reproduce Adaptations 3. An adaptation is a feature that allow an organism to better survive in its environment. – – Species are able to adapt to their environment. Adaptations can lead to genetic change in a population. Descent with Modification 4. Selection determines which individuals enter the adult breeding population This selection is done by the environment Those which are best suited reproduce They pass these well suited characteristics on to their young Fitness describes how reproductively successful an organism is in its environment. This lecture keeps evolving….. Survival of the Fittest means those who have the most offspring that reproduce ‘Descent with modification from a common ancestor, NOT random modification, but, modification shaped by natural selection’ Natural selection acts on existing variation. • Natural selection can act only on traits that already exist. • Structures take on new functions in addition to their original function. five digits wrist bone Other Evolutionary Theories Lamarckism Inheritance of acquired characteristics E.g., giraffes really wanted leaves, so they stretched their necks and….. ‘Cave dwelling fish don’t use their eyes so they disappear’ ‘We don’t use our appendix so it is disappearing’ Mechanisms of Change Gene Flow Migration & Emigration Genetic Drift Bottleneck Effect Founder Effect Speciation Non-random mating Sexual Selection Genetic Recombination Gene flow is the movement of alleles between populations. Gene flow occurs when individuals join new populations and reproduce. keeps neighboring populations similar. Low gene flow increases the chance that two populations will evolve into different species. bald eagle migration Migration & Emigration Gene flow moves alleles from one population to another. Genetic drift is a change in allele frequencies due to chance. Genetic drift causes a loss of genetic diversity. It is most common in small populations. A population bottleneck can lead to genetic drift. It occurs when an event drastically reduces population size. The bottleneck effect is genetic drift that occurs after a bottleneck event. Genetic Drift Genetic drift has negative effects on a population. – – – less likely to have some individuals that can adapt harmful alleles can become more common due to chance Genetic drift changes allele frequencies due to chance alone. Founder effect The founding of a small population can lead to genetic drift. – It occurs when a few individuals start a new population. – The founder effect is genetic drift that occurs after start of new population. Sexual selection occurs when certain traits increase mating success. Sexual selection occurs due to higher cost of reproduction for females. males produce many sperm continuously females are more limited in potential offspring each cycle Sexual selection selects for traits that improve mating success. Types of Sexual Selection There are two types of sexual selection. – – intrasexual selection: competition among males intersexual selection: males display certain traits to females Genetic Recombination Mutations produce the genetic variation needed for evolution. Exit Slip There are many different species of birds, but they all have different songs. Explain what kind of mechanism of change this is and how it works. Vocab Evolution Natural selection Variation Fitness Adaptation Descendant Vestigal structure Homologous structure Analogous structure Vocabulary Natural Selection Frequency Genetic Recombination Gene Flow Genetic Drift Speciation Non-random mating Behavioral Isolation Geographic Isolation Variation Adaptation Adaptive Radiation Taxonomy: Organisms can be classified based on physical similarities. Taxonomy = the science of naming and classifying organisms. White oak: Quercus alba • A taxon is a group of organisms in a classification system. Binomial nomenclature = two-part scientific naming system. – – – uses Latin words scientific names always written in italics two parts are the genus name and species descriptor A genus includes one or more physically similar species – Species in the same genus are thought to be closely related. – Genus name is always capitalized. • A species descriptor is the second part of a scientific name. – – always lowercase always follows genus name; never written alone Tyto alba Scientific names help scientists to communicate. – Some species have very similar common names. – Some species have many common names. Linnaeus’ classification system Each level is included in the level above it. Levels get increasingly specific from kingdom to species The Linnaean classification system has limitations. Linnaeus taxonomy doesn’t account for molecular evidence. The technology didn’t exist during Linneaus’ time. Linnaean system based only on physical similarities. Physical similarities are not always the result of close relationships. Genetic similarities more accurately show evolutionary relationships. KEY CONCEPT Modern classification is based on evolutionary relationships. Cladistics = classification based on common ancestry Phylogeny is the evolutionary history for a group of species. evidence from living species, fossil record, and molecular data shown with branching tree diagrams Cladistics is a common method to make evolutionary trees. – – classification based on common ancestry species placed in order that they descended from common ancestor • A cladogram is an evolutionary tree made using cladistics. – A clade is a group of species that shares a common ancestor. – Each species in a clade shares some traits with the ancestor. – Each species in a clade has traits that have changed. • – – – Derived characters are traits shared in different degrees by clade members. basis of arranging species in cladogram more closely related species share more derived characters represented on cladogram as hash marks 1 Tetrapoda clade 2 Amniota clade 3 Reptilia clade 4 Diapsida clade 5 Archosauria clade FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID FOUR LIMBS WITH DIGITS DERIVED CHARACTER • Nodes represent the most recent common ancestor of a clade. CLADE 1 Tetrapoda clade 2 Amniota clade 3 Reptilia clade • 4 Diapsida clade Clades can be identified by snipping a branch under a node. 5 Archosauria clade FEATHERS AND TOOTHLESS BEAKS. SKULL OPENINGS IN FRONT OF THE EYE AND IN THE JAW OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS BEHIND THE EYE EMBRYO PROTECTED BY AMNIOTIC FLUID NODE FOUR LIMBS WITH DIGITS DERIVED CHARACTER Molecular evidence reveals species’ relatedness. • Molecular data may confirm classification based on physical similarities. Molecular data may lead scientists to propose a new classification. DNA is usually given the last word by scientists. Peppered Moths An example of evolution of a species over the past 200 years Before the Industrial Revolution in England the trees were a mottled white color. Coal burning factories began producing soot that covered the forests, making the trees black in color. The peppered moth population responded to this change, by adapting to their environment Moth Activity