Biology 102 Bio 102
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This 9 page Class Notes was uploaded by Alyssa Shriver on Saturday February 6, 2016. The Class Notes belongs to Bio 102 at University of Tennessee - Knoxville taught by Dr. Jeremy Chandler in Spring 2016. Since its upload, it has received 16 views. For similar materials see Introduction to Biology in Biology at University of Tennessee - Knoxville.
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Date Created: 02/06/16
Lecture 2/2/16 Speciation and “sexual islands”, evidence for evolution What is a species? o Biological species concept Species is a Latin word meaning “kind” or “appearance” The biological species concept defines a species as “A group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring What is bacteria? o Contains cell wall, plasma membrane, prokaryotic chromosome Duplication of chromosome and separation of copies Continued elongation of the cell and movement of copies Division into two daughter cells o The biological species concept cannot be applied in all situations, including Asexual organisms Reproductive Isolation o Ecological Isolation Different environments. The Artic fox and the desert fox live in such different places, they never encounter each other o Temporal Isolation Mating behavior or fertility at different times. The leopard frog mates in early spring and the bullfrog mates in early summer o Behavioral Isolation Different mating activities. The prairie chicken is not attracted to the mating display of the ring necked pheasant o Mechanical Isolation Mating organs are incompatible. Plants pollinated by the hummingbird do not receive pollen from plants pollinated by the black bee o Gametic Isolation Gametes cannot unite. The gametes from a dog and a cat cannot unite to form a zygote o Hybrid Inviability Gametes unite but viable offspring cannot form. The goat and sheep can mate, but the zygote formed does not survive o Hybrid Infertility Viable hybrid offspring cannot reproduce. Zebras and horses are different species because their hybrid offspring, zebroids, cannot produce offspring of their own Sexual Selection o Inherited traits are more likely to foster offspring or produce more offspring o Often leads to sexual dimorphism differences in appearance between males and females of the same species, such as in color, shape, size, and structure, that are caused by the inheritance Reproductive Barriers between Species o Prezygotic barriers include Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation, and Gametic isolation o Prezygotic barriers operate if Interspecies mating occurs and Hybrid zygotes form o Postzygotic barriers include Reduced hybrid viability, Reduced hybrid fertility, and Hybrid breakdown Mechanisms of Speciation o A key event in the potential origin of a species occurs when a population is somehow cut off from other populations of the parent species o Species can form by Allopatric speciation, due to geographic isolation, or Sympatric speciation, without geographic isolation Evidence of Evolution o Evolution leaves observable signs o Five of the many lines of evidence in support of evolution The fossil record Biogeography Comparative anatomy Comparative embryology, and Molecular biology Georges Cuvier o 17691832 Naturalist that specialized in the anatomy of animals. One of the first paleontologists o One of the first to realize that fossilized remains were evidence of extinct organisms. (religiously troubling theory) o “Father of Paleontology” o Theory of cataclysms The Fossil Record o Paleontologists: scientists who study ancient life by means of the fossil record o Fossil: the preserved remains or impressions of onceliving organisms o Fossil record: an assemblage of fossils arranged in order of age, which provides evidence of changes in species over time Not every organism that dies forms a fossil. Organisms are more likely to fossilize if they have bony skeletons or hard shells. In addition, the organism must be covered quickly upon death or create an imprint in special types of sediment. Therefore, the fossil record is not a complete record of past life, but it has supplied an impressive body of evidence for evolution Fossil Process o Organism dies Organism is preserved by rapid freezing, desiccation, or burial in amber. In these cases, organisms are preserved largely in their original state. Organism is preserved by rapid burial in sediment layers. Quick burial in sediment (ex. By mudslide or volcanic eruption) protects the body from rapid decay Organism is fossilized by mineralization. Hard parts of the body such as teeth and bones do not decay rapidly. Over time minerals in water are deposited in the spaces within bones or replace the bone as it breaks down. The result is a mineralized fossil. Organism is fossilized by imprint or mold. The soft mud in which a dead organism is buried hardens into rock around the organism. Over time the organism decays, leaving a space in the surrounding rock. The space has the same shape as the exterior. Reading the fossil record o Discovered fossil remains of Tiktaalik o Important part of evolution of vertebrate Animals with bony or cartilaginous backbones o Tiktaalik Transition between fish and landdwelling animals o Descent with modification (aka evolution) All living things are related Different species emerged over time due to natural selection o Not all organisms are preserved o The fossil record is not a complete record of past life o Extensive enough to show arc of life o Shows an ordered succession of evolution o See changes over time in family of organisms The fossil record of horses supports the theory of descent with modification. Forelimb fossils are similar to one another, but show changes over time from the earliest horse ancestors to modernday horses as species diverged from a common ancestor. In the fossil record we can observe over time a reduction in toe number, as the central toe became dominant, allowing horses to move more rapidly in new prairielike environments. Reading the fossil record o Shows intermediate fossils like Tiktaalik o 375380 million years ago o No landdwelling vertebrates How are fossils dated? o Relative dating Determine age of the fossil from its position relative to layers of rocks or fossils of known age o Radiometric dating Use radioactive isotopes as a measure of age Evolution of life on land o 400350 million years ago o Most land submerged under water Age of fishes o Some plants and invertebrates on land animal without a backbone o Over time land became more available 2/4/16 Lecture Notes Evidence for Evolution Continued & life on Earth Evolution of life on land o 400350 million years ago o Most land submerged under water Age of fish o Some plants and invertebrates on land Animal without a backbone o Over time land because more available Evolution of life on land o Living on the land requires Sturdier structure Prevention of water loss A different way to take in oxygen Limbs o Tetrapods Vertebrate with four true limbs Jointed, bony appendages with digits o Tiktaalik Possess many features of a lobefinned fish Also had a jointed elbow, wrist, and fingerlike bones Common Ancestry o All tetrapods share the same forelimb bones arranged in the same order o Homology: Similarity due to common ancestry o Homologous structures: are those that are similar because they are inherited from the same ancestor The number, order, and underlying structure of the forelimb bones are similar in all the groups illustrated below. The differences in the relative width, length, and strength of each bone contribute to the specialized function of each forelimb. The anatomical homology is strong evidence that these organisms all have a common ancestor at some time in the distant past. The variations in bone shape and function reflect evolutionary Divergent Evolution o Accumulation of differences in populations which can lead to the formation of a new species o Vestigial Structures a structure which has lost much of its ancestral function In human examples: appendix, coccyx, goose bumps How old is Earth? o Rocks collected from Apollo missions o Estimate age of Earth: 4.5 billion years old o Radiometric dating Amount of radioactivity present in a rock is used as a geologic clock o Radioactive isotopes Unstable form of an element that decays into another element by emitting energetic particles (radiation) o The time it takes for half the isotopes in a sample to break down is called its halflife o Used to determine the age of the materials in which they’re found o Some rock types, like those produced during volcanic eruptions, contain radioactive minerals like zircon that can be used to determine the age of the rock. Because the isotope238 decays to lead at a constant rate, the age of rock layers containing these minerals can be calculated by measuring the ratio of uranium238 to lead206 in the mineral sample. When and how did life begin? o 3.5 billion years ago o Left no discernible evidence o Harold Urey and Stanley Miller hypothesized that they could synthesize organic molecules by replicating the chemical environment of early Earth o Their experiment yielded new organic molecules, including amino acids o Showed that it was possible to create molecules of life from inorganic materials What was life like million of years ago? o The geologic timeline shows that Earth’s geography and climate have gone through dramatic changes o Oldest known fossils date 3.5 billion years ago o Atmosphere lacked oxygen o Unicellular prokaryotes that used other gases as a fuel source o Emergence of unicellular photosynthetic organisms 3.0 to 2.5 billion years ago o Oxygen began to accumulate in the atmosphere o First multicellular eukaryotic organisms: green algae 1.2 billion years ago o Marine invertebrates arrived 600 million years ago o Diverse animal world in Cambrian explosion o Land colonized by primitive plants 450 million years ago o Periodic mass extinctions punctuate the fossil record Elimination of all individuals in a species o Survivors spread and diversified o Colonized newly open habitats o Adaptive radiation o Pattern of extinctions followed by adaptive radiation is seen in the fossil record o Punctuated equilibrium: periodic bursts of species change as a result of sudden environmental change Why are there no penguins at the North Pole, and no polar bears at the South Pole? o Distribution of organisms reflects their evolutionary history o Biogeography: study of how organisms are distributed in geographical space o Plate tectonics Movement of Earth’s upper mantle and crust Influences the geographical distribution of landmasses and organisms o Earliest penguin fossils were found near New Zealand and date from a time when what is now New Zealand was physically close to Antarctica. Penguins were able to distribute widely in the southern hemisphere with the movement of the tectonic plates. Are creatures that look alike always closely related? o Common ancestry is not the only reason that two species might appear similar o Convergent evolution Organisms that are not closely related evolve similar adaptations as a result of independent episodes of natural selection For example, cold water fish How many species are there on Earth, and how do scientists keep track of them? o Estimated 5 million to 30 million total number of species on Earth o 1.5 million or so have been formally described Taxonomy o How we classify different species o Systematically identifying, naming, and classifying organisms on the basis of shared traits o Organisms are classified into groups that are increasingly exclusive. In the broadest category (animal kingdom), all animals are included. Closely related organisms are grouped based on morphological, nutritional, and genetic characteristics. There are far fewer organisms in an order than in a phylum. Molecular methods o Based on molecular (DNA) and morphology (phenotype) Phylogeny o The evolutionary history of a group of organisms o Represented by a diagram called a phylogenetic tree Branch lengths can represent, genetic differences, time, or physical character changes o Evolutionary history, or phylogeny, is represented visually by a phylogenetic tree. Trees have a common structure, with a root, nodes, and branch points. To determine evolutionary relationships among living or extinct organisms, consider the most recent common ancestors. o Branch: process of natural selection leading to new species or groups of species o Root: this is the common ancestor of all organisms on the tree o Node: this is the last common ancestor of the organisms above this point in the tree How many branches does the tree of life have? o Since each living species sits on its own branch in a phylogenetic tree, the complete tree of life has as many branches as there are species in the world In 1977, Carl Woese was studying recently discovered prokaryotes in hot springs Analysis of the DNA revealed that these prokaryotes were a distinct form of life o He called them Archaea Carl Woese’s discovery replaced the five kingdoms with the three domains: o Bacteria Green nonsulfur bacteria Grampositive bacteria Proteobacteria Cyanbacteria Spirochetes Thermotogales o Archaea Creanarchaeota Hyperthermophiles Sulfur oxidizers Halophiles Euryarchaeota Methanogens o Eukarya Microsporidia Diplomonads Trichomonads Flagellates Ciliates Plants Fungi Animals Slime molds Entamebas How many branches does the tree of life have? o The highest category in modern classification is the domain The modern classification system today: o Domain Eurkarya o Kingdom Animalia o Phylum Chordate o Class Mammalia o Order Carnivore o Family Canidae o Genus Vulpes o Species Vulpes o Humans are a member of the Eukarya
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