Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Chapter 25 The History of Life on Earth
Document related concepts
Transcript
The History of Life on Earth Chapter 25 Objectives Conditions that led to origin of life on earth The history of life as seen in fossils Key events include origin of single-cellular and multi- cellular organisms and the development of terrestrial life The effects of continental drift, mass extinctions, and adaptive radiation on groups of animals Developmental genes can radically change body forms Understand why evolution is NOT goal oriented. Early earth Abiotic synthesis of amino acids and nucleotides Formation of macrocmolecules (proteins and nucleic acids) Packaging these molecules into protobionts Origin of self replicating molecules that led to inheritance Synthesis of organic compounds Oparin-Haldane hypothesis—Early earth was a reducing atmosphere that led to synthesis Miller and Urey tested the hypothesis which yielded amino acids Demonstrated that abiotic synthesis was possible Analysis of meteorites show presence of AAs Synthesis of macromolecules may have been initiated by formation of AA polymers Protobionts Protobionts are abiotically created molecules surrounded by a membrane. They can engage in simple reproduction and metabolism The can maintain an internal environment different than the external environment. Liposomes can spontaneously organize in water from lipids and organic molecules Self replicating RNA RNA catalysts are called ribozymes Protobionts with RNA were more successful The development of DNA provided a more stable molecule for genetic information Key events in earth’s history The First Eukaryote The First Eukaryote Origin of multicellularity First evidence of multicellular organisms (algae) ~1.2 billion years The fossil record indicates that the first major diversification of multicellularity was after a thaw ~565 million years Ediacaran biota The Cambrian explosion Colonization of land ~ 500 mya Adaptations developed to live on land Plants produced waterproof coating and a vascular system for internal transport Early plants had no roots or leaves Fungi followed plants Arthropods are the most abundant land animals Tetrapods arrived ~365mya Our species arrived 195,000 years ago Rise and fall of organisms Continental drift Formation of mountains Oceanic plates usually slide below terrestrial plates Continental drift Alters habitats Reroutes ocean currents Changes weather patterns Promotes allopatric speciation Helps explain why fossils in two different regions can be the same Mass Extinctions Permian extinction Cretaceous extinction Cretaceous extinction Consequences of mass extinctions Evolutionary lineages disappear Reduction in the diversity of an ecosystems Increase in predators Arising of adaptive radiations Mass extinction and predators Adaptive radiation An organism’s movement into a variety of different environments or exploitation of a variety of different food sources leads to adaptive radiation. The mass extinction of dinosaurs gave way to adaptive radiation of mammals 65 million years ago. Mammalian adaptive radiation The Silversword Alliance Dubautia laxa KAUAI 5.1 million years 1.3 million years MOLOKAI MAUI OAHU 3.7 LANAI million years Argyroxiphium sandwicense HAWAII 0.4 million years Dubautia waialealae Dubautia scabra Dubautia linearis Exaption Using a trait that evolved for one purpose for another purpose. The lightweight honeycombed bones of early non-flying birds were taken advantage of by birds that fly. Feathers were initially developed for camouflage, courtship, or thermoregulation. Later they developed for flight. Karel Liem, “Evolution is like modifying a machine while it is running.” Evo-devo Genes that control development have had a profound effect on evolution Effect growth rates of particular body parts Controls timing of the emergence of particular structures Controls spatial pattern of particular structures Evolution and development Genes control the rate, timing, and spatial pattern of development. Evolution and development Varying the rate of growth of different body regions leads to morphological changes. Heterochrony and salamanders Foot growth gets turned off later in ground dwelling salamanders. Paedomorphosis Changes in spatial pattern Homeotic genes, such as Hox genes control spatial organization of body features. Chicken leg bud Region of Hox gene expression Zebrafish fin bud Hypothetical vertebrate ancestor (invertebrate) with a single Hox cluster First Hox duplication Hypothetical early vertebrates (jawless) with two Hox clusters Second Hox duplication Vertebrates (with jaws) with four Hox clusters New developmental genes Gene regulation Evolved complexity Mollusc eye evolution Pigmented cells (photoreceptors) Pigmented cells Epithelium Nerve fibers Patch of pigmented cells Eyecup Slit shell Pleurotomania Limpet Patella Fluid-filled cavity Epithelium Optic nerve Nerve fibers Cellular fluid (lens) Pigmented layer (retina) Pinhole camera-type eye Nautilus Optic nerve Eye with primitive lens Marine snail Murex Cornea Lens Retina Optic nerve Complex camera-type eye Cornea Squid Loligo Recent Equus Hippidion and other genera Pleistocene Nannippus Pliohippus Hipparion Neohipparion Pliocene Sinohippus Megahippus Callippus Archaeohippus Merychippus Miocene Anchitherium Hypohippus Parahippus Miohippus Oligocene Mesohippus Paleotherium Epihippus Propalaeotherium Eocene Pachynolophus Orohippus Key Hyracotherium Grazers Browsers
