Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 26 The Tree of Life: An Introduction to Biological Diversity

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Changing Life on a Changing Earth Life is a continuum extending from the earliest organisms to the variety of species that exist today Geological events change the course of evolution Conversely, life changes the planet that it inhabits

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

Concept 26.1: Conditions on early Earth made the origin of life possible Chemical and physical processes on early Earth may have produced very simple cells through a sequence of stages: 1. Abiotic synthesis of small organic molecules 2. Joining of these small molecules into polymers 3. Packaging of molecules into “protobionts” 4. Origin of self-replicating molecules

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Synthesis of Organic Compounds on Early Earth Earth formed about 4.6 billion years ago, along with the rest of the solar system Earth’s early atmosphere contained water vapor and chemicals released by volcanic eruptions Experiments simulating an early Earth atmosphere produced organic molecules from inorganic precursors, but such an atmosphere on early Earth is unlikely

LE 26-2 Water vapor CH 4 NH 3 H2H2 Electrode Condenser Cold water Cooled water containing organic molecules Sample for chemical analysis H2OH2O Miller-Urey Experiment

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Instead of forming in the atmosphere, the first organic compounds may have been synthesized near submerged volcanoes and deep-sea vents Bubble Model Video: Hydrothermal Vent Video: Hydrothermal Vent Video: Tubeworms Video: Tubeworms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Extraterrestrial Sources of Organic Compounds Some organic compounds from which the first life on Earth arose may have come from space Carbon compounds have been found in some meteorites that landed on Earth Small organic molecules polymerize when they are concentrated on hot sand, clay, or rock

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protobionts Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure – Could have formed spontaneously – liposomes can form when lipids or other organic molecules are added to water

LE 26-4 Glucose-phosphate Phosphorylase Amylase Starch Maltose Phosphate Simple metabolismSimple reproduction 20  m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The “RNA World” and the Dawn of Natural Selection The first genetic material was probably RNA, not DNA RNA molecules called ribozymes have been found to catalyze many different reactions, including: – Self-splicing – Making complementary copies of short stretches of their own sequence or other short pieces of RNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Early protobionts with self-replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The absolute ages of fossils can be determined by radiometric dating – radioactive isotopes The magnetism of rocks can provide dating information Fossil Record and Dating

LE Accumulating “daughter” isotope Remaining “parent” isotope Ratio of parent isotope to daughter isotope Time (half-lives)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The geologic record is divided into three eons: the Archaean, the Proterozoic, and the Phanerozoic The Phanerozoic eon is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic Each era is a distinct age in the history of Earth and its life, with boundaries marked by mass extinctions seen in the fossil record Lesser extinctions mark boundaries of many periods within each era

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mass Extinctions The fossil record chronicles a number of occasions when global environmental changes were so rapid and disruptive that a majority of species were swept away Provides evidence for punctuated equilibrium rather than gradualism in evolution Animation: The Geologic Record Animation: The Geologic Record

LE 26-8 Millions of years ago Permian mass extinction Extinction rate Cretaceous mass extinction 0 2,500 2,000 1,500 1, Neogene Proterozoic eon CambrianOrdovicianSilurianDevonianCarboniferousPermianTriassicJurassicCretaceousPaleogene PaleozoicMesozoic Ceno- zoic Number of families ( ) Extinction rate ( ) Number of taxonomic families

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Permian extinction killed about 96% of marine animal species and 8 out of 27 orders of insects It may have been caused by volcanic eruptions The Cretaceous extinction doomed many marine and terrestrial organisms, notably the dinosaurs It may have been caused by a large meteor impact

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mass extinctions – opportunities for adaptive radiations into newly vacated ecological niches Drastic change in the environment would provide a lot of NATURAL SELECTION

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.3: As prokaryotes evolved, they exploited and changed young Earth The oldest known fossils are stromatolites, rocklike structures composed of many layers of bacteria and sediment Stromatolites date back 3.5 billion years ago Prokaryotes were Earth’s sole inhabitants from 3.5 to about 2 billion years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Systems Electron transport systems were essential to early life Some of their aspects may precede life itself The earliest types of photosynthesis did not produce oxygen Oxygenic photosynthesis probably evolved about 3.5 billion years ago in cyanobacteria

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Effects of oxygen accumulation in the atmosphere about 2.7 billion years ago: – Posed a challenge for life – Provided opportunity to gain energy from light – Allowed organisms to exploit new ecosystems

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.4: Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes Among the most fundamental questions in biology is how complex eukaryotic cells evolved from much simpler prokaryotic cells ENDOSYMBIOTIC THEORY

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosymbiotic Origin of Mitochondria and Plastids mitochondria and plastids were formerly small prokaryotes living within larger host cells Mito and plastids started as undigested prey or internal parasites In the process of becoming more interdependent, the host and endosymbionts would have become a single organism

LE Plasma membrane Cytoplasm DNA Ancestral prokaryote Endoplasmic reticulum Nuclear envelope Infolding of plasma membrane Engulfing of aerobic heterotrophic prokaryote Nucleus Cell with nucleus and endomembrane system Mitochondrion Engulfing of photosynthetic prokaryote in some cells Plastid Mitochondrion Ancestral heterotrophic eukaryote Ancestral photosynthetic eukaryote

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Key evidence supporting an endosymbiotic origin of mitochondria and plastids: – Similarities in inner membrane structures and functions – Both have their own circular DNA

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic Cells as Genetic Chimeras Endosymbiotic events and horizontal gene transfers may have contributed to the large genomes and complex cellular structures of eukaryotic cells Eukaryotic flagella and cilia may have evolved from symbiotic bacteria, based on symbiotic relationships between some bacteria and protozoans

LE  m

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.5: Multicellularity evolved several times in eukaryotes After the first eukaryotes evolved, a great range of unicellular forms evolved Multicellular forms evolved also

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Earliest Multicellular Eukaryotes Molecular clocks date the common ancestor of multicellular eukaryotes to 1.5 billion years The oldest known fossils of eukaryotes are of relatively small algae that lived about 1.2 billion years ago

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Larger organisms do not appear in the fossil record until several hundred million years later Chinese paleontologists recently described 570- million-year-old fossils that are probably animal embryos

LE  m200  m Two-celled stage of embryonic development (SEM) Later embryonic stage (SEM)

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Colonial Connection The first multicellular organisms were colonies, collections of autonomously replicating cells

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some cells in the colonies became specialized for different functions The first cellular specializations had already appeared in the prokaryotic world

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The “Cambrian Explosion” Most of the major phyla of animals appear in the fossil record of the first 20 million years of the Cambrian period Two animal phyla, Cnidaria and Porifera, are somewhat older, dating from the late Proterozoic Molecular evidence suggests that many animal phyla originated and began to diverge much earlier, between 1 billion and 700 million years ago

LE Early Paleozoic era (Cambrian period) Millions of years ago 542 Late Proterozoic eon SpongesCnidariansEchinodermsChordatesBrachiopodsAnnelidsMolluscsArthropods

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Colonization of Land by Plants, Fungi, and Animals Plants, fungi, and animals colonized land about 500 million years ago Symbiotic relationships between plants and fungi are common today and date from this time

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Continental Drift The continents drift across our planet’s surface on great plates of crust that float on the hot underlying mantle These plates often slide along the boundary of other plates, pulling apart or pushing each other

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.6: New information has revised our understanding of the tree of life Molecular data have provided insights into the deepest branches of the tree of life Early classification systems had two kingdoms: plants and animals Robert Whittaker proposed five kingdoms: Monera, Protista, Plantae, Fungi, and Animalia

LE PlantaeFungiAnimalia Protista Monera Eukaryotes Prokaryotes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reconstructing the Tree of Life: A Work in Progress The five kingdom system has been replaced by three domains: Archaea, Bacteria, and Eukarya Each domain has been split into kingdoms

LE 26-22a Chapter 27Chapter 28 ProteobacteriaChlamydiasSpirochetesCyanobacteria Gram-positive bacteriaKorarchaeotes Euryarchaeotes, crenarchaeotes, nanoarchaeotes Diplomonads, parabasalidsEuglenozoans Alveolates (dinoflagellates, apicomplexans, ciliates) Domain Archaea Universal ancestor Domain Bacteria Domain Eukarya Stramenopiles (water molds, diatoms, golden algae, brown algae) Cercozoans, radiolarians Red algae Chlorophytes Charophyceans

LE 26-22b Chapter 29 Bryophytes (mosses, liverworts, hornworts) Plants Fungi Animals Chapter 30Chapter 28 Seedless vascular plants (ferns)Gymnosperms Angiosperms Amoebozoans (amoebas, slime molds) Chytrids Chapter 31 Zygote fungi Arbuscular mycorrhizal fungi Chapter 32Chapters 33, 34 Sac fungiClub fungi Choanoflagellates Sponges Cnidarians (jellies, coral) Bilaterally symmetrical animals (annelids, arthropods, molluscs, echinoderms, vertebrates)