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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 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

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.1: Conditions on early Earth made the origin of life possible – That chemical and physical processes on early Earth produced very simple cells through a sequence of stages

3 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 Earths early atmosphere – Contained water vapor, sulfuric acid, methane etc

4 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings As material circulated through the apparatus, Miller and Urey periodically collected samples for analysis. They identified a variety of organic molecules, including amino acids such as alanine and glutamic acid that are common in the proteins of organisms. They also found many other amino acids and complex, oily hydrocarbons. RESULTS Figure 26.2 Miller and Urey set up a closed system in their laboratory to simulate conditions thought to have existed on early Earth. A warmed flask of water simulated the primeval sea. The strongly reducing atmosphere in the system consisted of H 2, methane (CH 4 ), ammonia (NH 3 ), and water vapor. Sparks were discharged in the synthetic atmosphere to mimic lightning. A condenser cooled the atmosphere, raining water and any dissolved compounds into the miniature sea. EXPERIMENT Electrode Condenser Cooled water containing organic molecules H2OH2O Sample for chemical analysis Cold water Water vapor CH 4 H2H2 NH 3 CONCLUSION Organic molecules, a first step in the origin of life, can form in a strongly reducing atmosphere. Laboratory experiments simulating an early Earth atmosphere – Have produced organic molecules from inorganic precursors.

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Abiotic Synthesis of Polymers Small organic molecules – Polymerize when they are concentrated on hot sand, clay, or rock

6 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Protobionts – Are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Protobionts-Could have formed spontaneously from abiotically produced organic compounds – Liposomes-Can form when lipids or other organic molecules are added to water

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 20 m (a)Simple reproduction. This lipo- some is giving birth to smaller liposomes (LM). (b)Simple metabolism. If enzymesin this case, phosphorylase and amylaseare included in the solution from which the droplets self-assemble, some liposomes can carry out simple metabolic reactions and export the products. Glucose-phosphate Phosphorylase Starch Amylase Maltose Phosphate Figure 26.4a, b

9 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The RNA World and the Dawn of Natural Selection The first genetic material – Was RNA, not DNA

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 Figure 26.5 Ribozyme (RNA molecule) Template Nucleotides Complementary RNA copy 3 5 5

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.2: The fossil record chronicles life on Earth

12 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings How Rocks and Fossils Are Dated Sedimentary strata – Reveal the relative ages of fossils

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Index fossils – Are similar fossils found in the same strata in different locations – Allow strata at one location to be correlated with strata at another location Figure 26.6

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The absolute ages of fossils – Can be determined by radiometric dating Figure Accumulating daughter isotope Ratio of parent isotope to daughter isotope Remaining parent isotope Time (half-lives)

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The geologic record Table 26.1

16 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 Figure 26.8 Cambrian Proterozoic eon Ordovician Silurian Devonian Carboniferous Permian Triassic Jurassic Cretaceous Paleogene Neogene Number of families ( ) Number of taxonomic families Extinction rate Cretaceous mass extinction Permian mass extinction Millions of years ago Extinction rate ( ) PaleozoicMesozoic ,500 1,500 1, ,000 Ceno- zoic

17 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings There were 2 major mass extinctions, the Permian & the Cretaceous The Permian extinction – Claimed about 96% of marine animal species and 8 out of 27 orders of insects – Is thought to have been caused by enormous volcanic eruptions

18 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cretaceous extinction – Doomed many marine and terrestrial organisms, most notably the dinosaurs – Is thought to have been caused by the impact of a large meteor Figure 26.9 NORTH AMERICA Chicxulub crater Yucatán Peninsula

19 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 layers of bacteria & sediment 3.5 billion years old

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Lynn Margulis (top right), of the University of Massachussetts, and Kenneth Nealson, of the University of Southern California, are shown collecting bacterial mats in a Baja California lagoon. The mats are produced by colonies of bacteria that live in environments inhospitable to most other life. A section through a mat (inset) shows layers of sediment that adhere to the sticky bacteria as the bacteria migrate upward. Some bacterial mats form rocklike structures called stromatolites, such as these in Shark Bay, Western Australia. The Shark Bay stromatolites began forming about 3,000 years ago. The inset shows a section through a fossilized stromatolite that is about 3.5 billion years old. (a) (b) Figure 26.11a, b

21 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The First Prokaryotes Prokaryotes were Earths sole inhabitants – From 3.5 to about 2 billion years ago

22 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport Systems – Were essential to early life

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis and the Oxygen Revolution The earliest types of photosynthesis – Did not produce oxygen

24 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Oxygenic photosynthesis – Probably evolved about 3.5 billion years ago in cyanobacteria Figure 26.12

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings When oxygen began to accumulate in the atmosphere about 2.7 billion years ago – It posed a challenge for life – It provided an opportunity to gain abundant energy from light – It provided organisms an opportunity to exploit new ecosystems

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 26.4: Eukaryotic cells arose from symbioses and genetic exchanges between prokaryotes

27 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The First Eukaryotes The oldest fossils of eukaryotic cells – Date back 2.1 billion years

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Endosymbiotic Origin of Mitochondria and Plastids The theory of endosymbiosis – = mitochondria and plastids were formerly small prokaryotes living within larger host cells

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The prokaryotic ancestors of mitochondria and plastids – Probably gained entry to the host cell as undigested prey or internal parasites Figure Cytoplasm DNA Plasma membrane Ancestral prokaryote Infolding of plasma membrane Endoplasmic reticulum Nuclear envelope Nucleus Engulfing of aerobic heterotrophic prokaryote Cell with nucleus and endomembrane system Mitochondrion Ancestral heterotrophic eukaryote Plastid Mitochondrion Engulfing of photosynthetic prokaryote in some cells Ancestral Photosynthetic eukaryote

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

31 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

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Earliest Multicellular Eukaryotes The oldest known fossils of eukaryotes – Are of relatively small algae that lived about 1.2 billion years ago

33 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chinese paleontologists recently described 570-million-year-old fossils – That are probably animal embryos Figure 26.15a, b 150 m200 m (a) Two-cell stage (b) Later stage

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

35 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

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cambrian Explosion Most of the major phyla of animals – Appear in the fossil record during the first 20 million years of the Cambrian period

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phyla of two animal phyla, Cnidaria and Porifera – Are somewhat older, dating from the late Proterozoic Figure Early Paleozoic era (Cambrian period) Millions of years ago Late Proterozoic eon Sponges Cnidarians Echinoderms Chordates Brachiopods Annelids Molluscs Arthropods

38 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

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Continental Drift Earths continents are not fixed – They drift across our planets surface on great plates of crust that float on the hot underlying mantle

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Figure North American Plate Caribbean Plate Juan de Fuca Plate Cocos Plate Pacific Plate Nazca Plate South American Plate African Plate Scotia Plate Antarctic Plate Arabian Plate Eurasian Plate Philippine Plate Indian Plate Australian Plate

41 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Many important geological processes – Occur at plate boundaries or at weak points in the plates themselves Volcanoes and volcanic islands Trench Oceanic ridge Oceanic crust Seafloor spreading Subduction zone Figure 26.19

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The formation of the supercontinent Pangaea during the late Paleozoic era – And its breakup during the Mesozoic era explain many biogeographic puzzles Figure India collided with Eurasia just 10 million years ago, forming the Himalayas, the tallest and youngest of Earths major mountain ranges. The continents continue to drift. By the end of the Mesozoic, Laurasia and Gondwana separated into the present-day continents. By the mid-Mesozoic, Pangaea split into northern (Laurasia) and southern (Gondwana) landmasses. Cenozoic North America Eurasia Africa South America India Madagascar Antarctica Australia Laurasia Mesozoic Gondwana At the end of the Paleozoic, all of Earths landmasses were joined in the supercontinent Pangaea. Pangaea Paleozoic Millions of years ago


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