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Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Tuesday 5/31 ● Today’s.

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Presentation on theme: "Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Tuesday 5/31 ● Today’s."— Presentation transcript:

1 Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Tuesday 5/31 ● Today’s Lecture: Chapters 14 and 15 ● Abstract and Lab Reports due this week ● Canned food drive – donation worth 5 extra credit points

2 Earth History and Macroevolution –The fossil record is: The sequence in which fossils appear in rock strata An archive of macroevolution

3 –Geologists have established a geologic time scale reflecting a consistent sequence of geologic periods. –Separated into four broad divisions: Precambrian Paleozoic Mesozoic Cenozoic Earth History and Macroevolution

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5 Carbon-14 in shell Time (thousands of years) Radioactive decay of carbon-14 How carbon-14 dating is used to determine the vintage of a fossilized clam shell Carbon-14 radioactivity (as % of living organism’s C-14 to C-12 ratio) Earth History and Macroevolution Fossils and radiometric dating

6 Major Episodes in the History of Life Earth was formed about 4.6 billion years ago. Prokaryotes Evolved by 3.5 billion years ago Began oxygen production about 2.7 billion years ago Lived alone for almost 2 billion years Precambrian Common ancestor to all present-day life Origin of Earth Earth cool enough for crust to solidify Oldest prokaryotic fossils Atmospheric oxygen begins to appear due to photosynthetic prokaryotes Millions of years ago 4,5004,0003,5003,0002,500

7 Major Episodes in the History of Life PaleozoicMesozoic Cenozoic Bacteria Archaea Plants Fungi Animals Prokaryotes Eukaryotes Protists Oldest eukaryotic fossils Origin of multicellular organisms Oldest animal fossils Plants and symbiotic fungi colonize land Extinction of dinosaurs First humans Millions of years ago Cambrian explosion 2,0001,5001,

8 Major Episodes in the History of Life –What if we use a clock analogy to tick down all of the major events in the history of life on Earth? Humans Origin of solar system and Earth Pre sent Animals Coloniz of land ation Multi eukar cellular yotes Sing eukar cel yotes le- led Atmo oxy sphe ric gen Bil ars ons of ago ye li kary otes Pro

9 Inorganic compounds Abiotic synthesis of organic monomers Abiotic synthesis of polymers Formation of pre-cells Self-replicating molecules Membrane-enclosed compartment Complementary chain Polymer Organic monomers The Origin of Life Four-Stage Hypothesis for the Origin of Life

10 Prokaryotes Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals

11 The Two Major Categories of Cells ● The countless cells on earth fall into two categories: Prokaryotic cells — Bacteria and Archaea Eukaryotic cells — Eukarya protists, plants, fungi, and animals ● All cells have several basic features. 1. They are all bound by a thin plasma membrane. 2. All cells have DNA. 3. All cells have ribosomes. Cytoplasm-the entire contents of a cell

12 Prokaryotic Cells Plasma membrane (encloses cytoplasm) Cell wall (provides Rigidity) Capsule (sticky coating) Prokaryotic flagellum (for propulsion) Ribosomes (synthesize proteins) Nucleoid (contains DNA) Pili (attachment structures) Colorized TEM ● Prokaryotes Are smaller than eukaryotic cells Lack internal structures surrounded by membranes Lack a nucleus Have a rigid cell wall

13 Colorized SEM Prokaryotes Are ecologically significant, recycling carbon and other vital chemical elements back and forth between organic matter, the soil, and atmosphere Cause about half of all human diseases Are more typically benign or beneficial Prokaryotic Cells

14 –Prokaryotes come in several shapes: Spherical (cocci) Rod-shaped (bacilli) Spiral Prokaryotic Cells SHAPES OF PROKARYOTIC CELLS Spherical (cocci)Rod-shaped (bacilli)Spiral Colorized SEM Colorized TEM

15 –Most prokaryotes can reproduce by binary fission and at very high rates if conditions are favorable. –Some prokaryotes Form endospores, thick-coated, protective cells that are produced within the cells when they are exposed to unfavorable conditions Can survive very harsh conditions for extended periods, even centuries Prokaryotic Cells Endospore Colorized SEM

16 MODES OF NUTRITION LightChemical Chemoautotrophs Photoautotrophs Photoheterotrophs Chemoheterotrophs Energy source Elodea, an aquatic plant Rhodopseudomonas Little Owl (Athene noctua) Bacteria from a hot spring Organic compounds Carbon source CO 2 Colorized TEM Prokaryotic Cells

17 –By comparing diverse prokaryotes at the molecular level, biologists have identified two major branches of prokaryotic evolution: Bacteria Archaea (more closely related to eukaryotes) Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals

18 –Bacteria and other organisms that cause disease are called pathogens. –Most pathogenic bacteria produce poisons. Exotoxins are poisonous proteins secreted by bacterial cells. Endotoxins are not cell secretions but instead chemical components of the outer membrane of certain bacteria. Bacteria That Cause Disease

19 Bioterrorism Humans have a long and ugly history of using organisms as weapons.

20 Prokaryotes and Chemical Recycling –Prokaryotes play essential roles in Chemical cycles in the environment The breakdown of organic wastes and dead organisms

21 Prokaryotes and Bioremediation –Bioremediation is the use of organisms to remove pollutants from Water Air Soil Liquid wastes Outflow Rotating spray arm Rock bed coated with aerobic prokaryotes and fungi

22 –Protists Are eukaryotic Evolved from prokaryotic ancestors Are ancestral to all other eukaryotes, which are –Plants –Fungi –Animals Protists Bacteria Archaea Prokaryotes Eukarya Protists Plants Fungi Animals Figure 15.UN08

23 The Origin of Eukaryotic Cells –Eukaryotic cells evolved by The infolding of the plasma membrane and (a) Origin of the endomembrane system Plasma membrane Ancestral prokaryote DNA Cytoplasm Endoplasmic reticulum Membrane infolding Nucleus Nuclear envelope Cell with nucleus and endomembrane system

24 The Origin of Eukaryotic Cells (b) Origin of mitochondria and chloroplasts Photosynthetic eukaryotic cell Photosynthetic prokaryote Aerobic heterotrophic prokaryote Endosymbiosis (Some cells) Mitochondrion Chloroplast –Eukaryotic cells evolved by Endosymbiosis – a free-living bacterium, came to reside inside a host cell, producing mitochondria and chloroplasts

25 –The classification of protists remains a work in progress. –The four major categories of protists, grouped by lifestyle, are Protozoans Slime molds Unicellular algae Seaweeds The Diversity of Protists

26 The Origin of Multicellular Life Multicellular organisms have interdependent, specialized cells that perform different functions, such as: feeding, waste disposal, gas exchange, protection (all are dependent on each other) Unicellular protist Colony Locomotor cells Food-synthesizing cells Early multicellular organism with specialized, interdependent cells Later organism with gametes and somatic cells Somatic cells Gamete


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