Announcements SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, ● 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 1

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

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

(as % of living organism’s Carbon-14 radioactivity Earth History and Macroevolution Fossils and radiometric dating Radioactive decay of carbon-14 100 75 (as % of living organism’s Carbon-14 radioactivity C-14 to C-12 ratio) 50 25 5.6 11.2 16.8 22.4 28.0 33.6 39.2 44.8 50.4 Time (thousands of years) How carbon-14 dating is used to determine the vintage of a fossilized clam shell Carbon-14 in shell

Common ancestor to all present-day life 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 Atmospheric oxygen begins to appear due to photosynthetic prokaryotes Origin of Earth Earth cool enough for crust to solidify Oldest prokaryotic fossils 4,500 4,000 3,500 3,000 2,500 Millions of years ago 6

Major Episodes in the History of Life Cenozoic Paleozoic Mesozoic Bacteria Prokaryotes Archaea Protists Eukaryotes Plants Fungi Animals Cambrian explosion Origin of multicellular organisms Oldest animal fossils Plants and symbiotic fungi colonize land Extinction of dinosaurs Oldest eukaryotic fossils First humans 2,000 1,500 1,000 500 Millions of years ago 7

Major Episodes in the History of Life Humans Origin of solar system and Earth 1 4 2 3 Pre sent Animals Coloniz of land ation Multi eukar cellular yotes Sing cel le- led Atmo oxy sphe ric gen Bil ars ons of ago ye li kary otes Pro What if we use a clock analogy to tick down all of the major events in the history of life on Earth? 8

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

Prokaryotes Bacteria Prokaryotes Archaea Protists Eukarya Plants Fungi Animals 10

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

Prokaryotic Cells Are smaller than eukaryotic cells ● Prokaryotes Are smaller than eukaryotic cells Lack internal structures surrounded by membranes Lack a nucleus Have a rigid cell wall 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

Prokaryotic Cells 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 Colorized SEM 13

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

Prokaryotic Cells 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 Endospore Colorized SEM

Prokaryotic Cells MODES OF NUTRITION Energy source Light Chemical Photoautotrophs Chemoautotrophs Colorized TEM CO2 Elodea, an aquatic plant Bacteria from a hot spring Carbon source Photoheterotrophs Chemoheterotrophs Colorized TEM Organic compounds Rhodopseudomonas Little Owl (Athene noctua)

Prokaryotic Cells 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 Prokaryotes Archaea Protists Eukarya Plants Fungi Animals

Bacteria That Cause Disease 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.

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

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

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

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

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

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

The Diversity of Protists 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 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 Gamete Food-synthesizing cells Somatic cells Locomotor cells Colony Early multicellular organism with specialized, interdependent cells Later organism with gametes and somatic cells