BIG IDEA I The process of evolution drives

BIG IDEA I The process of evolution drives the diversity and unity of life. Enduring Understanding 1. D The origin of living systems is explained by natural processes. Essential Knowledge 1. D. 1 There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Essential Knowledge 1. D. 1: There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence. • Learning Objectives: – (1. 27) The student is able to describe a scientific hypothesis about the origin of life of Earth. – (1. 28) The student is able to evaluate scientific questions based on hypotheses about the origin of life on Earth. – (1. 29) The student is able to describe the reasons for revisions of scientific hypotheses of the origin of life on Earth. – (1. 30) The student is able to evaluate scientific hypotheses about the origin of life on Earth. – (1. 31) The student is able to evaluate the accuracy and legitimacy of data to answer scientific questions about the origin of life on Earth. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Overview: Lost Worlds • Fossils in all parts of the world tell a similar, surprising story: past organisms were very different from those now alive. • The sweeping changes in life on Earth revealed by fossils illustrate macroevolution, the pattern of evolution over large time scales. • Specific examples of macroevolutionary change include the origin of key biochemical processes such as photosynthesis, the emergence of the first terrestrial vertebrates, and the long-term impact of a mass extinction on the diversity of life. • Taken together, such changes provide a grand view of the evolutionary history of life on Earth. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Early Earth Conditions • Conditions on early Earth made the origin of life possible. There is scientific evidence that Earth and the other planets of the solar system formed about 4. 6 billion years ago. • The earliest evidence of life on Earth comes from fossils of microorganisms that are about 3. 5 billion years old. • The current theory about how life arose indicates that chemical and physical processes on early Earth may have produced simple cells in a sequence of four main stages: 1. Primitive Earth provided inorganic precursors from which small organic molecules were abiotically synthesized due to the presence of available free energy and the absence of a significant quantity of oxygen. 2. These molecules served as monomers for the formation of more complex molecules, such as nucleic acids and nucleic nucleotides. 3. All these molecules were packaged into protobionts, membrane-containing droplets, whose internal chemistry differed from that of the external environment. 4. The joining of these monomers produced polymers with the ability to replicate, store and transfer information – which made inheritance possible. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Synthesis of Organic Compounds on Early Earth http: //highered. mcgraw-hill. com/sites/9834092339/student_view 0/chapter 26/animation_-_millerurey_experiment. html • The first atmosphere was probably thick with water vapor; along with various compounds released by volcanic eruptions, including nitrogen and oxides, carbon dioxide, methane, ammonia, hydrogen, and hydrogen sulfide. • As Earth cooled, the water vapor condensed into the oceans, and much of the hydrogen quickly escaped into space. • In the 1920 s, Russian and British chemists Oparin and Haldane hypothesized that Earth’s early atmosphere was a reducing (electronadding) environment, in which organic compounds could have formed from simple molecules. • They suggested that the early oceans were a solution of organic molecules, a “primitive soup” from which life arose. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Abiotic Synthesis of Macromolecules • The presence of small organic molecules, such as amino acids, is not sufficient for the emergence of life as we know it. • Every cell has an assortment of macromolecules – including enzymes and other proteins and nucleic acids that are essential for self-replication. • Experiments suggest that such molecules could have formed in early Earth. • Some models suggest that primitive life developed on biogenic surfaces, such as clay, that served as templates and catalysts for assembly of macromolecules. • By dripping solutions of amino acids into hot sand, clay, or rock, researchers have been able to produce amino acid polymers. The polymers formed spontaneously, without the help of enzymes or ribosomes. • It is possible that such polymers may have acted as weak catalysts for a variety of reactions on early Earth. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Protobionts • The necessary conditions for replication and metabolism early in life’s history may have been met by protobionts. • Protobionts are aggregates of abiotically produced molecules surrounded by a membrane or membrane-like structure. – Protobionts may exhibit some properties of life, such as simple reproduction and metabolism, as well as the maintenance of an internal chemical environment different from that of their surroundings. – Experiments demonstrate that protobionts could have formed spontaneously from abiotically produced organic compounds. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Protobionts Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Self Replicating RNA and the Dawn of Natural Selection • According to the RNA World hypothesis, the first genetic material was most likely RNA, not DNA. • RNA molecules called ribozymes have been found to catalyze many different reactions: – For example, ribozymes can make complementary copies of short stretches of their own sequence or other short pieces of RNA. • Early protobionts with self-replicating, catalytic RNA would have been more effective at using resources and would have increased in number through natural selection. • The early genetic material might have formed an “RNA world”. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

BIG IDEA I The process of evolution drives the diversity and unity of life. Enduring Understanding 1. D The origin of living systems is explained by natural processes. Essential Knowledge 1. D. 2 Scientific evidence from many different disciplines supports models of the origin of life. Power. Point® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Essential Knowledge 1. D. 2: Scientific evidence from many different disciplines supports models of the origin of life. • Learning Objectives: – (1. 32) The student is able to justify the selection of geological, physical, and chemical data that reveal early Earth conditions. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Geologic evidence provides support for models of the origin of life on Earth. Copyright

Key Events in Life’s History Copyright © 2008 Pearson Education, Inc. , publishing as

Key Events in Life’s History • The earliest living organisms were prokaryotes. • About 2. 7 billion years ago, oxygen began to accumulate in Earth’s atmosphere as a result of photosynthesis. • Eukaryotes appeared about 2. 1 billion years ago. • Multicellular eukaryotes evolved about 1. 2 billion years ago. • The colonization of land occurred about 500 million years ago, when plants, fungi, and animals began to appear on Earth. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The First Single-Celled Organisms Copyright © 2008 Pearson Education, Inc. , publishing as Pearson

Photosynthesis and the Oxygen Revolution • Most atmospheric oxygen gas is of biological origin, produced during the water-splitting steps of photosynthesis. • When oxygenic photosynthesis first evolved, the free O 2 produced probably dissolved in the surrounding water until it reached a high enough concentration to react with dissolved iron. • This would have caused the iron to precipitate as iron oxide, which accumulated as sediments. Once all of the dissolved iron had precipitated, additional O 2 dissolved in the water until the seas and lakes became saturated. • After this, O 2 began to “gas out” of the water and enter the atmosphere. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Photosynthesis and the Oxygen Revolution Copyright © 2008 Pearson Education, Inc. , publishing as

Effects of the Oxygen Revolution • The “oxygen revolution” had an enormous impact on life. • In certain chemical forms, oxygen attacks chemical bonds and can inhibit enzymes and damage cells. • As a result the rising concentrations of atmospheric O 2 probably doomed many prokaryotic groups. • Some species survived in anaerobic habitats, where we find their descendants living today. • Among other survivors, diverse adaptations to the changing atmosphere evolved, including cellular respiration, which uses O 2 in the process of harvesting the energy stored in organic molecules. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Endosymbiosis and the First Eukaryotes http: //highered. mcgraw-hill. com/sites/9834092339/student_view 0/chapter 4/animation_-_endosymbiosis. html • The oldest fossils of eukaryotic cells date back 2. 1 billion years. • The hypothesis of endosymbiosis proposes that mitochondria and plastids (chloroplasts and related organelles) were formerly small prokaryotes living within larger host cells • An endosymbiont is a cell that lives within a host cell. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Endosymbiosis Theory Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evidence Supporting the Endosymbiotic Theory • The endosymbiotic hypothesis proposes that mitochondria and plastids (chloroplasts) were formerly small prokaryotes that began living within larger cells. Evidence for this hypothesis includes: – Both organelles have enzymes and transport systems homologous to those found in the plasma membranes of living prokaryotes. – Both replicate by a splitting process similar to prokaryotes. – Both contain a single, circular DNA molecule, not associated with histone proteins. – Both have their own ribosomes which translate their DNA into proteins. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Origin of Multicellularity • The evolution of eukaryotic cells allowed for a greater range of unicellular forms. • A second wave of diversification occurred when multicellularity evolved and gave rise to algae, plants, fungi, and animals. • Comparisons of DNA sequences date the common ancestor of multicellular eukaryotes to 1. 5 billion years ago. • The oldest known fossils of multicellular eukaryotes are of small algae that lived about 1. 2 billion years ago. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Rise and Fall of Dominant Groups • Anaerobic prokaryotes originated, flourished, and then declined as the oxygen content of the atmosphere rose. • Billions of years later, the first tetrapods emerged from the sea, giving rise to amphibians that went on to dominate life on land for 100 millions years – until other tetrapods (dinosaurs and later, mammals) replaced them as the dominant terrestrial vertebrates. • These and other major changes in life on Earth have been influenced by large-scale processes such as continental drift, mass extinctions, and adaptive radiations. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Continental Drift http: //bcs. whfreeman. com/thelifewire/content/chp 22/22020. html • Continental drift is the movement of Earth’s continents on great plates that float on the hot, underlying mantle. • Plate movements rearrange geography slowly, but their cumulative effects are dramatic. In addition to reshaping physical features of our planet, continental drift has a major impact on life on Earth. • Formation of the supercontinent Pangaea about 250 million years ago had many effects: – A reduction in shallow water habitat; a colder and drier climate inland; changes in climate as continents moved toward and away from the poles; changes in ocean circulation patterns leading to global cooling. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The “Big Five” Mass Extinction Events Copyright © 2008 Pearson Education, Inc. , publishing

Consequences of Mass Extinctions Copyright © 2008 Pearson Education, Inc. , publishing as Pearson

Adaptive Radiations • Adaptive radiations are periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological niches. – Large-scale adaptive radiations occurred after each of the big five mass extinctions, when survivors became adapted to the many vacant ecological niches. – Fossil evidence indicates that mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs. – The disappearance of dinosaurs (except birds) allowed for the expansion of mammals in diversity and size. – Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Major Changes in Body Form • The fossil record tells us what the great changes in the history of life have been and when they occurred. • Our understanding of continental drift, mass extinction, and adaptive radiation provides a picture of how those changes came about. • We now must seek to understand the intrinsic biological mechanisms that underlie changes seen in the fossil record. • For this, we focus on genetic mechanisms of change, paying particular attention to genes that influence development. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evolutionary Novelty • Evolutionary novelty can arise when structures that originally played one role gradually acquire a different one. • Structures that evolve in one context but become coopted for another function are referred to as exaptations. – For example, it is possible that feathers of modern birds were co-opted for flight after functioning in some other capacity, such as thermoregulation. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

“Evo-Devo” • “Evo-devo” is a field of study in which evolutionary biology and developmental biology converge. • This field is illuminating how slight genetic divergences can be magnified into major morphological differences between species. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Heterochrony • Heterochrony is an evolutionary change in the rate or timing of developmental events. • Change relative rates of growth even slightly can change the adult form of an organisms substantially, thus contributing to the potential for evolutionary change. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Homeotic Genes • Homeotic genes are master regulatory genes that determine the location and organization of body parts. – Hox genes are one class of homeotic genes. – Changes in Hox genes and in the genes that regulate them can have a profound effect on morphology, thus contributing to the potential for evolutionary change. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Fig. 25 -21 Hypothetical vertebrate ancestor (invertebrate) with a single Hox cluster First Hox duplication Duplication of the single Hox complex occurs and provides genetic material associated with origin of first vertebrate. Dulpicate set of genes takes on new roles – such as development of backbone. Hypothetical early vertebrates (jawless) with two Hox clusters Second duplication of Hox complex may have allowed the development of even greater structural complexity – such as jaws and limbs. Vertebrates (with jaws) with four Hox clusters Second Hox duplication

Fig. 25 -22 Hox gene 6 Hox gene 7 Hox gene 8 Ubx About

Evolution is Not Goal Oriented • Evolution is like tinkering—it is a process in which new forms arise by the slight modification of existing forms: – Most novel biological structures evolve in many stages from previously existing structures. – Natural selection can only improve a structure in the context of its current utility. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evidence for the Origin of Life Hypotheses • Chemical experiments have shown that it is possible to form complex organic molecules from inorganic molecules in the absence of life. • In the 1920 s, Russian and British chemists Oparin and Haldane hypothesized that Earth’s early atmosphere was a reducing (electron-adding) environment, in which organic compounds could have formed from simple molecules. • They suggested that the early oceans were a solution of organic molecules, a “primitive soup” from which life arose. Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

The Miller-Urey experiment http: //bcs. whfreeman. com/thelifewire/content/chp 03/0301 s. swf

Sidney Fox and Proteinoids • In the 1960 s, Sidney Fox synthesized organic polymers such as polypeptides by dripping dilute solutions of organic monomers over hot sand, clay, or rock. • This method mimics the condensation of the Miller-Urey model, but with the idea that rain falling from the early atmosphere or waves washing onto hot substrate would be favorable to the formation of polypeptides and other organic polymers. • Once these polymers have formed, they can form aggregates, which spontaneously form into proteinoids (protobiont structures similar to living organisms). Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings

Evidence for the Origin of Life Hypotheses • Molecular and genetic evidence from extant and extinct organisms indicates that all organisms on Earth share a common ancestral origin of life. – Scientific evidence includes molecular building blocks that are common to all life forms (carbohydrates, proteins, lipids, amino acids). – Scientific evidence includes a common genetic code (DNA and RNA). Copyright © 2008 Pearson Education, Inc. , publishing as Pearson Benjamin Cummings