BIOL 108 Chp 10 pt 1 - The Origin and Diversification of Life on Earth
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BIOL 108 Chp 10 pt 1 - The Origin and Diversification of Life on Earth






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    BIOL 108 Chp 10 pt 1 - The Origin and Diversification of Life on Earth BIOL 108 Chp 10 pt 1 - The Origin and Diversification of Life on Earth Presentation Transcript

    • Chapter 10 pt 1 The Origin and Diversification of Life on Earth BIOL 108 Intro to Bio Sci Rob Swatski Assoc Prof Biology HACC-York 1
    • Learning Goals Life on earth Species are the most likely originated from basic units of nonliving biodiversity. materials. Evolutionary trees help us conceptualize and categorize biodiversity. Macroevolution An overview of and the the diversity of diversity of life. life on earth. 2
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    • 10.1 Complex organic molecules arise in non-living environments. 4
    • Phase 1: The Formation of Small Molecules Containing Carbon and Hydrogen 5
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    • The Urey-Miller Experiments The first demonstration that complex organic molecules could have arisen in earth’s early environment 8
    • Why is it important that Urey and Miller’s experiment produced amino acids? 1. Because they are the building blocks of DNA 2. Because they are the building blocks of RNA 3. Because they are the building blocks of protein 4. Because they are the building blocks of triglycerides 9
    • Take-Home Message 10.1 Under conditions similar to those on early earth, small organic molecules form which have some chemical properties of life. 10
    • 10.2 Cells and self-replicating systems evolved together to create the first life. Life on earth most likely originated from nonliving materials. 11
    • Phase 2: The Formation of Self-Replicating, Information-Containing Molecules. - RNA appears on the scene - RNA can catalyze reactions necessary for replication 12
    • The “RNA World” Hypothesis A selfreplicating system A precursor to cellular life? RNA-based life and DNAbased life 13
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    • Life Is Defined by Two Characteristics: 1) the ability to replicate 2) the ability to carry out some sort of metabolism 15
    • Phase 3: The Development of a Membrane, Enabling Metabolism, and Creating the First Cells Membranes make numerous aspects of metabolism possible. 16
    • How Did the First Cells Appear? Spontaneously? Mixtures of phospholipids Microspheres Compartmentalization within cells 17
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    • Take-Home Message 10.2 The earliest life on earth appeared about 3.5 billion years ago, not long after earth was formed. Self-replicating molecules— possibly RNA—may have formed in earth’s early environment and later acquired or developed membranes Membranes enabled these self-replicating molecules to replicate and make metabolism possible, the two conditions that define life. 19
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    • 10.3 What is a species? 21
    • Biological Species Concept  Species: different  Species kinds of organisms are natural populations of organisms that: • interbreed with each other or could possibly interbreed • cannot interbreed with organisms outside their own group (reproductive isolation) 22
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    • Two Key Features of the Biological Species Concept: 1) Actually interbreeding or could possibly interbreed 2) “Natural” populations 24
    • The biological species concept is not easily applied to bacteria and fossils. What other characteristics could we use to decide whether two different bacteria are two different species? 1. Observe asexual reproduction. 2. Measure the size of each bacteria. 3. Compare the sequences of specific genes in the bacteria. 4. All of the above. 25
    • Barriers to Reproduction 1) Prezygotic barriers 2) Postzygotic barriers 26
    • Prezygotic Barriers Make it impossible for individuals to mate with each other OR Make it impossible for the male’s reproductive cell to fertilize the female’s reproductive cell 27
    • Examples of Prezygotic Barriers Courtship systems Physical differences Physical or biochemical factors involving gametes 28
    • Postzygotic Barriers Occur after fertilization Generally prevent the production of fertile offspring Hybrids 29
    • Which answer below is considered to be a postzygotic barrier to reproduction? 1. Two species of frogs mate at different times in the spring. 2. Birds about to mate need to go through specific courtship rituals. 3. The male gamete (pollen) of one flower is not compatible with the female organs of another flower. 4. Fertilization occurs, but the embryo dies before it is born. 5. There is a mechanical isolation that prevents fertilization. 30
    • Take-Home Message 10.3 Species are generally defined as populations of individuals that interbreed with each other or could possibly interbreed. Species cannot interbreed with organisms outside their own group. This concept can be applied easily to most plants and animals, but for many other organisms it cannot be applied. 31
    • 10.4 How do we name species? We need an organizational system! 32
    • Carolus Linnaeus and Systema Naturae A scientific name consists of two parts: 1) Genus 2) Specific epithet 33
    • Hierarchical System Inclusive categories at the top… …leading to more and more exclusive categories below. 34
    • Take-Home Message 10.4 Each species on earth is given a unique name, using a hierarchical system of classification. Every species on earth falls into one of three domains. 35
    • 10.5 Species are not always easily defined. 36
    • Difficulties in Classifying Asexual Species  Doesn’t involve fertilization or even two individuals  Does not involve any interbreeding  Reproductive isolation is not meaningful 37
    • Chihuahuas and Great Danes generally can’t mate. Does that mean they are different species? 38
    • Difficulties in Classifying Ring Species  Example: insect-eating songbirds called greenish warblers  Unable to live at the higher elevations of the Tibetan mountain range  Live in a ring around the mountain range 39
    • Difficulties in Classifying Ring Species  Warblers interbreed at southern end of ring.  The population splits as the warblers move north along either side of mountain.  When the two “side” populations meet at northern end of ring, they can’t interbreed.  What happened?! 40
    • Difficulties in Classifying Ring Species  Gradual variation in the warblers on each side of the mountain range has accumulated…  …the two populations that meet have become reproductively incompatible…  …no exact point at which one species stops and the other begins 41
    • Difficulties in Classifying Hybridizing Species  Hybridization • the interbreeding of closely related species  Have postzygotic barriers evolved?  Are hybrids fertile? 42
    • Morphological Species Concept  Focus on aspects of organisms other than reproductive isolation as defining features  Characterizes species based on physical features such as body size and shape  Can be used effectively to classify asexual species 43
    • Which answer below would require the morphological species concept to delineate between the two species? 1. 2. 3. 4. Dog and cat Salmonella and E. coli Cow and goat Donkey and horse 44
    • Take-Home Message 10.5 The biological species concept is useful when describing most plants and animals. It falls short of representing a universal and definitive way of distinguishing many life forms. Difficulties arise when trying to classify asexual species, fossil species, speciation events that have occurred over long periods of time, ring species, and hybridizing species. In these cases, alternative approaches to defining species can be used. 45
    • 10.6 How do new species arise? 46
    • Speciation  One species splits into two distinct species.  Occurs in two distinct phases  Requires more than just evolutionary change in a population 47
    • Allopatric Speciation  Speciation with geographic isolation 48
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    • Speciation without Geographic Isolation 51
    • Polyploidy  Error during cell division in plants  Chromosomes are duplicated but a cell does not divide.  This doubling of the number of sets of chromosomes is called polyploidy. 52
    • Polyploidy  The individual with four sets can no longer interbreed with any individuals having only two sets of chromosomes  Self-fertilization or mating with other individuals that have four sets can occur.  Instant reproductive isolation, considered a new species. 53
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    • Take-Home Message 10.6 Speciation is the process by which one species splits into two distinct species that are reproductively isolated. It can occur by polyploidy or by a combination of reproductive isolation and genetic divergence together. 55
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    • 10.7 The history of life can be imagined as a tree. 57
    • Systematics and Phylogeny  Systematics names and arranges species in a manner that indicated: • the common ancestors they share • the points at which they diverged from each other 58
    • Systematics and Phylogeny  Phylogeny • evolutionary history, of organisms  Nodes • The common ancestor points at which species diverge 59
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    • Take-Home Message 10.7 The history of life can be visualized as a tree; tracing from the branches back toward the trunk follows the pathway of descendant back to ancestor. The tree reveals the evolutionary history of every species and the sequence of speciation events that gave rise to them. 61
    • 10.8 Evolutionary trees show ancestor-descendant relationships. 62
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    • Monophyletic Groups a group in which all of the individuals are more closely related to each other than to any individuals outside of that group  determined by looking at the nodes of the trees 66
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    • Which animals are represented in a monophyletic group indicated by the red arrow? 1. Fish, bird, human, rat, and mouse 2. Bird, human, rat and mouse 3. Human, rat, and mouse 4. Rat and mouse 68
    • Constructing evolutionary trees requires comparing similarities and differences between organisms. 69
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    • Below are genetic sequences for a gene found in four different species. Which species are the most closely related? Species A: Species B: Species C: Species D: 1. 2. 3. 4. AGT-CTA-CTT-ACT-ATC-CTA AGT-CTA-CTT-ACC-ATC-CTA AGT-AAA-CTT-ACC-ATC-CTA AGA-CTA-TTT-ACC-ATG-CTA Species A and B Species A and C Species A and D Species B and D 72
    • Take-Home Message 10.8 Evolutionary trees constructed by biologists are hypotheses about the ancestor-descendant relationships among species. The trees represent an attempt to tell us which groups are most closely related to which other groups based on physical features, usually DNA sequences. 73