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Chapter 14 How Biological Diversity Evolves Laura Coronado Bio 10 Chapter 14.

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Presentation on theme: "Chapter 14 How Biological Diversity Evolves Laura Coronado Bio 10 Chapter 14."— Presentation transcript:

1 Chapter 14 How Biological Diversity Evolves Laura Coronado Bio 10 Chapter 14

2 Biology and Society: The Sixth Mass Extinction – Over the past 600 million years the fossil record reveals five periods of extinction when 50–90% of living species suddenly died out. – Our current rate of extinction, over the past 400 years, indicates that we may be living in, and contributing to, the sixth mass extinction period. – Mass extinctions: Pave the way for the evolution of new and diverse forms, but Take millions of years for Earth to recover Laura Coronado Bio 10 Chapter 14

3 MACROEVOLUTION & THE DIVERSITY OF LIFE – Macroevolution: Encompasses the major biological changes evident in the fossil record Includes the formation of new species – Speciation: Is the focal point of macroevolution May occur based on two contrasting patterns Laura Coronado Bio 10 Chapter 14

4 MACROEVOLUTION & THE DIVERSITY OF LIFE – In nonbranching evolution: A population transforms but Does not create a new species – In branching evolution, one or more new species branch from a parent species that may: Continue to exist in much the same form or Change considerably Laura Coronado Bio 10 Chapter 14

5 Branching Evolution (results in speciation) Nonbranching Evolution (no new species) PATTERNS OF EVOLUTION Figure 14.1 Laura Coronado Bio 10 Chapter 14

6 THE ORIGIN OF SPECIES – Species is a Latin word meaning: “Kind” or “Appearance.” – The biological species concept defines a species as “A group of populations whose members have the potential to interbreed and produce fertile offspring” – The biological species concept cannot be applied in all situations, including: Fossils Asexual organisms Laura Coronado Bio 10 Chapter 14

7 Diversity within one species Similarity between different species Figure 14.2 Laura Coronado Bio 10 Chapter 14

8 Reproductive Barriers between Species – Prezygotic barriers prevent mating or fertilization between species. – Prezygotic barriers include: Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation Gametic isolation Laura Coronado Bio 10 Chapter 14

9 Reproductive Barriers between Species – Postzygotic barriers operate if: Interspecies mating occurs and Hybrid zygotes form – Postzygotic barriers include: Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Laura Coronado Bio 10 Chapter 14

10 VIABLE, FERTILE OFFSPRING Hybrid breakdown FERTILIZATION (ZYGOTE FORMS) INDIVIDUALS OF DIFFERENT SPECIES MATING ATTEMPT Reduced hybrid fertility Reduced hybrid viability Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation Gametic isolation Prezygotic Barriers Postzygotic Barriers Figure 14.3 Laura Coronado Bio 10 Chapter 14

11 Temporal Isolation Habitat Isolation PREZYGOTIC BARRIERS Mechanical IsolationGametic Isolation Behavioral Isolation Figure 14.4 Laura Coronado Bio 10 Chapter 14

12 Hybrid Breakdown Reduced Hybrid FertilityReduced Hybrid Viability POSTZYGOTIC BARRIERS Donkey Mule Horse Figure 14.5 Laura Coronado Bio 10 Chapter 14

13 Mechanisms of Speciation – A key event in the potential origin of a species occurs when a population is severed from other populations of the parent species. – Species can form by: Allopatric speciation, due to geologic processes that can fragment a population into two or more isolated geographic populations Sympatric speciation, without geographic isolation – Speciation occurs only with the evolution of reproductive barriers between the isolated population and its parent population. Laura Coronado Bio 10 Chapter 14

14 Sympatric speciation (occurs without geographic isolation) Allopatric speciation (occurs after geographic isolation) Parent population Figure 14.UN2 Laura Coronado Bio 10 Chapter 14

15 Ammospermophilus harrisii Ammospermophilus leucurus Figure 14.7 Laura Coronado Bio 10 Chapter 14

16 Geographic barrier Populations interbreed Time Populations become allopatric Populations become sympatric Populations cannot interbreed Reproductive isolation: Speciation has occurred Gene pools merge: No speciation Figure 14.8 Laura Coronado Bio 10 Chapter 14

17 Sympatric Speciation – Sympatric speciation occurs: Occurs when part of the population becomes a new species while in the midst of its parent population While the new & old species live in the same time and place Due to subgroups of a population that evolve adaptations for exploiting food sources in different habitats Due to sexual selection Most often if a genetic change produces a reproductive barrier between the new and old species – polyploids Laura Coronado Bio 10 Chapter 14

18 Polyploids – Originate from accidents during cell division which may produce an extra set of chromosomes Each cell has more than two sets of chromosomes Occurs in a single generation New species cannot produce fertile hybrids with its parent species Most often result from the hybridization of two parent species, e.g. domesticated plants: oats, potatoes, bananas, peanuts, apples, coffee & wheat Laura Coronado Bio 10 Chapter 14

19 Domesticated Triticum monococcum (14 chromosomes) T. turgidum Emmer wheat (28 chromosomes) Wild T. tauschii (14 chromosomes) Wild Triticum (14 chromosomes) T. aestivum Bread wheat (42 chromosomes) Sterile hybrid (14 chromosomes) Sterile hybrid (21 chromosomes) AA BB DD AA BBDD ABD AA BB AB Figure Laura Coronado Bio 10 Chapter 14

20 What Is the Tempo of Speciation? – There are two contrasting models of the pace of evolution: The gradual model, in which big changes (speciations) occur by the steady accumulation of many small changes The punctuated equilibria model, in which there are – Long periods of little change, equilibrium, punctuated by – Abrupt episodes of speciation Laura Coronado Bio 10 Chapter 14

21 Punctuated model Graduated model Time Figure Laura Coronado Bio 10 Chapter 14

22 THE EVOLUTION OF BIOLOGICAL NOVELTY – An exaptation: Is a structure that evolves in one context, but becomes adapted for another function Is a type of evolutionary remodeling Account for the gradual evolution of novel structures. – Birds: Are derived from a lineage of earthbound reptiles Evolved flight from flightless ancestors Laura Coronado Bio 10 Chapter 14

23 Wing claw (like reptile) Teeth (like reptile) Long tail with many vertebrae (like reptile) Feathers Fossil Artist’s reconstruction Figure Laura Coronado Bio 10 Chapter 14

24 Adaptations of Old Structures for New Functions – Birds: Are derived from a lineage of earthbound reptiles Evolved flight from flightless ancestors – Bird wings are modified forelimbs that were previously adapted for non-flight functions, such as: Thermal regulation Courtship displays Camouflage – The first flights may have been only glides or extended hops as the animal pursued prey or fled from a predator. Laura Coronado Bio 10 Chapter 14

25 Evo-Devo: Development & Evolutionary Novelty – A subtle change in a species’ genes that control the development from a zygote to an adult can have profound effects, changing the: Rate Timing Spatial pattern of development – Evo-devo, evolutionary developmental biology, is the study of the evolution of developmental processes in multicellular organisms. Laura Coronado Bio 10 Chapter 14

26 Paedomorphosis – Is the retention into adulthood of features that were solely juvenile in ancestral species – Has occurred in the evolution of Axolotl salamanders Humans Laura Coronado Bio 10 Chapter 14

27 Chimpanzee fetus Chimpanzee adult Human adult (paedomorphic features) Human fetus Figure Laura Coronado Bio 10 Chapter 14

28 Homeotic Genes – Master control genes that regulate: When structures develop How structures develop Where structures develop – Mutations in homeotic genes can profoundly affect body form. Laura Coronado Bio 10 Chapter 14

29 EARTH HISTORY AND MACROEVOLUTION – Macroevolution is closely tied to the history of the Earth. – The fossil record is: The sequence in which fossils appear in rock strata An archive of macroevolution – Geologists have established a geologic time scale reflecting a consistent sequence of geologic periods. Laura Coronado Bio 10 Chapter 14

30 Figure Laura Coronado Bio 10 Chapter 14

31 Table 14.1 Laura Coronado Bio 10 Chapter 14

32 Geologic Time & Fossil Record – Fossils are reliable chronological records only if we can determine their ages, using: The relative age of fossils, revealing the sequence in which groups of species evolved, or The absolute age of fossils, requiring other methods such as radiometric dating – Is the most common method for dating fossils – Is based on the decay of radioactive isotopes – Helped establish the geologic time scale Laura Coronado Bio 10 Chapter 14

33 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) Figure Laura Coronado Bio 10 Chapter 14

34 Plate Tectonics and Macroevolution – The continents are not locked in place. Continents drift about the Earth’s surface on plates of crust floating on a flexible layer called the mantle. – The San Andreas fault is: In California At a border where two plates slide past each other – Plate tectonics explains: Why Mesozoic reptiles in Ghana (West Africa) and Brazil look so similar How marsupials were free to evolve in isolation in Australia Laura Coronado Bio 10 Chapter 14

35 Figure Laura Coronado Bio 10 Chapter 14

36 – About 250 million years ago: Plate movements formed the supercontinent Pangaea The total amount of shoreline was reduced Sea levels dropped The dry continental interior increased in size Many extinctions occurred – About 180 million years ago: Pangaea began to break up Large continents drifted increasingly apart Climates changed The organisms of the different biogeographic realms diverged Laura Coronado Bio 10 Chapter 14

37 Pangaea Present Paleozoic Cenozoic Mesozoic 251 million years ago Laurasia Gondwana Eurasia India Madagascar North America Africa South America Antarctica Australia Figure Laura Coronado Bio 10 Chapter 14

38 Mass Extinctions & Explosive Diversifications of Life – The fossil record reveals that five mass extinctions have occurred over the last 600 million years. – The Permian mass extinction: Occurred at about the time the merging continents formed Pangaea (250 million years ago) Claimed about 96% of marine species – The Cretaceous extinction: Occurred at the end of the Cretaceous period, about 65 million years ago Included the extinction of all the dinosaurs except birds Permitted the rise of mammals Laura Coronado Bio 10 Chapter 14

39 The Process of Science: Did a Meteor Kill the Dinosaurs? – Observation: About 65 million years ago, the fossil record shows that: The climate cooled Seas were receding Many plant species died out Dinosaurs (except birds) became extinct A thin layer of clay rich in iridium was deposited – Question: Is the iridium layer the result of fallout from a huge cloud of dust that billowed into the atmosphere when a large meteor or asteroid hit Earth? Laura Coronado Bio 10 Chapter 14

40 The Process of Science: Did a Meteor Kill the Dinosaurs? – Hypothesis: The mass extinction 65 million years ago was caused by the impact of an extraterrestrial object. – Prediction: A huge impact crater of the right age should be found somewhere on Earth’s surface. – Results: Near the Yucatán Peninsula, a huge impact crater was found that: Dated from the predicted time Was about the right size Was capable of creating a cloud that could have blocked enough sunlight to change the Earth’s climate for months Laura Coronado Bio 10 Chapter 14

41 Chicxulub crater Figure Laura Coronado Bio 10 Chapter 14

42 CLASSIFYING THE DIVERSITY OF LIFE – Systematics focuses on: Classifying organisms Determining their evolutionary relationships – Taxonomy is the: Identification of species Naming of species Classification of species Laura Coronado Bio 10 Chapter 14

43 Some Basics of Taxonomy – Scientific names ease communication by: Unambiguously identifying organisms Making it easier to recognize the discovery of a new species – Carolus Linnaeus (1707–1778) proposed the current taxonomic system based upon: A two-part name for each species A hierarchical classification of species into broader groups of organisms Laura Coronado Bio 10 Chapter 14

44 Naming Species – Each species is assigned a two-part name or binomial, consisting of: The genus A name unique for each species – The scientific name for humans is Homo sapiens, a two part name, italicized and latinized, and with the first letter of the genus capitalized. Laura Coronado Bio 10 Chapter 14

45 Hierarchical Classification – Species that are closely related are placed into the same genus. – The taxonomic hierarchy extends to progressively broader categories of classification, from genus to: Family Order Class Phylum Kingdom Domain Laura Coronado Bio 10 Chapter 14

46 Jaguar (Panthera onca) Lion (Panthera leo) Tiger (Panthera tigris) Leopard (Panthera pardus) Figure Laura Coronado Bio 10 Chapter 14

47 Leopard (Panthera pardus) Species Panthera pardus Genus Panthera Family Felidae Order Carnivora Class Mammalia Phylum Chordata Kingdom Animalia Domain Eukarya Figure Laura Coronado Bio 10 Chapter 14

48 Classification and Phylogeny – The goal of systematics is to reflect evolutionary relationships. – Biologists use phylogenetic trees to: Depict hypotheses about the evolutionary history of species Reflect the hierarchical classification of groups nested within more inclusive groups Laura Coronado Bio 10 Chapter 14

49 Panthera pardus (leopard) Species Genus Felidae Order Carnivora Family Canis Lutra Panthera Mephitis Canidae Mustelidae Canis lupus (wolf) Canis latrans (coyote) Lutra lutra (European otter) Mephitis mephitis (striped skunk) Figure Laura Coronado Bio 10 Chapter 14

50 Sorting Homology from Analogy – Homologous structures: Reflect variations of a common ancestral plan Are the best sources of information used to – Develop phylogenetic trees – Classify organisms according to their evolutionary history – Convergent evolution: Involves superficially similar structures in unrelated organisms and is based on natural selection – Similarity due to convergence: Is called analogy, not homology and can obscure homologies Laura Coronado Bio 10 Chapter 14

51 Molecular Biology as a Tool in Systematics – Molecular systematics: Compares DNA and amino acid sequences between organisms Can reveal evolutionary relationships – Some fossils are preserved in such a way that DNA fragments can be extracted for comparison with living organisms. Laura Coronado Bio 10 Chapter 14

52 Figure Laura Coronado Bio 10 Chapter 14

53 The Cladistic Revolution – Cladistics is the scientific search for clades. – A clade: Consists of an ancestral species and all its descendants Forms a distinct branch in the tree of life – Cladistics has changed the traditional classification of some organisms, including the relationships between: Dinosaurs, Birds, Crocodiles, Lizards, & Snakes Laura Coronado Bio 10 Chapter 14

54 Hair, mammary glands Long gestation Gestation Duck-billed platypus Iguana Outgroup (reptile) Ingroup (mammals) Beaver Kangaroo Figure Laura Coronado Bio 10 Chapter 14

55 Lizards and snakes Crocodilians Saurischian dinosaurs Ornithischian dinosaurs Pterosaurs Birds Common ancestor of crocodilians, dinosaurs, and birds Figure Laura Coronado Bio 10 Chapter 14

56 Classification: A Work in Progress – Linnaeus: Divided all known forms of life between the plant & animal kingdoms Prevailed with his two-kingdom system for over 200 years – In the mid-1900s, the two-kingdom system was replaced by a five-kingdom system that: Placed all prokaryotes in one kingdom Divided the eukaryotes among four other kingdoms – In the late 20th century, molecular studies and cladistics led to the development of a three-domain system, recognizing: Two domains of prokaryotes (Bacteria and Archaea) One domain of eukaryotes (Eukarya) Laura Coronado Bio 10 Chapter 14

57 Kingdom Animalia Domain Archaea Earliest organisms Domain Bacteria Domain Eukarya Kingdom Fungi Kingdom Plantae The protists (multiple kingdoms) Figure Laura Coronado Bio 10 Chapter 14

58 Evolution Connection: Rise of the Mammals – Mass extinctions: Have repeatedly occurred throughout Earth’s history Were followed by a period of great evolutionary change – Fossil evidence indicates that: Mammals first appeared about 180 million years ago The number of mammalian species – Remained steady and low in number until about 65 million years ago and then – Greatly increased after most of the dinosaurs became extinct Laura Coronado Bio 10 Chapter 14

59 American black bear Eutherians (5,010 species) Millions of years ago Monotremes (5 species) Marsupials (324 species) Ancestral mammal Reptilian ancestor Extinction of dinosaurs Figure Laura Coronado Bio 10 Chapter 14

60 Postzygotic barriers Gametes Viable, fertile offspring Zygote Prezygotic barriers Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown Temporal isolation Habitat isolation Behavioral isolation Mechanical isolation Gametic isolation Figure 14.UN1 Laura Coronado Bio 10 Chapter 14


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