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

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

MACROEVOLUTION & THE DIVERSITY OF LIFE 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

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

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

Laura Coronado Bio 10 Chapter 14 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

Laura Coronado Bio 10 Chapter 14 Figure 14.2 The biological species concept is based on reproductive compatibility Similarity between different species Diversity within one species Laura Coronado Bio 10 Chapter 14 Figure 14.2

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

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

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

Laura Coronado Bio 10 Chapter 14 PREZYGOTIC BARRIERS Temporal Isolation Habitat Isolation Behavioral Isolation Mechanical Isolation Gametic Isolation Figure 14.4 Prezygotic barriers Laura Coronado Bio 10 Chapter 14 Figure 14.4

Laura Coronado Bio 10 Chapter 14 POSTZYGOTIC BARRIERS Reduced Hybrid Viability Reduced Hybrid Fertility Hybrid Breakdown Horse Donkey Figure 14.5 Postzygotic barriers Mule Laura Coronado Bio 10 Chapter 14 Figure 14.5

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

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

Laura Coronado Bio 10 Chapter 14 Ammospermophilus harrisii Ammospermophilus leucurus Figure 14.7 Allopatric speciation of antelope squirrels on opposite rims of the Grand Canyon Laura Coronado Bio 10 Chapter 14 Figure 14.7

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

Laura Coronado Bio 10 Chapter 14 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

Laura Coronado Bio 10 Chapter 14 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

Laura Coronado Bio 10 Chapter 14 Domesticated Triticum monococcum (14 chromosomes) Wild Triticum (14 chromosomes) AA BB AB Sterile hybrid (14 chromosomes) T. turgidum Emmer wheat (28 chromosomes) AA BB DD Wild T. tauschii (14 chromosomes) Figure 14.9 The evolution of wheat (Step 4) ABD Sterile hybrid (21 chromosomes) T. aestivum Bread wheat (42 chromosomes) AA BB DD Laura Coronado Bio 10 Chapter 14 Figure 14.9-4

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

Laura Coronado Bio 10 Chapter 14 Punctuated model Time Graduated model Figure 14.10 Two models for the tempo of evolution Laura Coronado Bio 10 Chapter 14 Figure 14.10

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

Laura Coronado Bio 10 Chapter 14 Wing claw (like reptile) Teeth (like reptile) Figure 14.11 An extinct bird: Archaeopteryx Feathers Long tail with many vertebrae (like reptile) Fossil Artist’s reconstruction Laura Coronado Bio 10 Chapter 14 Figure 14.11

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

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

Laura Coronado Bio 10 Chapter 14 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

Laura Coronado Bio 10 Chapter 14 Chimpanzee fetus Chimpanzee adult Figure 14.13 Comparison of human and chimpanzee skull development Human fetus Human adult (paedomorphic features) Laura Coronado Bio 10 Chapter 14 Figure 14.13

Laura Coronado Bio 10 Chapter 14 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

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

Laura Coronado Bio 10 Chapter 14 Figure 14.14 A gallery of fossils Laura Coronado Bio 10 Chapter 14 Figure 14.14

Laura Coronado Bio 10 Chapter 14 Table 14.1 The Geologic Time Scale Laura Coronado Bio 10 Chapter 14 Table 14.1

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

(as % of living organism’s Carbon-14 radioactivity 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 Figure 14.15 Radiometric dating Laura Coronado Bio 10 Chapter 14 Figure 14.15

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

Laura Coronado Bio 10 Chapter 14 Figure 14.16 California's San Andreas fault Laura Coronado Bio 10 Chapter 14 Figure 14.16

Laura Coronado Bio 10 Chapter 14 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

Laura Coronado Bio 10 Chapter 14 Present Cenozoic North America Eurasia 65 Africa South America India Madagascar Australia Antarctica Laurasia 135 Mesozoic Gondwana Figure 14.17 The history of plate tectonics 251 million years ago Pangaea Paleozoic Laura Coronado Bio 10 Chapter 14 Figure 14.17

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

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

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

Laura Coronado Bio 10 Chapter 14 Chicxulub crater Figure 14.18 Trauma for planet Earth and its Cretaceous life (Step 3) Laura Coronado Bio 10 Chapter 14 Figure 14.18-3

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

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

Laura Coronado Bio 10 Chapter 14 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

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

Laura Coronado Bio 10 Chapter 14 Leopard (Panthera pardus) Tiger (Panthera tigris) Lion (Panthera leo) Figure 14.19 The four species within the genus Panthera Laura Coronado Bio 10 Chapter 14 Jaguar (Panthera onca) Figure 14.19

Laura Coronado Bio 10 Chapter 14 Species Panthera pardus Genus Panthera Leopard (Panthera pardus) Family Felidae Order Carnivora Class Mammalia Figure 14.20 Hierarchical classification Phylum Chordata Kingdom Animalia Domain Eukarya Laura Coronado Bio 10 Chapter 14 Figure 14.20

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

Laura Coronado Bio 10 Chapter 14 Order Family Genus Species Panthera pardus (leopard) Felidae Panthera Mephitis mephitis (striped skunk) Mephitis Carnivora Mustelidae Lutra lutra (European otter) Lutra Figure 14.21 The relationship of classification and phylogeny for some members of the order Carnivora Canis latrans (coyote) Canidae Canis Canis lupus (wolf) Laura Coronado Bio 10 Chapter 14 Figure 14.21

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

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

Laura Coronado Bio 10 Chapter 14 Figure 14.22 Studying ancient DNA Laura Coronado Bio 10 Chapter 14 Figure 14.22

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

Laura Coronado Bio 10 Chapter 14 Iguana Outgroup (reptile) Duck-billed platypus Kangaroo Ingroup (mammals) Hair, mammary glands Figure 14.23 A simplified example of cladistics Gestation Beaver Long gestation Laura Coronado Bio 10 Chapter 14 Figure 14.23

Laura Coronado Bio 10 Chapter 14 Lizards and snakes Crocodilians Pterosaurs Common ancestor of crocodilians, dinosaurs, and birds Ornithischian dinosaurs Figure 14.24 How cladistics is shaking phylogenetic trees Saurischian dinosaurs Birds Laura Coronado Bio 10 Chapter 14 Figure 14.24

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

Laura Coronado Bio 10 Chapter 14 Domain Bacteria Earliest organisms Domain Archaea The protists (multiple kingdoms) Kingdom Plantae Domain Eukarya Figure 14.25 The three-domain classification system Kingdom Fungi Kingdom Animalia Laura Coronado Bio 10 Chapter 14 Figure 14.25

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

Laura Coronado Bio 10 Chapter 14 Ancestral mammal Monotremes (5 species) Extinction of dinosaurs Reptilian ancestor Marsupials (324 species) Eutherians (5,010 species) Figure 14.26 The increase in mammalian diversity after the extinction of dinosaurs 250 200 150 100 65 50 American black bear Millions of years ago Laura Coronado Bio 10 Chapter 14 Figure 14.26

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