Chapter 15 Origins of Biological Diversity How do biologists identify species? How do species arise?

15.1- The Diversity of Life is Based on the Origin of New Species What is a Species? Biological Species Concept: a species is a population or group of populations whose members can breed with one another in nature & produce fertile offspring. One species cannot interbred with members of other species. Concept helps biologists understand the origin of new species.

15.1 Notes… From Microevolution to Macroevolution Microevolution: change in allele frequencies in a population. Evolution on small scale, explains how pop. evolve. Macroevolution: major evolutionary changes evident in the fossil record 1. Speciation- origin of new species 2. Extinction of species 3. Evolution of new features = wings or flowers

15.1 Notes… Reproductive Barriers Between Species Reproductive Isolation: inability of different species to interbreed. Types of Barriers: 1. Timing- Different breeding seasons. e.g. Western spotted skunks breed in fall, eastern skunks breed in late winter. Coexist in Great Plains. 2. Behavior- Different courtship or mating behaviors. e.g. Eastern & western meadowlarks coexist in central U.S. but have different mating songs.

15.1 Notes… 3) Habitat- Different habitats in same location. e.g. 2 species of stickleback fish in lakes in BC, Canada. One feeds on bottom & other lives in open water. 4. Reproductive Incompatibility Physically Impossible In plants, insects only pollinate a single species Hybrid zygote fails to develop Adult offspring is infertile, e.g. mules

15.1 Notes… Geographic Isolation: separation of populations as a result of geographic change or dispersal to geographically isolated places. e.g. Grand Canyon & 2 species of Antelope squirrels  Isolated pop. evolves new adaptations to changed environment. (Genetic Drift, Nat. Selection)  Speciation occurs if pop. can no longer breed with other pop. Geographic Isolation and Speciation

15.1 Notes… Adaptive Radiation Adaptive radiation: evolution from common ancestor that results in diverse species adapted to different environments. e.g. native species of Hawaiian islands 1. Species A arrives from mainland 2. Species B evolves from A & colonizes nearby island 3. Species C evolves from B & colonizes nearby island 4. ↓ Due to Genetic Drift & adapting to new environment. Geographic isolation prevents species from breeding with parent pop.

15.1 Notes… The Tempo of Speciation Punctuated Equilibrium: Model suggesting species often diverge in spurts of relatively rapid change, followed by long periods of little change. Speciation can be rapid. In a few thousand generations, GD & N. Selection can cause change in a small population occupying a new environment. Relatively short amt. of time compared to the 1-5 million years a species could last.

15.2-Evolution is Usually a Remodeling Process Refinement of Existing Adaptations Some complex structures, such as eyes in mammals, evolve in small steps of adaptation from simpler structures.

15.2 Notes… Adaptation of Existing Structures to New Functions Some structures or materials adapt for certain functions and later fulfill different functions. Chitin (exoskeleton for arthropods-insects, spiders, scorpions & lobsters) Flippers of penguins

15.2 Notes… Evolution and Development What is the genetic basis for evolutionary remodeling of body form? Embryology: study of the processes of multicellular organisms as they develop from fertilized eggs to formed organisms. Possible Causes: Mutations in the genes that control the early development of the organism. e.g. mutation causing fly to grow legs in place of antennae Change in rate or timing of events in development. e.g. adaptation of feet in salamander species

15.3- The Fossil Record Provides Evidence of Life’s History How Fossils Form Fossils form from remains of organisms buried by sediments, dust or ash. Consist as footprints, animal burrows or impressions. Rare fossils contain organic matter.

15.3 Notes… The Fossil Record & Geologic Time Scale Geologic Time Scale: Earth’s history is organized into 4 distinct ages: Boundaries between eras show major change in the forms of life found in the fossil record Boundaries between eras and some periods are also marked by extinctions Precambrian Era Paleozoic Era Mesozoic Era Cenozoic Era → Periods → Epochs

15.3 Notes Dating Fossils Radiometric dating: measurement of certain radioactive isotopes in objects. Half-life: the number of years it takes for 50% of the original isotope samples to decay. Volcanic rock layers are dated with radioactive isotopes in order to estimate the age of the fossils found between them. e.g. uranium-238 “Carbon dating”-Used to date recent fossils containing carbon-12 and carbon-14.

15.3 Notes Continental Drift and Macroevolution Continental Drift: motion of continents about earth’s surface on plates of crust floating on the hot mantle. Two major events in history: 1. End of Paleozoic Era, 250mya, all land masses moved together into a “supercontinent” called Pangaea. Led to environmental changes, competition between species and mass extinction. e.g. Fossils found in West Africa & Brazil are the same. 2. During Mesozoic Era,180mya, continents drifted apart. Species evolved independently e.g. plants and animals of Australia

15.3 Notes Mass Extinctions Fossil records shows long periods of stability broken by episodes of mass extinction, or great species loss. 5-6 periods of mass extinction over last 600 million years. e.g. 65mya, end of Cretaceous period, large # of species are lost, including dinosaurs. Possible causes are cooling temp., shallow seas & a meteor that struck earth. Surviving species undergo adaptive radiation Meteor Impact near Yucatan Peninsula in Mexico

15.4- Modern Taxonomy Reflects Evolutionary History What is Taxonomy? Taxonomy: branch of biology that involves the identification, naming, and classification of species. Goals of taxonomy assign a universal scientific name to each know species. Organize and classify species into larger groups of related species.

15.4 Notes The Linnaean System of Classification Most widely used system developed by Carolus Linnaeus. This system has binomial, or two-part name, for each species. 1 st = the genus which species belongs 2 nd = refers to one species within genus e.g. Panthera pardus = leopard It also orders species into a hierarchy of broader groups.

15.4 Notes Classification and Evolution Biologists use phylogenetic trees and classifications to represent hypotheses about evolutionary history Phylogenetic Tree: branching diagram, suggesting evolutionary relationships, that classifies species into groups within groups. Homologous structures e.g. bats’ wings and whales’ flippers Function differently in different species but have basic underlying similarities if evolved from a structure in a common ancestor The greater # of homologous structures two species have, the more closely related. Analogous Structures Similar adaptations that result from convergent evolution, or the process in which unrelated species from similar environments have adaptations that seem similar. e.g. wings of insects and wings of birds Not to be mistaken for homologous structures. Structures are not inherited from a common ancestor, they evolved independently & are built from different structures.

15.4 Notes Molecular Data as a Taxonomic Tool Relatedness of species can be measured by comparing their genes & proteins. The more sequences that match up, the more closely related Provides a way to test hypotheses about evolutionary history. When independent types of evidence support the same hypothesis, it is strengthened. e.g. Fossil evidence & molecular data both suggest whales and a group of mammals (hippos, cows, deer & pigs) are closely related. Paired with computer technology, provides a new way to build phylogentic trees

15.4 Notes A Closer Look at Phylogenetic Trees Clade: Evolutionary branch in a phylogenetic tree. Clades can nest within larger clades. Every clade consists of an ancestral species and all its descendants. Cladistics: Method of determining sequencing of branching in a phylogenetic tree. All the organisms of a clade must share homologous structures, that do not occur outside the clade. Derived characters: unique features that unite the organisms as a clade. (homologous structures)

15.4 Notes Cladogram: phylogenetic diagram that specifies the derived characters of clades. Used by taxonomists to show relationships among organisms.

15.4 Notes Comparing Classification Schemes Two & Three-Kingdom Schemes 2 kingdom system divided life forms between the plant and animal system. Prevailed for 200 years, but had problems & was replaced. 3 kingdom system added protists as a new category, but the model failed over time. Five Kingdom scheme Includes: plants, fungi, animals, protists and monera Three Domains Based on molecular data. Within each domain there are multiple kingdoms.