Section 16-3 The Process of Speciation Holliston HS
POPULATION - localized group of individuals of same species SPECIES - individuals with potential to interbreed and produce fertile offspring SPECIATION- the formation of a new species GENE POOL - total aggregate of genes in a population; consists of all alleles in all individuals MORPHOLOGY - internal & external structure & appearance of an organism; chief criterion for classifying a species DEFINING TERMS
BIOLOGICAL SPECIES CONCEPT MAYR: A population whose members can interbreed with one another to produce viable, fertile offspring but cannot breed with other groups. Eastern Meadowlark Western Meadowlark The concept is based on interfertility rather than physical similarity.
What must happen for a species to evolve into two new species? REPRODUCTIVE ISOLATION: when members of two populations cannot interbreed and produce fertile offspring Prezygotic vs Postzygotic isolation Can develop in three different ways: Behavioral Isolation Geographic Isolation Temporal Isolation ISOLATING MECHANISMS
1) Behavioral Isolation Two populations are capable of interbreeding, but do not because of differences in their reproductive behavior such as courtship rituals (Example) eastern & western meadowlarks are very similar but will not mate with each other because they use different songs to attract mates
2) Geographic Isolation Two populations are separated by geographic barriers (river, mountain, etc) (Example) Abert squirrels in the southwest split into 2 species because of the Colorado River
3) Temporal Isolation Species reproduce at different time periods (Example) – 3 similar species of orchids live in the same rain forest but releases pollen on different days so they cannot pollinate each other
RATES OF SPECIATION Speciation did not happen gradually and smoothly, instead…. PUNCTUATED EQUILIBRIUM: species diverge in spurts of relatively rapid change; modified when first budded off parent then change little
CHAPTER 18 - CLASSIFICATION18-1 History of Taxonomy Why Classify? • Scientists use a classification system to name organisms and to group them in a logical manner Taxonomy The branch of biology that names and groups organisms according to their characteristics and evolutionary history.
A Need for Organization Carolus Linnaeus(Swedish naturalist 1707-1778) • Devised a system for grouping organisms into hierarchical categories. • Used an organism’s morphology (form & structure) to categorize it. • Categorization scheme used a nested hierarchy. • Seven different levels (TAXONS) of organization • Each level more specific than the last • Allowed organisms to be grouped with similar organisms
Linnaeus’s System of Classification includes seven levels (taxon) Kingdom Phylum Class Order Family Genus Do Kings play chess on fuzzy green stools? Species
Linnaeus’s System of Classification Levels of Classification
Linnaeus’s System • Species name (scientific name) of an organism has two parts. • Known as binomial nomenclature. • First part refers to Genus • Genus-group of closely related species • Second part is the species identifier, usually a descriptive word. • Species-if same; can mate and produce fertile offspring • Sometimes further split into varieties or subspecies • Genus is capitalized and the species is lowercase. • The Scientific name is always written in italics. • Names are Latinized-same in every language. • Used today, scientists around the world identify organisms by the same name.
Figure 18-5 Classification of Ursus arctos Coral snake Abert squirrel Sea star Grizzly bear Black bear Giant panda Red fox KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Ursidae GENUS Ursus Biology, Miller & Levine, pg 450. SPECIES Ursus arctos
What is our Scientific name? • Homo sapiens • “The scientific name Homo sapiens applies to humans. Homo is the generic name and derives from the Latin homo meaning ‘man'. The specific name sapiens derives from the Latin sapiens, meaning ‘wise'. “ www.dkimages.com http://www.cdtl.nus.edu.sg/success/sl43.htm
Section 18-2Modern Phylogentic Taxonomy • PHYLOGENY: evolutionary relationships among organism • PHYLOGENTIC TREE: family tree that shows evolutionary relationships though to exist among groups of organisms • SYSTEMATICS: grouping organisms together based on evolutionary history
CLADISTICS: Classification Using Cladograms • New system of phylogenetic classification. • Uses certain features of organisms to establish evolutionary relationships. • DERIVED CHARACTER – features that appear in recent parts of a lineage but not in its older members • CLADOGRAM - diagram that shows the evolutionary relationships among a group of organisms
CLADISTIC ANALYSIS: studying evolutionary relationships by looking at: • Fossil records • Morphology • Genetics • Embryological Patterns of Development • CLADOGRAM: tree based on series of tw0-way branches, each point representing divergence of 2 species Cladograms
Traditional Classification v. Cladogram Appendages Conical Shells Crustaceans Gastropod Crab Crab Limpet Limpet Barnacle Barnacle Molted exoskeleton Segmentation Tiny free-swimming larva CLASSIFICATION BASED ON VISIBLE SIMILARITIES CLADOGRAM Biology, Miller & Levine pg 452
Section 18-3SIX KINGDOM SYSTEM • For many years a classification based on five kingdoms was preferred. • Recent studies of bacteria have shown that there are two important subtypes with very different morphologies and properties. • This recent recognition has led to the acceptance of a new six kingdom system.
Six Kingdom System • EUBACTERIA • ARCHEBACTERIA • PROTISTA • FUNGI • PLANTAE • ANIMALIA • Organisms fall into one of six kingdoms based upon shared characteristics: • Cell type • Cell construction • Body type • Mode of Nutrition
Key Characteristics of Six Kingdoms and Three Domains Classification of Living Things DOMAIN KINGDOM CELL TYPE CELL STRUCTURES NUMBER OF CELLS MODE OF NUTRITION EXAMPLES Bacteria Eubacteria Prokaryote Cell walls with peptidoglycan Unicellular Autotroph or heterotroph Streptococcus, Escherichia coli Archaea Archaebacteria Prokaryote Cell walls without peptidoglycan Unicellular Autotroph or heterotroph Methanogens, halophiles Protista Eukaryote Cell walls of cellulose in some; some have chloroplasts Most unicellular; some colonial; some multicellular Autotroph or heterotroph Amoeba, Paramecium, slime molds, giant kelp Fungi Eukaryote Cell walls of chitin Most multicellular; some unicellular Heterotroph Mushrooms, yeasts Eukarya Plantae Eukaryote Cell walls of cellulose; chloroplasts Multicellular Autotroph Mosses, ferns, flowering plants Animalia Eukaryote No cell walls or chloroplasts Multicellular Heterotroph Sponges, worms, insects, fishes, mammals Biology, Miller & Levine, pg 459