DEFINITIONSMicroevolution: genetic change in a population from one generation to the nextMacroevolution: Processes through which new species arise
WHAT IS A SPECIES? Biological species concept: If organisms from two populations are capable of breeding naturally and can produce fertile offspring, then they are classified in the same species. X = Horse Donkey Mule
SPECIATION The formation of new species Gene flow keeps populations similar to one another. Reproductive Isolation: genetic isolation of populations that may cause them to become incapable of producing fertile offspring. Gene flow is the glue that holds species together.
SPECIATION: A TWO STEP PROCESS1. Reproductive Isolation Reduction of gene flow provides opportunity for speciation Does not always lead to speciation2. Genetic Divergence Other evolutionary forces change population enough so that fertile interbreeding is no longer possible
ANAGENESIS: “STRAIGHT-LINE”EVOLUTION Single species evolving into new species over time
CLADOGENESIS: “BRANCHING” EVOLUTION Formation of one or more new species from another over time
3 TYPES OF SPECIATION 1. Allopatric speciation-speciation in organisms with no geographic overlap. 2. Parapatric speciation-speciation in organisms with partial geographic overlap. 3. Sympatric speciation-speciation in organisms with complete geographic overlap.
Niche: the way of life of a species (How that species fits into the surrounding environment) Niche partitioning: species evolve to occupy different niches and avoid competition Ex. occupying different places in the habitat, feeding at different times, being active at different times of the year, etc. Bees and moths use the same food resource Bees diurnal, Moths nocturnal ☼ Can’t have two species occupying the same niche in the same area because this will lead to competition.
SPECIATION RATERate of Speciation: depends on # of empty nichesAdaptive Radiation: Rapid diversification by a small # of species to fill many open niches
TEMPO OF EVOLUTIONGradualism: Macroevolution is a relatively slow and gradual process.Punctuated Equilibrium: Long intervals of time with little change (stasis) interspersed with short intervals of rapid evolutionary change.
THE BIRTH OF SPECIES b) Gradualism with increase in rate of change a) Gradualism c) Punctuated Equilibrium = Staircase pattern
EXTINCTION The disappearance of a group of organisms such as a species. When a species cannot change fast enough to adapt to changes in its environment, it may become extinct.
NEARLY EVERYTHING THAT HAS EVER LIVED IS EXTINCT
PALEOSPECIESPaleospecies: Identified in the fossil record based on physical similarities to and differences from other speciesAssumption: physical similarity = genetic relatedness
CLASSIFICATIONClassification is used to order organisms into categories to show evolutionary relationships.
LINNAEAN SYSTEM OF CLASSIFICATION Hierarchical classification Involves a number of categories and subcategories reflecting evolutionary relationships Kingdom Phylum Class Order Family Genus Species Carl Linnaeus
HOW CAN WE MAKE SENSE OF ALL OFTHIS DIVERSITY?
PHYSICAL SIMILARITIES ARE ONLY USED TO CLASSIFY ORGANISMSIF THEY REFLECT EVOLUTIONARY RELATIONSHIPS Analogous traits: Traits similar due to common function Homologous traits: Traits similar due to common ancestry
NOT ALL HOMOLOGOUS TRAITS AREEQUALLY USEFUL FOR CLASSIFICATION Ancestral trait: Trait appearing early in the evolution of a lineage Derived trait: Traits that are modified from the ancestral condition
USING DERIVED TRAITS TO BUILD PHYLOGENIESDerived (Homologous) Analogous Traits Ancestral TraitsTraits
EVOLUTION OF THE COOTIEMOUTH (PHYLOGENETIC TREE)
QUESTIONS1. What is a phylogeny?2. What is the difference between analogous and homologous traits?3. What is the difference between ancestral and derived traits4. What is the difference between microevolution and macroevolution?5. What is the biological species concept?7. What are allopatric, parapatric, and sympatric speciation?8. What is an adaptive radiation?9. How do you identify a paleospecies and what are the problems with this method?