Chapter 14- Origin of Species Adaptive radiation Allopatric speciation Behavioral isolation Biological species concept Ecological species concept Gametic isolation Genealogical species concept Gradualist model Habitat isolation Hybrid breakdown Hybrid inviability Hybrid sterility Mechanical isolation Morphological species concept Polyploidy cells Punctuated equilibrium Reproductive barrier Speciation Sympatric speciation Taxonomy Temporal isolation

Something to remember: Most of the time evolution is gradual, sometimes though it can be observed over several generations

Speciation Evolution of a new species –Biological species concept- population or group of populations whose members can interbreed and produce fertile offspring Ring species- forms a ring around geographic feature (may cause speciation)

Speciation con’t –Morphological species concept- classify species by measureable phenotypic traits –Genealogical species concept- defines species by a set of organisms with unique genetic history –Ecological species concept- idendifies by ecological niche (role in env)

Reproductive barriers Keep species separate Can cause speciation –Ex: mosquitoes in London Underground

Prezygotic reproductive barriers Prevents mating Temporal isolation- mating/flowering occurs at different times/seasons Habitat isolation- populations live in different habitats and don’t meet Behavioral isolation- no attraction between sexes Mechanical isolation- genitalia structure/flowers differs, prevents copulation Gametic isolation- gametes die before uniting

Postzygotic reproductive barriers Prevents development of fertile adults Hybrid inviability- zygotes fail to develop or reach sexual maturity Hybrid sterility- don’t produce functional gametes Hybrid breakdown- offspring of hybrids are weak or infertile

Geographic isolation Causes speciation Allopatric speciation Ex: lakes dry up into smaller lakes, fish can’t move from one to another Ring species sometime end up as new species Occurs when gene pool changes to create a reproductive barrier More likely to happen in small, isolated pop’s

Geographic isolation con’t Galapagos finches Adaptive radiation- evolution of many species from a common ancestor due to new environments

Sympatric speciation Reproductive isolation develops and new species arise without geographic separation –Widespread in plants Accident in meiosis produces cells with extra chromosome sets Polyploid cells- cells that has more than 2 sets of chromosomes 2n gametes can self-fertilize and produce a 4n plant Production of a 4n cell is an instant speciation event, because it now can’t reproduce with parent species –Ex: strawberries 2n gamete fused with 1n gamete produces 3n which is sterile b/c odd chromosomes can’t form homologous pairs

Sympatric speciation con’t –Chemicals can be used to induce these errors to hybridize plants Ex: yield of wheat with resistance of rye –Polyploid crops: oats, potatoes, bananas, peanuts, barley, plums, apples, sugarcane, coffee, wheat, cotton, strawberries –25-50% of plant species are polyploid

Tempo of speciation

Tempo of Speciation con’t Gradualist- populations evolve gradually as they become adapted to new environments –Very few fossil sequences show the steady accumulation of small changes Punctuated equilibrium- long periods of little change with abrupt episodes of speciation * although evolution is jumpy when viewed as a whole its relatively steady