Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Natural Selection and Speciation
Document related concepts
Island restoration wikipedia , lookup
Biological Dynamics of Forest Fragments Project wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Theoretical ecology wikipedia , lookup
Habitat conservation wikipedia , lookup
Latitudinal gradients in species diversity wikipedia , lookup
Molecular ecology wikipedia , lookup
Ecological fitting wikipedia , lookup
Transcript
Natural Selection and Speciation Another way to look at it… Fitness • Directional Selection Trait Positive Directional Selection Trait Negative Directional Selection Fitness • Stabilizing selection average trait value Egg laying wasp that eventually kills the cactus Fitness • Disruptive Selection average trait value Black-bellied seed cracker (Pyrenestes ostrinus) • Smith, T. B. 1990. Evolution. 44(4):832 • Black-bellied seed crackers (Pyrenestes) in Cameroon Same birds different study Open portion of bar – Number hatched Black portion of bar – Number survived Two more types of selection • Correlational – working on combinations of traits at once. (body size) (Wing length) • Frequency Dependent Selection – Level of selection dependent upon most common phenotype (at the time) Genyochromis Scale eater Scalebiters – frequency dependent selection Right “mouthedness” Left “mouthedness” Frequency of left “mouthedness” Frequency of right “mouthedness” Time • Selection can lead to speciation • Speciation: – Splitting of one species into two or more species – Transformation of one species into a new species over time Anagenetic (gradual) versus Cladistic (punctuated) Speciation B A TIME TIME B A A PHENOTYPIC VARIATION PHENOTYPIC VARIATION Species • Many, many definitions • Biological species definition: A group of actually or potentially breeding individuals which are reproductively isolated from all other groups. • Doesn’t work in all situations – Fossils – Asexual organisms Isolating mechanisms • Prezygotic – • Postzygotic - • Pre-zygotic barriers include – Temporal isolation – Behavioral – Mechanical – Gametic Prezygotic I.M.s • Habitat isolation – Dendroica warblers in Eastern US Modes of speciation • Allopatric – allo = different, patri = fatherland • Sympatric – sym = together • Has to do with location or habitat Speciation only occurs with reproductive isolation Sympatric speciation • Polyploidy in plants • Hybrids Adaptive Radiation • Evolution of ecological (& morphological) diversity within a rapidly speciating lineage. • Hawaiian honeycreepers
