Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Natural selection wikipedia , lookup
Gene expression programming wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
The Selfish Gene wikipedia , lookup
Evidence of common descent wikipedia , lookup
Reproductive isolation wikipedia , lookup
Population genetics wikipedia , lookup
Organisms at high altitude wikipedia , lookup
Speciation • Defined: evolution of a new species • Species: group of organisms that can interbreed and produce fertile offspring • Isolation reduces gene flow – Reproductive – Geographical – Behavioral – Temporal • Gene pools & frequencies altered Gene Flow • Defined: Movement of alleles from 1 population to another • Increases variation • Keeps differing populations similar • If gene flow prevented: – No variations exchanged – Populations isolated – Organisms adapt to their own environment Genetic Drift • Defined: Changes in gene pool due to chance (not natural selection) • Bottleneck effect, founder effect • More likely in smaller populations • Ex: Forest fire destroys 90% of a forest – Survival unrelated to adaptations – Pre-forest fire (left picture): Blue is more advantageous – Post-forest fire (right picture): Due to more red survivors, red has the advantage to reproduce in this new environment Founder Effect: 14 Species of Galapagos Finches 1) Geographic Isolation • Mountains, rivers, canyons, oceans may separate a population • Each population adapts to its isolated environment (natural selection) • Because isolated, no gene flow 2) Behavioral Isolation • Although not geographically separated, reproduction is prevented – 1) Different mating rituals – 2) Use of pheromones • No gene flow: differing populations unable to reproduce 3) Temporal Isolation • Although not geographically separated, reproduction is prevented – 1) Mate at different seasons – 2) Some nocturnal • No gene flow: differing populations unable to reproduce End Result: Reproductive Isolation • Created as a result of behavioral, geographical, & temporal isolation • No mating between populations (no gene flow) • Two groups unable to reproduce – Sex organs don’t match, rituals don’t attract, physically separated • Final step to becoming different species • Ultimately leads to speciation. Quick Review • New species are created (speciation) when populations become isolated • A changing or new environment greatly affects natural selection