Species and Speciation PDF

Species and Speciation OBJECTIVES ✔ Define species, speciation. ✔ Explain the Biological Species Concept. ✔ Describe, giving examples, allopatric and sympatric speciation.  Biological Species Concept A species is a group of organisms, with similar features, that ca...

Species and Speciation OBJECTIVES ✔ Define species, speciation. ✔ Explain the Biological Species Concept. ✔ Describe, giving examples, allopatric and sympatric speciation.  Biological Species Concept A species is a group of organisms, with similar features, that can interbreed and produce viable, fertile offspring Biological Species Concept ❖ Assumptions ✔ Common characteristics ✔ Genetically compatible/common ancestry ✔ Interbreed under natural conditions ✔ Sexual Reproduction  Drawbacks of Biological Species Concept – Cannot be used with exclusively asexual organisms – Prokaryotes – Amoeba & some other protists – Some animals, plants & fungi Drawbacks: Isolated Populations –How do you test for interbreeding under natural conditions? –Can a deer in Portland interbreed with one in Westmoreland? Drawbacks –Can a Great Dane interbreed with a Chihuahua? – Photo Credit: David Shankbone, 2006, Wikimedia Commons Drawbacks – Some species look and behave differently – Can interbreed and have viable, fertile offspring – Example: coyotes, wolves, dogs Drawbacks: Fossil Species – Cannot tell if fossil organisms were capable of interbreeding – Normally can’t compare genes of different fossil species Biological Species Concept: Reproductive Isolation – Barriers between species – Prevent viable fertile offspring Reproductive Isolating Mechanisms – Prezygotic mechanisms – Before fertilization – Postzygotic mechanisms – After fertilization Prezygotic Mechanisms – Prevents: – mating from occurring – gametes from forming a zygote  Prezygotic Mechanisms: Geographic Isolation – Isolated by a barrier – Separated from each other by mountain, canyon, rivers, oceans, etc. Prezygotic Mechanisms: Temporal Isolation –Isolated by time –May breed: – Different times of day – Different seasons – Different years Prezygotic Mechanisms: Habitat Isolation – Same geographic area – Different habitats Prezygotic Mechanisms: Behavioural Isolation –Different courtship rituals – Blue-Footed Booby Video: http://www.youtube.com/watch?v=4 MPfTzXEZdY Behavioural Isolation Eastern and Western Meadowlarks – Isolated by Songs – Listen to both species Summary – isolating mechanisms Prevents hybrid zygotes from Postzygotic developing into viable, fertile adults Mechanisms Postzygotic Mechanism: Reduced Hybrid Viability –If Sheep and goats mate Hybrid zygotes –Die before birth Postzygotic Mechanism: Reduced Hybrid Fertility Male donkey x Female horse Mule Mules: Healthy Sterile (viable)  The Amoeba sister on speciation – https://www.youtube.com/watch?v=udZUaNKXbJA Speciation –Process of species formation from an existing species. –Two main mechanisms: Allopatric speciation Sympatric speciation Allopatric Speciation Geographic separation The definition of barrier depends on the ability of Genetic exchange a population to disperse Populations become genetically different Reproductive isolation CARIBBEAN ANOLIS LIZARDS Sympatric Speciation Populations not geographically separated Can be due to rapid genetic changes: Alter Alter habitat behaviour preferences Allopatric vs sympatric speciation  Links –https://www.youtube.com/watch?v=8yvE Dqrc3XE –https://www.youtube.com/watch?v=udZ UaNKXbJA