4.3 Notes on Species Formation PDF

CH 4.3: How Species Form (Pg. 136 – 142)  What is a species? Biological species – populations which can interbreed and produce viable offspring, which can also interbreed in nature Or… reproductively isolated from other species Speciation Formation of a new species How? 1.Transform...

CH 4.3: How Species Form (Pg. 136 – 142)  What is a species? Biological species – populations which can interbreed and produce viable offspring, which can also interbreed in nature Or… reproductively isolated from other species Speciation Formation of a new species How? 1.Transformation – one species gradually replaces the old one Due to an accumulation of changes (mutations and adaptations) in the population over a long time 2.Divergence – new species arise from a parent species which continues to exist  Transformation Divergence Which method increases biodiversity?  For speciation to occur, the populations must be reproductively isolated. Geographical barriers Physically separates populations E.g. river, mountain, etc. Speciation Mechanisms  Biological Barriers Factors that prevent mating even if the species live in the same place E.g. behaviour, courtship songs, habitat selection, pheromones, etc. Speciation has occurred once the populations are reproductively incompatible Even if they are brought back together they cannot reproduce successfully  Adaptive Radiation Many species arise from one common ancestor E.g. finches, cichlids  Cichlids Live in same general area but different habitats, using different resources  Pace of Evolution How fast does evolution happen? Controversial 1.Gradualism – small changes are constantly occurring, adding up to large changes over a long time Rarely shown in fossil record Species appear and disappear suddenly in the fossil record Pace of Evolution 2.Punctuated equilibrium - long periods of little change (equilibrium) interrupted (punctuated) by short periods of rapid change Species change the most right after it diverges from the parent species Little change happens after the initial adaptation Common after major environmental changes or when colonizing new areas The Theory of Evolution by Natural Selection - summarized Life forms develop from ancestral species All living things are related by common descent (some more closely than others) All living things share one common ancestor Beneficial mutations are passed on to offspring more often than harmful mutations Successful adaptations can eventually become common throughout the population (then the whole population changes) Extra review Read: Pg. 136 - 142 Comprehension Questions # 15-17 Section Review Pg. 142