Chapter 22 The Origin of Species AP Biology

22.1 The Nature of Species Sympatric – species occurring in the same area but are phenotypically different Example – birds at a bird feeder Different species will utilize different parts of a habitat

22.2 The Biological Species Concept Group of organisms that are reproductively isolated from each other – different species cannot mate with other species and produce viable offspring – reproductively isolated

1. Geographic Isolation – species occur in different areas separated by a barrier – river, mountain range 2. Ecological Isolation – species are in the same area, but do not live in the same habitat and do not interact with each other 3. Behavioral Isolation – species differ in mating rituals 4. Temporal Isolation – reproduction of species occurs at different times

5. Mechanical Isolation – structural differences between species prevent mating 6. Prevention of Gamete Fusion – fertilization is “blocked” 7. Hybrid Inviability or Infertility – embryos do not develop properly or adults are infertile

22.3 The Evolution of Reproductive Isolation Cladogenesis – one species evolving into two Over time groups need to become reproductively isolated

22.4 The Role of Genetic Drift and Natural Selection in Speciation Genetic Drift – Conditions favor one phenotype (and therefore genotype) within a population because it may be better suited Adaptation leads to speciation

22.5 The Geography of Speciation Allopatric populations (separated geographically) will evolve differently because they do not interbreed Sympatric Speciation – occurs due to Polyploidy Individuals with more than two sets of chromosomes – common in plants

2 types of polyploidy 1. Autopolyploidy – all chromosomes come from a single species 2. Allopolyploidy – due to hybridization – more common In either case most offspring are infertile b/c of meiosis but can reproduce asexually

22.6 Species Clusters: Evidence of Rapid Evolution Adaptive Radiation – closely related species found in different parts of an environment --Galapagos Islands Key Innovation – new trait that appears and allows a species to use part of the environment that it was not able to use before

Groups Hawaiian Drosophila Darwin’s Finches Lake Victoria Cichlid Fish New Zealand Alpine Buttercups