1. Chapter 24

2.  Evolution leads to potential speciation  One species becoming two or more species  Speciation leads to macroevolution  Broad changes beyond the species level  Speciation occurring

3.  Members of a species in a population have the potential to interbreed and produce viable offspring  Species can remain distinct if they can not interbreed  Ex. Humans vs. Chimps  However, gene flow between species in a population can hold the population together genetically

4.  Reproductive Isolation  Biological factors that impede two members of a species from mating  This blocks gene flow between species  Limits the production of hybrids  Prezygotic vs. Postzygotic barriers

5.  Behavioral Isolation  Two populations will not breed because of differences in courtship  Fireflies

6.  Geographical Isolation  Rivers, mountains, or bodies of water separate two populations  Snapping Shrimp and placental vs. marsupial mammals

7.  Temporal Isolation  Different species mate at different times  Times of day  Times of year  Trees and plants

8.  Mechanical Isolation  Mating is attempted by morphological differences prevent completion  Ex. Ophrys orchids and bees

9.  Gametic Isolation  Sperm from one species may not be able to fertilize the egg of another  Sperm may not survive reproductive tract  Biochemical mechanisms may prevent sperm entry into an egg

10.  Reduced Hybrid Viability  Genes of different parent species may interact in ways that impair hybrid’s survival or development  Ex. Salamanders of genus Enstania occasionally hybridize but the offspring often don’t develop or are very frail

11.  Reduced Hybrid Fertility  Hybrids are born sterile  Often due to differing chromosome numbers between species

12.  Hybrid Breakdown  Initial offspring may be fertile but after mating with one another or parents the hybrid produced is sterile

13.  Morphological Species Concept  Characterizes species based on shape and various features  In practice, most scientists use this concept  Ecological Species Concept  Views species in regards to their ecological niche  Two species may resemble one another, but have differ in diets or mating habits  Phylogenic Species Concept  The smallest group of species that share a common ancestor  Difficulty is determining the degree of difference between different species

14.  Can take place with or without geographic separation  Types of speciation  Allopatric  Sympatric