Zoology101: Animal Biology Last Lecture Outline Lecture 36 1.Conservation2. Sexual selection Current Lecture 1. Evolutionary trap2. Speciation and Macroevolution Evolutionary Trap• An organism uses particular set of cues in order to make a choice • Cue → produces information presumably associated with a particular outcome (successful reproduction)Speciation and Macroevolution • What is speciation? ◦ Evolution of a new species • Macroevolution: evolutionary change above the species level; the evolutionary components of speciation • Microevolution: change in allele frequency in a local population in time • What is a species?◦ Not simple to define◦ Biological species concept: individuals are members of the same species if they are capable of interbreeding and producing fertile offspring ◦ BSC often used but may not work in all cases▪ Asexually reproducing species ▪ Ecological species concept (Niches)▪ Morphological species concept (Similar size and shape → same species) • Reproductive isolation: key component of BSC; the existence of biological factors (reproductive behaviors) that prevent 2 individuals from interbreeding and producing a viable offspring ◦ a single barrier may not necessarily lead to reproductive isolation, many barriers act in concert ▪ Zygote = fusion of sperm and egg▪ Barriers can be prezygotic or post zygotic ▪ pre: preventing mating, prevent fertilization, mechanical isolation, mating may be attempted but prevented by morphological differences; gametic- sperm of one species may not be able to fertilize the eggs of another species ▪ Post: anything after the zygote has formed, reduced hybrid viability (offspring don't survive well) • Hybrid breakdown: hybrids are nonviable or sterile in subsequent generation • Speciation occurs in 2 ways:◦ Allopatric: ▪ geographic separation of population (rivers, islands)▪ Divergence • greatly reduced gene flow• genetic drift (founder effect)• Natural selection ◦ Sympatric: Not covered in class
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