56 min video•september 20, 2018
In this session, we begin by reviewing last week’s lesson. We move on to macro-evolutions, showing the difference between micro vs macro, and showing that in macro-evolutions, all species had a common ancestor. We discuss speciation and reproductive isolation (covering hybrids and barriers). We examine the ways a species can become reproductively isolated, with prezygotic and postzygotic barriers explained. We show what happens when gene flow is prevented, and show 2 types of ways new species can be produced (allopatric [away] and sympatric [same]). We use porkfish near the isthmus of Panama to discuss allopatric and apple maggot flies for sympatric. We show 3 ways to decrease gene flow in sympatric speciation. We cover examples of sexual selection, as well as polyploidy (chromosome) vocabulary (haploid, diploid, triploid, tetraploid). We show fertilization errors, show how adaptive radiation spread in finches. The phylogenetic tree teaches us how far removed a species is from a common ancestor, and we conclude with practice questions.
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