-new species formed from a small pop isolated at the edge of a larger pop
-version of allopatric & happens when one of the isolated pops has very few individuals
-ex: intrepid fruit flies venture off mainland on bunch of rotting bananas, banana bunch washes up on island:
1. now geographically isolated
2. rare genes survive (by chance carries rare gene from mainland and causes variation in mating dance and another to male genitalia (founder effect))
3. gene frequencies drift- those diffs drift to fixation over generations
4. more changes- sexual selection causes unique reproductive features
-changes improve male/female genitalia fit, and nat. sel. favors those suited to island climate & food.
5. speciation- flies reproductively isolated from mainland flies

Peripatric speciation

Explanation:

Peripatric speciation usually is an occurrence which happens when a small group of individuals break off of the main group to form a new species. This is similar to allopatric speciation, in this case, the two groups are separated by physical barriers such as mountain ranges or waterways, making it almost impossible for the two groups to interbreed.

There is always a special gene in the smaller group that had been isolated from the parent group. This special gene could allow the particular species to develop thicker fur, longer limbs or even, in extremely rare cases, an entirely new body part.

i only have part a but here is the first one: - lewis and clark are born

- lewis marries sacajawea and clark is jealous  

- clark drowns lewis and then goes to jail

answer; principled stage;