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unit 7 chp 22 notes Cheat Sheet by

unit 7 chapter 22 notes

SPECIATION

the process by which one species splits into 2 or more species
-focal point of evolut­ionary theory because the appearance of new species is the source of biological diversity
-it forms the bridge between microe­vol­ution and macroe­vol­ution

PREZYGOTIC BARRIERS

impede mating or hinder fertil­ization if mating does occur
- habitat isolation
-temporal isolation
-behavior isolation
-mecha­nical isolation
-gametic isolation

HOW FAST DOES SPECIATION OCCUR?

-the time interval between speciation events varies consid­erable, from a few thousand years to tens of millions of years
- punctuated equill­ibrium: isolated episodes of rapid speciation between long periods of little to no change
gradua­lism: accumu­lation of gradual changes over time
 

WHAT IS A SPECIES

a group of popula­tions whose members can interbreed in nature and produce viable, fertile offspring, but cannot produce viable, fertile offspring with other such groups

POSTZY­GOTIC BARRIERS

barriers that prevent the hybrid zygote from developing into a viable, fertile adult
-reduced hybrid viability
-reduced hybrid fertility
-hybrid breakdown

TYPES OF SPECIATION

Allopatric Speciation
geographic barrier between the 2 popula­tions
Sympatric Speciation
popula­tions that live in the same geographic area
-polyp­loidy
-habitat differ­ent­iation
-sexual selection
 

WHY DOES SPECIATION OCCUR

reprod­uctive isolation
the existence of biological barriers that impede members of 2 species from interb­reeding and producing viable offspring

HOW DOES SPECIATION OCCUR?

- speciation can occur in 2 main ways depending on how gene flow is interr­upted between popula­tions of the existing species
- allopatric specia­tio­n-g­eog­raphic isolation
-sympatric specia­tion- no geographic isolation
 

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