Download Ch. 23- Speciation Notesheet

Name ____________________________________ Date ____________ Period _____
Speciation- The Origin of Species
Raven Ch. 23
Big Idea 1: THE PROCESS OF EVOLUTION DRIVES THE DIVERSITY AND UNITY OF LIFE.
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to
change.
― Charles Darwin (1859)
Essential Knowledge:
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Natural selection is a major mechanism of evolution
Natural selection acts on phenotypic variations within populations.
Evolutionary change is also driven by random processes.
Biological evolution is supported by scientific evidence from many disciplines including mathematics
Organisms share many conserved core processes and features that evolved and are widely distributed among
organisms today.
Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be
tested
Speciation and extinction have occurred throughout the Earth’s history.
Speciation may occur when two populations become reproductively isolated from each other.
Populations of organisms continue to evolve.
There are several hypotheses about the origin of life on Earth, each with supporting scientific evidence.
Scientific evidence from many different disciplines supports models of the origin of life.
Biological Species Concept:
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Defined by Ernst Mayr
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Population whose members can ___________________ & produce _______________,
___________ offspring
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Reproductively _______________________
How do new species originate?
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Populations must become ___________________
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_______________________
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_______________________
isolated populations _______________________
Isolation
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_______________________
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geographic separation
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“other country”
_______________________
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still live in same area
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“same country”
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PRE-reproduction barriers (_______________________________________________)
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Obstacle to _________________ or to _____________________ if mating occurs
_________________________ Isolation (__________________ speciation)
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Species occur in different areas
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___________________________
Harris’s antelope squirrel inhabits the canyon’s south rim (L). Just a few miles away on the north rim (R)
lives the closely related white-tailed antelope squirrel
Ecological isolation (__________________ speciation)
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Species occur in same region, but occupy different __________________ so rarely encounter each
other
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Examples:
________________________ isolated
_____________________________________________________,
_____________________________________________________,
Temporal isolation (__________________ speciation)
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Species that breed during different times of _________________, different ___________, or different
__________________ cannot mix gametes
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Examples:
________________________ isolation
_____________________________________________________,
_____________________________________________________,
Behavioral isolation (__________________ speciation)
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Unique _______________________ patterns & ______________________ isolate species
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identifies members of species
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Examples:
attract mates of same species
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courtship rituals, mating calls
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______________________ isolation
_____________________________________________________,
_____________________________________________________,
Mechanical isolation (__________________ speciation)
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_________________________ differences can prevent successful mating
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_______________________ isolation
For many insects, male & female sex organs of closely related species do not fit together, preventing
sperm transfer
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lack of “fit” between sexual organs:
hard to imagine for us… but a big issue for insects with different shaped genitals!
Examples:
_____________________________________________________,
_____________________________________________________,
Gametic isolation (__________________ speciation)
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Sperm of one species may not be able to __________________ eggs of another species
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mechanisms
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_________________________________ so sperm cannot penetrate egg
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Examples:
receptor recognition: lock & key between egg & sperm
sperm cannot survive in female reproductive tract
_____________________________________________________,
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POST-reproduction barriers: (___________________________________________)
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Prevent _______________________ from developing into a viable, fertile adult
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_______________________________________
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_______________________________________
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Reduced hybrid viability (__________________ speciation)
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Genes of different parent species may interact & impair the hybrid’s development
Examples:
_____________________________________________________,
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_____________________________________________________,
Reduced hybrid fertility (__________________ speciation)
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Even if hybrids are vigorous they may be _____________________________
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chromosomes of parents may differ in ___________________ or ______________ & meiosis in
hybrids may fail to produce ________________________ gametes
Hybrid breakdown (__________________ speciation)
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Hybrids may be _______________________ in first generation, but when they mate offspring are
______________________________
Examples:
_____________________________________________________,
_____________________________________________________,
Rate of Speciation
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Does speciation happen ________________ or __________________?
Gradualism vs. Punctuated Equilibrium
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_______________________________ (Who?____________________________________)
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______________________ divergence over _______________ spans of time
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assume that big changes occur as the ____________________ of many small ones
_______________________________ (Who?____________________________________)
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________________________ bursts of change
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long periods of __________ or _________ change
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species undergo rapid change when they 1st bud from parent population
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Evolution is not goal-oriented
An evolutionary trend does not mean that evolution is goal-oriented.
Surviving species do not represent the peak of perfection. There is compromise & random chance
involved as well. Remember that for humans as well! Evolution is not the survival of the fittest. Rather it is the
survival of the just good enough.
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