Download PPT NOTES_AP Biology Chapter 24 Notes

AP Biology Chapter 24 Notes
The Origin of Species
What you need to know…
 The difference between ___________________ and _______________________.
 The biological concept of __________________.
 _________________________ and ________________________ barriers that maintain
reproductive isolation in natural populations.
 How ________________________ and sympatric _________________________ are similar and
different.
 How an ____________________________ or an _______________________________
chromsomal change can lead to sympatric speciation.
 How _________________________ equilibrium and _________________________ describe 2
different tempos of speciation.
____________________________ - the origin of new species, is at the focal point of evolutionary theory
______________evolution consists of adaptations that evolve within a population, confined to one gene pool
______________evolution refers to evolutionary change above the species level
Concept 24.1: The biological species concept emphasizes reproductive isolation
 ________________________ species concept - states that a species is a group of populations whose
members have the potential to interbreed in nature and produce viable, fertile offspring; they do not
breed successfully with other populations
o Gene flow between populations holds the phenotype of a population together
 ______________________________ isolation is the existence of biological factors (barriers) that
impede two species from producing viable, fertile offspring
o ___________________ are the offspring of crosses between different species (Ex. Mule)
 Label the Pictures
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_________________________ barriers block fertilization from occurring by:
o Impeding different species from attempting to ___________
o Preventing the successful _________________________ of mating
o Hindering _________________________ if mating is successful
o Include:
 Habitat isolation (next slide) -Two species encounter each other _____________, or
not at all, because they occupy different habitats, even though not isolated by physical
barriers
 behavioral isolation (next slides) -Courtship rituals and other behaviors
_____________ to a species are effective barriers
 temporal isolation (next slides) -Species that breed at different ____________ of the
day, different seasons, or different years cannot mix their gametes
 mechanical isolation (next slides) -Morphological differences can prevent successful
___________________
 gametic isolation (next slides) - Sperm of one species may not be able to fertilize eggs
of another species
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____________________________ barriers prevent the hybrid zygote from developing into a viable,
fertile adult:
o ___________________ hybrid viability (next slides) - Genes of the different parent species
may interact and __________________ the hybrid’s development
o Reduced ____________________ fertility (next slides) - Even if ________________ are
vigorous, they may be _____________________
o Hybrid ________________________ - (next slides) - Some first-generation hybrids are
_____________, but when they mate with another species or with either parent species,
offspring of the next generation are feeble or sterile

The biological species concept cannot be applied to fossils or asexual organisms (including all
prokaryotes)
o The _____________________________ species concept defines a species by structural
features
 It applies to sexual and asexual species but relies on subjective criteria
o The ____________________________ species concept views a species in terms of its
ecological niche
 It applies to sexual and asexual species and emphasizes the role of disruptive selection
o The ____________________________ species concept: defines a species as the smallest
group of individuals on a phylogenetic tree
 It applies to sexual and asexual species, but it can be difficult to determine the degree of
difference required for separate species
Concept 24.2: Speciation can take place with or without geographic separation
 Speciation can occur in two ways:
o Allopatric speciation (next slides) - gene flow is ____________________ or
______________________ when a population is ____________________ into geographically
isolated subpopulations
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o Sympatric speciation (next slides) - speciation takes place in geographically
______________________ populations
_______________________ is the presence of _______________ sets of chromosomes due to
accidents during cell division
An _______________________ is an individual with more than ____________ chromosome sets,
derived from one species
An ______________________ is a species with _________________ sets of chromosomes derived
from different species
Concept 24.3: Hybrid zones provide opportunities to study factors that cause reproductive isolation
 A _________________ zone is a region in which members of different species mate and produce
hybrids
o A hybrid zone can occur in a ________________ band where adjacent species meet
o Hybrids often have ____________________ fitness compared with parent species
o The distribution of hybrid zones can be more complex if parent species are found in multiple
habitats within the same region
o When closely related species meet in a hybrid zone, there are three possible outcomes:
 ________________________ of reproductive barriers
 _________________________ of reproductive barriers
 _________________________ formation of hybrid individuals
Concept 24.4: Speciation can occur rapidly or slowly and can result from changes in few or many genes
 ____________________________ equilibrium to describe periods of apparent stasis punctuated by
sudden change
 Gradualism - gradual _____________________ in a species’ existence
 Label the picture
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You should now be able to…
1. Define and discuss the limitations of the __________ species concepts
2. Describe and provide examples of _______________ and ________________ reproductive
barriers
3. Distinguish between and provide examples of ______________ and _______________
speciation
4. Explain how _____________________ can cause reproductive isolation
5. Define the term ________________ and describe three outcomes for hybrid zones over time