Essential knowledge 1.C.1:_
Speciation and extinction
have occurred throughout
the Earth’s history.
Speciation and
Extinction
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a.
b. Species extinction rates are rapid at times of ecological stress. [See also
4.C.3]
To foster student understanding of this concept, instructors can choose an illustrative
example such as:
• Five major extinctions
• Human impact on ecosystems and species extinction rates
✘✘ The names and dates of these extinctions are beyond the scope of this course
and the AP Exam.
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Essential knowledge 1.C.3: Populations of organisms continue to evolve.
To foster student understanding of this concept, instructors can choose an illustrative
example such as:
• Chemical resistance (mutations for resistance to antibiotics, pesticides,
herbicides or chemotherapy drugs occur in the absence of the chemical)
• Emergent diseases
• Observed directional phenotypic change in a population (Grants’
observations of Darwin’s finches in the Galapagos)
• A eukaryotic example that describes evolution of a structure or process
such as heart chambers, limbs, the brain and the immune system
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Speciation rates can vary, especially when
adaptive radiation occurs when new habitats
become available.
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Adaptive Radiation - a process in which
organisms diversify rapidly into a multitude
of new forms
Often occurs when a change in the
environment makes new resources available
and opens environmental niches
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Species extinction rates are rapid at
times of ecological stress.
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5 Major extinctions
6th mass extinction?
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Human impact on ecosystems and species
extinction rates
Speciation and Extinction Bozeman
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https://www.youtube.com/watch?v=yJLRl2
G41nQ&list=PLFCE4D99C4124A27A&in
dex=9
Macroevolution: the origin of new taxonomic groups
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Speciation: the origin of new
species
What is a species?
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Biological species concept
(Mayr): a population or group
of populations whose members
have the potential to interbreed
and produce viable, fertile offspring
(genetic exchange is possible and
that is genetically isolated from
other populations)
Reproductive Isolation (isolation of gene pools), I
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Prezygotic barriers: impede mating
between species or hinder the fertilization of
the ova
Habitat (snakes; water/terrestrial)
Behavioral (fireflies; mate signaling)
Temporal (salmon; seasonal mating)
Mechanical (flowers; pollination
anatomy)
Gametic (frogs; egg coat receptors)
Reproductive Isolation, II
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Postzygotic barriers: fertilization occurs, but the
hybrid zygote does not develop into a viable,
fertile adult
Reduced hybrid viability (frogs; zygotes
fail to develop or reach sexual
maturity)
Reduced hybrid fertility (mule; horse x
donkey; cannot backbreed)
Hybrid breakdown (cotton; 2nd
generation hybrids are sterile)
Modes of speciation
how gene flow is interrupted)
 Allopatric:
populations segregated by
a geographical barrier; can
result in adaptive radiation
(island species)
 Sympatric:
reproductively isolated
subpopulation in the midst
of its parent population
(change in genome);
polyploidy in plants; cichlid
fishes
(based on
Punctuated equilibria
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Tempo of speciation:
gradual vs. divergence in rapid
bursts; Niles Eldredge and
Stephen Jay Gould (1972);
helped explain the nongradual appearance of species
in the fossil record
Essential knowledge 1.C.3:
Populations of organisms continue to evolve.
Two significant concepts:
1. Scientific evidence supports the idea that
evolution has occurred in all species.
 All life on Earth is descended from a last
universal ancestor that lived
approximately 3.8 billion years ago.
 Repeated speciation and the divergence
of life can be inferred from shared sets
of biochemical and morphological traits,
or by shared DNA sequences
Two significant concepts:
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2. Scientific evidence supports the idea that
evolution continues to occur.
Examples: • Chemical resistance (mutations for
resistance to antibiotics, pesticides, herbicides or
chemotherapy drugs occur in the absence of the
chemical)
• Emergent diseases
• Observed directional phenotypic change in a
population (Grants’ observations of Darwin’s
finches in the Galapagos)
• A eukaryotic example that describes evolution
of a structure or process such as heart chambers,
limbs, the brain and the immune system
Speciation – Bozeman

https://www.youtub
e.com/watch?v=rlf
Nvoyijmo&list=PLF
CE4D99C4124A27
A