Download AP Biology Chapter 24 The Origin of Species Guided Notes

LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 24
The Origin of Species
Lectures by
Erin Barley
Kathleen Fitzpatrick
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Overview: That “Mystery of Mysteries”
• In the Galápagos Islands Darwin discovered
plants and animals found nowhere else on Earth
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Figure 24.1
• ______________, the origin of new species, is at
the focal point of evolutionary theory
• Evolutionary theory must explain how _________
_______________and how populations evolve
• _________________ consists of changes in allele
frequency in a population over time
• _________________refers to broad patterns of
evolutionary change above the species level
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Concept 24.1: The biological species
concept emphasizes reproductive isolation
• ___________ is a Latin word meaning “kind”
or “appearance”
• Biologists compare ________________
____________________________________
sequences when grouping organisms
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The Biological Species Concept
• The ______________________states that a
________________ 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
• _________________ between populations holds
the phenotype of a population together
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Figure 24.2
(a) Similarity between different species
(b) Diversity within a species
Reproductive Isolation
• ____________________ is the existence of
biological factors (barriers) that impede two
species from producing viable, fertile offspring
• _____________ are the offspring of crosses
between different species
• Reproductive isolation can be classified by
whether factors act __________ or __________
___________________
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Figure 24.3_b
Prezygotic barriers
Habitat
Isolation
Temporal
Isolation
Individuals
of
different
species
(a)
MATING
ATTEMPT
(c)
(d)
(b)
Gametic
Isolation
Mechanical
Isolation
Behavioral
Isolation
(e)
(f)
FERTILIZATION
(g)
Figure 24.3_c
Postzygotic barriers
Reduced Hybrid
Viability
Reduced Hybrid
Fertility
Hybrid
Breakdown
VIABLE,
FERTILE
OFFSPRING
FERTILIZATION
(h)
(i)
(j)
(k)
(l)
• _________________ block fertilization from
occurring by:
– ______________________________________
– ______________________________________
_______________
- ______________________________ if mating
is successful
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• __________________: Two species encounter
each other rarely, or not at all, because they
occupy different habitats, even though not isolated
by physical barriers
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• ___________________: Species that breed
at ________________________, different
seasons, or different years cannot mix their
gametes
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• ___________________: Courtship rituals and
other behaviors unique to a species are effective
barriers
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• _______________________: Morphological
differences can prevent successful mating
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• ____________________: Sperm of one species
may not be able to fertilize eggs of another
species
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• ______________________prevent the hybrid
zygote from developing into a viable, fertile adult:
– Reduced hybrid ___________________
– Reduced hybrid ___________________
– ___________________________
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• _____________________: Genes of the different
parent species may interact and impair the
hybrid’s development
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• _______________________: Even if hybrids
are vigorous, they may be sterile
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• __________________: Some first-generation
hybrids are fertile, but when they mate with
another species or with either parent species,
offspring of the next generation are feeble or
sterile
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Limitations of the Biological Species Concept
• The biological species concept cannot be
applied to ________________________
(including all prokaryotes)
• The biological species concept emphasizes
___________________________
• However, gene flow can occur between
distinct species
– For example, grizzly bears and polar bears
can mate to produce “______________”
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Figure 24.4
Grizzly bear (U. arctos)
Polar bear (U. maritimus)
Hybrid “grolar bear”
Other Definitions of Species
• Other species concepts emphasize the
_________ within a species rather than the
separateness of different species
• The ______________________defines a species
by structural features
– It applies to sexual and asexual species but relies
on ______________________________
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• The __________________________views a
species in terms of its ___________________
– It applies to sexual and asexual species and
emphasizes the role of ____________________
• The _______________________defines a
species as the ________________ group of
individuals on a phylogenetic tree
– It applies to sexual and asexual species, but it can
be difficult to determine the ______________
required for separate species
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Concept 24.2: Speciation can take place
with or without geographic separation
• Speciation can occur in two ways:
– ____________ speciation
– ____________ speciation
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Figure 24.5
(a) Allopatric speciation.
A population forms a
new species while
geographically isolated
from its parent population.
(b) Sympatric speciation.
A subset of a population
forms a new species
without geographic
separation.
Allopatric (“Other Country”) Speciation
• In ____________________, gene flow is
interrupted or reduced when a population is
divided into geographically isolated
subpopulations
– For example, the flightless ____________ of
the Galápagos likely originated from a flying
species on the mainland
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The Process of Allopatric Speciation
• The definition of _____________depends on the
ability of a population to disperse
– For example, a ________________ may create a
barrier for small rodents, but not birds, coyotes, or
pollen
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Figure 24.6
A. harrisii
A. leucurus
• Separate populations may evolve independently
through _________________________________
• _______________________ may arise as a result
of genetic divergence
– For example, _________________ in the
Bahamas comprise several isolated populations in
different ponds
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Evidence of Allopatric Speciation
• 15 pairs of sibling species of ___________
(Alpheus) are separated by the Isthmus of
Panama
• These species originated 9 to 13 million years
ago, when the Isthmus of Panama formed and
separated the Atlantic and Pacific waters
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Figure 24.8
A. formosus
A. nuttingi
Atlantic Ocean
Isthmus of Panama
Pacific Ocean
A. panamensis
A. millsae
• Regions with many geographic barriers
typically have ___________than do regions
with fewer barriers
• Reproductive isolation between populations
generally ____________________ as the
distance between them increases
– For example, reproductive isolation
increases between dusky salamanders that
live further apart
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• Barriers to reproduction are _____________;
separation itself is not a biological barrier
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EXPERIMENT
Initial population
of fruit flies
(Drosophila
pseudoobscura)
Some flies raised on
maltose medium
Some flies raised
on starch medium
Mating experiments
after 40 generations
RESULTS
Female
22
9
8
20
Male
Maltose
Starch
Starch
population 1 population 2
Number of matings
in experimental group
Starch
Starch
population 2 population 1
Starch
Starch
Male
Female
Maltose
Figure 24.10
18
15
12
15
Number of matings
in control group
Sympatric (“Same Country”) Speciation
• In ___________________, speciation takes
place in geographically overlapping populations
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Polyploidy
• __________________ is the presence of
extra sets of chromosomes due to accidents
during cell division
• Polyploidy is much more common in _______
than in animals
• An __________________ is an individual
with more than two chromosome sets,
derived from one species
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• An __________________ is a species with
multiple sets of chromosomes derived from
different species
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Figure 24.11-4
Species A
2n = 6
Normal
gamete
n=3
Species B
2n = 4
Meiotic error;
chromosome number not
reduced from 2n to n
Unreduced gamete
with 4 chromosomes
Hybrid with
7 chromosomes
Normal
gamete
n=3
Unreduced gamete
with 7 chromosomes
New species:
viable fertile hybrid
(allopolyploid) 2n = 10
• Many important crops (oats, cotton, potatoes,
tobacco, and wheat) are ___________________
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Habitat Differentiation
• _____________________ can also result from the
appearance of new ecological niches
• For example, the North American maggot fly can
live on native hawthorn trees as well as more
recently introduced apple trees
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Sexual Selection
• _________________ can drive sympatric
speciation
• Sexual selection for mates of different colors has
likely contributed to speciation in cichlid fish in
Lake Victoria
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Figure 24.12
EXPERIMENT
Normal light
P. pundamilia
P. nyererei
Monochromatic
orange light
Allopatric and Sympatric Speciation:
A Review
• In _________________ speciation, geographic
isolation restricts gene flow between populations
• Reproductive isolation may then arise by _______
___________________in the isolated populations
• Even if contact is restored between populations,
interbreeding is ___________________
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• In _____________ speciation, a reproductive
barrier isolates a subset of a population without
geographic separation from the parent species
• Sympatric speciation can result from ________
________________________________________
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Concept 24.3: Hybrid zones reveal factors
that cause reproductive isolation
• A _______________ is a region in which
members of different species mate and produce
hybrids
• Hybrids are the result of mating between species
with ____________________________________
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Patterns Within Hybrid Zones
• A hybrid zone can occur in a single band where
______________________
– For example, two species of toad in the genus Bombina
interbreed in a long and narrow hybrid zone
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Figure 24.13
EUROPE
Fire-bellied
toad range
Hybrid zone
Fire-bellied toad, Bombina bombina
Yellow-bellied
toad, Bombina
variegata
Frequency of
B. variegata-specific allele
Yellow-bellied
toad range
0.99
Hybrid
zone
0.9
Yellow-bellied
toad range
0.5
Fire-bellied
toad range
0.1
0.01
40
10
0
20
10
20
30
Distance from hybrid zone center (km)
• Hybrids often have __________________
compared with parent species
• The distribution of hybrid zones can be more
complex if parent species are found in _________
within the same region
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Hybrid Zones over Time
• When closely related species meet in a hybrid
zone, there are three possible outcomes:
– __________________
– __________________
– __________________
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Figure 24.14-4
Possible
outcomes:
Isolated
population
diverges
Hybrid
zone
Reinforcement
OR
Fusion
OR
Gene flow
Population
Barrier to
gene flow
Hybrid
individual
Stability
Reinforcement: Strengthening Reproductive
Barriers
• The ________________ of barriers occurs when
_________________ than the parent species
• Over time, the rate of hybridization ___________
• Where reinforcement occurs, reproductive barriers
should be ________________ for sympatric than
allopatric species
– For example, in populations of flycatchers, males
are more similar in allopatric populations than
sympatric populations
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Figure 24.15
Females choosing between
these males:
28
Number of females
24
Females choosing between
these males:
Sympatric pied male
Allopatric pied male
Sympatric collared male
Allopatric collared male
20
16
12
8
4
(none)
0
Own
species
Other
species
Female mate choice
Own
species
Other
species
Female mate choice
Fusion: Weakening Reproductive Barriers
• If hybrids are as fit as parents, there can be
substantial _______________between
species
• If gene flow is great enough, the parent
species can _________________________
• For example, researchers think that pollution
in Lake Victoria has reduced the ability of
female cichlids to distinguish males of
different species
• This might be causing the _______________
_________________________
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Figure 24.16
Pundamilia nyererei
Pundamilia pundamilia
Pundamilia “turbid water,”
hybrid offspring from a location
with turbid water
Stability: Continued Formation of Hybrid
Individuals
• Extensive gene flow from outside the hybrid zone
can _________________ for increased
reproductive isolation inside the hybrid zone
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Concept 24.4: Speciation can occur rapidly
or slowly and can result from changes in
few or many genes
• Many questions remain concerning __________ it
takes for new species to form, or _____________
_______________ need to differ between species
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The Time Course of Speciation
• Broad patterns in speciation can be studied
using the fossil record, morphological data, or
molecular data
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Patterns in the Fossil Record
• The ______________ includes examples of
species that appear suddenly, persist essentially
unchanged for some time, and then apparently
disappear
• Niles Eldredge and Stephen Jay Gould coined
the term ______________to describe periods of
apparent stasis punctuated by sudden change
• The punctuated equilibrium model ____________
with a model of gradual change in a species’
existence
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Figure 24.17
(a) Punctuated
pattern
Time
(b) Gradual
pattern
Speciation Rates
• The punctuated pattern in the fossil record and
evidence from lab studies suggest that speciation
can be _______________
– For example, the sunflower Helianthus anomalus
originated from the hybridization of two other
sunflower species
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Figure 24.19
EXPERIMENT
H. annuus
gamete
H. petiolarus
gamete
F1 experimental hybrid
(4 of the 2n = 34
chromosomes are shown)
RESULTS
H. anomalus
Chromosome 1
Experimental hybrid
H. anomalus
Chromosome 2
Experimental hybrid
• The interval between speciation events can range
from __________ years (some cichlids) to ______
_____________ years (some beetles), with an
average of ______ million years
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Studying the Genetics of Speciation
• A fundamental question of evolutionary biology
persists: ___________________ when a new
species forms?
• Depending on the species in question, speciation
might require the change of only a _________
________________________________
• For example, in Japanese Euhadra snails, the
direction of shell spiral affects mating and is controlled
by a single gene
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• In monkey flowers (Mimulus), two loci
affect________________ , which influences
pollinator preference
• Pollination that is dominated by either
hummingbirds or bees can lead to ___________
_____________________of the flowers
• In other species, speciation can be influenced by
__________________ and _________________
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Figure 24.20
(a) Typical
Mimulus
lewisii
(b) M. lewisii with an
M. cardinalis flower-color
allele
(c) Typical
Mimulus
cardinalis
(d) M. cardinalis with an
M. lewisii flower-color
allele
From Speciation to Macroevolution
• _________________ is the cumulative effect of
many speciation and extinction events
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