chapter 24 the origin of species. hummingbirds of costa rica species
TRANSCRIPT
Chapter 24
The Origin of Species
Hummingbirds of Costa Rica
Species
Biological Species Concept
Species
A population whose members can potentially interbreed in nature
to produce viable, fertile offspring
In practice, we recognize two populations as separate species if each has distinguishing
characteristics relative to the other, and members of each population lack the potential to interbreed in nature with members of the other
population
Reproductive Barriers
A complete barrier would result in no
gene flow
An incomplete barrier could still reduce
gene flow
Isolate populations from one another
Reproductive Barriers
Pre-zygotic vs. post-zygotic
A complete barrier would result in no
gene flow
An incomplete barrier could still reduce
gene flow
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation
Roseate spoonbill
Eurasian spoonbill
Pre-zygotic
Habitat isolation Geographic isolation
Reproductive Barriers
North America
Central America
Madagascar
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation Ecological isolation
Hawthorns or apples for oviposition
Rhagoletis pomonella
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation
Blue-footed boobies
Red-footed booby
Galapagos Islands
Satin Bowerbirds & their bowers
Tooth-billed Catbird’s leaf display
Australia
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation
Periodical(12 year)
Dog-day(17 year)
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation Mechanical isolation
C. wapleri Thompson Creek, W. Feliciana Parish
Reproductive Barriers
Pre-zygotic
Habitat isolation Geographic isolation Ecological isolation Behavioral (mate choice) isolation Temporal isolation Mechanical isolation Gametic isolation
acrosome
head
midpiece
tail
ovum
Buffon (1811)
Reproductive Barriers
Post-zygotic
Reduced hybrid viability Reduced hybrid fertility Hybrid sterility (in the extreme)
x =
sterile
♀
♂
Reproductive Barriers
Post-zygotic
Reduced hybrid viability Reduced hybrid fertility Hybrid sterility (in the extreme) Hybrid breakdown (reduced viability or fertility occurs in the offspring of hybrids)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 24.4
Individualsof differentspecies
Matingattempt
Habitat isolation
Temporal isolation
Behavioral isolation
Mechanical isolation
HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION
Reproductive Barriers
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Viablefertile
offspring
Reducehybrid
viability
Reducehybridfertility
Hybridbreakdown
Fertilization
Gameticisolation
GAMETIC ISOLATION REDUCED HYBRID VIABILITY
REDUCED HYBRID FERTILITY HYBRID BREAKDOWN
Reproductive Barriers
Figure 24.4
Speciation
The process by which new species form
Two requirements:
Reproductive isolation of populations (gene flow sufficiently reduced) Genetic divergence (divergent evolution)
Two main modes:
Allopatric vs. sympatric
Allopatric speciationDivergence occurs in geographic isolation
Sympatric speciationDivergence occurs despite lack of geographic isolation
Allopatric vs. sympatric speciation
Figure24.5
Hawthorns or apples for oviposition
Rhagoletis pomonella
Sympatric speciation
Sympatric speciationDivergence occurs despite lack of geographic isolation
Polyploids
Organisms with extra sets of chromosomes; can result in sympatric speciation in one generation
The origin of a polyploid individual is usually a mistake in meiosis or mitosis
Autopolyploidy vs. allopolyploidy
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An autopolyploid
Is an individual that has > two chromosome sets, all from a single species
Figure 24.8
2n = 64n = 12
2n
4n
Failure of cell divisionin a cell of a growing diploid plant produces a tetraploid branch.
Gametes produced by flowers on this branch will be diploid.
If offspring are viable and fertile, it is a new biological species.
Sympatric speciation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
An allopolyploid
Is an individual with > two chromosome sets, derived from different species
Meiotic error;chromosomenumber notreduced from2n to n
Unreduced gametewith 4 chromosomes
Hybrid with7 chromosomes
Unreduced gametewith 7 chromosomes Viable fertile
hybrid
Normal gameten = 3
Normal gameten = 3
Species A 2n = 4
Species B 2n = 6
2n = 10
Sympatric speciation
Figure 24.9
Polyploidy is especially common in
plants
From Micro- to Macro-Evolution
Microevolution – Population and species-level
evolution, including speciation
Macroevolution – Speciation and all
broader-scale evolutionary patterns and
processes
Anagenesis Cladogenesis
Sufficient micro-evolutionary changes may occur that the earlier population is considered a separate species from the later population
timeBranchingevolutionoccurs as
speciationevents
accumulate.
The formationof each new
branch is amacroevolutionary
event.
Figure24.2
Anagenesis Cladogenesis
Sufficient micro-evolutionary changes may occur that the earlier population is considered a separate species from the later population
timeBranchingevolutionoccurs as
speciationevents
accumulate
The formationof each new
branch is amacroevolutionary
event
Broad patterns acrossthe resulting tree are also within the scope
of macroevolutionFigure24.2
Adaptive Radiation
One species gives rise to many others in a geologically short period of time
E.g., Darwin’s finches
Islands are good places to find adaptive radiations
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
E.g., Hawaiian silverswords
Figure 24.12
Adaptive Radiation
Gradualism Punctuated
Equilibrium
Tempo of Evolution
time
Figure 24.13
Gradualism Punctuated
Equilibrium
Tempo of Evolution
time
Figure 24.13
Evolutionary Novelties
Evolutionary novelties usually arise as modifications of existing traits
Figure 24.14
Evolutionary Development (Evo-Devo)
Slight alterations in development can have profound effects on adults
Heterochrony = change in the rate or timing of development, relative to an ancestor
E.g., paedomorphosis = heterochronic retention of juvenile structures in adulthood
Evolutionary Development (Evo-Devo)
Slight alterations in development can have profound effects on adults
Heterotopy = change in the physical position of a trait during development, relative to an ancestor
E.g., feathers from one part of a bird’s body may become expressed on another part
Evolutionary Development (Evo-Devo)
Allometric growth = relative growth rates of different body parts within a species during development
Evolutionary Development (Evo-Devo)
Allometric growth = relative growth rates of different body parts within a species during development
E.g., allometric growth in horned scarab beetles; certain clusters of cells grow faster than others
Evolutionary Development (Evo-Devo)
Phanaeus imperator
Evolutionary Development (Evo-Devo)
Evolution is not “goal oriented”
Evolution is a genetic response to the interaction between the individuals of a population and their
current environment (which includes other individuals)
Natural selection can only act on the phenotypic variation present, and selection can only cause
evolutionary change if phenotypic variation results (at least in part) from genetic variation
Evolution is not “goal oriented”
Therefore, even if female tigers in a population would prefer blue males, blue tigers will never evolve if the
population lacks variation that includes blue fur
He’s not blue, but he’s better than nothing!
YES! But he exists only
in my dreams.