EVOLUTION Chapter 11. CH. 11 THE PROCESS OF SPECIATION I. Speciation A. Speciation - the formation...
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Transcript of EVOLUTION Chapter 11. CH. 11 THE PROCESS OF SPECIATION I. Speciation A. Speciation - the formation...
EVOLUTION
Chapter 11
CH. 11 THE PROCESS OF SPECIATION
I. SpeciationA. Speciation - the formation of new
species.B. Species - is a group of organisms
that breed with one another and produce fertile offspring.
CH. 11 THE PROCESS OF SPECIATION
1. This means that individuals in the same species share a common gene pool.
2. A genetic change that occurs in one individual can spread through the population.
3. If the genetic change increases fitness, that allele will eventually be found in many individuals of that population.
CH. 11 THE PROCESS OF SPECIATION
II. ISOLATING MECHANISMSA. The gene pools of two populations
must become separated for them to become new species.
1. As new species evolve, populations become reproductively isolated from each other.
CH. 11 THE PROCESS OF SPECIATION
a. reproductive isolation - when the members of two populations cannot interbreed and produce fertile offspring.
b. Populations respond to natural selection or genetic drift as separate units.
B. Reproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.
CH. 11 THE PROCESS OF SPECIATION
1. BEHAVIORAL ISOLATION – occurs when two populations are capable of interbreeding but have differences in courtship rituals or other reproductive strategies that involve behavior. Example: eastern and western meadowlarks use different songs to attract mates.
CH. 11 THE PROCESS OF SPECIATION
2. GEOGRAPHIC ISOLATION – two populations are separated by geographic barriers such as rivers, mountains, or bodies of water. Example: the Abert squirrel and the Kaibab squirrel.
3. TEMPORAL ISOLATION – two or more species reproduce at different times. Example: three species of orchids release pollen on different days.
Concept Map
results from
which include
produced by produced byproduced by
which result in
which result in
Reproductive Isolation
Isolating mechanisms
Behavioral isolation Temporal isolationGeographic isolation
Behavioral differences Different mating timesPhysical separation
Independentlyevolving populations
Formation ofnew species
CH. 11 THE PROCESS OF SPECIATION
IV. SPECIATION IN DARWIN’S FINCHESA. Natural selection can lead to speciation 1. Speciation in the Galapagos finches
occurred by founders forming a new population, geographic isolation, changes in the new population’s gene pool, reproductive isolation, and ecological competition.
CH. 11 THE PROCESS OF SPECIATION
B. FOUNDERS ARRIVE 1. Many years ago, a few finches
(species A) flew and high winds transported them from South America to the Galapagos islands.
2. Once they arrived, they managed to survive and reproduce.
CH. 11 THE PROCESS OF SPECIATION
C. SEPARATION OF POPULATIONS 1. Later a few finches flew to another
island.2. They became isolated from each
other because finch do not fly over open water.
3. They no longer share the same gene pool.
CH. 11 THE PROCESS OF SPECIATION
D. CHANGES IN THE GENE POOL – 1. Over time, populations on each
island became adapted to their local environments.
2. Food supplies may have been different and one group developed larger beaks forming a separate population.
CH. 11 THE PROCESS OF SPECIATION
E. REPRODUCTIVE ISOLATION 1. Finches mate with other finches
that have bills the same size as their own.
2. Even if the finches wind up on the same island, the gene pools of the two bird populations remain reproductively isolated.
3. The two population then become separate species.
CH. 11 THE PROCESS OF SPECIATION
F. ECOLOGICAL COMPETITION1. If the two types of finches wind up
on the same island there will be competition for food.
2. The more specialized birds have less competition for food.
3. Over time, species evolve in a way that increases the differences between them.
CH. 11 THE PROCESS OF SPECIATION
G. CONTINUED EVOLUTION 1. The process of isolation on different
islands, genetic change, and reproductive isolation probably repeated itself time and time again across the entire Galapagos island chain.
2. Over many generations it produced 13 different finch species.
Patterns of Evolution
I. Macroevolution- large-scale evolutionary patterns and processes that occur over long periods of time
II. ExtinctionA. Extinctions happen for reasons
Darwin proposed1. Species compete for resources and
environments change
Patterns of Evolution
2. Some species adapt and survive, and others gradually become extinct in ways that are often caused by natural selection
3. Many paleontologists think mass extinctions were caused by several geological factors
Patterns of Evolution
4. Each disappearance of so many species left habitats open and provided ecological opportunities for those organisms that survived.
Ex: the extinction of dinosaurs cleared the way for the evolution of modern mammals and birds
Patterns of Evolution
III. Adaptive RadiationA. Adaptive radiation - a single species
or a small group of species has evolved into diverse forms that live in different ways
1. Ex: Darwin’s finches -more that a dozen species evolved from one single species
Patterns of Evolution
IV. Convergent EvolutionA. Convergent evolution - the process by
which unrelated organisms come to resemble one another
1. caused by similar environmental demands, such as moving through air, moving through water, or eating similar foods
2. Ex.: the streamlined body and various appendages of a shark (fish), a penguin (bird), and a dolphin (mammal)
Patterns of Evolution
V. CoevolutionA. coevolution - the process by which
two species evolve in response to changes in each other over time
1. caused by the ecological interactions between organisms
2. Ex.: shape of flower and moth’s feeding tube
Patterns of Evolution
VI. Punctuated EquilibriumA. Evidence suggests that evolution
has often occurred at different rates for different organisms at different times during the history of Earth
B. punctuated equilibrium - pattern of long, stable periods interrupted by brief periods of more rapid change
Flowchart
that are
can undergo can undergo can undergo can undergo can undergo
in underunderform inin
Species
Unrelated Related
Inter-relationshiops
Similar environments
Intense environmental
pressure
Small populations
Different environments
Coevolution Convergent evolution
ExtinctionPunctuated equilibrium
Adaptive radiation