Process of Speciation Ch 16.3. Intro to Speciation Recall, biologists define a species as a group of individuals that breed and produce fertile offspring

Process of SpeciationProcess of Speciation

Ch 16.3Ch 16.3

Intro to SpeciationIntro to Speciation

Recall, biologists define a Recall, biologists define a speciesspecies

as a as a groupgroup of of individualsindividuals that that breedbreed

and produce and produce fertile offspringfertile offspring


Therefore individuals of the same Therefore individuals of the same species species share a common gene poolshare a common gene pool. .


As genetic change As genetic change

occurs in one individual, occurs in one individual,

it can spread through it can spread through

the populationthe population via via

its offspring.its offspring.


If this change increases “If this change increases “fitnessfitness” it will ” it will soon be found in many within the soon be found in many within the populationpopulation..

SpeciationSpeciation

Defined as- Defined as-

The formation of The formation of new speciesnew species

As new species evolve, As new species evolve, populations become populations become reproductively isolatedreproductively isolated

Reproductive IsolationReproductive Isolation

* Breeding can be prevented due * Breeding can be prevented due to changes in to changes in behaviorbehavior (eating, (eating, mating mating ritualsrituals, timing) , timing) environmentenvironment (niches, food source, (niches, food source, geographicgeographic barriers) or barriers) or mechanicsmechanics (breeding, (breeding, fertilizationfertilization, , development)development)

Defined as- Defined as-

When When membersmembers of two of two populationspopulations cannot cannot interbreedinterbreed

Isolating MechanismsIsolating Mechanisms

Reproductive isolation can occur Reproductive isolation can occur as a result of:as a result of:

BehavioralBehavioral Isolation IsolationGeographicGeographic Isolation IsolationTemporalTemporal Isolation IsolationMechanicalMechanical Isolation Isolation

Defined as- the isolating mechanism that Defined as- the isolating mechanism that operates through differences in operates through differences in courtship behavioral patternscourtship behavioral patterns

Different mating Different mating locationlocation, mating , mating timetime, or , or mating mating ritualsrituals

If one species If one species displays a displays a certain courtshipcertain courtship patternpattern, , it it won’t bewon’t berecognizedrecognized by bythose of the those of the other species other species

Behavioral IsolationBehavioral Isolation

This is the mechanism which This is the mechanism which separates wolfs from dogsseparates wolfs from dogs, , their their courtship courtship patternspatterns are different are different in the wildin the wild


MeadowlarksMeadowlarks Western EasternWestern Eastern



Difference in Difference in courtship rituals courtship rituals

Western and Eastern Meadowlark

(Different mating songs)

Different species of Different species of bowerbird bowerbird construct elaborate construct elaborate bowers and decorate them with different colors in bowers and decorate them with different colors in order to woo females. The Satin bowerbird (left) order to woo females. The Satin bowerbird (left) builds a channel between upright sticks, and builds a channel between upright sticks, and decorates with bright blue objects, while the decorates with bright blue objects, while the MacGregor’s Bowerbird (right) builds a tall tower MacGregor’s Bowerbird (right) builds a tall tower of sticks and decorates with bits of charcoal. of sticks and decorates with bits of charcoal. Evolutionary Evolutionary changes in mating rituals, such as changes in mating rituals, such as bower constructionbower construction, can contribute to speciation., can contribute to speciation.



Feeding Habits Feeding Habits

- change in food - change in food

preferencepreference

Fruit flies switched from Hawthorn fruit to Apple fruit introduced from England

No gene flow occurs now because they eat, mate, and lay their eggs on different hosts (fruit).

Geographic IsolationGeographic Isolation

When two populations are separated When two populations are separated physicallyphysically when their original habitat when their original habitat becomes becomes divideddivided by barriers such as by barriers such as riversrivers, , mountains, mountains, or bodies or bodies of of waterwater

Geographic IsolationGeographic Isolation

Another Example of Speciation due Another Example of Speciation due to Geographic Isolationto Geographic Isolation

((Colorado RiverColorado River – 10,000 years ago) – 10,000 years ago)

Kaibab SquirrelKaibab Squirrel (Sciurus aberti kaibabensis)

Abert SquirrelAbert Squirrel (Sciurus aberti)

Grand CanyonGrand Canyon

Geographic IsolationGeographic Isolation Separated the Separated the

Galapagos Galapagos finches, finches, tortoises, iguanastortoises, iguanas, , and other species and other species

Island/Bodies of water

Geographic IsolationGeographic Isolation Speciation in action?Speciation in action? In the summer of 1995, at least 15 iguanas In the summer of 1995, at least 15 iguanas

survived Hurricane Marilyn on a raft of uprooted survived Hurricane Marilyn on a raft of uprooted trees. trees.

They rode the high seas for a month before They rode the high seas for a month before colonizing the Caribbean island, Anguilla.colonizing the Caribbean island, Anguilla.

Evolutionary biologists would love to know what Evolutionary biologists would love to know what happens next: happens next: – will the colonizing iguanas die out, will the colonizing iguanas die out, – will they survive and change only will they survive and change only

slightly, or slightly, or – will they become reproductively will they become reproductively

isolated from other isolated from other Iguana iguanaIguana iguanaand become a new species?and become a new species?

Temporal IsolationTemporal Isolation

Two or more Two or more speciesspecies reproduce reproduce at different at different timestimes..

The time periods could differ The time periods could differ simply by simply by hourshours, , or by or by seasonsseasons


If one species reproduces in the If one species reproduces in the spring, while the other spring, while the other reproduces in the fall, the two reproduces in the fall, the two species aren’t able to breed species aren’t able to breed


Example:Example:

3 similar species of3 similar species of

orchidorchid in same forest in same forest

release pollen on release pollen on different daysdifferent days (can not pollinate (can not pollinate one another) one another)

Mechanical IsolationMechanical Isolation

Deals with the actual mechanics of Deals with the actual mechanics of the the reproductivereproductive organs organs

Occurs when there is incompatibility Occurs when there is incompatibility in in structurestructure of the male and female of the male and female sex organs sex organs

Mechanical IsolationMechanical Isolation

Isolates species by Isolates species by preventing preventing matingmating between two different between two different species species

Isolation also occurs when the Isolation also occurs when the gametesgametes of the two species are of the two species are chemicallychemically incompatible incompatible

Prevents Prevents fertilizationfertilization

Darwin’s DiscoveryDarwin’s Discovery

Galapagos Galapagos Island FinchesIsland Finches

Darwin’s DiscoveryDarwin’s Discovery

The finches looked soThe finches looked sodifferent he thought different he thought they were they were blackbirds,blackbirds,warblerswarblers, & other kinds, & other kindsof birds.of birds.After returning home, After returning home, an ornithologist toldan ornithologist toldhim they were all him they were all finchesfinches

Darwin’s DiscoveryDarwin’s DiscoveryHe then hypothesized:He then hypothesized:

– They had descended from a They had descended from a common common ancestorancestor. .

– Natural selectionNatural selection shaped the beaks as shaped the beaks as they adapted to eat they adapted to eat different foodsdifferent foods

Concept MapConcept 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

a) Founders Arrive

b) Separation of Populations

c) Changes in the Gene Pool

d) Reproductive Isolation

e) Ecological Competition

f) Continued Evolution

SouthAmerica

GalapagosIslands

A

A

A

A

B

A

BB

A

BC

A

BC

E

D

Speciation of Finches in the Speciation of Finches in the Galapagos IslandsGalapagos Islands

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Process of Speciation Ch 16.3. Intro to Speciation Recall, biologists define a species as a group of individuals that breed and produce fertile offspring