Speciation Drives Evolution Unit 6: Evolution Ch Unit 6: Evolution Ch. 16-3

Speciation Speciation  Speciation  Speciation: changes that lead to the formation of a new species  Isolation often drives speciation  Species  Species are individuals who can successfully reproduce  Species share the same gene pool (alleles)  When 2 animals cannot mate, they are considered different species  Speciation  Speciation: changes that lead to the formation of a new species  Isolation often drives speciation  Species  Species are individuals who can successfully reproduce  Species share the same gene pool (alleles)  When 2 animals cannot mate, they are considered different species

Reproductive Barriers Reproductive Barriers  A. Pre-zygotic Barriers:  A. Pre-zygotic Barriers: isolating mechanism that prevent mating from happening at all (5 Types)

Geographic Isolation-  1. Geographic Isolation- population is separated by geographic barriers  Mountains, rivers, oceans, etc.  Ex: 2 squirrel species separated at the Grand Canyon Geographic Isolation-  1. Geographic Isolation- population is separated by geographic barriers  Mountains, rivers, oceans, etc.  Ex: 2 squirrel species separated at the Grand Canyon

Although they are in the same region, the white tailed antelope squirrel inhabits desert to the north of the canyon, while Harris’s antelope squirrel (above) has a more limited range to the south.

Habitat Isolation-  2. Habitat Isolation- Population uses different parts of the habitat  EX: One species of bird lives on the ground and the other lives in the trees Habitat Isolation-  2. Habitat Isolation- Population uses different parts of the habitat  EX: One species of bird lives on the ground and the other lives in the trees

Temporal Isolation-  3. Temporal Isolation- Individuals reproduce at different times  When some are ready to reproduce, others are not  EX: Squirrels reproducing at different times Temporal Isolation-  3. Temporal Isolation- Individuals reproduce at different times  When some are ready to reproduce, others are not  EX: Squirrels reproducing at different times

Mechanical Isolation-  4. Mechanical Isolation- individuals physically do not fit together to mate  anatomy does not correspond  EX: If a beetle’s reproductive organs (male & female) do not fit Mechanical Isolation-  4. Mechanical Isolation- individuals physically do not fit together to mate  anatomy does not correspond  EX: If a beetle’s reproductive organs (male & female) do not fit

Behavioral Isolation-  5. Behavioral Isolation- changes in courtship rituals cause indviduals not to breed  change in song or dance- they don’t recognize it so they don’t mate Grebes (birds) must dance together before they accept each other to mate  EX: Grebes (birds) must dance together before they accept each other to mate Behavioral Isolation-  5. Behavioral Isolation- changes in courtship rituals cause indviduals not to breed  change in song or dance- they don’t recognize it so they don’t mate Grebes (birds) must dance together before they accept each other to mate  EX: Grebes (birds) must dance together before they accept each other to mate

Let’s Dance!

Blue-footed boobies display their blue feet when courting potential mates.

Red-footed boobies are not impressed by the display.

Post-zygotic Barriers:  B. Post-zygotic Barriers: after reproduction occurs, this prevents a hybrid offspring from surviving or reproducing  EX: A mule (horse x donkey) is sterile, cannot produce offspring  EX: A liger (lion x tiger) never stops growing and will die Post-zygotic Barriers:  B. Post-zygotic Barriers: after reproduction occurs, this prevents a hybrid offspring from surviving or reproducing  EX: A mule (horse x donkey) is sterile, cannot produce offspring  EX: A liger (lion x tiger) never stops growing and will die

Types of Speciation Sympatric Speciation: same geographic area genetic changes  1. Sympatric Speciation: organisms live in same geographic area and speciation occurs due to genetic changes

Allopatric Speciation different areas geographic isolation  2. Allopatric Speciation: organisms live in different areas and speciation occurs due to geographic isolation

Speciation & Evolution Speciation & Evolution  Speciation drives evolution.  Microevolution  Microevolution is small changes in a species over time  DNA changes are used as evidence  Speciation drives evolution.  Microevolution  Microevolution is small changes in a species over time  DNA changes are used as evidence

 Macroevolution  Macroevolution is major changes in the history of live on Earth over millions of years  Due to microevolution over long period of time  Fossils are used as evidence  Macroevolution  Macroevolution is major changes in the history of live on Earth over millions of years  Due to microevolution over long period of time  Fossils are used as evidence

Mass Extinctions  Mass extinction is when a whole species goes extinct  Due to rapid, global environmental changes like ice ages, comet impacts, etc…  Mass extinction is when a whole species goes extinct  Due to rapid, global environmental changes like ice ages, comet impacts, etc…

 Adaptive radiation  Adaptive radiation: after a mass extinction there are many new niches open to be filled by survivors  EX: After dinosaurs went extinct, mammals evolved relatively quickly by using the new habitats and resources available and many new species arose  Adaptive radiation  Adaptive radiation: after a mass extinction there are many new niches open to be filled by survivors  EX: After dinosaurs went extinct, mammals evolved relatively quickly by using the new habitats and resources available and many new species arose