Speciation How does a population evolve into separate species? Adapted from: Evolution 101: Reproductive Isolation. University of California Museum of.

SpeciationSpeciation

How does a population How does a population evolve into separate evolve into separate

species?species?

Adapted from: Evolution 101: Reproductive Isolation. University of California Museum of Paleontology, http://evolution.berkeley.edu/evolibrary/article//evo_44

What is Geographic What is Geographic Isolation?Isolation?

• One population of One population of organisms separated organisms separated into two smaller into two smaller populations by a populations by a physical barrierphysical barrier..

• Human modification Human modification of the environmentof the environment can also cause can also cause geographic isolation geographic isolation of populations.of populations.

Types of Types of Geographic Geographic Barriers:Barriers:

• MountainsMountains• Bodies of waterBodies of water• DesertsDeserts• ValleysValleys• Shopping malls Shopping malls • Large Large

expresswaysexpressways

The SceneThe Scene

• A population of wild fruit flies were A population of wild fruit flies were minding its own business, cheerfully minding its own business, cheerfully laying their eggs in a bunch of mushy laying their eggs in a bunch of mushy bananas when…bananas when…

Disaster Strikes!Disaster Strikes!• A hurricane washes the bananas A hurricane washes the bananas

carrying the immature fruit flies out to carrying the immature fruit flies out to sea. sea.

• The banana bunch eventually The banana bunch eventually washes up on an island off the coast of washes up on an island off the coast of the mainland.the mainland.

• The fruit flies The fruit flies emerge from emerge from their slimy their slimy nursery and nursery and explore their explore their new island new island home.home.

Selective PressuresSelective Pressures• Ecological conditions on this island Ecological conditions on this island

were different than on the mainland.were different than on the mainland.

• Different fruits were abundant on Different fruits were abundant on this island. this island.

• How will the fruit flies survive?How will the fruit flies survive?

Survival of the FittestSurvival of the Fittest

• Selective pressures favored those fruit Selective pressures favored those fruit flies that preferred mangos.flies that preferred mangos.

• Hanging around the mangos, these flies Hanging around the mangos, these flies had greater chances of finding mates had greater chances of finding mates and passing their “fit” genes to their and passing their “fit” genes to their offspring.offspring.

They Meet Again!They Meet Again!

• When another storm When another storm reintroduces the reintroduces the island flies to the island flies to the mainland, they do mainland, they do not readily mate not readily mate with the mainland with the mainland flies because of flies because of different food different food preferences and preferences and courtship behaviors. courtship behaviors.

The Populations DivergeThe Populations Diverge• The island fruit flies experienced The island fruit flies experienced

random mutations and different random mutations and different selection pressures.selection pressures.

• Morphology, food preferences, and Morphology, food preferences, and courtship displays change over the courtship displays change over the course of many generations of course of many generations of natural selectionnatural selection

Speciation OccursSpeciation Occurs• The few that do mate with mainland flies, The few that do mate with mainland flies,

produce eggs that are not viable due to produce eggs that are not viable due to other genetic differences between the other genetic differences between the two populations from random mutations two populations from random mutations and genetic shuffling.and genetic shuffling.

• Since genes cannot flow between the Since genes cannot flow between the populations, they are now considered two populations, they are now considered two separate species!separate species!

So What Exactly So What Exactly Happened?Happened?

• Geographic isolation began the speciation Geographic isolation began the speciation process, genetic changes are necessary to process, genetic changes are necessary to complete the process.complete the process.

• Selection pressures favored flies that Selection pressures favored flies that preferred mangos. These flies mated with preferred mangos. These flies mated with each other.each other.

• Random mutations and genetic shuffling Random mutations and genetic shuffling added further variations to the island added further variations to the island population.population.

• Over many generations, the island and Over many generations, the island and mainland populations diverged and became mainland populations diverged and became separate species. separate species.

Adaptive RadiationAdaptive Radiation

• Darwin's finches are an excellent Darwin's finches are an excellent example of the way in which species' example of the way in which species' gene pools have adapted in order for gene pools have adapted in order for long term survival via their offspring. long term survival via their offspring.

• Darwin's Finches illustrate the way the Darwin's Finches illustrate the way the finch has adapted to take advantage of finch has adapted to take advantage of feeding in different ecological niches. feeding in different ecological niches.

• Their beaks have evolved over time to Their beaks have evolved over time to

be best suited to their functionbe best suited to their function..

The End!The End!