1. Evolution & Speciation
16-3 & 17-4

2. 16–3 The Process of Speciation
Speciation- formation of a new species
Review-
Species- group of organisms that breed & can produce fertile offspring
Population with shared gene pool-
Genetic change in individual can spread
Genetic change increases fitness-
Allele found in many of population

3. Isolating Mechanisms
Populations become reproductively isolated from each other as new species evolve
Reproductive Isolation- members of 2 populations cannot interbreed & produce fertile offspring
--- gene pools have separated
Types:
1. Behavioral Isolation
2. Geographic Isolation
3. Temporal Isolation

4. Behavioral Isolation
2 populations are capable of interbreeding but have different mating behaviors & reproductive strategies
Courtship Dance
Mating Call
Nest Building

5. Isolating Mechanisms : 2. Geographical Isolation
2 populations separated by geographic barriers
Rivers, mountains, oceans
Genetic changes in 1 group not passed to other groups
Doesn’t guarantee new species will form- if they can interbreed successfully they are not separate species
flightless birds

6. Isolating Mechanisms : 3. Temporal Isolation
2 or more species reproduce at different times
Seasons
Night vs. day
Different days

7. Testing Natural Selection in Nature
Peter & Rosemary Grant- Tested Darwin’s hypothesis
1) For Beak Size & shape to evolve- must have inheritable traits to provide for natural selection
2) Differences in Beak Size & Shape must produce differences in fitness causing natural selection
Peter & Rosemary Grant---Tested these Hypotheses on the medium ground finch found on Daphne Major (Galapagos)

8. Peter & Rosemary Grant’s Research
Variation- captured & recaptured birds measuring and taking data on characteristics
--data indicated lots of variation among finches
Natural Selection
--- early researchers visited during rainy season(lots of food)
--Grants discovered during droughts- beak size important
---Largest beaks- survived
---Mating- larger beaked birds tended to mate with other big-beaked birds
--Observed beak size in finches increased

9. Peter & Rosemary Grant’s Research
Rapid Evolution-
--Grants documentation provided evidence of evolution in the wild
--Important Result- Finding Natural Selection takes place frequently & sometimes rapidly
--Different from Darwin’s vision of slow, gradual evolution

10. Speciation of Darwin’s Finches
Hypothetical scenario for Galapagos finches development of new species
Speciation occurred by:
founding a new population
Geographic isolation
Changes in the new populations gene pool
Reproductive isolation
Ecological competition

11. Speciation in Darwin’s Finches
Finches from South America arrive on Island 1, survive, & reproduce
Some birds from Island 1 move to Island 2- become isolated from other island’s finches
Over time- populations on both islands adapt to habitats- evolve differently
A few Island 2 birds return to Island 1- adaptations have also caused them to choose mates differently so don’t interbreed- gene pool remains isolated
Competition for food occurs between the 2 different species & birds become more specialized to reduce competition
Process probably continued over & over- 13 different species of finches

12. Evolution Since Darwin
Scientific evidence continues to support Darwin’s work
Current Research Limitations- Grants showed natural selection, but not development of new species
Questions Unanswered-all of evolutions processes are not completely understood & scientists are still studying it

13. 17–4 Patterns of Evolution
Macroevolution- large scale evolutionary patterns & processes occurring over long periods of time
Mass Extinctions
Adaptive Radiation
Convergent Evolution
Coevolution
Punctuated Equilibrium
Developmental Genes and Body Plans

14. Extinction Causes: Competition & Environmental change
Mass Extinctions- Entire ecosystems gone
environmental collapsed- not failure to compete (not like normal natural selection)
Proposed Causes of:
1 major event- dinosaurs & meteor
Several factors-volcanoes erupting, continents moving, sea levels changing
Effect of extinctions-
Habitats open to ecological succession by other species, lots of evolutionary change
Dinosaurs extinction led to mammals & bird evolution

15. Adaptive Radiation
Single species or small group of species evolved into diverse forms that live in different ways

16. Convergent Evolution
Unrelated organisms independently evolve similarities when adapting to similar environments

17. Coevolution
2 species evolve in response to changes in each other over time
Pollinators
Predatory insects
Many mutualistic relationships

18. Rate of Evolution
Darwin advocated slow & steady change (Gradualism Model)
Evidence suggests:
-some species have changed very little over time
-other have had rapid evolution in short time span after a long period of equilibrium (Punctuated Equilibrium)
-migration of small population to new area
- geographic isolation from main part of population -