1. SPECIATION When does an evolutionary branch become a new species?

2. WHAT IS A SPECIES? Historically, scientists have used morphology to classify organisms  eg. a monkey and tiger look different so they are different species  BUT a Chihuahua and German Shepherd look different and are both of the same species (Canus lupus)

3. WHAT IS A SPECIES? Species – (according to Oxford dictionary) a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding to produce reproductively viable offspring.*

4. SPECIATION The process by which members of the same species split into 2 (or more) new species is called SPECIATION It’s hard to tell when a new species has evolved because… a)it’s a long, gradual process b)not all evolutionary changes result in a new species

5. SPECIATION For speciation to occur, members of an ancestral species must become isolated from each other This isolation prevents the flow of genes between gene pools Selective forces may effect each gene pool differently

6. TYPES OF SPECIATION

7. ALLOPATRIC SPECIATION Speciation that results when a population is separated by a physical barrier (this is the most common form of speciation)  The formation of Panama 3.5 mya by tectonic shifts caused pockets of isolation of the predominant lobster species at the time  These small gene pools gave rise to new species of South American lobsters  Nene geese evolved when, 5mya, Canadian geese migrated to the Hawaiian islands and never returned  Nene geese have adaptations for surviving on volcanic terrain

8. PERIPATRIC SPECIATION Speciation that results when a small group of members inhabiting a peripheral region of the range become reproductively isolated (very similar to allopatric)  Polar bears evolved due to glaciation that cut-off a small group of brown bears from the main population  Members of the community acquired traits such as white fur, extreme temperature tolerance and the ability to swim long distances

9. PARAPATRIC SPECIATION Speciation that results from partial separation of 2 diverging species Individuals of each developing species may come into contact occasionally but selection for behaviours/mechanisms prevent interbreeding  The Bullock’s and Baltimore orioles evolved from a common species that spanned the USA  Over time western and eastern orioles came to rely on different songs to call mates and this led to speciation

10. SYMPATRIC SPECIATION Speciation in which a new species evolves while living in the same location as the original one  >200 species of Cichlids in East Africa arose from a shared common ancestor that dwelt in the same lake system 113mya  Behavioural preferences such as mating depth, colouration, etc. within the same population led to speciation

11. REPRODUCTIVE ISOLATION The inability of 2 species to mate anymore is called REPRODUCTIVE ISOLATION (sometimes called ‘pre-zygotic isolation’) There are 5 types of reproductive isolation: 1.Spatial isolation  Species can’t mate because they live in different areas

12. REPRODUCTIVE ISOLATION The inability of 2 species to mate anymore is called REPRODUCTIVE ISOLATION (sometimes called ‘pre-zygotic isolation’) There are 5 types of reproductive isolation: 2.Temporal isolation  Species can’t mate because they look for mates at different times of year

13. REPRODUCTIVE ISOLATION The inability of 2 species to mate anymore is called REPRODUCTIVE ISOLATION (sometimes called ‘pre-zygotic isolation’) There are 5 types of reproductive isolation: 3.Mechanical isolation  Species can’t mate because their reproductive organs are incompatible  eg. Bush babies

14. REPRODUCTIVE ISOLATION The inability of 2 species to mate anymore is called REPRODUCTIVE ISOLATION (sometimes called ‘pre-zygotic isolation’) There are 5 types of reproductive isolation: 4.Behavioural isolation  Species can’t mate because their mating rituals are too different

15. REPRODUCTIVE ISOLATION The inability of 2 species to mate anymore is called REPRODUCTIVE ISOLATION (sometimes called ‘pre-zygotic isolation’) There are 5 types of reproductive isolation: 5.Gametic isolation  Species can’t mate because their gametes can’t fuse