1. Before studying this unit you should read and understand the contents of this website: http://evolution.berkeley.edu/evolibra ry/article/evo_01

2. What is a species? Members of a species are similar to each other but different to members of another species This similarities can be: –Physical –Biochemical –Immunilogical –Developmental –Ecological

3. What is a species? Dictionary definition 1: ‘A class of individuals or objects grouped by virtue of their common attributes and assigned a common name; a division subordinate to a genus’ The American Heritage® Dictionary of the English Language Dictionary definition 2: ‘A group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding’ Oxford English Dictionary

4. Biological definition Two organisms are the same species if: a)They have the potential to breed b)Their offspring are fertile ‘A population or group of populations whose members have the potential to interbreed to produce viable, fertile offspring’

5. How do species occur? Often called EVOLUTION: the species we see and know now have evolved from other species This idea is central to biological classification The formation of new species from existing species due to an increasing genetic difference of a population that leads to a lack of interbreeding Speciation

6. Hybridisation The production of offspring from parents of two genetically different species

7. Polyploidy A random mutation that causes a sterile hybrid to double its chromosome number and become fertile Occurs very rarely in animals More common in plants especially angiosperms (flowering plants)

8. How speciation occurs Isolation Reproductive barriers Genetic Isolation New species formation

9. Reproductive isolation Organism cannot interbreed or mate with another group. This could be because: incompatible gametes, wrong courtship, anatomical differences, geographical barrier, etc

10. Allopatric Speciation A mode of speciation that occurs when the ancestral population becomes segregated by a geographical barriers Mountain range Rivers/Oceans Glaciers

11. Geographical speciation process: Populations separated by physical barrier No mixing of gene pools Different selection pressures Adaptation to local environment Survival and reproduction Mutations in one group different from mutations on the other group Change in allele frequency RESULT : 2 DIFERENT SPECIES THAT CAN NOT INTERBREED

12. Sympatric speciation A mode of speciation that occurs without geographical isolation. Relatively quick Genetic differences occur through strong forces of natural selection or mutations New species arise within the range of the parent population

13. Charles Robert Darwin 1809Born in Shrewsbury, England 1831- 1836 Naturalist onboard HMS Beagle on a worldwide voyage. Sep 1835 Reached the Galapagos Islands and collected various finches among many animal and plant samples July 1837 Starts notes on ’The Origin of species’ 1858Alfred Wallace sends Darwin his own manuscript 1859Darwin publishes ‘On the Origin of the Species’ which was highly controversial 1882Dies and is buried in Westminster Abbey

14. Darwins Finches Different beak sizes developed from eating different food sources: Nuts Insects Fruits Blood!

15. Pre-mating barriers to interbreeding Explanation Geographical separationInhabit different continents, islands or sides of a canyon Habitat IsolationPopulations inhabit different local habitats within one environment Temporal IsolationPopulations use the same environment but are reproductively active at different times (times of day/seasons) Behavioural IsolationCourtship rituals and songs of birds may be specific to a particular species and do not attract similar species Mechanical IsolationFail to mate due to physical incompatibility (pollinators for flowers)

16. Post-mating barriers to interbreeding Explanation Gametic IsolationFemale might kill sperm of wrong genotypes or pollen of wrong genotype fails to germinate Hybrid not viableHybrid fails to develop maturity, zygote may be aborted during development Hybrid sterilityHybrid grows to maturity but is sterile (e.g. mule) Hybrid breakdownFirst generation may be viable but 2 nd generation are sterile, become weak or defective.