1. D2: Species and Speciation
5 hours

2. D.2.1 Define allele frequency, gene pool.
% of certain allele (variation of a gene) in the population for a certain locus/gene
Gene pool
All genetic info of reproducing members of the population
Variation

3. Mutation introduces new alleles Old alleles “die out”
D.2.2 State that evolution involves a change in allele frequency in a population’s gene pool over a number of generations.
Mutation introduces new alleles
Old alleles “die out”
Advantageous  survives
Change in allele freq = evolution
SEVERAL generations!

4. D.2.3 Discuss the definition of the term species. Xref- species- 5.1.1
Organisms have similar physiological and morphological characteristics
Ability to interbreed, produce fertile offspring
Genetically distinct from other species
Common phylogeny
Not exactly that simple, but good enough for now!

7. SEPARATE POPULATIONS...MAY LEAD TO SPECIATION geographical isolation
D.2.4 Describe three examples of barriers between gene pools. Examples include
SEPARATE POPULATIONS...MAY LEAD TO SPECIATION
geographical isolation
Physical barriers (land, water formation) prevent males/females from meeting & interbreeding—populations are separated
hybrid infertility
2nd generation unlikely
Genetic barrier between species
temporal isolation
Incompatible time frames for mating (flowers blooming/seasons; hibernations; migrations)
behavioural isolation
Lifestyle, habits incompatible with other population
Courtship displays

8. Cell division mistakes, chromosomes don’t separate completely
D.2.5 Explain how polyploidy can contribute to speciation. Xref- Meiosis / 10.1
Avoid examples involving hybridization as well as polyploidy, such as the evolution of wheat.
3n, 4n, 5n, etc.
Cell division mistakes, chromosomes don’t separate completely
Common in plants
Extra chroms  plant more vigorous
Replication errors more common
2 populations could evolve at different rates b/c of difference in ploidy
Could lead to speciation

9. D.2.6 Compare allopatric speciation, sympatric speciation.
Speciation: the formation of a new species by splitting of an existing species.
Sympatric: in the same geographical area—Temporal, behavioural isolation
Pheromones, mating calls, etc. may be changed slightly, allow for mates or not
Allopatric: in different geographical areas—geographic isolation
2 pops separated, evolve separately
If allowed to mingle in future, may not be able to interbreed...new species
Snow geese (Chen caerulescens)
SawFly (Tenthredo livida)
Fertilisation
Pin and thrumb primroses (Primula vulgaris)

10. Genetic Hybrid inviability Hybrid offspring die
Hybrid infertility Hybrids survive but are incapable of producing gametes
Zedonk

11. D.2.7 Outline the process of adaptive radiation.
“Rapid” evolution from 1 (or a few) species into more
Slightly diff niches, more successful
Natural selection
Speciation event(s) (isolation)
EX-finches, lemurs
Lemurs once widespread b/c no competition (apes, monkeys)
Lots phenotypic diversity
Some better adapted to certain niches, led to adaptive radiation
Apes, monkeys...outcompete lemurs, so lemurs not found

12. Mechanisms of speciation
Madagascar Google earth
Isolation of a population so that it cannot breed freely with others is necessary
Geographic
Ecological
Behavioural
Mechanical/anatomical
Physiological
Genetic
Ringtailed lemurs
(Lemur catta)
© 2008 Paul Billiet ODWS

13. D.2.8 Compare convergent evolution, divergent evolution.
Not a recent common ancestor
2 species or characteristics look similar
Australia & N America: marsupials vs placentals
Wings (bat, bird); bioluminescence (bacteria, fungi)
Divergent
Recent common ancestor
Less similar over time

14. Gradualism: small, continuous, slow change from one form to another
D.2.9 Discuss ideas on the pace of evolution including gradualism and punctuated equilibrium.
Gradualism: small, continuous, slow change from one form to another
Fossil record
Present day examples
P. 429 diagrams
Punctuated equilibrium: long periods without appreciable change and short periods of rapid evolution
Response to change in environment
Volcanic eruptions and meteor impacts affecting evolution on Earth
65mya...dinosaurs extinct; mammals survived
Until a big environmental change, little/no change in fossil record

15. Evolution of new species
Two possible ways from gradualism
PHYLETIC TRANSFORMATION
ALLOPATRIC SPECIATION
© 2008 Paul Billiet ODWS

16. PHYLETIC TRANSFORMATION
Gradual accumulation of small genetic variations preserved by natural selection
A whole population imperceptibly to evolve in to a new species
Impossible to draw a clear line between the end of the first species and the beginning of its descendant species
There would be a long period of intermediate forms
© 2008 Paul Billiet ODWS

17. ALLOPATRIC SPECIATION
Geographical or reproductive isolation of a part of the population would allow it to evolve in a different direction
Possibly more rapidly than the main population
If the isolated population is small, it might be very difficult to find fossils of the intermediate stages
© 2008 Paul Billiet ODWS

18. Evolution Time Species X Species Z Species Y Species Y Species W
Allopatric speciation of Species W into species X due to the isolation of a small population of Species W
Evolution
Time
Species X
Species Z
Species Y
Allopatric speciation of species Y into species Z due to the isolation of a small population of species Y
Species Y
Phyletic transition of species W into Species Y due to the slow gradual accumulation of mutations in Species W
Species W
© 2008 Paul Billiet ODWS

19. THE PUNCTUATED EQUILIBRIUM MODEL
They observed that the fossil record gives a different picture for the evolution
They claim that there were long periods of stasis (4-10 million years) involving little evolutionary change
Then occasional rapid formation of new species
As little as 5, ,000 years
Stephen J
Gould
Niles Eldredge
© 2008 Paul Billiet ODWS

20. Time Evolution Species Y Species Z Species X Species W
Rapid speciation
Stasis
Species W
Species X
Species Y
Species Z
© 2008 Paul Billiet ODWS

21. Problems... Fossil evidence is the only evidence of either theory
Not all characteristics of a species are present in fossil record
Not necessarily proof of phylogeny

22. NATURAL SELECTION AT THE LEVEL OF THE ALLELE
Sickle cell anemia
Biston betularia

23. D.2.10 Describe one example of transient polymorphism.
Polymorphisms = many “shapes” (phenotypes)
Industrial melanism: peppered moth
Biston betularia
Peppered (grey)
Melanic (black)
Pre-Industrial Revolution: advantageous to be grey, camouflaged on tree bark
Ind. Rev.  soot on trees, black bark; black p’types survived (more fit)
Natural selection!
Clean Air Act…grey more fit
Temporary change  TRANSIENT polymorphism

24. D.2.11 Describe sickle-cell anemia (SCA) as an example of balanced polymorphism. Xref- SCA-4.1.4; malaria
2/more alleles of population are not transient and changing. They’re stabilized by natural selection.
Sickle-cell anemia
Balanced polymorphism
Heterozygotes have advantage in malarial regions
HbAHbS
More fit than either homozygote
AA = very susceptible to malaria
SS = sickle cell, but resistant to malaria
AS = some sickled cells, but usually not anemic; K-deficient sickled cells kills Plasmodium parasite
“S” Selected for & selected against ... balanced