1. Evolution
SBI3U

2. Evolution is change over time caused by the accumulation of inherited characteristics over many generations.
A characteristic that helps an organism to survive and reproduce in its environment is called an adaptation.
Similarities in DNA and physical structures indicate that all organisms are related to common ancestors.

3. The Fossil Record
fossil - preserved remains or traces of an organism or its activity
created when organisms are buried in sediment
calcium in bone, shell, teeth become mineralized - compressed - hardened and converted into sediment rock
Fossils of simple organisms can be found at all depths, but more complex forms are in shallower deposits

4. Early Ideas About Evolution Jean Baptist Lamarck
1st to recognize the key role played by the environment on evolution
reasoned that for species to survive - must be able to adapt to changing environment
thought organisms adapted because body became stronger and larger
thought these characteristics could then be passed on to offspring
called it inheritance of acquired characteristics

5. Lamarck’s Idea of Evolution

6. Darwin and Evolution
set on a voyage on a British ship called the HMS Beagle
observed species of different parts of the world
noticed species living in cooler regions of South America were more closely related to species living in tropical regions of South America than in cooler regions of Europe

7. The Galapagos Islands
Darwin stopped 5 weeks in this group of 20 small islands
Observed 13 species of finches
each type of finch had different shape of beak which were adaptations for eating different foods
suggested they were all modified from ancestral form
made Darwin notice that many species produce high number of offspring but population level remains constant

8. The Theory of Natural Selection
Darwin realized individuals had to somehow struggle to survive - came up with theory of natural selection
favourable traits increase survival - passed on to offspring
did not use word evolution because it implied progress but natural selection does not demonstrate progress, it has no direction - only ability to survive in local environmental conditions
 called ideas “Descent and Modification”

9. What Darwin Observed Evidence of Evolution
Homologous structures
- similar structure, different function
(ex. Forelimbs of mammals)
Analogous Structures
-similar function, different structure
(ex. Wings of insects and birds)

10. Homologous Structures

11. Analogous Structures

12. Vestigial Structures
structures with no apparent function that resemble the formerly functional structures of ancestors
(ex. Pelvic bone in whales)

13. Vestigial Structures
Whale Pelvis
Human Pelvis

14. Artificial Selection breeding organisms with desired traits
Darwin recognized that all species possess inherited variations that can be selected to change the species in desirable ways
he reasoned that if people could alter the appearance or behaviour of species through artificial selection, then the environment could have similar effect on wild species

16. Theory of Natural Selection
Natural Selection - process where some organisms in environment possess genetic attributes that better adapt them to survive and reproduce more, creating more surviving offspring
causes a change in allele frequencies from generation to generation

17. About Mutations There is a constant rate of random mutation in nature
Most mutations are lethal
A very small number of mutations result in advantages to individuals within a population.
These mutations increase survival, therefore increase the number of offspring, and therefore will be passed on to future generations.

18. Examples of Natural Selection
Peppered moth during industrial England
Light coloured was more common until the industrial revolution, then dark was more common
Sickle Cell Anemia
More common in Africa than North America due to protection against Malaria

19. The Peppered Moth

20. Sickle Cell Anemia

21. The Hardy-Weinberg Principle (i. e
The Hardy-Weinberg Principle (i.e. What Happens when No Change Happens)
In randomly mating populations, with no outside stresses acting, the frequency of alleles in the population remains unchanged from generation to generation.
Example. If a population of pea plants has 60% ‘T’ and 40% ‘t’ alleles, this ratio will not change if the population mates randomly and experiences not outside stresses.

22. Hardy-Weinberg Punnet Square

23. Factors Altering the H-W Equilibrium (i.e. How does change Happen?)
Genetic Drift
bottleneck effect and founder effect
Gene Flow
migration
Mutation
Non-random mating
Selection

24. Genetic Drift The random loss of alleles by chance alone
Founder Effect - when one or a few individuals of a population become founders of a new, isolated population far from place of origin, the alleles they carry are important - even if rare in original population, will be large fraction of new population

25. bottle-neck effect- a small founder population becomes the sole source of alleles for a given species as a result of a drastic reduction in population number

26. Genetic Drift
Bottleneck Effect
Founder Effect

27. Patterns of Selection Stabilizing Directional Disruptive
average individual preferred, eg. Birth weight
Directional
one extreme favoured eg. Long beak
Disruptive
average individual unfavoured

28. Stabilizing Selection

29. Disruptive Selection

30. Directional Selection

31. Two main types of Evolution
Micro-evolution
also called ‘variation’
these are small changes within species
occur over shorter time intervals
eg. Penicillin resistance in bacteria
Macro-evolution
these are changes of species
require long timeframes
accumulation of many mutations
as a result, can no longer intergrade.

32. Speciation
New species are said to have formed if they have accumulated so many differences that they can no longer produce successful offspring
Requires long periods of reproductive isolation for mutations to accumulate

33. Reproductive Isolating Mechanisms
Pre-zygotic
behaviourial isolation
ecological isolation
temporal isolation
mechanical isolation
gametic isolation

34. Reproductive Isolating Mechanisms
Post-zygotic
hybrid mortality
hybrid inviability
hybrid infertility/sterility

35. Modes of Speciation Allopatric Speciation Sympatric Speciation
evolution of separate species as a result of geographic isolation
Sympatric Speciation
evolution of separate species within the same geographic area but each in a particular niche.

36. Allopatric Speciation