1. Evolution
Evolution is the idea that living species are descendants of ancestral species that were different from present-day ones
Evolution describes the genetic changes (mutations) in an organism over time

2. Evolution Organisms are adapted to their environment
As descendants of a remote ancestor spread into various habitats over millions and millions of years, they accumulate diverse modifications (adaptations) that fit them to specific ways of life

3. Evolution
Natural variation among individuals is based on heredity (and mutation). These variations enable organisms to become adapted to their environment over time

4. Natural Selection
Natural selection is the process by which favorable, inherited traits become more numerous in future generations of a population of reproducing organisms
Over time, natural selection leads to species that are well adapted (highly evolved) to their environments

5. Natural Selection
The concept of natural selection was developed by Charles Darwin; a naturalist who sailed around the world and noted the unique adaptations of animals in many diverse environments (most notably the Galapagos Islands)

6. The Principles of Natural Selection
Variation
Some individuals, due to heredity or mutation, possess characteristics which make them better adapted to their environment

7. The Principles of Natural Selection
Inheritance of Traits
Best-suited organisms will survive to produce more individuals that share same adaptation

8. The Principles of Natural Selection
Struggle for existence/Competition
More offspring are produced than can be supported by resources
King Penguin Rookery © Momatiuk - Eastcott/Corbis

9. “Survival of the Fittest”
Organisms are adapted to their environment through natural selection

10. Population with varied inherited traits1
Elimination of individuals with certain traits 2
Reproduction of survivors 3
Certain individuals with one particular inherited trait will be eliminated, while others with a different inherited trait will avoid elimination

11. Let’s look at an example…
Normal allele; vulnerable to pesticides
Alternate allele; resistant to pesticides
Survivors
‘Resistant’ allele passed to next generation

12. Mechanisms of Evolution
Evolution is dependent on genetics
Reproductive component – organisms must reproduce
Heredity component – offspring must resemble parents (traits passed on to offspring)
Variation component – there must be genetic variation among individuals of population
genetic variation leads to variation in fitness (the ability to survive and reproduce)

13. Evolution
Remember, evolution is the genetic change in populations over time
Individuals do NOT evolve; evolution refers to generation-to-generation changes
Evolution does not lead to perfectly-adapted organisms; natural selection results from environmental factors that vary from place to place and from time to time (a trait that is favorable in one situation may be detrimental in another)

14. Evolution
Evolution is a gradual change over time

15. Evidence for Evolution
Fossils!!! – the fossil record (the sequence in which fossils appear in layers of sedimentary rocks) provide some of the strongest evidence of evolution
Sedimentary rocks form from sand and mud that settles to the bottom of seas, lakes and swamps; when organisms die, they settle along with the sediments and are preserved as fossils

16. Evidence for Evolution
Allosaurus: 65 mya
Seed fern: 150 mya
Trilobite: 230 mya

17. Artificial Selection
Artificial selection – the process by which humans have modified other species by selectively breeding for desired traits
All dogs are domesticated breeds of the Gray wolf, Canis lupus

18. Evidence for Evolution
Homologous structures – similar characteristics that result from a common ancestry
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat

19. Developmental similarities reflect descent from a common ancestor

20. Evidence for Evolution
A prime (and very amusing) example of homologous structures are vestigial organs; remnants of structures that have no apparent function, but served important functions in organism’s ancestors

21. Evidence for Evolution
A good example of homologous structures are vestigial organs; remnants of structures that have no apparent function, but served important functions in organism’s ancestors

22. Evidence for Evolution
Vestigial structures of a whale

23. Evidence for Evolution
In contrast to homologous structures, analogous structures also provide evidence for evolution
Analogous structures are structures that share functional similarities, not due to common ancestry
Analogous structures arise among unrelated organisms in response to similar needs or similar environmental factors

24. Analogous Structures
Examples: wings of insects and birds; flippers of seals and penguins

25. Evidence for Evolution
Remember, evolution uses the materials and processes that are already available (it fashions adaptations, rather than starting from scratch)
Evolution is a tinkerer, not a master engineer (a tinkerer uses tools already there to improve)
Adaptations are not perfect
Evolution is constant; traits that are helpful for adaptation today may not be so helpful in the future

26. Evidence for Natural Selection
Darwin’s fishes of the Galapagos Islands
14 species of finch; 1 common ancestor (from the mainland); different beaks

27. Mutations and sexual reproduction are the driving forces of evolution
New alleles originate by mutation, a change in the nucleotide sequence of DNA
Only mutations in cells that produce gametes can be passed along to offspring
Most mutations are harmful, however a mutant allele may improve the adaptation of an individual to its environment and enhance its reproductive success

28. Mutations and sexual reproduction are the driving forces of evolution
Spontaneous mutation rates in animals and plants average ~1 in every 100,000 genes per generation (a slow process)
Sexual reproduction provides a means of increasing genetic diversity and variation, creating genetically-distinct individuals with new combinations of alleles (which may enhance adaptation and reproductive success)

29. Evolution
Evolution is a widely accepted scientific theory that describes the observed changes in living things over time
Scientists use evolution to explain the great diversity of life, but some dispute its ability to describe the origins of life on Earth

30. Other theories out there
Name Descent with modification? Common ancestor? Extinction?
Creation (A) No No No
Transformism (B) Yes No No
Evolution (C) Yes Yes Yes
extinction
(A)
(B)
(C)
change
change
change

31. Evolution
Remember, evolution is an accepted (and well-supported) scientific theory
Scientific theories can never be proven (you cannot prove a hypothesis) but can be supported or rejected; must also be testable and falsifiable