1. Charles Darwin, Evolution of Species, and Natural Selection

2. Natural Selection
Individuals with favorable traits are more likely to leave more offspring better suited for their environment.
Example:
English peppered moth (Biston betularia)
- light and dark phases

3. Artificial Selection
The selective breeding of domesticated plants and animals by humans.
Question:
What’s the ancestor of the domesticated dog?
Answer: WOLF

4. Species
Individuals have the potential to interbreed and produce viable or fertile offspring.
A localized group of individuals belonging to the same species.

5. Gene Pool
The total collection of genes in a population at any one time.

6. Four Mechanisms of Natural Selection (things that cause evolution)
1. Genetic drift:
Change in the gene pool of a small population due to chance.
Two examples:
a. Bottleneck effect- drastic reduction in population size
b. Founder effect- resulting from the colonization of a new location by a small number of individuals.

7. Four Mechanisms of Natural Selection
2. Gene Flow:
The gain or loss of alleles from a population by the movement of individuals or gametes.
Immigration or emigration. 3. Mutation:
Change in an organism’s DNA that creates a new allele.
4. Non-random mating:
The selection of mates other than by chance.

8. Speciation
The evolution or formation of new species.

9. Spontaneous Generation or Abiogenesis
The idea that life could arise from non-living matter
People used to think that beetles came from dung and maggots came from meat left standing in the open for days
Today, we know that this is not true

10. Evolution It is defined by the simple phrase “change over time.”
It’s a process by which modern organisms have descended from ancient organisms
There are many scientists included in the evolutionary discussion, but none more so than Charles Darwin.

11. Charles Darwin
His observations led to a revolutionary theory about the way life changes over time.
An English scientist
In 1831, he set sail on the H.M.S. Beagle around the world.
Darwin conducted a large amount of his studies on the Galapagos Islands.

12. Galapagos
Darwin noticed differences between the beaks of finches and the shells of tortoises in the different islands of the Galapagos.
He notes that what once was one species had evolved into different species suited to live in their specific environment

13. Finches
As you can see, the finches, over time, developed a beak that best suit their survival on each particular island of the Galapogos.

14. The Origin of Species
Was a book that Darwin published that shocked the world and everything it knew about life, especially from a religious standpoint.

15. Mass Extinction
Mass extinction - when many types of living things become extinct at the same time
Extinct - the species died out
At the end of the Paleozoic Era, a mass extinction affected both plants & animals on land & in the sea
95% of life in the oceans disappeared

16. Evidence of Evolution The Fossil Record:
Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time

17. Evidence of Evolution Geographic Distribution of Living Species:
Darwin realized that similar animals in different locations were the product of different lines of evolutionary descent

18. Evidence of Evolution Homologous Body Structures:
Homologous structures - structures that have different mature forms but develop from the same embryonic tissues
Not all homologous structures serve important functions
Organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs

19. Homologous Structures

20. Evidence of Evolution Homologous Body Structures:
Vestigial organs - may resemble miniature legs, tails, or other structures, a trace of a homologous structure

21. Evidence of Evolution Similarities in Early Development:
The early stages or embryos, of many animals with backbones are very similar

22. Patterns of Evolution Extinction:
More than 99% of all species are now extinct
It usually happens for a reason; species compete for resources, & environments change
Some species adapt & survive, others become extinct

23. Patterns of Evolution
Adaptive radiation - when a single species has evolved, through NS, into diverse forms that live in different ways
Ex.) Darwin’s Finches

24. Patterns of Evolution
Punctuated equilibrium - a pattern of long, stable periods interrupted by brief periods of more rapid change

25. Summary of Darwin’s Theory
Individual organisms differ, & some of this variation is heritable
Organisms produce more offspring than can survive, & many that do survive do not reproduce

26. Summary of Darwin’s Theory
Because more organisms are produced than can survive, they compete for limited resources
Individuals best suited to their environ., survive & reproduce most successfully

27. Summary of Darwin’s Theory
These organisms pass their heritable traits to their offspring
This process of NS causes species to change over time

28. Summary of Darwin’s Theory
Species alive today are descended with modification from ancestral species that lived in the distant past
This process, where diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life

29. The Puzzle of Life’s Diversity
Evolution - modern organisms have descended from ancient organisms (change over time)
Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world

30. Voyage of the Beagle
Charles Darwin contributed most to our understanding of evolution
He made observations & collected evidence that led him to propose a hypothesis about the way life changes over time

31. Darwin’s Observations
Darwin collected the preserved remains of ancient organisms - Fossils
Some of these fossils resembled organisms that were still alive
Others looked unlike any creature ever seen

32. Darwin’s Observations
The Galapagos Islands influenced Darwin the most
He observed that the characteristics of animals & plants varied among the different Islands

33. Darwin Presents His Case
Darwin published the results of his work in a book, On the Origin of Species
In his book, he proposed a mechanism for evolution called natural selection
He stated that evolution has been taking place for millions of years, & continues in all living things

34. Inherited Variation & Artificial Selection
Artificial selection - nature provided the variation, & humans selected those variations that they found useful
It has produced diverse plants & animals by selectively breeding for different traits

35. Evolution by Natural Selection
Struggle for existence - the members of each species compete regularly to obtain food, living space, & other necessities of life
Predators that are faster & better at catching prey are more likely to survive

36. Evolution by Natural Selection
Fitness - the ability of the organism to survive & reproduce in its specific environ.
Fitness is the result of adaptations

37. Evolution by Natural Selection
Individuals that are better suited to their environ., with adaptations that enable fitness, survive & reproduce most successfully - Survival of the Fittest

38. Evolution by Natural Selection
Since it is similar to artificial selection, Darwin referred to survival of the fittest as - Natural Selection
In both AS & NS, only certain individuals of a population produce new individuals
However, in NS, the traits being selected, & therefore, increasing over time, contribute to an organism’s fitness
NS takes place without human control or direction

39. Evolution by Natural Selection
NS results in changes in the inherited characteristics of a population, that increase a species’ fitness in its environ.
Over time, NS produces organisms that have different structures, & occupy different habitats

40. Evolution by Natural Selection
As a result, species today look different from their ancestors
Each living species has descended, with changes, from other species over time - Descent with Modification

41. Evolution by Natural Selection
Descent with modification also implies that all living organisms are related to each other
Common descent - all species (living & extinct) were derived from common ancestors

42. Evidence of Evolution
Darwin argued that living things have been evolving on Earth for millions of years
Evidence of this could be found: in the fossil record, the geographical distribution of living species, homologous structures of living organisms, & similarities in early development

43. Evidence of Evolution The Fossil Record:
Darwin noticed that the sizes, shapes, & varieties of related organisms preserved in the fossil record, changed over time

44. Evidence of Evolution Geographic Distribution of Living Species:
Darwin realized that similar animals in different locations were the product of different lines of evolutionary descent