1. Darwin & Natural Selection
Evolution
Darwin & Natural Selection

2. Broad concept
Evolution is the result of genetic changes that occur in constantly changing environments. Over many generations, changes in the genetic make-up of populations may affect biodiversity through speciation and extinction.

3. Learning Objectives
Explain how evolution is demonstrated by evidence from the fossil record, comparative anatomy, genetics, molecular biology, and examples of natural selection

4. What is evolutionary theory?
Evolution = change over time
Evolution is often called the “unifying theory of biology” because it organizes all of the observations gathered by biologists and proposes and explanation for those observations.
Two men that made important contributions to the theory of evolution are Lamarck and Darwin.

5. This is our current "best guess" for the beginning of life on Earth.
3.8 billion years ago
This is our current "best guess" for the beginning of life on Earth.
530 million years ago
The first true vertebrate – an animal with a backbone – appears

6. What ideas preceded evolution?
Before Darwin, most people believed that living things had been created no more than years ago.
BUT…old fossils were being discovered that were MILLIONS of years old.
Why did so many species disappear and are they related to living species?

7. Fossils
When an organism dies, it's bone structure is often preserved when debris or dirt packs on top of it for thousands - millions of years.
This is how researchers know what many of the dinosaurs looked like, which led to discovery of how they lived and interacted with the ecosystem.

8. What ideas preceded evolution?
James Hutton: proposed that Earth had to be much older than ~3000 years old
Charles Lyell: proposed that geologic features on Earth change over time… so Darwin wondered if life changed too!

9. What ideas preceded evolution?
Jean-Baptiste Lamarck: “Use/Disuse Theory”…first ‘evolution- like’ theory
If an organism used/did not use a particular feature in its lifetime, this use/disuse would be passed on to offspring
(If a man was a bodybuilder, his child would be naturally muscular.)
WRONG!!! (but it was an interesting idea)

10. What ideas preceded evolution?
Thomas Malthus: if the human population grew continuously, we would hit the Earth’s carrying capacity and people would die.
Darwin thought…
“WHY haven’t plants/animals grown continuously over time? WHAT causes some to survive and others to die?

11. Darwin’s Background Born in England, 1809
Studied Medicine at Edinburgh University
Transferred to Cambridge University – earned a degree in theology.
the study of religious faith, practice, and experience; especially: the study of God and of God's relation to the world
Studied to be a Minister
Library of Congress, Prints and Photographs Division [reproduction number, e.g., LC-USZ61-104].

12. Darwin Darwin was a naturalist who observed many species.
He is famous for his trips to the Galapagos Islands, his observations of the finches (and other animals) and the book he wrote: The Origin of Species

13. Three Main Parts of Charles Darwin’s Life
1809 – 1831: Age
Childhood, education, college
1831 – 1836: Age 22 to 27
Voyaging on the HMS Beagle
1836 – 1882: Age 27 to 73
Scientist and author

14. Darwin’s Schooling 1817 – 1818: Attended day-school of Reverend Case
1818 – 1825: Attended Shrewsbury School, a boarding school run by Dr. Samuel Butler (grandfather of the Samuel Butler who wrote Erewhon and The Way of All Flesh). He could readily walk back home from this school, although he was a boarder.
1825 – 1827: Studied medicine at University of Edinburgh, where his father and brother had studied, but discovered medicine was not to his liking.
1828 – 1831: Attended and graduated from Cambridge University (theology) intending to become a clergyman.

15. Darwin’s Expedition - 1831 Hired as a Naturalist on H.M.S. Beagle
Job was to collect specimens
Sailed on five year scientific expedition around the world
Main mission of the Beagle was to chart the South American coastline
Down east coast of South America
Up pacific coast to Galapagos Islands
Made stops on mainland and islands
Observed variety of life and habitats
Collected fossils, rocks, plants & animals

17. Galapagos Islands
a group of 18 islands in the Pacific off South America (500 miles off coast of Ecuador). Formed by volcanoes & geologic uplift between million years ago.

18. Galapagos Islands
Animal Species include: finches, green turtle, land iguanas, marine iguanas, Galapagos penguin, lava gulls, sea lions, whale, red-footed & blue-footed boobies, frigates, tortoises, waved albatross, pelicans, sharks, rays, flamingos, crabs
Most of these animals live only on these islands! However, they look like species living on the mainland

20. Died June 2012 Lonesome George
The last known individual of the Pinta Island tortoise which is one of eight to fifteen subspecies of Galápagos tortoise
Rarest creature in the world!
~ years old!!!!
First seen in 1971 & relocated for his safety to the Charles Darwin Research Station, George was penned with two females of a different subspecies… no viable eggs
Recently – other subspecies/Pinta hybrids with ~1/2 of George’s genotype have been discovered.
Died June 2012

21. Galapagos giant tortoises
Evolved from a common ancestor that arrived from the mainland (likely a pregnant female or breeding pair)
Original ancestor was much smaller and evolved into the present-day giants. Gigantism evolves because there is no longer any need to hide from predators and because there are no other similar animals to compete with for food.
The tortoises spread around the islands and evolved differently in order to adapt to the different environments

22. Shells
Some tortoises developed domed carapaces (top shells) while other developed saddleback carapaces. (along with variations in between)
Domed – turtles can retreat back into their shell (protection). Low vegetation
Saddleback – due to higher vegetation on drier islands, tortoises needed a longer neck to s-t-r-e-t-c-h

23. 250,000 down to 15,000
~250,000 tortoises inhabited the islands when they were discovered.
12-15 subspecies
Today only about 15,000 are left 
Now only 11 subspecies
After the arrival of humans…
Hunting tortoises for meat!
Whalers would capture hundreds and keep on ships for food
Destruction caused by goats released in 1950’s – invasive species!
Competed for food
Other invasive species – pigs, dogs, cats, rats, plants

24. Darwin found…many unique species
Many of Darwin’s observations made him wonder… Why?
Darwin asked:
Why were these creatures found only on the Galapagos Islands?

25. Darwin found…clues in the fossils
present day Armadillos
Darwin found:
Evidence that creatures have changed over time
ancient Armadillo
Darwin asked:
Why should extinct armadillos & modern armadillos be found on same continent?

26. Darwin found… birds Darwin found:
Many different birds on the Galapagos Islands.
Finch?
Sparrow?
Woodpecker?
Warbler?
He thought he found very different kinds…

27. But Darwin found… a lot of finches
Darwin was amazed to find out:
All 14 species of birds were finches…
But there is only one species of finch on the mainland!
Darwin asked:
If the Galapagos finches came from the mainland, why are they so different now?

28. The finches cinched it! Darwin said:
Darwin found:
The differences between species of finches were associated with the different food they ate.
Finch?
Sparrow?
Woodpecker?
Warbler?
Darwin said:
Ahaaaa! A flock of South American finches were stranded on the Galapagos…
different beaks are inherited variations
serve as adaptations that help birds compete for food
these birds survive & reproduce
pass on the genes for those more fit beaks
over time nature selected for different species with different beaks
Large ground finch
Big seed eater
Small ground finch
Small seed eater

29. Darwin’s observations of finches (birds) on the Galapagos Islands led him to believe that different species may have descended from a common ancestor.

31. Relationship between species (beaks) & food

32. Darwin’s conclusions Darwin’s finches variations in beaks
differences in beaks in the original flock
adaptations to foods available on islands
natural selection for most fit
over many generations, the finches were selected for specific beaks & behaviors
offspring inherit successful traits
accumulation of winning traits: both beaks & behaviors
separate into different species

33. From 1 species to 14 species…
Warbler finch
Woodpecker finch
Small insectivorous
tree finch
Large
insectivorous
Vegetarian
Cactus finch
Sharp-beaked finch
Small ground
finch
Medium
ground finch
Large ground
Insect eaters
Bud eater
Seed eaters
Cactus
eater
Warbler
Tree finches
Ground finches
natural selection for best survival & reproduction
variation

34. Darwin’s view of Evolution
giraffes that already have long necks survive better
leave more offspring who inherit their long necks
variation
selection & survival
reproduction & inheritance of more fit traits

35. Darwin found… more fossils
present day Sloth
Darwin found:
Evidence that creatures have changed over time
(extinct) Giant ground sloth
Darwin asked:
Why should extinct sloths & modern sloths be found on the same continent?

36. Natural selection is the process by which those heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. It is a key mechanism of evolution.

37. It follows logically that …
Some individuals will be better suited to their environment - they will survive and reproduce more successfully than individuals without those characteristics
Future generations will thus contain more genes from better-suited individuals.
As a result, characteristics will evolve over time to resemble those of the better-suited ancestors.

38. Survival of the Fittest
the environment limits the growth of population by increasing the rate of death or decreasing the rate of reproduction, or both.
Organisms with certain (+) variations survive, reproduce, and pass their variations on to the next generations.
Organisms without these variations are less likely to survive and reproduce.

39. Darwin Presents His Case
Darwin returns to England in 1836 with specimens from around the world.
On the Origin of Species:
book – foundation of evolutionary biology. HUGE impact on science!!!
1859 – published
Topics included…
NATURAL SELECTION
PHYSICAL EVIDENCE FOR EVOLUTION

40. Darwin was afraid to publish his work!
Why?????
during the first half of the 19th century the English scientific establishment was closely tied to the Church of England, while science was part of natural theology.
Ideas about the transmutation of species (evolution) were controversial as they conflicted with the beliefs that species were unchanging parts of a designed hierarchy and that humans were unique, unrelated to animals.

41. On the Origins of Species
Darwin's book introduced the scientific theory that populations evolve over the course of generations through a process of natural selection.
included evidence that he had gathered on the Beagle expedition in the 1830s and his subsequent findings from research, correspondence, and experimentation

42. On the Origin of Species
the evidence he presented generated scientific, philosophical, and religious discussion.

43. Darwin Presents His Case
Artificial selection: nature provides genetic variation and humans select desirable traits for further mating…crops/livestock were undergoing an “artificial evolution”!
Struggle for existence: animals survive that are better adapted for their environment (faster, camouflaged, smarter etc.) than those who are not (slower, weaker etc.)

44. Darwin Presents His Case
Survival of the fittest: individuals with adaptations that enable fitness survive and reproduce most successfully
Also called - NATURAL SELECTION
The mechanism of evolution!
Adaptation = an inherited characteristic
Fitness = ability of an organism to survive in its environment and reproduce

45. Darwin Presents His Case
Over time, Natural Selection results in changes in the inherited characteristics (the genes) of a population!
Descent with modification: each species in existence today came from other species over time…they just changed in some way(s)
Every living thing has a common, single ancient organism it descended from
Think about it… there had to be a first cell !

46. Darwin’s Evidence of Evolution
1) Fossils: a person can “see” an organism evolving through history by looking at fossils of different ages
2) Geographic distribution: UNRELATED animals/plants were living in areas of the world with similar environments

47. Darwin’s Evidence of Evolution
3) Homologous body structures: organs or limbs differ in form or function, but contain SAME basic structures
Turtle leg, alligator leg, bird wing, human finger all have similar bone structure and likely all came from a specific ancient fish fin
4) Embryology: early embryos of many animals look almost EXACTLY the same!

48. Homologous Structures

51. the chomping front teeth of a beaver look quite different than the tusks of an elephant…
Homologous????

52. YES!
The beaver uses its teeth for chewing through tree trunks, and the elephant uses its tusks for a number of tasks including digging, peeling bark from trees, and fighting.
But if you examine these two structures closely, you will see that each is a modification of the basic incisor tooth structure. Over time, evolution adapted each of these animals' incisors to perform different functions. They are homologous structures, inherited from a common ancestor with incisor teeth.

53. Homologous?

54. NO SHARKS Skeleton made of cartilage
Use gills to get oxygen from water
Don’t nurse their young
Don’t have hair
DOLPHINS
Skeleton made of bones
Go to the surface & breathe atmospheric air through their blowholes
Do nurse their young
Do have hair (small hairs around noses)

55. Sharks & Dolphins are ANALOGIES
They may share the same basic shape, but underneath their skins, sharks and dolphins are very different!

57. HOMOLOGY
In everyday life, people look like one another for different reasons.
Two sisters, for example, might look alike because they both inherited brown eyes and black hair from their father.
On the other hand, two people attending an Elvis impersonators' convention may look alike because they are both wearing rhinestone studded suits and long sideburns. The similarity between the sisters is inherited, but the similarity between the Elvis impersonators is not.

58. Summary of Darwin’s Theory
Heritable variations exist among individuals.
The students in a classroom all look different
Organisms compete to survive and reproduce.
A sunflower produces hundreds of seeds but only a % germinate
Through natural selection, the fittest individuals (best suited to environment) reproduce and pass traits to their offspring.
Tall sunflowers produce tall sunflower seeds
Species evolved from common ancestors.
Bat, human, alligator, primate all evolved from same ancestor!

60. Patterns of Evolution
Extinction – more than 99% of all species that have ever lived are now extinct. 
Adaptive Radiation – Single species evolve into diverse forms living in different ways.
ex. Darwin’s finches

61. Darwin’ Finches illustrate adaptive radiation.
Common Ancestry
Change in food/environment  new species of finches formed

62. Adaptive Radiation
A type of divergent evolution in which a species migrates to different areas and the subpopulations adapt to their new environments

63. Convergent Evolution- Species separated by geography, but living in similar conditions, evolve in similar ways.
Birds and butterflies have both evolved the ability to fly (independent of one another).

64. Patterns of Evolution
Coevolution – process where two species evolve in response to changes in each other. Over time they become dependent upon one another.
Example: flowers and their pollinators

65. CO-EVOLUTION For example:
Plants attracting hummingbirds are usually bright (red), petals that curve back and have no smell.
Flowers that are pollinated by bats open up at night, have little color and a musty smell.

66. PATTERNS OF EVOLUTION
Punctuated Equilibrium – term to describe long, stable periods of evolution interrupted by brief periods of more rapid change.

67. Geographic Isolation
A lack of gene flow (mating) between the two groups in a population (which are now divided)
Natural Selection (different environments favor different traits)

68. Artificial Selection
when nature provides the variation, and humans select the variations that are most useful to them.
This speeds up the process of evolution through selective breeding
ex. Dog breeds are all the same species, that man has selective bred for thousands of years.

69. Darwin’s Reputation after his death
The fact of evolution was well established and believed by all biologists.
Natural selection was considered the most important cause of evolution by very few biologists. Many other biologists were “saltationists,” believing in the role of major sudden changes (as by large mutations)

70. Darwin’s Reputation (continued)…
Until about 1900, inheritance was poorly understood, and the favored theory of “blending inheritance” was not capable of leading to the evolutionary changes required by Darwin’s theory. This changed after geneticists (beginning with Mendel in 1865)
About 1930 the concept of gradualism was received more favorably, and the geneticists and naturalists found out how their approaches meshed, leading to the “Modern (Darwinian) Synthesis.”
The discovery in the last half of the 20th century of the role of DNA and genes largely completed the triumph of Darwin’s ideas.

71. Terms to know Evolution Natural Selection Adaptation Fossil Record
Comparative Anatomy
Molecular Evidence
Comparative Embryology
Geographic Isolation
Speciation
Extinction
Biodiversity
Variation
Fitness
Phenotype
Genotype
Inheritance
Vestigial structures
Homologous structures

72. Evolution - is the result of genetic changes that occur in constantly changing environments
Natural Selection - is the process by which those heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations.
Adaptation - change by which an organism or species becomes better suited to its environment

73. Fossil Record - the accumulation of fossils and related geological data that give us clues about the past and its taxonomic history.
Comparative Anatomy - The comparison of the structure (anatomy) of one animal or plant with the structure of a different animal or plant. compares similar body structures in different species of animals in order to understand the adaptive changes they have undergone in the course of evolution
Molecular Evidence – how DNA, RNA & proteins play a role in evolution. Organisms are similar but at a molecular (genetic) level, differences are observed.

74. Comparative Embryology - comparison of the development of embryos of two or more species
Geographic Isolation - Separation of populations of a species by geographic means (distance, mountains, rivers, oceans, etc.) that lead to reproductive isolation of those populations.
Speciation - The formation of new and distinct species in the course of evolution

75. Extinction – no longer in existence
Extinction – no longer in existence All individuals are deceased (dead)
Biodiversity - degree of variation of life forms within a given ecosystem, biome, or on an entire planet.
Variation - different or distinct form or version of something

76. Pattern variation in the harlequin ladybird

77. Fitness - An organism's ability to survive and reproduce in a particular environment
Phenotype – physical characteristics. what an organism looks like as a consequence of the interaction of its genotype and the environment
Genotype - The set of genes possessed by an individual organism.

78. Inheritance - Acquiring traits/genes from one's parents
Inheritance - Acquiring traits/genes from one's parents. Traits such as eye color or hair color are inherited from a parent through genes.
Vestigial structures - Nonfunctional remains of organs that were functional in ancestral species and may still be functional in related species.
Examples:
Pelvis & femur in whales
dew claws on dogs

79. Homologous structures - organs or limbs differ in form or function, but contain SAME basic structures
Turtle leg, alligator leg, bird wing, human finger all have similar bone structure and likely all came from a specific ancient fish fin

80. Recipe for evolution!
cipe/

81. Peppered Moth Activity
Explanation: 3_moth_change.swf
Simulation:
/pepperMoths.swf

82. Natural selection simulation
Butterfly island!
ain.html
No where to hide! nowherehide/