1. Darwin’s Theory of Evolution
Chapter 15

2. The Puzzle of Life’s Diversity
Biological Diversity – the variety of living things
- describes the millions of different shapes, sizes & habitats on Earth
Evolutionary Theory – a possible answer to explain the diversity of living things
- a collection of scientific facts, observations, and hypotheses.

3. Evolution Change over time
The process by which modern organisms have descended from ancient organism

4. Charles Darwin Born in England on Feb. 12, 1809
(same day as A. Lincoln)
In 1831, he set sailed on the H.M.S Beagle for a trip around the world

5. Darwin’s Observations
Patterns of Diversity:
1. plants and animals seem remarkably well adapted to whatever environment they inhabit (live)
2. organisms have many different ways to survive & produce offspring
3. certain animals were only found on specific continents, even though other continents had similar environments .

6. Darwin’s Observations
Living Organisms and Fossils:
1. Darwin collected many fossils:
- preserved remains of ancient organisms
2. he realized that some resembled living organisms and others looked completely unlike any other creature.
3. These fossils made Darwin wonder how so many species disappeared & if they were related to living things now

7. Charles Darwin

8. Galapagos Islands Small group of islands located off S. America
Very different climates even though there are close together
Darwin used his observations from these islands to create his Theory of Evolution
He studied land tortoises & marine iguanas and observed differences between each island
Most importantly he studied birds called a Finch and observed and analyzed their differences in their beaks

9. Land Tortoises of the Galapagos Islands.
Pinta
Tower
Pinta Island Intermediate shell
Marchena
James
Fernandina
Santa Cruz
Isabela
Santa Fe
Hood Island
Saddle-backed shell
Floreana
Hood
Isabela Island
Dome-shaped shell

10. Land Tortoises

11. Land Iguana

12. Marine Iguanas

13. Marine Iguanas

14. Galapagos Islands from Space

15. H.M.S. Beagle

16. Finches

17. Finches

18. Finches

20. The Journey Home
Upon returning to England, Darwin thought about his observations & asked himself 3 very important questions:
1. Were the animals living on the different islands once members of the same species?
2. If they were, how did these species evolve after being separated onto the different islands?
3. If they did evolve (change) how did they do it?

21. Ideas that Shaped Darwin’s Thinking
Before Darwin’s time, most Europeans believed that Earth and all life forms:
1. were created only a few 1000 years ago
2. had not changed since creation
During Darwin’s life, a lot of evidence was discovered to change this way of thought
This made Darwin dramatically change his way of thinking.

22. An Ancient, Changing Earth
During the 18th and 19th centuries, scientists recognize:
1. Earth is millions of years old
2. processes that changed Earth in the past are the same processes that are happening today
James Hutton
Charles Lyell
Jean Baptiste Lamarck
Thomas Malthus

23. James Hutton - 1795 He believed:
1. geological forces have shaped Earth
2. Earth was made of layers of rocks that form very slowly
3. rocks move up by forces beneath the surface & others are buried & others are pushed up to make mountains
4. outer layer is shaped by natural forces – rain, wind, heat & cold temperatures
5. All of these processes operate extremely slow – over millions of years
6. Concluded that Earth is millions of years old

24. Charles Lyell Wrote book called “Principles of Ecology”
Darwin read it when on the Beagle
He stressed that scientists must study past events to understand the events they are observing now
His work explained how geological features could be build up & broken down over long periods of time
It also helped Darwin understand how important geological phenomena is on the location and findings of fossils

25. Jean Baptiste Lamarck French scientist who was one of the first to:
1. recognize that living things have changed over time
2. all species were descended from other species
3. organisms somehow adapted to their environments
Lamarck’s work was published in 1809, the same year Darwin was born

26. Lamarck’s Evolution Hypothesis
He proposed that by:
1. use or disuse of organs, organisms gained or lose certain traits during
their lifetime.
2. These traits could then be passed on to their offspring
3. Over time, this process led to change in a species

27. Tendency Toward Perfection
Lamarck proposed that all organisms have an innate tendency toward complexity & perfection.
As a result, living things are always changing & acquiring new traits to help to adapt & survive

28. Use and Disuse
Lamarck proposed that organisms could change the shape and size of certain organs by using their bodies in new ways
If the organism used a new part of body, it would develop into a new structure
If the organism disused the part of body, it would decrease in size and over many generations disappear.

29. Inheritance of Acquired Traits
Lamarck thought that acquired characteristics could be inherited
Acquired Characteristics – traits you gain from your own experiences and training
Example – if you spent your life lifting weights to build your muscles, then your children would inherit big muscles too!

30. Evaluating Lamarck’s Hypothesis
Incorrect in many ways:
1. He did not know how traits are inherited
2. He did not know that an organism’s behavior has no effect on its inheritable characteristics
** Lamarck was the 1st to develop a hypothesis of evolution & to realize that organisms can adapt to their environment.**

31. Thomas Malthus Important influence on Darwin
In 1798, Malthus published a book that stated:
“If the human population continued to grow unchecked, sooner or later there would be insufficient living space & food for everyone”
He felt that the only forces that could fight against this were: war, famine, & disease

32. Darwin’s Thoughts on Malthus
He realized Malthus’ ideas applied to plants and animals even more
Because animals & plants can reproduce much faster & more numbers than humans
What Darwin did not realize at this time was:
1. majority of offspring die
2. only a few survive long enough to reproduce themselves
** Trying to figure out why the above occurs was the central idea behind his explanation of evolutionary change.**

33. When Is a Flipper a Wing?
All living things are related. Some relationships are easy to see—your pet cat may not roar like a lion, but it clearly resembles one. Other relationships are less obvious.

34. 1. In your notebook, construct a table that has 5 columns & 6 rows
1. In your notebook, construct a table that has 5 columns & 6 rows. In the columns, write the following headings:
Animal Group, Example, Legs, Fins, and Tail.
Then, place the following animal groups in their own row: Mammal, Bird, Fish, Amphibian, Reptile, and Insect.
2. Give one example for each group, and then fill in the information for that example.
For Legs, write in the number of legs that each animal has.
Do animals with fins have legs?
Do animals with wings have legs? If so, how many?
3. Can you tell from your table if a fish is more closely related to a bird or to an amphibian? Explain your answer.

35. Animal Example Legs Fins Tail
Mammal
Bird
Fish
Amphibian
Reptile
Insect

36. Mammal Bird Fish Amphibian Reptile Insect
Animal Example Legs Fins Tail
Mammal
elephant 4 No
Yes
Bird
Seagull 2
Fish
Shark
Amphibian
Frog
Yes/no
Reptile
Turtle
Insect
Ant 6

37. Darwin Presents His Case
It took 25 years for Darwin to present his
Theory of Evolution
1859 – “On the Origin of Species”
This book proposed:
1. a mechanism for Evolution called
Natural Selection
2. Evolution has been taking place for millions of years & continues today

38. Details of the Origin of Species
Inherited Variations – differences that are passed from parents to offspring
- Darwin had no idea how it happened
- We now know it is caused by variations in genes
- variations are found in both wild and domesticated living things

39. Artificial Selection
When nature provides the variations and humans select specific variations that they find useful
Produces many diverse domestic animals & plants
Example – breeding only the fastest horses

40. The Struggle for Existence
Darwin was convinced that Artificial Selection worked in nature.
He knew that:
↑ birth rates & ↓ of basic needs = competition of resources
Struggle For Existence:
Members of each species regularly compete for the necessities of life
Ex. Faster, bigger predators catch more prey
Faster, camouflaged, & protected prey will not be eaten

41. The Struggle for Existence (cont.)
Key Factor – how well suited an organism to its environment
Fitness – ability of an individual to survive & reproduce in its own environment
**the ability to ADAPT = ↑ FITNESS**

42. Adaptations
Any inherited characteristics that increases an organisms chance of survival
3 types:
1. Anatomical – porcupine develops sharp quills
2. Physiological – plants being able to make own food
3. Behavioral – living in groups & hunting

43. Survival of the Fittest
Individuals with traits that are not well suited to their environment (low levels of fitness) will die or leave few offspring
Individuals with traits that are well suited to their environment (adaptations that enable fitness) will survive & reproduce successfully
Darwin referred to Survival of the Fittest as
NATURAL SELECTION because it has similarities to Artificial Selection.

44. Natural Selection Traits being selected increase over time
Contribute to an organism’s fitness in its environment
Over time, it results in changes in the inherited traits of a population
Can only be observed as changes in a population over many successive generations
Cannot be seen directly

45. Descent with Modification
Each living thing has descended with changes from other species over time
Species today look different from their ancestors
Natural selection over long periods of time, produce organisms with:
1. different structures
2. occupy different habitats
3. establish different niches
(place on the food web)
Also implies that all living organisms are related to one another

46. Common Descent
All species – living and extinct – are from common ancestors
A single “Tree of Life” links all living things

47. Evidence of Evolution
Darwin argued that living things have been evolving on Earth for millions of years.
Evidence for this process could be found in the:
1. fossil record
2. the geographical distribution of living species
3. homologous structures of living organisms
4. similarities in early development, or embryology

48. Fossils Record Darwin saw fossils as a record of the history of life
By comparing fossils in older layers with ones from younger layers, we can document the indeed life has changed over time
Transitional Fossils (between modern & ancient species) have shorten the gap between the two
Gaps in the fossil record point out uncertainties in our understanding of exactly how some species evolved.

49. Geographical Distribution of Living Things
Similar animals in different locations were the product of different lines of evolutionary descent
However, because some animals on each continent were living under similar ecological conditions, they were exposed to similar pressures of natural selection
Because of this, different animals ended up evolving certain common features.

50. Figure 15–14 Geographic Distribution of Living Species
Section 15-3
Beaver
Beaver
Muskrat
Beaver and Muskrat
Coypu
Capybara
Coypu and Capybara
NORTH AMERICA
Muskrat
Capybara
SOUTH AMERICA
Coypu

51. Homologous Body Structures
Structures that have different mature forms but develop from the same embryonic tissue
Evidence of evolution can also be found in living animals
This provides strong evidence that all 4-limbed vertebrates (has a backbone) have descended, with modifications, from common ancestors
Vestigial Organs – homologous organs that have been reduced in size – resemble miniature legs, tails, or other structures. Does not effect the organisms ability to survive or reproduce.

52. Figure 15–15 Homologous Body Structures
Turtle
Alligator
Bird
Mammals
Typical primitive fish

53. Similarities in Embryology
Embryos of many animals with backbones are very similar
Embryos look especially similar during early stages of development
The same group of embryonic cells develop in the same order and in similar patterns to produce tissues and organs
These common cells & tissues, growing in similar ways, produce the Homologous Structures

54. Strengths & Weaknesses of Evolutionary Theory
Scientific advances in biology, geology and physics, have confirmed and expanded most of Darwin’s hypotheses.
Today, evolutionary theory offers great information to all biological and biomedical science.
Evolution is known as the “great unifying theory of the life sciences”

55. Strengths & Weaknesses of Evolutionary Theory
Like any theory, it continues to change as new data is gathered & new ways of thinking come about.
Researchers still debate:
1. how new species arise
2. why species become extinct
3. how life began

56. Summary of Darwin’s Theory
Page 386 – copy the 5 main points into your notebook.