1. Changes in Organisms Over Time1

2. Cosmos: Some things that Molecules do2
Unit Learning Goals
a. Trace the history of the theory.
b. Explain the history of life in terms of biodiversity, ancestry, and the rates of evolution.
d. Relate natural selection to changes in organisms.
e. Recognize the role of evolution to biological resistance (pesticide & antibiotic resistance).
c. Explain how fossil & biochemical evidence support the theory.
Cosmos: Some things that Molecules do

3. Where do I live? 4 What type of environment am I best “fit” for?
Hot/cold????
Wet/dry???
Why
Organisms have traits (GENES) that help them to survive in different environments.

4. A variation is a small change in a trait that makes an individual slightly different from other members of its species.
All organisms in a population are not the same. Variation/diversity exist.
What causes this variation??

5. What is Fitness? 5
Fitness is a measure of reproductive success. (survive long enough to reproduce)
Reproductive success: Having traits so that an organism is able to pass on genes onto the next generation (and in a way so that the next generation can also pass those genes on)
Any trait that promotes survival — at least until one's reproductive years are over — increases fitness.
Such traits are called adaptations.
GAME

6. What if an organism has a trait
What if an organism has a trait. that makes it impossible to live in its environment? 6
The organism will not survive.
If it does not survive— it CANNOT reproduce.
If it does not reproduce—its genes are not passed to the next generation.

7. What if the environment changes?7
If they do not have the traits (genes) that enable them to survive…they die, and DO NOT reproduce.
If they do have the traits, then they survive…and reproduce.
SO… the next generation has more of the “fit” traits for THAT environment.
The population then CHANGES!
This is a very slow process….does not occur over night…many generations must past before any change in the population can be seen.
Natural Selection

8. Current Theory … Natural Selection8
Also know as “survival of the fittest.”
Only certain members of the population will survive and reproduce.
Ones that survive are most suited to the environment—they are the most fit!!.
survival of the fittest

9. Humans have been doing this for 1000s of years!9
Artificial selection provides a model that helps us understand natural selection. People have been artificially selecting domesticated plants and animals for thousands of years.
Broccoli and brussels sprouts bear little superficial resemblance to their wild mustard relatives (left).

10. Humans select and breed for certain traits.
Dog Breeds
Corn
Pigs
Humans select and breed for certain traits.
Examples: The largest hog, the cow that gives the most milk, fastest horse, or cutest dog.

11. Where do NEW traits come from?10
Where do NEW traits come from?

12. How do new traits arise? Mutations. Sexual Reproduction. 11
Mixing of genes makes new combinations
A combo of traits may be necessary for survival……so… sexual reproduction and crossing over can create new combination of traits.

13. Decent with modifications12
Overtime natural selection produces organisms that have different structures, established different niches, or occupy different habitats.
Organisms that were once the same have now grown “apart” and have become different organisms.
These changes increase a species’ fitness in their environment.

14. These traits will be passed on to the next generation. 13
THE BASICS: A review
ADAPTATIONS (traits) that are favorable become more prevalent within that population.
These traits will be passed on to the next generation.
The GENE POOL of a population CHANGES in favor of the “FITTEST” phenotype & genotype!!!

15. Environment selecting “good” traits for THAT environment.
Natural
Selection
Examples 14

16. Example: Peppered Moth15
Two versions of the moth-
Black and peppered
During the industrial revolution on England
Population of moths changed

17. 16

18. the larger birds were favored over the smaller ones
From 1976 through 1977, a severe drought struck an island in the Galapagos. 17
Sampling the birds that died as well as those that survived showed that
the larger birds were favored over the smaller ones
those with larger beaks were favored over those with smaller ones.
of Small beaks
Beak length (mm)
Beak depth (mm)
Dead birds
10.68
9.42
Survivors
11.07
9.96
Some phenotypes are more fit than others when it comes to competing for resources. The more “FIT” phenotype will survive and have the possibility of passing its alleles to the next generation.

19. 18

20. 19

21. 20
History
Review Clip

22. History 21
James Hutton Proposed that the Earth is millions of years old.
Many land formations took millions of years to form.
Known as the founder of modern geology.

23. History Thomas Malthus -1798-22
Thomas Malthus
Proposed that populations outgrew their food supplies, causing competition between organisms and a struggle for one species to survive against another
This "struggle for existence" drives population change.

24. History Jean-Baptiste Lamark -1809-23
Jean-Baptiste Lamark
Believed that all life forms evolved and that the driving force of evolution was the inheritance of acquired characteristics.
He believed that organisms changed due to the demands of their environment.

25. What we understand now:24
What we understand now:

26. the present is the key to understanding the past25
Charles Lyell proposed that plant and animal species had arisen, developed variations, and then became extinct over time.
He believed that every animal or plant, including humankind, was adapted to the niche in which it was created.
the present is the key to understanding the past
He also believed that the Earth’s physical landscape changed over a long period of time.
15.1

27. Alfred Russel Wallace -185826
Alfred Russel Wallace -1858
Emphasis was based on the idea of competition for resources as the main force in natural selection.
Best known for independently proposing a theory of natural selection which prompted Charles Darwin to publish on his own theory
15.2

28. Charles Darwin -1859- Publishes “On the Origin of Species”27
Charles Darwin Publishes “On the Origin of Species”
Believed that Natural Selection is the driving force for evolution.

29. Charles Darwin British Naturalist 1809 -1882 28
“I have called this principle, by which each slight variation, if useful, is preserved, by the term Natural Selection.” —Charles Darwin from "The Origin of Species"

30. From 1831 to 1836 Darwin served as a naturalist aboard the H. M. S
From 1831 to 1836 Darwin served as a naturalist aboard the H.M.S. Beagle on a British science expedition around the world.
In South America Darwin found fossils of extinct animals that were similar to modern species.
On the Galapagos Islands in the Pacific Ocean he noticed many variations among plants and animals of the same general type as those in South America. 29
CLIP

31. Summary of Darwin’s Ideas30
Individual organisms differ, and some of this variation is heritable.
Organisms produce more offspring than can survive, and many that do survive do not reproduce.
Because more organisms are produced than can survive, they compete for limited resources.
Individuals best suited to their environment survive and reproduce most successfully.

32. Summary of Darwin’s Ideas31
These organisms pass their heritable traits to their offspring. Other individuals die or leave fewer offspring.
This process of natural selection causes species to change over time.
Species alive today are descended with modification from ancestral species that lived in the distant past.
This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life.
Review Clip

33. Evidence 32 Review Clip: 10min
Whale Video Clip- Intro to evidence ( Questions in packet)

34. Evidence for Change Over Time33
Fossil Record
Fossils that show how the same organism looked millions of years ago.
Paleontology
Use rock layers
1) Isotope dating
Clip

35. Fossil Record 34

36. 2) Relative Dating 35

37. 36

38. Homologous structures 37
Structures that have different mature forms in different organisms but have developed from the same type of tissue.

39. Homologous structures38

40. Analogous versus Homologous Structures

41. 39
Embryology
Early development of the organism

42. 40
Stages of Development

43. Vestigial organs 41
Organs or structures that do not seem to be used by the organism any longer.
They are usually reduced in size.

44. Vestigial Organs 42 c

45. DNA sequences in organisms are close 43
Genetics
DNA sequences in organisms are close
Sources of genetic variation in species:
Mutations
Gene Shuffling
Crossing over during meiosis
Sexual Reproduction
Things that cause change.
Why we are all a little bit different…

46. Genetic Comparison 44

47. The numbers represent the number of amino acid differences between the beta chain of humans and the hemoglobins of the other species.
In general, the number is inversely proportional to the closeness of kinship.

48. GEOGRAPHIC DISTRIBUTION45
Organisms that are related change/adapt according to their environment.

49. Adaptive Radiation 46
The evolution of many diversely adapted species from a common ancestor
Relatively rapid
Usually occurs when a population colonizes an area of diverse geographic or ecological conditions.
New niches
Each species becomes specialized for a different set of conditions

50. 47