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“Survival of the Fittest”

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1 “Survival of the Fittest”
Changes through time Photos (L to R): 1. African lion attempting to take down a cape buffalo as an example of a predator-prey relationship. The traits of those who survive long enough to reproduce are those past on to the next generation while the traits of those who do not survive are not past on. This is the basis for natural selection – or “survival of the fittest.” 2. A Colorado Potato Beetle. Populations of the potato beetle have become resistant to certain pesticides. This is an example of changes in populations occurring within our lifetime. 3. Fossil of a fish found in the Green River formation near Kemmerer, Wyoming. The fossil record provides much detail on how populations have changed over time. “Survival of the Fittest”

2 Evidence that life has changed and is now changing
Images: Left to right Layers of sedimentary rock show relative position of fossils near Lake Powell, UT Trilobite fossil from Utah Shale – Millard County, UT. Trilobites once inhabited much of Utah and are now extinct. Antibiotic resistance in bacteria is an example of change in populations observed in our lifetime. There has been much concern recently about “super bugs” such as antibiotic resistant staph infections contracted in hospitals.

3 Fossil Record Fossils are remains or traces of organisms that lived in the past. Photo: Dinosaur fossils in the Morrison Formation, Dinosaur National Monument near Vernal, UT

4 Fossil Record Fossils are usually found in sedimentary rock.
Organisms are buried soon after death and the hard parts become fossilized. Photos: Dinosaur tracks at Dinosaur Discovery site, Johnson Farm, St. George, Utah, UT. Copyright Calvin Hamilton. Used with permission. Additional photos can be found at

5 Fossil Record Fossils indicate a great deal about the actual structure of the organisms and their environment. Left: Morrison Formation in Utah near Dinosaur National Park.  Steeply dipping sandstone and shale beds are seen in the picture. Right: Navajo Sandstone Formation viewed from Hidden Canyon Trail, Zion National Park.

6 Types of fossils Petrified Bones
Photos (Left to Right): Petrified bones from Dinosaur National Monument near Vernal; Allosaurus (“Al”) mold at the College of Eastern Utah Prehistoric Museum in Price.

7 Types of fossils Imprints
Dinosaur imprints from San Rafael Swell – Buckhorn Wash near Castledale, UT

8 Types of fossils Molds/Casts
Left to Right: Fossil mold found near Provo, UT; Cast Fossil of Cephalopod

9 Fossils preserved in tar, amber, or ice
Types of fossils Fossils preserved in tar, amber, or ice Left to Right: Saber-toothed cat fossil from the La Brea Tar Pits in Los Angeles; Insect preserved in amber; Remains of a man from stone age found preserved in a glacier in the Alps; Columbian Mammoth Fossil found in Huntington Canyon near Price, UT. It had been preserved in ice cold mud.

10 Relative Age of Fossils
Layering of fossils: Older fossils are found in the lower levels of sediment

11 Relative Age of Fossils
Layering of fossils: Newer fossils deposited on top of older fossils and sediment Sometimes flipped by earthquakes, etc.

12 Relative Age of Fossils

13 Relative Age of Fossils
Fossils in each layer usually of those organisms that lived at the time the layer was formed. Fossils in lower layers represent species that lived earlier than those found in the upper layers. Relative position only tells which are older and which younger.

14 Evolution of the Horse Over time (higher layers of sediment) horse fossils became larger Separate toes became a single-toed hoof Teeth became adapted to grinding grasses

15 Radiometric Dating Some elements, such as uranium, undergo radioactive decay to produce other elements. Scientists have observed that radioactive elements (isotopes) decay at a constant rate over time

16 Radiometric Dating The amount of radioactive elements remaining in a rock can help scientists determine how much time has elapsed since the rock was formed and cooled. Common isotopes used for long-term dating (old rocks) include uranium as it decays to lead, and potassium as it decays to argon. The carbon-14 isotope can be used for dating of more recent fossils and artifacts

17 Radiocarbon Dating Carbon-14 is a radioactive isotope found in all living organisms. It decays at a known rate. Carbon-12 does not decay. By comparing the ratio of C-12 to C-14 scientists believe they can determine the age of a fossil

18 Radiocarbon Dating

19 A timescale Based on radiometric data, scientists have proposed a timeline for the history of the earth. Composed of four primary “eras” Archeozoic (oldest) [aka Precambrian period] Paleozoic Mesozoic Cenozoic (most recent)

20 Contemporary Changes Evidences we can observe within our lifetime
Pesticide resistance in insects Pictures (L): Diamondback moth developed resistance to Bacillus thuringiensis (Bt). The Colorado Potato Beetle has developed resistance to certain pesticides.

21 Contemporary Changes Evidences we can observe within our lifetime
Antibiotic resistant bacteria Pictures: “Superbugs” are becoming more of a concern as bacteria are found, primarily in hospitals, that are resistant to antibiotics.

22 Indirect evidences Scientists cite these indirect evidences as evidence of common ancestry Homologous structures Embryonic development patterns Biochemical evidence Vestigial organs They at least demonstrate a common pattern of development

23 Parts of the body with similar structure (homologous)
Human Cat Whale Bat

24 Similar patterns of embryonic development (homologous)
Human Swine Reptile Bird Yes, you had a tail as an embryo!

25 Homologous Development – actual photos of embryos
Reptile Bird Rabbit Human

26 Biochemical similarities – DNA and Proteins
The ability to analyze individual biological molecules (DNA and proteins) has provided evidence for biochemical similarities

27 Methods of Change

28 Jean Baptiste Larmarck
French naturalist and evolutionary theorist Proposed the inheritance of acquired characteristics Based on an “inner need” to change

29 Larmarck’s theory His theory was disproved

30 Charles Darwin and Natural Selection (1859)
Naturalist on the HMS Beagle

31 Charles Darwin and Natural Selection (1859)
Exploration of South America (3 ½ years) Visited the Galapagos Islands

32 Darwin’s theory of Natural Selection
Living things increase in number geometrically (overproduction) There is no net increase in the number of individuals over a long period of time Spider eggs: Many more produced than will survive

33 Darwin’s theory of Natural Selection
A “struggle for existence” since not all individuals can survive No two individuals exactly alike (variation)

34 Darwin’s theory of Natural Selection
In the struggle for existence, those variations which are better adapted to their environment leave behind them proportionately more offspring than those less adapted “Survival of the Fittest”

35 A Modern Perspective Mutation – a sudden change in the genetic material (a source of variation) Example: The DNA of one bacteria changes (becomes mutated), allowing it to become resistant to an antibiotic. It survives long enough to reproduce. Each succeeding generation has the mutated copy and is resistant to the antibiotic.

36 A Modern Perspective Recombination of genes within a population (sexual reproduction) Provides new combinations for natural selection to try. Shows how the percentage of a gene in a population can change.

37 A Modern Perspective Isolation – separation of a population from others of the same kind (species) Prevents recombination of genes Species become different overtime Example: A species of primrose existed together where the Promontory Range (Northern Utah) now exists. When the range lifted up, it isolated two groups. Both became different as they adapted to the different environments on either side of the range. They have become so different they can no longer reproduce.

38 A Modern Perspective Natural Selection – certain traits give an adaptive advantage to organisms and they leave behind more offspring They survive long enough to reproduce and pass on their genetic information INDIVIDUALS DO NOT EVOLVE . . . POPULATIONS EVOLVE OVER TIME

39 Species A group of individuals that LOOK similar and are capable of producing FERTILE offspring in the natural environment.

40 Population All of the members of the same SPECIES that live in particular AREA at the same TIME.

41 Variation in a population
Bell Curve - The distribution of traits (Average is the middle.) Mode - The number that occurs most often (High pt.) Range - The lowest number to the highest number


43 Sexual Selection Preferential choice of a MATE based on the presence of a specific trait

44 The formation of new SPECIES
Speciation The formation of new SPECIES

45 Separation of a formerly successful BREEDING population
Isolation Separation of a formerly successful BREEDING population

46 Separated PHYSICALLY from each other
Geographic Isolation Separated PHYSICALLY from each other

47 Reproductive Isolation
Can no longer produce FERTILE offspring

48 When an entire SPECIES dies off.
Extinction When an entire SPECIES dies off.

49 The collection of GENES for all of the traits in a POPULATION
Gene pool The collection of GENES for all of the traits in a POPULATION

50 Hardy-Weinberg Principle
Genetic Equilibrium – no CHANGE in the gene pool

51 Conditions that must exist for genetic equilibrium

52 Natural Selection Three types of selection 1. Stabilizing Selection 2. Directional Selection 3. Disruptive Selection

53 Stabilizing Selection
Individuals with the AVERAGE form have the ADVANTAGE Example – lizards that are small are not fast enough to avoid predators; lizards that are large cannot hide easily from predators; those of average size are both fast enough to get away from predators and small enough to hide – giving them the selective advantage.


55 Directional Selection
Individuals with one of the EXTREME forms have the ADVANTAGE Example – Peppermoth in Great Britain during the industrial revolution – “melanistic” (dark colored) moths had the selective advantage after trees where covered in coal soot. After air quality improved, the selection advantage returned to the lighter colored moths.

56 Directional Selection
Peppermoth – find two moths per picture

57 As the ants dig deeper, anteaters with longer tongues have the adaptive advantage – survive to reproduce.

58 Disruptive Selection Individuals with either of the EXTREME forms have the ADVANTAGE Example: a shellfish living in shallow ocean water is preyed upon by a bird. Originally those with the neutral color (sand colored) had the advantage because they were camouflaged in the sand. As the birds fed on the shellfish and left their feces behind in the water, the ocean floor became white in color. Those shellfish that were sand colored are now easily found while the lighter colored shellfish are able to blend in, as are the darker colored shellfish if they are found on the darker rocks.


60 How have crops and livestock changed over the last 50 years?
In producing better livestock or crops, what are some examples of traits for which producers select?

61 Then

62 Now

63 Then

64 Now

65 Then

66 Now

67 Then

68 Now

69 Then Removing Seeds

70 Now Seedless

71 Then Dehorning

72 Now Polled

73 Natural Selection an organisms’ ability to SURVIVE and pass on its GENETIC information to its offspring.

74 Selective Breeding Also known as Artificial Selection
Human control over organisms passing on their genetic information. Human determination of those crops and livestock allowed to reproduce Based on desired traits

75 Selective Breeding In what ways is selective breeding similar to natural selection? In what ways is it different?

76 Archeozoic Era Oldest known rocks and fossils
Animals without backbones Jelly-fish, worms, sponges Bacteria and blue-green algae

77 Paleozoic Era Estimated from 248-550 million years ago
Animals: Fish, amphibians, and insects Plants: Algae and simple plants; first conifers

78 Mesozoic Era Estimated from 65-248 million years ago
Age of the Dinosaurs Animals: Reptiles and birds Plants: Conifers and first flowering plants

79 Cenozoic Era Estimated from present to 65 million years ago
Age of the Mammals Animals: Mammals and birds Plants: Flowering plants

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