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Nature of Science.

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Presentation on theme: "Nature of Science."— Presentation transcript:

1 Nature of Science

2 Science T/F Science is a system of beliefs.
Scientists rely heavily on imagination to carry out their work. 3. Scientists are totally objective in their work

3 Science T/F 4. The scientific method is the accepted guide for conducting research. 5. Experiments are carried out to prove cause-and-effect relationships.

4 Science T/F 6. All scientific ideas are discovered and tested by controlled experiments. 7. A hypothesis is an educated guess. 8. Scientific ideas are tentative and can be modified or disproved.

5 What is Science? It uses previous knowledge and theories to gain new knowledge and to produce new and better theories through observations of the natural world.

6 What is science? Science is a process to build understanding.
Example: The earth was once believed to be flat. Do we still think this today? Why?

7 What science is NOT? Is not a system of beliefs
Does not prove anything! It can only accept the best explanation at that time until it is disproved.

8 What science is NOT? Science cannot make decisions about morals, laws, literature, visual arts, music, etc. It cannot draw conclusions about things it cannot measure or manipulate.

9 Science as moral solution?
Can science offer a solution to whether stem cell research is right or wrong? NO! It can offer only information gained from research and observations in order for people to make their decisions.

10 Hypothesis, Laws, and Theories
Hypothesis: testable explanation based on previous observations Law: general statement that describes a natural phenomena Theory: explanation of how a law works

11 Laws and Theories Atomic Theory explains the Law of Conservation of Mass Chromosomal theory of inheritance explains the Law of Heredity

12 14.1 Darwin Developed a Theory of Evolution

13 I. Idea’s From Darwin’s Time
A. Evolution is all of the changes that have transformed life over time In the mid 1700’s George Buffon suggested that the Earth is older than 10,000 years old In the early 1800’s Jean Baptiste Lamarck developed the idea of Inheritance of Acquired Characteristics

14 II. The Voyage of the Beagle
A. In 1831 The HMS Beagle left England for a five year voyage around the world B. Darwin studied the geology, plants, and animals he encountered

15 III. Darwin’s Observations
A. Darwin maintained extensive journals of his observations, studies and thoughts Darwin noticed the animals and plants he observed were uniquely South American Darwin was especially intrigued by the Galapagos Islands because of their diversity

16 IV. Ideas from Geology A. Darwin read books from Charles Lyell that proposed Earth’s features today could be explained by geological processes B. From this Darwin made two conclusions 1. The Earth must be very old 2. Slow and gradual processes occurring over vast amounts of time could cause tremendous change

17 V. Darwin Publishes His Theory
A. Over many years after his return, Darwin developed his theory based on observations, inferences and ideas B. In 1844 Darwin wrote a 200 page essay that outlined his idea C. In 1859 Darwin released his findings to the public in the book The Origin of Species

18 VI. Darwin’s Two Main Points
A. Darwin’s first point was that the species of organisms living on Earth today descended from ancestral species, Descent with Modification B. Darwin’s second main point was that Natural Selection is the mechanism for evolution

19 Natural Selection

20 14.2 Evolution has left much evidence

21 I. The Fossil Record A. Preserved remains or markings left by organisms that lived in the past are called fossils B. The positions of fossils in the rock strata can reveal relative age C. The fossil record is this chronological collection of life’s remains in the rock layers

22 Fossil Formation

23 Fossil Evidence Basilosaurus

24 II. Geographic Distribution
A. The differences and similarities between organisms and different parts of the world shows how species today evolved from ancestral forms B. Geographic distribution gives clues as to how modern species evolved


26 III. Similarities in Structure
A. Similar structures in species sharing a common ancestor are called homologous structures B. Vestigial structures are remnants of structures that may have had important functions in an ancestral species, but have no clear function today

27 Homologous Structure

28 IV. Similarities in Development
A. Embryos of closely related organisms often have similar stages in development B. Comparing the development of organisms supports other evidence of homologous structures

29 Embryo Similarities

30 V. Molecular Biology The closer two organisms DNA sequence match, the closer the relationship DNA and protein analysis are new tools for testing hypothesis about evolution C. There is molecular evidence that there are common genetic codes shared by all species

31 Human DNA into Bacterial DNA

32 GFP in Mice

33 Similar Amino Acids

34 14.3 Darwin proposed natural selection as the mechanism of evolution

35 I. Darwin’s Theory of Natural Selection
A. A population is a group of individuals of the same species in the same area at the same time B. Populations in different areas become more and more different, leading to new species

36 II. Observations Lead to A Question
A. There are 13 species of finches unique to the Galápagos Islands B. They most closely resemble one finch species living on the South American mainland

37 III. More Observations Lead to an Idea
A. Darwin recognized that all species tend to produce excessive numbers of offspring B. Darwin also recognized there was variation among the individuals of a population

38 Stabilizing Selection

39 Directional Selection

40 Disruptive Selection

41 IV. Artificial Selection
A. Artificial selection is the selective breeding of domesticated plants and animals to produce offspring with traits that humans value B. You see this change in Dog’s over the last 500 years

42 Lion & Liger

43 Tiger and Tigon

44 Dog Breeding

45 Labradoodle

46 V. Pesticides-Natural Selection in Action
A. When a new pesticide is sprayed it will kill about 99% of the insects targeted B. As time goes on, more insects are resistant to the pesticide

47 Cockroaches

48 Pesticides- natural selection
C. This illustrates two key points about natural selection 1. natural selection is a “screening” of the traits available 2. natural selection favors those characteristics in a varying population that fit the specific current, local environment

49 Pesticide Resistance

50 Natural Selection

51 Necrotizing Fasciitis - NF

52 Opening the Wound

53 Draining the Wound

54 Closing the Wound

55 14.4 Microevolution is a change in a population’s gene pool

56 I. Populations and Their Gene Pools
A population is the smallest level at which evolution can occur The gene pool consists of all the alleles in all the individuals in a population

57 II. Changes in Gene Pools
A. Natural selection is not random B. Microevolution is a change in the frequencies of alleles from generation to generation C. The Hardy-Weinberg Equilibrium is when a populations gene frequencies are not changing, i.e. not evolving

58 Hardy-Weinberg p + q = 1 p =% of dominant allele (decimal)
q = % of recessive allele (decimal) R= 70% so p = 0.7 r = 30% so q = 0.3

59 Hardy-Weinberg p2 + 2pq + q2 = 1 p2= Homozygous dominant %
2pq = Heterozygous % q2 = Homozygous recessive %

60 p2 + 2pq + q2 = 1 p= q=0.3 So RR= 0.49 Rr = 0.42 rr = 0.09

61 III. Genetic Drift A. A change in the gene pool due to chance is called genetic drift B. The smaller the population the greater the impact C. The Bottleneck Effect is when a disaster reduces the size of a gene pool D. The Founder Effect is when a few individuals colonize a new habitat



64 Bottleneck Effect

65 Cheetahs

66 IV. Gene Flow and Mutation
A. The exchange of genes with another population is called gene flow B. A mutation is a change in an organism’s DNA

67 V. Natural Selection and Darwinian Fitness
A. Natural Selection is a blend of chance and sorting B. Darwinian Fitness is the contribution of one individual to the gene pool compared to others

68 VII. A Return to the Galapagos
A. Peter and Rosemary Grant have studied finches on Daphne Major in the Galapagos B. Their data has provided clear evidence of natural selection

69 Finches

70 Genetic Drift

71 14.5 Evolutionary Biology is important in health science

72 I. Natural Selection and Sickle Cell Disease
A. Sickle Cell disease is a recessive disorder which affects the shape of red blood cells at a ate of 1 out of 25 people in some African populations

73 Natural Selection and Sickle Cell Disease
B. Individuals with one copy of the allele are resistant to developing malaria C. Natural Selection has selected for those individuals which are resistant even with the negative affects of the sickle cell allele

74 Malaria Life Cycle

75 Distribution of Malaria

76 II. Evolution of Antibiotic Resistance in Bacteria
A. Antibiotics kill or slow the growth of bacteria B. An antibiotic will kill most of the bacteria in a population but leave those which are resistant behind soon a greater percentage of the bacteria is resistant to the antibiotic

77 Antibiotic Resistance in Bacteria
C. In New York City, there are strains of the bacteria which causes Tuberculosis which are resistant to all three antibiotics used to treat the disease D. The overuse of antibiotics is the speeding up the evolution of these strains

78 Flesh eating bacteria

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