The Science of Biology

1. The Science of Biology Fred Searcy Broward Community College

2. How Do We Make Discoveries In Science? • Thought Processes • Inductive Reasoning • Deductive Reasoning

3. Inductive Reasoning • Reasoning from the specific to the general • Today, the sun rose in the east • Yesterday, the sun rose in the east • The day before yesterday, the sun rose in the east • Conclusion - the sun rises in the east.

4. Deductive Reasoning • Reasoning from the general to the specific • Syllogism - the simplest form of deductive thought processes • A syllogism consists of • major premise • minor premise • conclusion

5. Syllogism • Major Premise: • All naval officers must pass a test for color blindness • Minor Premise: • Robert Smith is a naval officer • Conclusion:? • Robert Smith passed a test for colorblindness

6. Is the Conclusion Valid? • For the conclusion to be valid, the major and minor premises must be “true” • What is truth? • Agreement with fact • Caution: What is true today may not be true tomorrow.

7. In 1694, Nicolaas Haratsoeker described what appeared to be “animalcules” in the sperm of humans and other animals. This tiny human inside sperm was called the homunculus. From the National Library of Medicine, “Essay de dioptrique”, Paris, 1694, p. 230.

8. New Syllogism • Major Premise: • All men are strong • Minor Premise: • William is a man • Conclusion? • Conclusion: • William is strong

9. Which Form of Reasoning Do Scientists Use? • Inductive? • Deductive? • Both • Primarily, scientists use inductive thought

10. Scientific Method • Recognize a problem • Collect data • Organize data • Put forth a hypothesis • Test the hypothesis(variables)(controls)

11. An Example of How Scientific Method Has Been Used • 1981, CDC Atlanta received five requests for the drug pentamidine isothionate • this drug, at the time, was solely administered by the CDC • used to treat an extremely rare type of pneumonia caused • by Pneumocystis jiroveci (formerly carinii), a protozoan • between 1967 and 1979, only 2 previous requests for the drug Pneumocystis jiroveci (formerly carinii). Photo courtesy of Centers for Disease Control & Prevention, National Center for Infectious Diseases,Division of Parasitic Diseases.

12. CDC knew the drug was mostly used for transplant patients whose immune system had been artificially depressed to allow transplant to take • these five requests were not transplant patients • was there a unifying factor with these five?

13. About same time, CDC received an increase in reports of a rare form of cancer, Kaposi’s sarcoma • found usually in Jews of eastern Mediterranean origin • also transplant patients • 26 cases reported in a 30 month span

14. When CDC investigated, they wished to find a common thread among all these cases • Upon checking with the sources of the reports, most of these people were dead • In the U.S. eventually, most of these cases were traced to male homosexuals • 1982 confirmed three patients with hemophilia having P. jiroveci • 1983, two cases of heterosexual IV drug users

15. Recognize A Problem • People are dying of what are seemingly opportunistic infections (normally harmless) where the immune system seems to be depressed • This appears to be an acquired immune deficiency • What can cause a healthy person’s immune system to become artificially depressed?

16. Agents of Disease • Environmental factors • Protozoans • Bacteria • Viruses • today we know of prions

17. Collect Data • Reports coming into CDC • Pneumocystis jiroveci • Kaposi’s sarcoma • lymphadenophathy • diffuse, undifferentiated non-Hodgkin’s lymphoma • thrush (Candida albicans) • encephalopathy Kaposi’s sarcoma. Image courtesy of Dermatlas.com

18. Collect Data • Cases diagnosed in 1981, 92% deceased as of 1988 • homosexual or bisexual men • heterosexual IV drug users • hemophiliacs • heterosexual men and women

19. Organize Data • CDC served as clearing house • Koch’s postulates • isolate a single organism common only to diseased individuals • inoculate healthy individuals with proposed disease causing agent • if healthy individual comes down with the disease, that is the disease causing agent. Robert Koch (1843-1910) Image courtesy of the Library of Congress. Image: LC-USZ62-43604 (b&w film copy neg.)

20. What Is the Causative Agent? • Protozoans? • Bacteria? • Viruses? • 1980 Robert Gallo of National Institute of Health, isolated first human retrovirus: human T-lymphotrophic virus type I (HTLVI) • retroviruses reverse the usual flow of genetic information from DNA-->RNA-->protein • retroviruses are RNA viruses

21. Retroviruses • HTLVI infects white blood cells and cause adult T-cell leukemia • Gallo also isolated HTLVII (causes hairy-cell leukemia • 1983 Gallo and/or Luc Montagnier of Pasteur Institute claim HTLVIII as causative agent of AIDS • Virus later renamed to Human Immunodeficiency Virus (HIV)

22. Hypothesis • HIV is the causative agent of AIDS

23. Test the Hypothesis • ? • Any volunteers to be injected with HIV? • How do you test the hypothesis? • Animal models • Which animal? • Best is chimpanzee • share 99% of our genome with chimp

24. Is HIV the Causative Agent of AIDS? • Peter Duesberg, UC Berkeley says no • Shyh-Ching Lo (Armed Forces Institute of Pathology) replicates symptoms with mycoplasmas

25. Who Should Consider Themselves in the High Risk Category? • homosexual or bisexual men • heterosexual IV drug users • hemophiliacs • heterosexual men and women • you

26. Safe Sex • Hugging • petting • light kissing

27. Possibly Safe • Sexual intercourse with condom • Condom with nonoxyl-9

28. Unsafe Sex • Any sexual intercourse without condom • Any exchange of bodily fluids (semen, saliva, tears, blood)

29. Charles Goodyear • Crude rubber • ultraviolet light • vulcanization of rubber • sulfur and heat Charles Goodyear (1839-1930) Image courtesy of the Library of Congress. Image: LC-USZ6-7162 (b&w film copy neg.)