Invitation to Biology. Chapter 1

Transcription

1 Invitation to Biology Chapter 1

2 How to Learn Biology 10 percent of what they read 26 percent of what they hear 30 percent of what they see 50 percent of what they see and hear 70 percent of what they discuss with others 80 percent of personal experience 90 percent of what they say as they do it 95 percent of what they teach Most importantly, students learn when they are inspired. How can I inspire you to success in this course?

3 The Scope of this Course Approximately what do we cover in this course, and in what order? 1. Cell structure and function 2. Cell division and inheritance 3. Evolutionary processes

4 Cell Structure and Function Major cellular structures Chemistry and organic molecules of life Cell membranes and enzymes Cellular energy photosynthesis and respiration Major types of biological molecules

5 Cell Division and Inheritance Cell divisions mitosis and meiosis Genetics and inheritance Human inheritance Human genetic diseases DNA and protein synthesis The full human chromosome set XX

6 Evolutionary Processes History of evolutionary ideas Microevolution changes in the genetic makeup of populations within a species Speciation development of new species through deep time The continents have moved, making the modern Earth look totally different than it did in ancient times

7 Biology 101, 102, 103 How are these courses related to each other?

8 What Makes up Living Things? The elements (atoms) The molecules - some very complex The major structures, cellular organelles Finally, the cells themselves, the fundamental units of life

9 Living Cells Eukaryotic cells Plant cell Animal cell Prokaryotic (bacterial) cell

10 The Nature of Living Things What are 10 (more or less) attributes that living things have, that distinguish them from inanimate objects, such as rocks?

11 5 Characteristics of Life All living things are composed of one or more cells Living things are highly organized Living things grow and reproduce They contain genetic information in the form of DNA They pass heritable information from one generation to another

12 5 More Characteristics of Life They carry out metabolism (chemical transformations) They maintain a state of homeostasis They respond to their surroundings They adapt in the short term (individuals, during their lives) They evolve in the long term (alterations in a species over many generations)

13 Biology: Scientific Study of Life We have now discussed the question, what is life? However, what is science? How does the scientific method work?

14 What are five major steps in the scientific method?

15 The Scientific Method in Action Observations, Questions Results and Analysis Hypotheses Experimental Tests Testable Predictions Apply for money Be awarded research grants Do the work Publish results

16 Early Example of Scientific Approach Childbed fever scourge of maternity wards Bacteria infected mothers bloodstreams during childbirth, high fatality rates 1840s: Ignaz Semmelweis managed two maternity wards in Vienna hospital Ward 1: medical students, high infection rate Ward 2: midwives, low infection rate Why?

17 Cause of the High Infection Rates Idea of microbes causing disease not known Medical students studied human anatomy by performing autopsies Then delivered babies without washing hands! One doctor cut his hand during an autopsy, later died from childbed fever A very important clue in the medical mystery

18 Test of an Idea Semmelweis thought that cadaver matter might spread the disease Ordered doctors to sanitize hands after autopsies Cut infection rate to same low rate as in Ward 2 (midwives)

19 What were the Scientific Steps? Two observations: Women died after being treated by doctors doing autopsies; so did doctor who cut himself during autopsy Hypothesis: Something from the cadavers causes the disease Prediction: Sanitation will prevent disease Test the prediction: Sanitize hands Analysis of results: The prediction was true!

20 A Scientific Mystery: Sickle-Cell Anemia Sickle-cell anemia: causes normal red blood cells to become rigid, elongated, stick together Blood cells clump, plug small blood vessels Organ damage and death can result What causes the disease (and a much more common, but much less severe form called sickle-cell trait)?

21 Human Blood Cells Normal red blood cell Sickle cell

22 Sickle-Cell Trait, Where it Exists

23 Causes of Sickle-Cell? What are some possible causes of sickle-cell anemeia (and the much more common, though less harmful, sickle-cell trait)? Genetic reasons that is, some people inherit the disease from their ancestors? Infectious disease, caused by an organism such as a type of bacteria? Caused by environmental factors? How would we tell?

24 A Clue: The Historic Range of Malaria Malaria parasites inside red blood cell

25 Solution to the Mystery In a population has some people with sicklecell anemia, there are always a much larger number of people with sickle-cell trait. Sickle-cell trait provides resistance against malaria, a very deadly infectious disease Thus, in places with a high incidence of malaria, sickle-cell trait provides some compensating protection against it Protection comes at the expense of the unlucky few with sickle-cell anemia

26 Role of Experiments in Science Used to study a phenomenon under known conditions Allows you to test whether a hypothesis may be correct Scientific conclusions should always be considered tentative more data could still overturn a well-established idea

27 A Possible Experiment Suppose the following: You walk out to your car this morning and it will not start How would we design and carry out an experiment to test the cause of the car not starting?

28 Observation Auto will not start Hypothesis 1 battery dead Hypothesis 2 ignition is a problem Hypothesis 3 out of gas Experiment turn on headlights Experiment Check gas gauge Experiment long stick into tank

29 Analysis headlight shine brightly Analysis gauge says half tank but no stick on gas Analysis strong ignition spark Principle generalized gas gauge is not accurate, car needs gas

30 Experimental Design Control group and treatment group Control gives a standard for comparison Control group receives a fake drug (placebo), people don t know which is which Identical to treatment group, except for variable being studied Groups should be large (to improve precision), and randomly chosen from the larger population (prevents skewing of results)

31 Hypothesis vs. Theory A hypothesis is an educated guess that needs to be thoroughly tested A theory is an explanation that has passed many tests (theory is much more mature than a hypothesis) A theory has wide-ranging explanatory power Examples: Cell theory of life Germ theory of disease Theory of evolution