Lecture 1


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Lecture 1

  1. 1. Lecture 1: Introduction and Scientific Method Covers Chapter 1.1, 1.3, 1.4
  2. 2. Organization of Matter • Elements: all matter is composed of substances called elements (ex: carbon, nitrogen, gold, silver, etc) • Atom: the smallest unit of matter in an element (ex: an atom of carbon, nitrogen, etc) • Molecules: two or more atoms bonded together. (ex: 1 carbon atom + 2 oxygen atoms = carbon dioxide) • MORE ABOUT ELEMENTS, ATOMS AND MOLECULES IN THE NEXT LECTURE!
  3. 3. Organization of Matter • Cell: basic unit of living organisms – Contains simple and complex ORGANIC molecules – Definition of “Organic”: a molecule that contains carbon • Tissues: a group of similar cells • Organs: collection of tissues that serve a common function • Organ systems (ex: CV system) • Organism/Individual
  4. 4. Copyright © 2011 Pearson Education, Inc. Figure 1-1 Levels of organization of matter
  5. 5. Organization beyond the individual* • Species: organisms of same type capable of interbreeding • Population: group of organisms of same species living in a given area • Community: collection of populations of DIFFERENT species that interact with one another • Ecosystem: a community and its nonliving environment • Biosphere: entire surface of Earth, including living and nonliving components
  6. 6. What is science? • “Organized enterprise that gathers knowledge about the world and condenses it into testable laws and principles.” • Biologists always want to answer questions, also known as “scientific inquiry”.
  7. 7. Scientific Inquiry is based on a small number of assumptions • Natural Causality: all events can be traced to natural causes • Natural Laws are timeless: always been that way and law applies everywhere (ex: gravity, evolution, etc) • People are able to perceive and measure events. These perceptions/measurements provide us with reliable objective information about the natural world. • Judgements about these events can differ as a result of cultural/religious beliefs (ex: evolution)
  8. 8. So how do biologists study life? • Answer: the scientific method! • Method for making observations of specific phenomena and searching for the order that underlies this phenomena • Example here:
  9. 9. Scientific Method* • 6 interrelated elements: – Observation – Question – Hypothesis – Prediction – Experiment or Observation – Conclusion
  10. 10. Copyright © 2011 Pearson Education, Inc. The car won't start. Why won't the car start? The car won't start because the battery is dead. Propose a new hypothesis. IF the hypothesis is correct, THEN the car will start if the battery is replaced. The battery is replaced. If the car doesn’t start: If the car starts: The dead battery hypothesis is supported. Observation Question Hypothesis Prediction Experiment or Observation Conclusion
  11. 11. Observation & Question • Maggots can be seen on rotting meat left out after a few days. • It was thought that the maggots came FROM the meat. (spontaneous generation). • However, Redi also saw flies swarming on the meat. • Question: COULD THE FLIES BE THE SOURCE OF THE MAGGOTS?
  12. 12. Hypothesis & Prediction • Hypothesis: A supposition (guess), based on observations, that is offered as an answer to the question or explanation for the observed phenomena. • To be useful, hypothesis must lead to a prediction. Expressed as if….then. – Ex: If the maggots came from the flies, then keeping the flies off the meat will prevent maggots.
  13. 13. Experiment and Observation • Experiments require controls: situations that keep untested variables constant – Put one piece of meat in an airtight container AND – Have one piece of meat left out (control) – All other variables are the same – (If he put one piece of meat in a container AND put that container in a bucket of ice, then he would be changing two variables.)
  14. 14. Copyright © 2011 Pearson Education, Inc. Experimental variable: gauze prevents the entry of flies Controlled variables: time, temperature, place Results Control situation Experimental situation Place meat in each jar Obtain identical pieces of meat and two identical jars Flies swarm around and maggots appear Leave the jar uncovered Leave exposed for several days Flies are kept from the meat; no maggots appear Cover the jar with gauze Leave covered for several days Experiment: Observation: Flies swarm around meat left in the open; maggots appear on the meat. Question: Where do maggots on the meat come from? Hypothesis: Flies produce the maggots. Prediction: IF the hypothesis is correct, THEN keeping the flies away from the meat will prevent the appearance of maggots. Conclusion: The experiment supports the hypothesis that flies are the source of maggots and that spontaneous generation of maggots does not occur.
  15. 15. Example in every day life • Car won’t start. • Battery dead? • If battery dead, then car will start with new battery. • Change battery (BUT DON’T CHANGE ANYTHING ELSE – STARTER, IGNITION COIL) • Car starts…it was the battery!
  16. 16. Use in medicine • Testing new drugs • Always a control and experimental group (try to get a large, broad experimental group so results can be applied to the WHOLE population) • But people differ in many environments (nutrition level, population density, access to clean water, etc). Best weapon against sampling error is large experimental group) • Placebos often used (fake pills) • Experiments can also be – Blind – Double blind To prevent bias
  17. 17. Conclusion • After experiment is done, then either – Accept hypothesis – Do not accept hypothesis (reject) • Accepted hypotheses must be repeatable and testable by many different scientists. If it continues to be accepted, eventually may become a common scientific theory. • If rejected, scientists may re-examine method and re-test with different parameters
  18. 18. Scientific Theories • As a result of scientific method, we now have many scientific theories: a general explanation for important natural phenomena that has been EXTENSIVELY TESTED AND REPRODUCED. Scientists believe these theories to be fact. • EX: law of gravity, atomic law, cell theory.
  19. 19. Cell Theory (COVERED Extensively in lecture 4) • The cell is the basic unit of life. • Cells have elaborate structures: – Genes: more about DNA later – Organelles: structures that perform specific functions (obtain energy, movement, making larger molecules) – Plasma Membrane – Nucleus
  20. 20. Copyright © 2011 Pearson Education, Inc.
  21. 21. Copyright © 2011 Pearson Education, Inc. mitochondrion cytoplasmic fluid flagellum vesicle ribosomes on rough ER centriole intermediate filaments (cytoskeleton) Golgi apparatus cytoplasm lysosome exocytosis of material from the cell polyribosome nuclear pore basal body nuclear envelope chromatin (DNA) nucleolus nucleus plasma membrane rough endoplasmic reticulum free ribosome smooth endoplasmic reticulum microtubules (cytoskeleton) microfilaments
  22. 22. What else characterizes living things?* • 1.) living things made of cells • 2.) organisms maintain homeostasis (body temp, etc.) Energy is used to maintain homeostasis. • 3.) living things respond to stimuli • 4.) Living things acquire materials (to grow and reproduce) • 5.) Living things grow • 6.) Living things reproduce themselves • 7.) Living things have the capacity to evolve • WE HAVE TO HAVE A WAY OF CATEGORIZING ALL OF THE LIFE FORMS ON EARTH.
  23. 23. Categorizing life* • 3 domains: – Bacteria – Archaea – Eukarya • First 2 are procaryotes (no nucleus-genetic material in cytoplasm) , made of simple, single cells (usually) • Eukarya has bodies composed of one or more complex cells. They are eucaryotes (membrane enclosed sac containing cell’s genetic material)
  24. 24. Copyright © 2011 Pearson Education, Inc. BACTERIA ARCHAEA EUKARYA animals fungi plants protists FIRST CELLS
  25. 25. Eukarya* • Further divided into: • Fungi • Plants • Animalia • Protists
  26. 26. Copyright © 2011 Pearson Education, Inc. Tree of life
  27. 27. Last way to categorize life* (how organisms get energy) • Autotrophs (Arch, bact, some protists) – Self feeding: photosynthesis – Convert inorganic carbon (CO2) to carbs, fats and proteins (organic carbons) to be used by them or ingested by heterotrophs • Heterotrophs(arch, bact, and eukarya) – Other feeding: need to eat other organisms to get energy. Cannot make their own carbs, fats, proteins. More about how WE get energy in Lecture 5?6?
  28. 28. Autotrophs & heterotrophs