The Scientific Study of Life: Life in the Trees and the Scope of Biology

1. CHAPTER 1Introduction: The Scientific Study of Life Modules 1.1 – 1.3

2. Life in the Trees • The lives of gray-headed flying foxes are closely entwined with the lives of the eucalyptus trees that form their habitat • Eucalyptus trees provide food and roosting sites for the flying foxes • Flying foxes aid in eucalyptus pollinationand help disperse the resulting seeds

3. Flying foxes are becoming an endangered species, partly because of habitat destruction

4. THE SCOPE OF BIOLOGY • Biology is the scientific study of life • Interactions between different kinds of organisms affect the lives of all • Recall the example of flying foxes and eucalyptus trees

5. 1.1 Life’s levels of organization define the scope of biology • A structural hierarchy of life, from molecules to ecosystems, defines the scope of biology • An ecosystem consists of: • all organisms living in a particular area • all nonliving physical components of the environment that affect the organisms (soil, water)

6. ECOSYSTEM LEVELEucalyptus forest • Ecosystems include: • all the organisms in an area, which make up a community • interbreeding organisms of the same species, a population • At the top of life’s hierarchy is the ecosystem COMMUNITY LEVELAll organisms ineucalyptus forest POPULATION LEVELGroup of flying foxes ORGANISM LEVELFlying fox Brain Spinal cord ORGAN SYSTEM LEVELNervous system ORGAN LEVELBrain Nerve TISSUE LEVELNervous tissue CELLULAR LEVELNerve cell MOLECULAR LEVELMolecule of DNA Figure 1.1

7. organ systems • organs • tissues • cells • molecules ECOSYSTEM LEVELEucalyptus forest • Organisms are made up of: COMMUNITY LEVELAll organisms ineucalyptus forest POPULATION LEVELGroup of flying foxes ORGANISM LEVELFlying fox Brain Spinal cord ORGAN SYSTEM LEVELNervous system ORGAN LEVELBrain Nerve TISSUE LEVELNervous tissue CELLULAR LEVELNerve cell MOLECULAR LEVELMolecule of DNA Figure 1.1

8. THE PROCESS OF SCIENCE 1.2 Scientists use two main approaches to learn about nature • In discovery science, scientists describe some aspect of the world and use inductive reasoning to draw general conclusions • Example: scientists have described how newborn flying foxes cling to their mother’s chest for the first weeks of life Figure 1.2

9. They propose a hypothesis • They make deductions leading to predictions • They then test the hypothesis by seeing if the predictions come true • In hypothesis-driven science, scientists use the “scientific method”

10. 1.3 With the scientific method, we pose and test hypotheses Observation • The main steps of the scientific method Question Hypothesis Prediction Test does notsupport hypothesis; revise hypothesis or pose new one Test supports hypothesis; make additional predictions and test them Test: Experiment oradditionalobservation Figure 1.3A

11. If a hypothesis is correct, and we test it, then we can expect a particular outcome • Case study: flashlight failure • Deductive reasoning is used in testing hypotheses Figure 1.3B

12. Control groups must be tested along with experimental groups for the meaning of the results to be clear • Experiments designed to test hypotheses must be controlled experiments

13. Case study: spider mimicry Figure 1.3C Pounce rate (% of trials in which spider jumped on fly) Control group(untreated flies) Experimental group(wing markings masked) Figure 1.3D

14. Another test of the spider mimic hypothesis: wing transplants Number of stalk andattack responsesby spiders Wingmarkings Wingwaving Normalspidermimic Mimic withmimic wing transplant Mimic withhousefly wing transplant Housefly withmimic wing transplant Normalhousefly Figure 1.3E Controls Experimentals