Biol 1107 Chapter 1I. Biology – science of lifeA. What is life? 1. Characteristics of all living thingsa. Made of cells – basic unit of organisms i. May be unicellular – ex, bacteriaii. May be multicellular – ex, us, trees, antsb. Living things grow – size and/or number of cells increasei. May grow continuously – ex, treesii. May only grow during a short period – ex, animalsc. Have metabolisms – sum of all the chemical reactions in the organismi. Energy is essential for life- needed to maintain function, grow, repair, etc.ii. Metabolism is carefully controllediii. Must maintain homeostasis – balanced internal environmentd. Respond to stimuli – changes in internal or external environmenti. Stimuli include light, sound, temperature, chemicals, etc.ii. Response always involves some sort of movement- Not always visible or large scalee. Organisms reproduce – make more of themselvesi. May be asexual – one parent gives rise to identical offspring- Ex, bacteria, some plantsii. May be sexual – two parents give rise to non-identical offspring- Ex, almost all animals, most plantsf. Organisms evolve – populations change over time to become better adapted to their environmenti. Ex, thick layers of blubber on animals that live arctic regionsii. Adaptations come in different forms- Structural – ex, spines on cactii- Physiological/biochemical – lizards secrete nitrogenous waste as a dry paste- Behavioral – most desert animals are inactive during peakdaylightB. Life requires constant energy input1. Most originates from the suna. Some bacteria and archaea are exceptions2. Autotrophs produce food from simple ingredientsa. Also called producersi. Plants, algae, some bacteriab. Most use photosynthesisi. Capture light energy to make chemical bondsii. CO2 + H2O  sugar + O23. Heterotrophs breakdown food made by autotrophsa. Also called consumersi. Animals, fungi, most bacteriab. Usually use cellular respirationi. Chemical bonds are broken to release energyii. Sugar + O2  CO2 + H20c. Producers also use cellular respiration4. Uses for energya. Make building blocksb. Maintain homeostasisc. Growthd. Repaire. Movementf. etc.C. Life requires a lot of information1. Organisms have to do a lot of complex things just righta. Requires accurate and timely information2. Information must be transmitted internallya. Very important in multicellular organismsi. Endocrine system uses hormonesii. Nervous system uses electrical impulses and chemicalsb. Have to coordinate activities3. Information is transmitted between individualsa. May be same or different speciesb. May be chemicals, sounds, visual displays, etc.i. Animals marking territory with scentsii. People talking4. Information must be transmitted between generationsa. Extremely important that it be accurateb. Information is stored as a chemicali. DNA – deoxyribonucleic acidii. DNA is the building block for genes- genes are individual pieces of information c. DNA is passed from parent to offspringi. Carries information on how to do all the life processesD. Evolution is the central underpinning of biology1. Theory of evolution explains how populations of organisms have changed over timea. Over time, populations adapt to their environmenti. Adaptations always come from changes in the DNA information ii. Evolution is the accumulation of adaptations2. Evolution is driven by natural selection – mechanism by which beneficialtraits become more common in populations over timea. Four basic observations support thisi. Individuals of a species have variationii. Organisms produce more offspring than will survive toreproduceiii. Organisms compete for resources- Helpful adaptations make for better competitors- Better competitors are more likely to survive and reproduceiv. Survivors pass on their adaptations to offspring- Over time, larger and larger part of the population has the adaptationII. Biology uses the scientific methodA. Systematic process with defined steps1. Observation – closely examine something a. Formulate a question2. Hypothesis – come up with a plausible explanationa. Look into what others have foundb. Adapt existing information to your scenario3. Experiment – test your hypothesis a. Must set up experiments properlyi. Controls, large sample size, repeatable, etc.4. Analyze – does experimental data support or reject hypothesis?a. Reject – go back to step 2 and alter or replace hypothesisb. Support – test hypothesis in new ways to see if it still holdsB. A hypothesis can never be proven true1. Always possible some new experiment will reject ita. Scientists try to prove hypotheses false2. The more times a hypothesis stands up to experiment, the more trust is placed in it3. Very strong hypotheses may become part of a theoryC. Theory – an integrated explanation of something in the natural world1. Based on numerous well-tested hypothesesa. Note the difference between the scientific use and popular culture usageof theory3. When we talk about the theory of evolution:a. It’s an integrated explanation of a natural phenomenoni. ie, species change over timeb. Based on many well-tested hypothesesi. Better adapted individuals reproduce moreii. DNA stores informationiii. DNA passed to offspringiv. Good adaptations become more