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Understanding Scientific Methods in Biology: Controlled Investigations and Field Studies

Learn about the two basic methods used in biological studies - controlled investigations in labs and field studies, and how they are applied to solve problems in living things. Explore examples, the scientific design process, and steps to test solutions effectively.

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Understanding Scientific Methods in Biology: Controlled Investigations and Field Studies

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  1. Scientific methods are used to study living things

  2. Two Basic Methods • Controlled Investigation • Field Study

  3. Controlled Investigation • Usually done in the lab • Has only 1 manipulated variable • Scientist tries to keep all things the same EXCEPT the manipulated variable

  4. Example of a Controlled Investigation How does amount of water affect growth of sunflower plants over a 3 month period? • Manipulated Variable: Amount of water • Responding Variable: Growth of sunflower plant • Controlled Variables: size of pot, type of soil, amount of light, type of plant

  5. Field Study • Can be done in the lab or out of the lab • Scientist aims to test how a manipulated variable affects a responding variable OR aims to understand why a phenomena is occurring • Not all variables can be controlled

  6. Example of a Field Study How does type and amount of vegetation affect reproductive rates of desert tortoises? • Manipulated: type AND amount of vegetation • Responding: Number of eggs per spring • Controlled: Type of tortoise • CAN NOT CONTROL: Temperature, Rainfall, Soil type, Location, Elevation, Land disturbance

  7. Sometimes data collected indicates a problem Example: Marbled Murrelet (a bird) populations are declining in California. Example: Desert Tortoise populations are declining

  8. Biologists will often try to figure out how to fix a problem This is done using the Scientific Design Process

  9. Scientific Design Process • Identify a problem • Gather information about the problem (this can include data already collected) • Explore Ideas to solve problem • Choose a plan to solve problem • Write steps to do plan including a way to measure it’s effectiveness • Make a diagram of the plan

  10. Example of Scientific Design Process • Problem: Marbled Murrelet populations are falling • Gather information about the problem: Ask a scientist: Where do they live? Where do they eat? What do they eat? Observe murrelets for a month and record what their predators are. • Explore Ideas to solve problem: plant more trees for nests, make more parks, educate public about predators so predator populations will decline • Choose a plan to solve problem: Educate public about predators so that we can keep predators away from Murreletsso that Murrelet population will increase • Make a diagram of your design solution: NEXT SLIDE! • Write steps to do plan: NEXT SLIDE! • Scientifically test solution: NEXT SLIDE!

  11. Steps to do the plan • Create signs about predators of Murrelets • Make sure signs tell visitors that birds attracted to picnics and trash (ravens, crows, jays) prey on Murrelet eggs • Post signs in areas where Murrelets have their nests • Diagram Test Solution • Count and record the number of predators in nesting area before and after education plan to measure effectiveness of plan

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