The study of Biology lecture 1.3

Science as a process Uses an organized approach to learn how the natural world works. Uses an organized approach to learn how the natural world works. Principle: (a) events have natural causes Principle: (a) events have natural causes (b) Uniformity: the laws of nature act the same everywhere (b) Uniformity: the laws of nature act the same everywhere fertilization Where stars are born

Owl experiment Question: do owls hunt by hearing? Question: do owls hunt by hearing? Hypothesis: an if…….then statement Hypothesis: an if…….then statement Prediction: what will happen if the H. is true? Prediction: what will happen if the H. is true? Experiment: independent variable: light/dark Experiment: independent variable: light/dark Dependent variable.: distance from owl’s strike to mouse Dependent variable.: distance from owl’s strike to mouse Analyze data: owls hunt by sound in the dark, by sight in the light Analyze data: owls hunt by sound in the dark, by sight in the light Communicate results: paper, internet, peer review Communicate results: paper, internet, peer review

Compound light microscope To see cells, small organisms To see cells, small organisms Eyepiece: X10 Objective lenses: X 10- X60 Stage: supports the slide Light: illuminates from below

Magnification Increases in the object’s apparent size Increases in the object’s apparent size Multiply eyepiece X lens Multiply eyepiece X lens 10X 60 = 600X 10X 60 = 600X Resolution Clarity of image, ability to show detail Clarity of image, ability to show detail Breast cancer cells Onion membrane

Electron microscopes Shoots a beam of electrons at a sample Creates black & white images (colored later) Creates black & white images (colored later) SEM: gives 3D pictures of surfaces of cells, 100,000X magnification SEM: gives 3D pictures of surfaces of cells, 100,000X magnification TEM: scans slices of specimens 200,000 X magnification 200,000 X magnification Hydrothermal worms: FEI scanner Plant cell

Metric system Measurement system used by all scientists Measurement system used by all scientists Based on powers of 10 Based on powers of 10