Scientific Method - Biology - Lecture Slides, Slides of Biology

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Biology and the “Tree of Life”

 How does science work?

 “Scientific Method”

 Observation  Hypothesis –  Predictions and Experiments  Conclusions  Publication

Scientific Method

 Propose a question

 Observation – Statements determined by using the senses.

Scientific Method

 Hypothesis – “either of a suggested explanation for a phenomenon (an event that is observable),or of a reasoned proposal suggesting a possible correlation between multiple phenomena.”

 Hypothesis – “a provisional idea whose merit requires evaluation”

Scientific Method

 Propose a question

 Observation – Statements determined by using the senses.

 Make one or more hypothesis.

 Predict an outcome from the “guess” or hypothesis. (Also a “null” hypothesis)

Experimental Design

 Experimental Design  Examine one variable at the time. A variable is a factor that can be changed or that may be different among the samples.  Include one or more controls.  Negative control does not contain the variable and tests for the effects of other factors that may influence the outcome of the experiment.  Positive control(s) contain the variable and tests the measurement method.  Repeat the experiment to verify results.

What is a Theory?

What is a Theory?

 Common usage: a “guess” or a “hunch”

 Scientific usage: a testable model built on observation of phenomena, and capable of predicting future occurrences of the same type.

 Some are verifiable -

4 Key Theories in Biology

 Cell theory

 DNA provides the molecular basis of inheritance.

 Theory of evolution

 Evolution involves the conservation of certain characteristics.

Cell Theory - History

 Robert Hook and van Leeuwenhock

 Constructed microscopes  Examined specimens and discovered “cells” and “animalcules”.

 Evidence accumulated from other scientists resulting in the “cell theory”.

Cell Theory

 What is a cell?

 Highly organized compartment, bounded by a thin flexible structure called a cell membrane.  Contains all of the chemicals components necessary for life.  Chemical reactions maintain chemical content and provide energy and structure.

Spontaneous Generation?

 Where do cells come from? Other cells

Next Theory - Evolution