Biology It Begins Chp 1 pg 2 31

+ Biology… It Begins! Chp 1, pg 2 -31

+ Why is biology important? n Questions you’ve asked yourself? n Why can birds fly? n How do I work? n What makes me who I am? n How did life begin? n All things biology tries to answer. n Unfortunately, biology cannot answer all of these.

+ Some disclaimers n NOT a collection of never-changing facts. n As technology opens up new possibilities, more in-depth experimenting can occur. n Facts are observable, repeatable, and testable. n If these steps cannot be done, and inference is made. n Theories are well-tested explanation that unifies many observations and hypotheses. n Though theories may be the dominant view among the majority of scientists, no theory is considered absolute truth.

+ Some disclaimers n New evidence can revise or replace a theory with a more useful explanation. n Open-mindedness is important. We must always be questioning and be able to accept new evidence. n Science is subject to biased, based on what scientist want to believe. n Do not just take your teachers word for it! Do your own research!

+ What science is and is not… n Goals of science: n provide natural explanations for events in the natural world. n use those explanations to understand patterns in nature and to make useful predictions about natural events.

+ The scientific method n Observing n Making and asking questions inferences and forming hypotheses n Conducting n Collecting n Drawing controlled experiments and analyzing data conclusions.

Observing and Asking Questions n Begin with observation - act of noticing and describing events in a careful, orderly way. n For example, researchers observed that marsh grass grows taller in some places than others. This observation led to a question: Why do marsh grasses grow to different heights in different places?

Inferring and Forming a Hypothesis Scientists use observations to make inferences - logical interpretations based on what is already known. n Inference lead to a hypothesis - a scientific explanation for a set of observations that can be tested in ways that support or reject it. n n Based on their knowledge of salt marshes, they hypothesized that marsh grass growth is limited by available nitrogen.

Designing Controlled Experiments Design experiment that keeps track of Variables - various factors that can change. n Examples of variables include temperature, light, time, and availability of nutrients. n n n In the hypothesis and experiment, only one variable is changed. All other variables should be unchanged, or controlled. This type of experiment is called a controlled experiment.

Controlling Variables The variable that is deliberately changed is called the independent variable (also called the manipulated variable). n The variable that is observed and that changes in response to the independent variable is called the dependent variable (also called the responding variable). ** n

Control and Experimental Groups n n Two groups: control & experimental groups. Control group - does not receive the independent variable. Experimental group receives the independent variable. Which is the control? Experimental?

Designing Controlled Experiments For example, researchers selected plots of grass with similar plant density, soil type, and input of freshwater. n The plots were divided into control and experimental groups. n Which plot receives the independent variable? n Added nitrogen fertilizer (the independent variable) to the experimental plots. n Observed the growth of marsh grass in both experimental and control plots. n What is the dependent variable? n Amount of growth n

Collecting and Analyzing Data n n Collect data – information from recorded observations Two types: Quantitative data - numbers obtained by counting or measuring. n Ex) number of plants per plot, plant sizes, and growth rates. Qualitative data - descriptive and involve characteristics that cannot usually be counted. n Ex) foreign objects in the plots, or whether the grass was growing upright or sideways.

Data

Drawing Conclusions n Use experimental data as evidence to support, refute, or revise the hypothesis being tested, and to draw a valid conclusion. n Conclusion: Nitrogen helps these marsh plants grow.