CHAPTER 1 – THE SCIENCE OF BIOLOGY

1-1 What is Science

The goal of science is to investigate and understand nature, to explain events in nature, and to use those explanations to make useful predictions.

Science is an organized way of using evidence to learn about the natural world. Science deals with the natural world. Scientists collect and organize information in a careful, orderly way, looking for patterns and connections between events Scientists propose explanations that can be tested by examining evidence

Science starts with observation. Observation – involves using one or more of the senses – sight, hearing, touch, smell, and sometimes taste – to gather information Data – the information gathered from observations There are two types of observations: quantitative and qualitative Quantitative observations – involve numbers (counting or measuring objects) Qualitative observations- involve characteristics that can’t be easily measured or counted (color or texture)

It is important to understand what has been observed. Scientists follow observations with inferences. Inference – a logical interpretation based on prior knowledge and experience Hypothesis – a possible explanation for a set of observations or an answer to a scientific question. Scientists test their hypotheses to see if they are correct or not. A few hypotheses may be made and as evidences is collected, the incorrect hypotheses can be rules out and the correct explanation would eventually be found.

1-2 How Scientists Work

Designing an Experiment About 2300 years ago, the Greek philosopher Aristotle made extensive observation of the natural world. People used to think that living things can be brought into being from non-living things (ex – maggots) About 400 years ago, some people began to challenge these ideas. They also began to use experiments to answer their questions about life.

Stating the Problem For many years, observations seemed to show that some living things could just suddenly appear (maggots on meat, mice on grain, beetles on cow dung). People were curious and wondered how these events happened.

Forming a Hypothesis For years, people accepted the fact that living things can form from non-living things. Scientists gave a name to it – spontaneous generation In 1668 Francesco Redi, an Italian physician, proposed a different hypothesis, that flied laid eggs on the meat too small for people to see. So, his hypothesis was that flies produce maggots. His next step was to test his hypothesis.

Setting Up a Controlled Experiment Testing a hypothesis involves designing an experiment. Variables are the factors that can change (ex – equipment used, type of material, amount of material, temperature, light, and time) Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged, or controlled. This is a controlled experiment

Manipulated variable or Independent Variable – the variable that is deliberately changed Responding variable or Dependent Variable – the variable that is observed and that changes in response to the manipulated variable (the outcome) Redi made a prediction that keeping flies away from meat would prevent the appearance of maggots. To test this hypothesis, he did the following:

His investigations showed that maggots appeared on the meat in the control jars. No maggots appeared in the jars that were covered.

It is important for scientists to keep written records of their observations, or data so that other scientists can see their work. It is important for other scientists to repeat experiments to make sure the same results are produced.

In 1864, a French scientist, Louis Pasteur, did an experiment to settle the question of spontaneous generation. He showed that all living things come from other living things. This change in thinking caused a major shift in the way scientists viewed living things.

How a Theory Develops Theory – a hypothesis that becomes well supported because of numerous observations A theory enables scientist to make accurate predictions about new situations

1-3 Studying Life

Biology – the study of life. It’s the science that seeks to understand the living world.

Characteristics of Living Things Living things are made up of units called cells. A cell is a collection of living matter enclosed by a barrier that separates the cell from its surrounds. They are the smallest units of an organism Living things reproduce. Sexual reproduction – two cells from different parents unite to produce the first cell of the new organism Asexual reproduction – the new organism has a single parent Living things are based on a universal genetic code Living things grow and develop Living things obtain and use materials and energy Living things respond to their environment Living things maintain a stable internal environment (homeostasis) Taken as a group, living things change over time (evolution)

Branches of Biology The many levels at which life can be studies include molecules, cells, organisms, populations of a single organism, communities or populations living in the same area, and the biosphere.

1-4 Tools and Procedures

Tools play a major role in science. Electronic balances, microscopes, telescopes, and computers are just a few of the things that help scientists make important observations and collect data.

A Common Measurement System Most scientists use the metric system when collecting data and performing experiments. Metric system – a decimal system of measurement whose units are based on certain physical standards and are scaled on the multiples of 10.

Graphs can help scientists analyze data. It can make a pattern much easier to recognize and understand.

Microscopes – devices that produce magnified images of structure that are too small to see with the unaided eye Light microscopes produce magnified images by focusing visible light rays. Electron microscopes produce magnified images by focusing beams of electrons.

Laboratory Techniques Biologists use a variety of techniques to study cells. Two common laboratory techniques are cell culturing and cell fractionation. Cell cultures – biologists sometimes place a single cell into a dish containing a nutrient solution. The cell reproduces so that a group of cells, called a cell culture, develops from the single original cell. Cell Fractionation – a procedure used to separate the different cell parts.