Biology The Science of Life

Themes of Biology The World of Biology Scientific Methods Microscopy and Measurement

Themes of Biology Biology is the study of all of the many kinds of organisms that have ever lived on the Earth. Biology studies the structures present in living things and their functions, but it also studies the interactions between living things and the nonliving world. That’s a lot to study! The complex science of biology is unified by six recurring themes: 1. Cell structure and function 2. Stability and homeostasis 3. Reproduction and inheritance 4. Evolution 5. Interdependence of organisms 6. Matter, energy, and organization

Cell Structure and Function

Stability and Homeostasis Living things are highly ordered. The Second Law of Thermodynamics says that disorder increases as time passes. To stay alive, living things must expend energy to maintain their order and stability. This is the process of homeostasis.

Reproduction and Inheritance All living things produce offspring that are like themselves. All living things pass on certain characteristics to their offspring. Laws of Inheritance control which traits are passed on and how.

Evolution Living things change over time. Species become extinct and new species appear. All living things are related to each other. Populations that are best suited to their environment are more likely to survive. Original Ancestor Eubacteria Archaea Protista Fungi Animalia Plantae

Interdependence of Organisms Living things affect the environment and each other.

Matter, Energy, and Organization Atoms and Molecules Cells Tissues and Organs Organ Systems and an Organism

The World of Biology All living things are made of cells. All living things are highly organized all the way to the molecular level. All living things use energy to break apart or to build molecules that they need to survive. This process is called metabolism. All living things keep their internal conditions constant. This ability is called homeostasis. All living things grow by the process of cell division. Since no living thing lives forever, all living things must reproduce, either asexually or sexually. All living things share certain characteristics that separate them from nonliving matter:

Scientific Methods of Biology State the problem. All scientific investigations begin with a question that the scientist wants to answer. Gather background information. Scientists study what others have already learned about the problem. Form a hypothesis. A scientist then decides on a possible answer to the problem that can be tested. Test the hypothesis. The fun part of science is designing and performing an experiment to test the hypothesis. Gather and organize data. Scientists write their observations and measurements in charts, tables, or graphs to make them easier to study. Analyze data and form conclusions. Was the hypothesis supported by the data? Where do you go now?

State the Problem When a scientist observes something that is interesting or doesn’t seem to make sense, he/she puts it in the form of a question. That’s the beginning of the search for the answer. Why is the sky blue? How do ants know where to go to find food? Why do toadstools in the woods grow in a circle? Why does poop smell bad? Why can’t fish breathe air?

Gather Background Information Once the scientist has put the problem in the form of a question, the next step is to find out everything that other people have already found out about that question.

Form a Hypothesis After researching the problem thoroughly, the scientist thinks he/she knows an answer to the problem. This idea is the hypothesis. The hypothesis may be right or wrong. The scientist won’t know until the hypothesis has been tested!

Test the Hypothesis The scientist designs and performs an experiment to see if the hypothesis is the correct answer to the problem being investigated.

Gather and Organize Data During the experiment, the scientist makes careful observations and measurements about what is happening. The observations and measurements are often put in a chart, a table, or a graph.

Analyze Data and Form Conclusions Finally, when the experiment is complete, the scientist has to decide if the data that was collected supports the original hypothesis. If it does not support the hypothesis, the scientist may look for sources of error, repeat the experiment, or change the hypothesis to fit the data.

Controlled Experiment – Part 1 Many times, biologists perform controlled experiments. In a controlled experiment, two groups of samples are always used: the control group and the experimental group. The two groups are exactly alike in all of the factors that can be changed except one. A controlled experiment can only test one variable at a time. The factors that are alike in both groups are called controls, and the factor that is different in the two groups is called the independent variable. The results of the experiment (the dependent variable) are analyzed, conclusion are drawn, and the results are shared with other scientists.

Controlled Experiment – Part 2 A model is an explanation that is supported by data that has been gathered. Scientists have made a model of the structure of an atom by studying how atoms behave. An inference is a conclusion made because of known facts but without direct observation. If you see smoke, you know there is a fire, for example. A theory in science is not just a guess, but is a broad statement of what is thought to be true. It is based on the data from many many experiments and often ties together several related hypotheses. The theory of relativity, the atomic theory, and the theory of evolution through natural selection are current examples of scientific theories. Scientists have several ways to figure out what their data means:

Microscopy A compound light microscope is used in the classroom to see most organisms you will examine. You will need to know the parts of the microscope and how to use them. Dissecting microscopes will also be used in the classroom. Biologists also use electron microscopes, which magnify objects much more than light microscopes and show tiny structures with excellent resolution, but cannot view living things. There are two kinds of electron microscopes: TEM and SEM. Microscopes are used to view small structures in detail. The increase in size is called magnification. The ability to show detail clearly is called resolution. The quality of a microscope depends on its resolution, as well as its magnification.

Compound Light Microscope eyepiece body tube nosepiece low power objective fine adjustment coarse adjustment arm base medium power objective high power objective stage clip stage light source with condenser slide with specimen

Measurement Length (m) – meter Mass (kg) – kilogram Volume (l) – liter Time (s) – second Temperature ( o C or K) – degree Celsius or Kelvin Mega (M) – 1,000,000 x ___ Kilo (k)– 1,000 x ___ Centi (c) – 0.01 x ___ Milli (m) – x ___ Micro (μ) – x ___ Nano (n) – x ___ Scientists use a standard system of measurement called the metric system or SI Units. Commonly used metric units are listed below. Prefixes are added to make smaller or larger units, as needed. The most common prefixes are also shown below.

Scientific Notation Scientists use scientific notation to write numbers that are either very large or very small. 241,000,000 can be written as 2.41 x can be written as 2.41 x ,600,000 = _______ 1,050 = _______ 7,080,100 = ______ 290 = _______ = _______ = _______ = _______ = _______ = _______ = _______

Working with Scientific Notation When numbers in scientific notation are multiplied, the exponents are added. (2.4x10 3 )(1.5x10 2 )=3.6x10 5 (4.0x10 -3 )(2.0x10 2 )=8x10 -1 ) When numbers in scientific notation are divided, subtract the exponents. (8.8x10 6 )/(4.0x10 3 )=2.2x10 2 (5.0x10 -2 )/2.5x10 -5 )=2.0x10 3 When adding or subtracting numbers written in scientific notation, the numbers must have the same exponent. 8.44x10 4 = 84.4x x10 3 = - 3.8x x x10 4 = 2100x x10 2 = + 21X x10 2