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Chapter 1 The Science of Biology. 1–1 What Is Science?. Science is a process of inquiry , asking questions, the answers to which produce a body of knowledge, which is subject to change and revision .
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1–1 What Is Science? • Science is a process of inquiry, asking questions, the answers to which produce a body of knowledge, which is subject to change and revision. • The goal of science is to investigate and understand the natural world, to explain events in the natural world and to use those explanations to make useful predictions.
Science only deals with the natural world. Biology is a field in science that focuses on the study of life. • An understanding of science and the scientific approach is essential to making intelligent decisions.
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. Scientists try to explain events logically and analytically.
Scientific thinking begins with observation, the process of gathering information about events or processes in a careful, orderly way. • Observation generally involves using the senses, particularly sight and hearing. The information gathered from observations is called data. Data consists of observations that do not differ whether collected by one person or another.
Two types of data: • Quantitative data: expressed in numbers, obtained by counting or measuring. • Qualitative data: descriptive and involves characteristics that can’t usually be counted.
Scientists use data to make inferences, a logical interpretation based on prior knowledge or experience. • After initial observations, a hypothesis is proposed. A hypothesis is a proposed scientific explanation for a set of observations. • Scientific hypotheses must be proposed in a way that enables them to be tested.
Science is an ongoing process, knowledge is constantly being reevaluated, revised and updated because of new tools, techniques and discoveries. • Good scientists are skeptics, questioning existing ideas and new hypotheses. • Common steps for scientists to gather information and answer questions are known as scientific methods. Not every scientific investigation uses every method nor do all investigations lead to scientific theory.
1-2 How Scientists Work • While there are no fixed steps, generally the scientific method involves: • MAKE OBSERVATIONS: observations utilize the senses to gather information. Scientific discovery often takes place when a scientist observes something no one has noticed before.
ASK A QUESTION: observations may lead to unanswered questions. (Research may provide information about previous investigations of the question or suggest appropriate approaches to the problem.) • FORM A HYPOTHESIS: an explanation for a question or a problem that can be formally tested. A good hypothesis predicts a relationship between cause and effect.
SET UP A CONTROLLED EXPERIMENT: While we use the term experiment informally, a scientific experiment is an investigation that tests a hypothesis by the process of collecting information under controlled conditions. A controlled experiment involves two groups:
Variable (Experimental) group: test group that receives experimental treatment. A variable is the factor of an experiment that can change. In a controlled experiment, only one variable is tested at a time. There are three types of variables: • Controlled (constant) variables: same for both the control and variable group. • Manipulated (independent) variable: variable that is deliberately changed. • Responding (dependent) variable: changes in response to the manipulated variable (what happened).
Control group: group that receives no experimental treatment, the standard against which results are compared.
RECORD AND ANALYZE RESULTS: keeping a written record of observations and data. Data from an investigation can be considered confirmed only if repeating the investigation several times yields similar results. • DRAWING A CONCLUSION: Use evidence to determine whether the hypothesis was supported or refuted.
REPORTING RESULTS: Results are only useful if they are made available to other scientists for peer review. Other scientists can try to verify the results by repeating the procedure.
It is not always possible to do an experiment to test a hypothesis. • Alternative investigations may utilize fieldwork or surveys or large groups of subjects, controlling as many variables as possible. • As evidence accumulates from scientific investigations, a particular hypothesis may become so well supported that scientists consider it a theory. A theory is a well-tested explanation that unifies a broad range of observations. • No theory is considered absolute truth. As new evidence is uncovered, a theory may be revised or replaced.
1 – 3 Studying Life • The word biology means the study of life. A biologist is someone who uses scientific methods to study living things. • Describing what makes something alive is not easy. • No single characteristic is enough to describe a living thing. • Some non-living things share one or more traits with living things.
All living things show an orderly structure, known as organization. • Although living things are very diverse, they are all unified in having cellular organization. • A cell is a collection of living matter enclosed by a barrier (cell membrane) that separates the cell from its surroundings. • The cell is the lowest level of structure capable of performing all of the activities of life. • Cells are complex and highly organized despite their small size. • Unicellular organisms are living things that consist of only a single cell. • Multicellular organisms contain hundreds, thousands or even trillions of cells with a variety of shapes and sizes. Each type of cell is specialized to perform a different function.
All organisms produce new organisms (offspring) through a process called reproduction. • Reproduction is essential for the continuation of an organism’s species (group of organisms that can interbreed and produce fertile offspring in nature.) • There are two types of reproduction: • Sexual reproduction: two cells from different parents unite to produce the first cell of the new organism. Offspring differ from their parents in some ways. • Asexual reproduction: new organism has a single parent. Offspring and parents have the same traits.
The directions for inheritance are carried by a molecule called deoxyribonucleic acid (DNA). • Every organism, with a few minor variations, interprets the genetic code of DNA in the same way.
Growth is an increase in the amount of living material and the formation of new structures. • Growth can occur by increasing the size of a single cell or increasing the number of cells. • Development is all of the changes that take place during the life of an organism. • The development of specialized cells from a single fertilized egg cell is called differentiation, because the cells produced look different and perform different functions.
Organisms take in energy and transform it to do many kinds of work. • Organisms use a constant supply of materials and energy to grow, develop, reproduce, and stay alive. • The combination of chemical reactions through which an organism builds up or breaks down materials as it carries out life processes is called metabolism. • All organisms get the material they need from their surroundings, or environment. The way organisms obtain energy varies. • Plants, some bacteria and most algae obtain their energy directly from sunlight through photosynthesis. They convert light into a form of stored energy in molecules ready to be used when needed. • Other organisms rely on photosynthetic organisms for their energy by eating plants or indirectly by eating organisms that ate plants. Decomposers obtain energy from organisms that have died.
Organisms live in a constant interface with their surroundings, or environment, which includes other living organisms (biotic factors) as well as non-living factors (abiotic factors) like air, water, temperature and weather. • Anything in an organism’s external or internal environment that causes to react is a stimulus. A reaction to a stimulus is a response. • External stimuli, which come from the environment outside an organism, include light and temperature. • Internal stimuli come from within an organism. For example, trees that drop their leaves in the fall conserve water and avoid freezing during the winter.
Even though conditions in the external environment may vary widely, the internal conditions of most organisms stay fairly constant. • The process by which they do this is called homeostasis. • A breakdown in homeostasis can result in disease or even death. • Homeostasis often involves internal feedback mechanisms, which respond to internal stimuli. A thermostat in your home maintains a constant temperature in your home.
A similar “thermostat” regulates human body temperature. • Human body temperature is a constant 37oC (98.6oF), regardless of the external temperature of the environment. • If the external temperature gets too hot and causes the human body temperature to rise, the body responds by sweating, which helps remove excess heat from the skin. • If the external temperature gets too cold and causes the human body temperature to drop, the body responds by shivering. • The muscle contraction when shivering produces heat, warming the body.
Another example of homeostasis: human blood sugar levels. • The blood contains a constant amount of sugar in the blood. Yet the amount of sugar available to the body changes. • After you eat a meal high in sugar, blood sugar levels rise. • This stimulates the pancreas to produce a hormone (chemical signal) called insulin. • Insulin targets the liver and muscle cells of the body and tells them to take up the excess sugar and store it, bringing blood sugar levels back to normal. • After several hours of not eating, the sugar in the blood is used by the cells for energy, causing the blood sugar levels to drop. • This stimulates the production of a second hormone from the pancreas called glucagon. • Glucagon stimulates the liver and muscles to release sugar into the blood and help raise the blood sugar levels back to normal.
Animals are not the only organisms to use homeostasis. • Plants must regulate carbon dioxide intake and water loss. • Plants use structures call stomata (singular: stoma) to do so. • Stomata are microscopic holes in a plant leaf (usually on the underside) that allow gases to enter and leave and water vapor to leave as well. • Each stoma consists of two guard cells, which control the opening and closing of stomata by responding to changes in water pressure. • When guard cells are swollen with water, the stoma is open. • When the guard cell loses water, the opening closes, limiting further water loss from the leaf.
Although individual organisms experience many changes during their lives, the basic traits they inherited from their parents usually do not change. • A group of organisms, however, can change over time through the process of evolution. • Any inherited structure, behavior or internal process that enables an organism to respond to environmental factors and live to produce offspring is called an adaptation.
There are always some differences in the adaptations of individuals within any population of organisms. • As the environment changes, some individuals have adaptations that make them better suited to the new conditions and more likely to survive and reproduce. As a result, individuals with these adaptations become more numerous in the population. • Over time, the characteristics of a species will change so that all individuals have the adaptation. • This process of change over time is called evolution. Life evolves as a result of the interaction between organisms and their environments.
