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Biology: The Science of Life

  1. Life as we perceive it
    1. Public perception and acceptance of science is often based on a media-inspired belief that scientific progress occurs in giant leaps and with dramatic announcements.
    2. Reality shows us that scientific progress usually occurs in a series of small, incremental steps occurring over a protracted period of time.
    3. In today's fast-paced environment, this seeming contradiction often leads to misunderstanding, frustration, and disillusionment, since steps taken today may have implications that will not emerge for a long time.
  2. The subject matter of science consists of generalizations and concepts that provide the content.
    1. Science is more than collecting and organizing facts and ideas. More important is what is done with the facts at hand.
    2. The way in which conclusions are drawn, generalizations made, and predictions tested form the methodology of science.
    3. The methods by which content is obtained-experimentation, observation, reasoning from known examples-represent the procedure of science. The procedure used is often called the Scientific Method, but it is not unique to scientists.
    4. Scientific methodology involves logic and common sense. Observations are made, background information is reviewed and collected, hypotheses are suggested, experimentation using control and experimental groups is carried out to determine whether the hypothesis may be accepted or rejected. Conclusions are drawn that may require revision of hypotheses. (Refer also to Section IV below.)
    5. Scientists are concerned with factual data, obtained by empirical methods (through the five senses) and use a mechanistic approach.
    6. Limits of science and technology
      1. Science never proves anything in an absolute sense.
      2. The only product of science is information.
      3. Science is limited by the state of the art at any given time, the precision of the measuring instrumentation, and legal, political, economic, religious, and cultural constraints.
  3. Data and its implications
    1. Observations and/or experimentation provide data, which may be either quantitative or qualitative.
      1. Quantitative data are the result of measurements and/or can be expressed in some definitive and precise form, usually in numbers. Quantitative data tell how much, how many, or what concentration.
      2. Such numerical data are preferred because
        1. they are easily verified
        2. a relationship between two factors is more readily apparent
        3. they are a more precise and meaningful way to communicate between scientists
        4. they can be subjected to statistical analysis
      3. Qualitative data do not lend themselves to precise numerical expression; more subjective or descriptive terms are used (taller, better, wider, heavier); this type of data may tell you what types of materials or molecules are present, but not how much.
      4. Data of each type provides information. The information received depends on the questions asked. There is no guarantee that the information is true.
      5. Information that has been shown to be true or, more precisely, has not been disproved, is called a fact.
      6. There is a difference in the way that scientists talk about a theory and the way the public understands it. For the layperson, a theory often is thought of as a guess. For a scientist, a theory shows a meaningful pattern in the facts collected. A theory that has not been disproved for a long time may be called a law.
  4. Scientific Methodology frequently includes the following:
    1. Asking a question based on observation of the natural world (or just out of curiosity) and gathering information regarding the problem.
    2. Proposing a hypothesis or tentative solution.
    3. Predicting the observations that will occur if the hypothesis is correct (your educated guess).
    4. Testing the prediction by performing an experiment. A control is included to check the experiment. Repeating the experiment a number of times is also a necessity.
    5. Making the information available to other scientists through talks at meetings or publications in journals, so that it becomes available for verification.
    6. The scientific method does not apply to matters of religion, politics, culture, ethics, or art.

    Before you move into the next section you will want to look over the following site on classification. From the Introduction you can move into several other topics. Each of the topic areas has a Practice Quiz that you can take.


    As cited in the Fall 2000 issue of Natural Selection, a publication of the Biological Science Curriculum Study group, about 13% of the earth's estimated 13.6 million species have been described. The majority are arthropods, with land plants a distant second.

    Source: United Nations Environment Programme. 1995 Global biodiversity assessment. Cambridge, U.K.: Cambridge University Press. (The data were compiled by BSCS staff biologist David Hanych.)

    *"Land plants" refers to mosses, liverworts, ferns, and seed plants. "Protoctists" refers to eukaryotes that are not plants, animals or fungi. "Bacteria" refers to Archaea and Eubacteria (after Margulis and Schwartz, 1998). "Viruses" refers to parasitic, self-replicating nucleic acid entities.

  5. Biologists identify and classify life forms.
    1. Carolus Linnaeus (also known as Carl Linne) devised the binomial system of nomenclature. This system utilizes two names to identify each organism.
      1. Each organism is assigned a two-word name: the genus (or generic name) and species (or specific name). Think of these names as the way you often have to fill out forms: Last Name, First Name.
        1. A genus is a group of very similar organisms related by common descent to a recent ancestor. These organisms share similar physical traits.
        2. The standard definition of a species includes members that share the same set of structural features and that can interbreed and produce fertile offspring. The advent of genetic engineering has clouded the definition.
      2. Each organism is placed in a series of taxonomic groups: species, genus, family, order, class, phylum (or division) and kingdom. This grouping provides a sorting mechanism; classification groups are a little like file folders in a file cabinet.
    2. Biologists organize living things into groups based on their similarities. Closely related individuals are grouped into species. A genus includes similar species; related genera are grouped into families, families into orders, orders into classes, classes into phyla or divisions, and phyla into kingdoms. Each of these groups is subdivided into superclasses and subclasses. Species may be further divided into subspecies, varieties, serotypes, and other categories. This is a human-generated system that is constantly evolving (like updating the filing system).
    3. Biologists currently recognize five kingdoms. Natural Perspective contains more information about the five kingdoms and classification.
      1. The kingdom Monera includes bacteria whose cellular organization lacks membrane-bound organelles, including a nucleus. This type of cellular organization is known as Prokaryotic organization. Monera may be divided into several branches. The Archaebacteria (also known as the Extremophiles) are as different from other bacteria as they are from eukaryotes. They have provided us with information that has allowed us to extend the current classification system into three overarching categories known as domains.
      2. Protista are more complicated single-celled organisms. The Protozoa are considered animal-like, the Algae are plant-like, and there are many that are fungus-like.
      3. Fungi include mostly multicelled organisms that absorb energy and materials from living or dead organisms. Single-celled fungi are known as yeast.
      4. Plants are usually multicelled and generate their own food (organic molecules) using the energy in specific wavelengths of light, such as sunlight.
      5. Animals are multicelled and get their energy by ingesting other organisms.
    4. Taxonomy makes it easier to identify and establish evolutionary relationships between and among species.
  6. All living things, whether single-celled or multicelled, no matter the kingdom or domain, must deal with some of the same basic problems.
    1. It's easy to become disorganized. All things tend toward disorder (the fancy term for this tendency is "entropy"). The reasons will be discussed more fully in a later lesson. Suffice it to say that we are not 100% efficient in using the energy and matter that is available to us. Living things fight entropy by taking energy and material from their surroundings (such as the food we eat) and using them as fuel and raw materials for growth, repair, and maintenance, as well as other survival activities.
    2. Continuation of the species is the role of reproduction at the population level. At the organism level, reproduction provides for replacement and growth of the individual's cells and tissues. Through reproduction, life continues despite the death of individuals.
  7. Life is defined through a set of observable characteristics.
    1. Some authors have grouped traits under categories such as "overcoming disorganization":
      1. Order or organization refers to a precise arrangement of structures and their associated functions. This will require a continuous input of energy for maintenance or growth.
      2. Adaptations include structures and functions that make an organism better suited to its environment over the long term. These are not developed overnight and have passed the test of natural selection.
      3. Metabolism is the sum of all chemical processing of energy compounds. This includes collecting, concentrating, and converting both energy and matter.
      4. Movement or irritability describes the tendency of an organism to sense and react to its surroundings. This occurs at all organizational levels, from cell to organism.
    2. Characteristics that help the survival of the individual and ensure the passing of traits to future generations include:
      1. Reproduction, which may be simple or complex, sexual or asexual (biparental or uniparental).
      2. Development, the orderly sequence of structural and behavioral changes during an organism's life cycles. Such development is often programmed into an organism's genes, the units of genetic information and, thus, inheritance.
      3. Genes, the heritable units of information that direct the development and determine the traits of an individual. The activation or deactivation of the genes may be triggered by environmental factors, such as temperature or light.
        1. Genes are segments or parts of DNA molecules coding for proteins or nucleic acids.
        2. Mutations are genetic variations that arise occasionally. Many mutations are harmful, but a few are advantageous. The gradual accumulation of mutations provides a supply of modified genetic information that can be acted upon by natural selection, leading to a process of change called evolution.
      4. Evolutionary change often alters a species' traits over time.
    3. Life forms evolve as time passes.
      1. All living things are derived from a common ancestor as the result of genetic modification taking place in species that lived before them. Note some of the early theories of evolution.
      2. Natural selection, a concept developed by Charles Darwin and A.R. Wallace, is a major mechanism of evolution.
        1. Lamarck suggested that evolution occurred by the inheritance of acquired characteristics, a theory not supported by observation and experimentation.
        2. Darwin observed that
          1. There is a tendency for organisms to reproduce in geometric progression. If all their offspring survived, the earth would be covered by them.
          2. The earth is not overrun (although this is still an open question in regard to humans), since the finite resources available to the offspring creates competition, a "struggle for existence."
      3. Darwin concluded that individuals with traits that allow them to survive in a particular environment leave more offspring than individuals with less-adaptive traits. As a result, certain inherited characteristics of the survivors become more common in succeeding generations.
      4. Natural selection makes it possible for the best-adapted individuals in a particular environment to become parents and pass on the advantageous genetic information.
    However, natural selection is not the cause of the variations. Rather, variations are products of gene mutations and are thus part of the raw material of evolutionary change.
  8. Thus, life is characterized by unity (the unity of genetic information and related biochemical processing) and diversity (millions of variations among organisms resulting from the interaction of genetic information with environmental factors). Both the unity and the related diversity are products of evolution.
    1. All living things share the same genetic code.
    2. Organisms are varied in size, shape, and life habits.
  9. A biological unit is a living unit of any size or degree of complexity that has a structural and functional integrity. It displays certain properties which, taken together, distinguish it from all nonliving systems.
    1. It embodies a recognizable structure.
    2. It carries out orderly functional processes.
    3. It undergoes a regular pattern of development and maturation.
    4. It reproduces itself more or less exactly.
    5. It is capable of long-range, orderly genetic change.
    6. It survives only within a certain prescribed range of environmental conditions.
    7. It maintains its integrity in the face of a hostile environment.
    8. Its structure and function are finely adjusted to operate under the environmental conditions to which it is normally subjected.
    9. It possesses internal regulatory mechanisms that permit it to offset or to recover from the effects of moderate deviations from the usual environmental conditions (homeostatic mechanisms).
    10. It cannot cope with severe deviations from the usual conditions. These result in permanent damage or death.

    Although generally characteristic of all living systems, these principles vary in detail when applied to different systems of a given level, and especially when applied to systems of different levels of biological organization. (List excerpted from T.C. Emmel, Global Perspectives on Ecology, Mayfield Publishing, 1977.)

  10. The property of organization or order is evident throughout the living and nonliving world. However, at each level of biological organization, emergent properties appear that were not present in the organizational level that came before. Maintaining organization requires both matter and energy.
    1. Levels of organization of the biosphere include ecosystems made of communities of organisms and their physical environments. Communities are made of populations of interbreeding organisms.
    2. Each organism is made up of organ systems comprising organs made of tissues composed of cells, the least complicated units that are truly alive.
    3. Cells include organelles and are made of molecules, clusters of atoms composed of subatomic particles.
  11. Energy flows and materials cycle through living communities.
    1. Energy from the sun flows through plants, animals, fungi, and microbes and is eventually lost to space as heat energy.
    2. Materials continually cycle between the living and nonliving components of the biosphere.
  12. Biology is a science with tremendous potential to help us deal with the vexing problems of the present and future. How do we feed, clothe and house the increasing human population without deforestation, loss of natural resources, malnutrition, and disease? The discipline undergoes continual revolution with the advent of new knowledge, such as genetic manipulation and better understanding of how organisms and ecosystems function at the molecular as well as organismic levels. Every day brings new bioethical challenges.