Biology: The Science of Life
- Life as we perceive it
- 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.
- Reality shows us that scientific progress usually occurs in a
series of small, incremental steps occurring over a protracted period of
- 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
- The subject matter of science consists of generalizations and concepts
that provide the content.
- Science is more than collecting and organizing facts and ideas. More important
is what is done with the facts at hand.
- The way in which conclusions are drawn, generalizations made,
and predictions tested form the methodology of science.
- 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.
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
- Scientists are concerned with factual data, obtained by empirical
methods (through the five senses) and use a mechanistic approach.
- Limits of science and technology
- Science never proves anything in an absolute sense.
- The only product of science is information.
- 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.
- Data and its implications
- Observations and/or experimentation provide data, which may be
either quantitative or qualitative.
- 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.
- Such numerical data are preferred because
- they are easily verified
- a relationship between two factors is more readily apparent
- they are a more precise and meaningful way to communicate
- they can be subjected to statistical analysis
- 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.
- Data of each type provides information. The
information received depends on the questions asked. There is no guarantee
that the information is true.
- Information that has been shown to be true or, more precisely,
has not been disproved, is called a fact.
- 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.
Methodology frequently includes the following:
- Asking a question based on observation of the natural world (or
just out of curiosity) and gathering information regarding the problem.
- Proposing a hypothesis or tentative solution.
- Predicting the observations that will occur if the hypothesis
is correct (your educated guess).
- 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.
- Making the information available to other scientists through
talks at meetings or publications in journals, so that it becomes available
- 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.
- Biologists identify and classify
- Carolus Linnaeus (also known as Carl Linne) devised the binomial
system of nomenclature. This system utilizes two names to identify
- 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,
- A genus is a group of very similar organisms related by common
descent to a recent ancestor. These organisms share similar physical
- 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
- 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.
- 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).
- Biologists currently recognize five kingdoms. Natural Perspective contains more information about the five kingdoms and classification.
- 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.
- 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.
- Fungi include mostly multicelled organisms
that absorb energy and materials from living or dead organisms. Single-celled
fungi are known as yeast.
- Plants are usually multicelled and generate
their own food (organic molecules) using the energy in specific wavelengths
of light, such as sunlight.
- Animals are multicelled and get their energy
by ingesting other organisms.
- Taxonomy makes it easier to identify and establish evolutionary
relationships between and among species.
- All living things, whether single-celled or multicelled, no matter
the kingdom or domain, must deal with some of the same basic problems.
- 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.
- 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.
- Life is defined through a set of observable characteristics.
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.
- Some authors have grouped traits under categories such as "overcoming
- 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.
- 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
- Metabolism is the sum of all chemical processing
of energy compounds. This includes collecting, concentrating, and converting
both energy and matter.
- 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.
- Characteristics that help the survival of the individual and
ensure the passing of traits to future generations include:
- Reproduction, which may be simple or complex,
sexual or asexual (biparental or uniparental).
- 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.
- 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.
- Genes are segments or parts of DNA molecules coding for proteins
or nucleic acids.
- 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.
- Evolutionary change often alters a species'
traits over time.
- Life forms evolve as time passes.
- 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
- Natural selection, a concept developed by
Charles Darwin and A.R. Wallace, is a major mechanism of evolution.
- Lamarck suggested that evolution occurred by the inheritance
of acquired characteristics, a theory not supported by observation and
- Darwin observed that
- There is a tendency for organisms to reproduce in geometric
progression. If all their offspring survived, the earth would be covered
- 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."
- 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.
- Natural selection makes it possible for the best-adapted individuals
in a particular environment to become parents and pass on the advantageous
- 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.
- All living things share the same genetic code.
- Organisms are varied in size, shape, and life habits.
- 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.
- It embodies a recognizable structure.
- It carries out orderly functional processes.
- It undergoes a regular pattern of development and maturation.
- It reproduces itself more or less exactly.
- It is capable of long-range, orderly genetic change.
- It survives only within a certain prescribed range of environmental
- It maintains its integrity in the face of a hostile environment.
- Its structure and function are finely adjusted to operate under
the environmental conditions to which it is normally subjected.
- 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).
- 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,
- 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.
- Levels of organization of the biosphere include
ecosystems made of communities of organisms
and their physical environments. Communities are made of populations of
- Each organism is made up of organ systems comprising
organs made of tissues composed of cells,
the least complicated units that are truly alive.
- Cells include organelles and are made of molecules,
clusters of atoms composed of subatomic particles.
- Energy flows and materials cycle through living communities.
- Energy from the sun flows through plants, animals, fungi, and
microbes and is eventually lost to space as heat energy.
- Materials continually cycle between the living and nonliving
components of the biosphere.
- 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