Ecology meaning and scope

Chapter 1                        ECOLOGY: MEANING AND SCOPE

DEFINITION

Ecology describes and studies the patterns seen in nature, studies the interactions among organisms and their environment, and the mechanisms involved in biological diversity.

Ecology was first defined by...

• The word "ecology" was first used in 1866 by German scientist Ernst Heinrich Haeckel (1834-1919).
• Ernst Haeckel in 1866 in Generelle Morphologie der Organismen.
• Oikos = home, family household.
• Ecology literally means "the study of the household."
• He defined it as the scientific study of the relationships of organisms to their environment and to one another.
• Emphasis on scientific rigor.
• Interpretation of ecological phenomena in terms of evolution.

THE DEVELOPMENT OF ECOLOGY

There is no agreement on the beginnings of ecology. Some historians tie origin of ecology to Greek and Roman philosophers (Theophrastus, Aristotle, Pliny); others to the Renaissance naturalists/taxonomists Caesalpino, Linnaeaus, De Candolle, Tournefort, Buffon and Darwin.

United States and Germany were the principal countries involved in the early stages of ecology.

 

PLANT ECOLOGY

The modern impetus of ecology came from plant geographers. They noticed that although plants differ in different parts of the world, there are some similarities and differences that required an explanation.

In Europe:

• Carl Ludwig Willdenow (1765-1812) pointed out that similar climates supported similar vegetation forms, e.g. deciduous forest, although the species were different.

 

• 1805 Alexander von Humboldt traveled extensively in South America. He recognized plant communities and related plant distribution to the physical aspects of the environment. He coined the term association.

• The Danish botanist Johannes Warming (1841-1924) worked in Brazil and emphasized the importance of temperature, moisture and soil in patterns of vegetation.

 

• Andreas Schimper (1856-1901) explained the differences in vegetation as a function of moisture and temperature. He attempted to explain the physiological basis for plant distribution.

• 1863. Anton Kerner von Maurilaun - Plant life in the Danube Basin. Kerner is widely read in German and has been very influential in Europe. He began to develop the idea of forest succession

 

• 1891 and 1896 Jozef Paczoski (Poland) defines "phytosociology", the organization of plant communities. He later published textbook (1921). Described how plants modify the environment by creating microenvironments.

"Phytosociology is the study of the characteristics, classification, relationships, and distribution of plant communities (The American Heritage Dictionary, 3rd ed). It is useful to collect such data to describe the population dynamics of each species studied and how they relate to the other species in the same community. Subtle differences in species composition and structure may point to differing abiotic conditions such as soil moisture, light availability, temperature, exposure to prevailing wind, etc. When tracked over time, species and individual dynamics can reveal patterns of response to disturbance and how the community changes over." http://www.yale.edu/fes519b/saltonstall/page3.htm

• Christen Raunkier (1860-1938) prepared a scheme of life from classification and quantitative methods of sampling vegetation, and the data collected can be treated statistically.

 

• Josias Braun-Blanquet (Swiss; 1930's) set up Station Internationale de Geobotanique Mediterrenne et Alpine (SIGMA) at Montpellier, France. He founded the Zurich-Monpellier  School of phytosociology. He developed methods of community sampling and classification of and nomenclature of plant communities.

• Sir Arthur Tansley (1930's), noted British plant ecologist who founded British Ecological Society. He encouraged an experimental approach to ecology and coined word "ecosystem.

 

In the United States:

The destruction of forests during the settlement years of the 19th century triggered an interest in how plant communities developed and vegetation dynamics and succession.

• Henry Chandler Cowles - studies dune succession and develops dynamic ecology (1899), University of Chicago, a center for botany, trains many graduate students.

 

• In the first 35 years of the 20th. century, Frederick E. Clements (1874-1945), with support of the Carnegie Institute publishes huge and numerous volumes on succession, research methods in ecology, plant indicators, phytogeography and history of ecology; later becomes much maligned due to his largely “descriptive” approaches, yet is actually a giant in the intellectual development of ecology and one of the first to recognize many concepts.

 

ANIMAL ECOLOGY

Animal ecology developed separately from plant ecology. R. Hesse of Germany and C. Elton of England were the pioneers.

Animal ecologists emphasized the study of animal communities and their relationships.

• 1877 Karl Möbius - German zoologist publishes paper on oyster beds and uses the word “biocœnosis” as a descriptor of an animal community; may be first use of “community” in modern ecological sense; also develops idea of community equilibrium

 

• R. Hesse, Ecological Animal Geography. 1939.

• C. Elton (English) published "Animal Ecology" (1927), emphasizing regulation of population size, ecological niches and food chains.

 

• Early 1900s Victor Shelford and C.C. Adams - contemporaries of Cowles, looked at animal communities in the same manner that plant ecologists did, classification and dynamics, Shelford is first president of Ecological Society of America established in 1915;

• Shelford publishes book in 1913 on Animal Communities of the Chicago area; He emphasized the interaction of plants and animals.
• Adams calls ecology the “new natural history” and publishes first book devoted to animal ecology (1913).

 

• Allee, Emerson, Park, Park and Schmidt published the comprehensive book named Principles of Animal Ecology (1949). It emphasized energy budgets, population dynamics, evolution and natural selection.

Darwin's ideas on natural selection and evolution led to the study of animal behavior during their interaction with the environment.

• Behaviorism: a school of thought in psychology that studies the mechanisms of objective behavior; it influenced ecological studies giving origin to behavioral ecology.
• Ethology: function and evolution of behavior: Konrad Lorenz: genetically programmed behavior; Niko Tinbergen: causation, development, evolution, function; K. V. Frish: bee communities and behavior.
• Behavioral ecology: studies the interaction of animals with their living and non-living environment.
• Sociobiology: studies the interaction of group of animals and their social behavior.

 

ECOPHYSIOLOGY

Ecophysiology is the study of physiological adaptations of organisms to their non-living environment and habitat.

• How the organism responds to moisture, temperature, light, nutrients, etc.

 

• J. Leibig (1840): studied limiting factor and the limited supplies of nutrients in growth and development of plants.

• F. F. Blackman (1905): factors interaction e.g. lights, CO2, assimilation rate, etc.

 

As mechanisms of photosynthesis and water relations in plants were deciphered, ecophysiologists related these functions to plant distributions and adaptations.

• V. E. Shelford (1913): Animal communities in Temperate America. He developed the Law of Tolerance, which linked and organisms to its environment.

 

• Chemical ecology studies the role of chemicals in species recognition, defense, courtship, etc.

 

POPULATION ECOLOGY

Population ecology is the branch of ecology that studies the structure and dynamics of populations.

Darwin was greatly influenced in his ideas by Robert Thomas Malthus, an economist and sociologist who proposed the principle that populations grow geometrically while resources grew in an arithmetic fashion. This combination of growth will eventually result in the exhaustion of supplies and the increase in struggle between groups and individuals as they compete for fewer resources.

• Gregor Mendel (1822-1884) studied the inheritance of traits and led to the development of  population genetics.

 

• P.F. Verhulst (1838) developed formula for population growth when resources are limiting

• G. H. Hardy and W. Weinberg (1908) independently wrote the classic papers on genetic equilibrium in populations that make the beginning of population genetics.

 

"Population genetics studies gene frequencies and microevolution in populations. Selective advantages depend on the success of organisms in their survival, reproduction and competition. And these processes are studied in population ecology. Population ecology and population genetics are often considered together and called "population biology". Evolutionary ecology is one of the major topics in population biology."
http://www.ento.vt.edu/~sharov/PopEcol/lec1/whatis.html

 

• Alfred J. Lotka (1925) publishes "The Elements of Physical Biology", includes laws of thermodynamics; along with Vito Volterra, an Italian mathematician, and Raymond Pearl devised basic equations later widely used in population and community ecology (1920s = “golden age of mathematical population ecology”). They studied population growth under limiting conditions, predation and competition.

Their work established the foundation population ecology, concerned with population growth, regulation, and intraspecific and interspecific competition.

Evolutionary ecology combines ideas from population ecology and population genetics.

• Evolutionary ecology studies the interactions of population dynamics, genetics, natural selection and evolution.

 

There is no clear distinction between population ecology and community ecology. Community ecology is concerned with the interaction between species and its influence on distribution and abundance.

Theoretical ecologists take hypotheses developed by mathematicians, physicists and economists and apply them to ecological questions.

• They attempt to provide a mathematical foundation for ecological concepts so predictions can be made.
• Theoretical ecology has many hypotheses that are untested or impossible to test in the field.

 

Other important concepts:

Physiology studies individual characteristics and individual processes. These are use as a basis for prediction of processes at the population level.

Community ecology studies the structure and dynamics of animal and plant communities. Population ecology provides modeling tools that can be used for predicting community structure and dynamics.

 

ECOSYSTEM ECOLOGY

With time ecology different specializations within ecology developed.

The two major divisions are holistic ecosystem ecology and reductionist evolutionary and population ecology.

• Holistic ecosystem ecology: an integration of living organisms and their environment into a system. This was Tansley's approach.

 

• Reductionist evolutionary and population ecology see ecosystems as the sum of parts that can be studied separately to discover ecosystem functions.

• Stephen A. Forbes publishes "The Lake as a microcosm" (1887)- foundation of modern limnology; self-educated zoologist, published many other key ecology papers before1900.

 

• F.A. Forel, Swiss, in 1895 coins and “founds” science of limnology

• August Thienemann introduced in 1926 the idea of organic nutrient cycling and feeding levels, using the terms producers and consumers.

 

• C. Juday and A. E. Birge studied in Wisconsin, the accumulation of energy by aquatic plants over a year.

• Raymond Lindeman, University of Minnesota, trophic dynamic concept (succession described using energy flow) published a paper in 1942 to explain community dynamics based in what we think of as ecosystem ecology.

 

• G.E. Hutchinson (1957, 1969): limnologist and zoologist, publishes many very influential books and papers on niche, energy flow and nutrient budgets.

• Odum brothers (Howard T. And Eugene P.), J. Ovington (England), and Rodin and Bazilevic (Soviet Union)  - begin ecosystem studies, synthesize relatively new ideas on ecosystem ecology and have enormous influence on many ecologists.

 

Systems ecology is the application of general systems theory and methods to ecology. The ability to measure energy flows and nutrient cycling by means of radioactive tracers and to analyze large amounts of data with computers permitted the development system ecology.

"Systems ecology is a relatively new ecological discipline which studies interaction of human population with environment. One of the major concepts is optimization of ecosystem exploitation and sustainable ecosystem management."
http://www.ento.vt.edu/~sharov/PopEcol/lec1/whatis.html

The National Science Foundation (NSF) began the program called Long Term Ecological Research (LTER) in 1980.

• 21 study sites, from Puerto Rico to Alaska.
• Temperate and tropical forest, grasslands, deserts, wetlands, agriculture, rivers, and urban sites.
• Urban sites to study the ecological and socioeconomic interaction.
• The objectives are to understand the long-term patterns and controls of food webs, population abundance and distribution organic matter accumulation primary production, etc.

 

TENSIONS WITHIN ECOLOGY

Plant and animal ecologists worked as if the other group did not exist. Clements and Shelford were instrumental in bringing both camps together in 1939.

Clements looked at plant communities as a single organism. He saw vegetation moving through different stages until reaching maturity, the climax community.

William Morton Wheeler saw ant colonies as organisms that gathered food, defended themselves, reproduced, etc. He proposed that animal associations have certain emergent properties that arose from lower levels of organization.

Wheeler called this association a biocenosis. Everything in a biocenosis is related to everything else.

Tansley, Gleason and others rejected the organismic idea and proposed that plant associations change gradually according to environmental condition, and there are no clean-cut boundaries between the communities.

Tansley proposed the concept of ecosystem that includes the non-living environmental factors.

A holistic approach to ecology studies all the attributes of the ecosystem. According to holistic ecologists, the ecosystem can be studied only as a functional unit.

• Ecosystem ecologists are interested in how the system works now.

 

The reductionist approach studies each part of the ecosystem separately in order to understand the entire system.

• Population ecologists (reductionists) are concerned with the ultimate answer: why natural selection favored different adaptive responses among species over evolutionary time.

 

APPLIED ECOLOGY

Applied ecology is concerned with the application of ecological principles to major environmental and resource management problems.

Applied ecology includes forest, range, wildlife and fisheries management, conservation biology, restoration ecology, and landscape ecology.

• Solutions to environmental problems must be based on sound theories developed through research.

 

Applied ecology began in the early 1930's with the work of H. Stoddard on the ecology of fire, A. Leopold on the application of ecological principles to wildlife management.

The conservation movement started in Europe, in Germany with Ernst Haekel, then moved to northern Europe, England and the United States.

Rachel Carson published in the U. S. Silent Spring in 1962, which brought environmental problems to the attention of the public.

Conservation biology is concerned with maintaining biological diversity. It is an interdisciplinary field that includes ecology, biogeography, population genetics, economics, sociology, anthropology, philosophy, etc.

Restoration ecology uses ecological principles in the restoration and management of ecosystems. It is concerned with the restoration of degraded habitats to conditions as similar as possible to its original undisturbed state.

Restoration ecology is devoted to "returning damaged ecosystems to a condition that is structurally and functionally similar to the predisturbance state." (Cairns, 1995).

 

Landscape ecology is the study of a landscape structure and its processes;  how spatial patterns shape the processes that occur in them.

• A mosaic of visually distinctive patches (landscape elements): parcels of forest surrounded by towns or agricultural land.
• It considers human influence.
• Its structure includes the size, shape, composition number, and position of different ecosystems within a landscape.
• The structure influences the flow of energy, materials and species between the ecosystems in the landscape.

 

"Landscape ecology is also a relatively new area in ecology. It studies regional large-scale ecosystems with the aid of computer-based geographic information systems. Population dynamics can be studied at the landscape level, and this is the link between landscape- and population ecology." http://www.ento.vt.edu/~sharov/PopEcol/lec1/whatis.html

Ecosystem management integrates ecological, economic and social goals in an unified, systems approach.

• It is concerned with long-term sustainability.

• It recognizes that social goals, environmental quality and economic health are inextricably interlinked.
• Social goals cannot be achieved in a deteriorating environment or economy.
• It attempts to integrate ecological, economic and social goals in an unified systems approach.

 

Environmental studies are the multidisciplinary study of the relationship of humans to the environment. It includes philosophy, sociology, economics, political science, theology, anthropology and science (ecology, biology, geology, climatology, hydrology, chemistry, physics, behavior, etc.).

 

ECOLOGY: AN EMPIRICAL AND EXPERIMENTAL SCIENCE

Ecology has evolved from a descriptive to an experimental approach emphasizing the testing of hypothesis.

A hypothesis is an educated guess, a statement that can be tested.

Ecology follows the scientific method of study: observations, measurements, hypothesis, etc.

• Inductive method: from specific observations to a general conclusion.

 

• Deductive method: the scientist develops a general idea about a phenomenon, conducts experiments, and from them makes specific predictions that can be tested again. It goes from a general idea to a specific prediction.

Hypotheses are tested through experimentation.

Experimentation involves simplification by manipulating one or a few variables while holding others constant.

The response of one variable, the dependent variable, to changes in another variable, the independent variable.

Control group: in a controlled experiment, the groups in which all variables are held constant.

Models or paradigms are abstractions of real systems. They are typically formulated in a mathematical way.

Models or paradigms are developed based on research data. These models are abstractions and simplifications of natural occurrences.

Validation  is the test of the model's ability to do what it is supposed to do. By testing the model, we test the underlying assumptions on which it is based.

Skepticism often contributes to a paradigm shift, a replacement of an old paradigm.

Ecology is usually studied a three levels: organism, population, and ecosystem.

 

SUMMARY

Early Period: Distribution of Organisms and Communities.

• In the early stages of ecology, scientists concentrated on the distribution of organisms, biogeography, patterns in nature, etc.
• Carl Ludwig Willdenow (1765-1812); 1805 Alexander von Humboldt; 1866 Ernst Haeckel; 1887 Stephen Forbes; 1898 R. Pounds and F. Clements; 1899 H. Cowles; 1909 C. Adams;  1913 V. Shelford; 1927 C. Elton (English); 1929 Clements and Weaver.

 

Diversification Period: Transition to an emphasis on the study of population ecology, energy flow and evolutionary ecology.

• In the late 1940s and early 50s emphasis shifted to the study of population dynamics, energetics and evolutionary ecology.
• 1942 R. A. Lindeman; 1949 Allee, Emerson, et al.; 1953 E. Odum; 1964-74 International Biological Program conducted many studies of energy flow and nutrient cycling in different biomes.
• In the 1960s and 70s people began to realize that many world and societal problems were in the last analysis ecological problems.

 

Modern Period: Application to societal problems.

• In the 1960s and 70s there was a dramatic turning point in our understanding of the dangerous consequences of pollution and our demands to be protected from it.
• National Environmental Policy Act is created in 1969 by an Act of Congress. NEPA is involved in making national environmental policy and requires environmental impact statements.
• Environmental Protection Agency is created in 1970 by an Act of Congress. It is a cabinet level department and answers to the President of U.S.A.
• 1970s marked a rapid growth with an emphasis on the application of ecological principles: ecology and economic analysis, environmental law, ecological consultation, and education.
• More than 27 major federal laws for environmental protection and hundreds of administrative regulations were established in the decade of the 70s.
• Appearance of organizations dedicated to the conservation of the environment: Nature Conservancy, Greenpeace, and Natural Resources Defense Council.
• In the last 25 years, over 170 international treaties and conventions have been negotiated to protect our global environment.
• 1992 United Nations conducted the "Earth Summit" in Rio de Janeiro, Brazil, to discuss the state of the earth, development and the environment.
• 1997 International meeting in Kyoto, Japan, about global warming. Countries committed themselves to cut back in greenhouse gases. Kyoto Protocol.

 

Tensions within ecology:

Plant ecology vs. animal ecology.
Organismal vs. individualistic ecology
Holism vs. reductionism

Applied ecology:

Conservation biology is concerned with maintaining biological diversity.
Restoration ecology uses ecological principles in the restoration and management of ecosystems.
Landscape ecology is the study of a landscape structure and its processes.
Ecosystem management integrates ecological, economic and social goals in an unified, systems approach.
Environmental studies are the multidisciplinary study of the relationship of humans to the environment.

 

Experimentation:

Inductive method: specific to general.
Deductive method: general to specific.

Dependent variable reacts to changes in another variable, the independent variable.

Control group: in a controlled experiment, the groups in which all variables are held constant.

Models or paradigms are abstractions of real systems.