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Chapter 1: Introduction
Robert E. Ricklefs
The Economy of Nature, Fifth Edition
Background
❚ Human perceptions of nature and mankind’s relation to nature:
❙ there is a balance of nature
❙ nature is pristine in the absence of humans
❚ Ecological studies conclude otherwise:
❙ there is historical variation in nature
❙ the pervasive influence of human activities extends to the most remote
regions of the earth
What is Ecology? ❚ By ecology, we mean the body of knowledge concerning the economy of nature -- the investigation of the total relations of the animal both to its organic and to its inorganic environment; including above all, its friendly and inimical relation with those animals and plants with which it comes directly or indirectly into contact -- in a word, ecology is the study of all the complex interrelationships referred to by Darwin as the conditions of the struggle for existence. Ernst Haeckel, 1870.
So, what is ecology?
❚ Ecology is the science by which we study how organisms (animals, plants,
and microbes) interact in and with the natural world.
❚ Please note the important key words in the above definition!
Ecology - A Science for Today
❚ We have a great need for ecological understanding:
❙ what are the best policies for managing our environmental support systems
-- our watersheds, agricultural lands, wetlands?
❙ we must apply ecological principles to:
❘ solve or prevent environmental problems ❘ inform our economic, political, and social thought and practice
Our Objectives...
❚ We are on the road to ecological thinking:
❙ we’ll have many vantage points of varying complexity
❙ we’ll understand ecological systems and the interdependence of their
components
❙ we’ll establish a core of principles regarding:
❘ physical and chemical attributes ❘ regulation of structure and function ❘ evolutionary change Ecological Systems Large and Small
❚ Organism (“No smaller unit in biology ... has a separate life in the
environment...”)
❚ Population (many organisms of the same kind living together)
❚ Guild (a group of populations that utilizes resources in essentially the same
way)
Ecological Systems Large and Small
❚ Community (many populations of different kinds living in the same place)
❚ Ecosystem (assemblages of organisms together with their physical
environment)
❚ Biosphere (the global ecosystem, all organisms and environments on earth)
Perspectives of Ecologists: Organism Approach
❚ How do form, physiology, and behavior lead to survival?
❚ Focus is on adaptations, modifications of structure and function, that suit the
organism for life in its environment: ❙ adaptations result from evolutionary change by natural selection, a natural link to population approach... Perspectives of Ecologists: Population Approach
❚ What determines the numbers of individuals and their variations in time and
space?
❚ Focus is on processes of birth and death, immigration and emigration,
influenced by: ❙ the physical environment ❙ evolutionary processes ❙ interactions with other populations, a natural link to community approach...
Perspectives of Ecologists: Community Approach
❚ How are communities structured from their component populations?
❚ Focus is on the diversity and relative abundance of different kinds of
organisms living together, affected by: ❙ population interactions, promoting and limiting coexistence ❙ feeding relationships, responsible for fluxes of energy and materials, a natural link to ecosystem approach...
Perspectives of Ecologists: Ecosystem Approach
❚ How can we account for the activities of populations in the common
“currencies” of energy and materials?
❚ Focus is on movements of energy and materials and influences of:
❙ organisms large and small ❙ climate and other physical factors, including those acting on a global scale, a natural link to biosphere approach... Perspectives of Ecologists: Biosphere Approach
❚ How can we understand the global movements of air and water, and the
energy and chemical elements they contain?
❚ Focus is on the global circulation of matter and energy, affecting:
❙ distributions of organisms ❙ changes in populations
symbioses :
❙ each partner provides something the other lacks
❙ examples of symbiotic relationships include:
❘ lichens (fungus and alga) ❘ bacteria fermenting plant material in a cow’s gut ❘ beneficial fungi associated with the roots of plants ❘ photosynthetic algae in corals and clams ❘ nitrogen-fixing bacteria in root nodules of legumes
Habitat and Niche
❚ The habitat is a place or physical setting in which an organism lives.
Examples include:
❙ forests
❙ deserts
❙ coral reefs
❚ The habitat is characterized by:
❙ conspicuous physical features
❙ dominant plant (or animal) life
Classifying habitats is useful but difficult!
❚ The habitat concept is useful; it emphasizes conditions experienced by
organisms.
❚ Classification systems are varied and typically hierarchical:
❙ aquatic habitats (vs. terrestrial)
❘ marine habitats (vs. freshwater)
- oceanic habitats (vs. estuarine)
- benthic habitats (vs. pelagic)
❚ Finer subdivisions overlap rather broadly!
Niche
❚ The niche of an organism encompasses:
❙ ranges of conditions tolerated
❙ role in ecological systems
❚ No two species have the same niche:
❙ each has distinctive form and function
❚ No organism can live under all conditions:
❙ each has unique habitat requirements
❙ each has a unique niche
Systems and Processes: Dimensions in Time and Space
❚ Nothing in nature is static: anything we can measure (conditions, number of
organisms) exhibits variation.
❚ Variation has temporal and spatial components.
❚ Variation in each measurement has a characteristic scale; for the same degree
of change: ❙ air temperature varies over hours ❙ ocean temperature varies over weeks or months
Temporal Variation
❚ Consider two kinds of temporal variation :
❙ predictable, cyclic variations (daily, seasonal)
❙ unpredictable, irregular variations
❚ A temporal “rule of thumb”:
❙ the more extreme the condition, the less frequent (compare cold fronts and
hurricanes)
❙ but frequency and severity are relative terms that depend on the organism!
Spatial Variation
❚ Spatial variation occurs at very small (forest sunflecks) and very large
(latitudinal variation in solar flux) scales.
❚ Scale of variation importance is a function of the organism:
❙ the two sides of a leaf are different to an aphid
❙ a moose eats the whole leaf, aphid and all
Time and Space
❚ A few generalizations:
❙ moving organisms experience spatial variation as temporal variation
❙ the faster an individual moves:
❘ the smaller the scale of spatial variation ❘ the more quickly it encounters new environments ❘ the shorter the temporal scale of variation
❙ spatial and temporal scales are correlated
❙ frequency is inversely related to extent/severity
Physical and Biological Principles 1
❚ Ecological systems are physical entities :
❙ life builds on physical properties and chemical reactions of matter
❙ all processes obey the physical laws of thermodynamics
❙ but life still pursues many varied options
Physical and Biological Principles 2
❚ Ecological systems exist in dynamic steady states :
❙ despite substantial fluxes of energy and matter, ecological systems remain
more or less unchanged
❙ gains and losses are more or less balanced
❙ steady states apply to fluxes of materials and energy at all levels of
ecological organization
Physical and Biological Principles 3
❚ The maintenance of living systems requires the expenditure of
energy :
❙ life forms exist out of equilibrium with their physical environment
❙ losses must be replaced by energy or materials procured by the organism
❙ the price of maintaining a dynamic steady state is energy
Physical and Biological Principles 4
❚ Ecological systems undergo evolutionary change through time :
❘ models of global carbon
Humans are a prominent part of the biosphere.
❚ Why study ecology?
❙ the wonders of the natural world stimulate our curiosity and our desire to
understand our surroundings
❙ a growing human population increasingly stresses the natural world,
causing two related problems: ❘ impact of humans on natural systems ❘ deterioration of our own environment
A Focus on Human Impacts
❚ Human impacts are everywhere...
❚ We are inundated with environmental problems (disappearing tropical forests,
ozone hole, depleted fish stocks, etc.).
❚ Increasingly, the only effective means of preserving natural resources is
through conservation of entire ecological systems and management of broad- scale processes.
Success Stories
❚ Many positive efforts are underway:
❙ cleanup of rivers, lakes, and air
❙ reduction in acid rain
❙ reduction in release of chlorofluorocarbons
❙ widespread focus on CO 2 and global warming
❙ protection of endangered species
❙ international cooperation (IUCN, WWW)
❙ international agreements (CITES, Rio)
Summary 1
❚ Ecology is the scientific study of the natural environment and the relationships
of organisms to one another and to their surroundings.
❚ Ecologists study a variety of organisms and processes, spanning a wide range
of spatial and temporal scales.
❚ Individual organisms live in habitats and have unique niches reflecting
conditions tolerated and functional role.
Summary 2
❚ All ecological systems obey natural laws and are subject to evolutionary
change.
❚ Ecologists employ the scientific method.
❚ Humans are part of the global ecosystem and have created numerous
environmental problems. Solving these problems will require application of ecological principles.
