An Introduction to Ecology and the Biosphere By: Caitie, Alex, Kara, and Garris
The Scope of Ecology • Organisms are open systems that interact continuously with their environment. • Ecology is the scientific study of the interactions between organisms and the environment.
Ecology • Ecology has a long history as a descriptive science but is also a rigorous experimental science. • Ecology and evolutionary biology are closely related sciences. • The environment of any organism includes abiotic, or nonliving, components – chemical and physical factors such as temperature, light, water, and nutrients – and biotic, or living, components – all the organisms, or the biota, that are part of the individual’s environment.
Ecology Contd. • Ecologists generally need to consider multiple factors and alternative hypotheses when attempting to explain patterns of distribution and abundance. • Ecology can be divided into areas of study ranging from the ecology of individual organisms to the dynamics of ecosystems and landscapes.
Subfields of Ecology • Organismal ecology concerns how an organism’s structure, physiology, and (animals) behavior meet the challenges posed by the environment. • A population is a group of individuals of the same species living in a particular geographic area. • Population ecology concentrates mainly on factors that affect how many individuals of a particular species live in an area. • A community consists of all the organisms of all the species that inhabit a particular area. • Community ecology deals with the whole array of interacting species in a community.
Subfields of Ecology Contd. • An ecosystem consists of all the abiotic factors in addition to the entire community of species that exist in a certain area. • In ecosystem ecology the emphasis is on energy flow and chemical cycling among the various biotic and abiotic components. • Landscape ecology deals with arrays of ecosystems and how they are arranged in a geographic region. • Every landscape or seascape consists of a mosaic of different types of “patches,” and environmental characteristic ecologists refer to as patchiness. • The biosphere is the global ecosystem – the sum of all the planet’s ecosystems. • The precautionary principle is a guiding principle in making decisions about the environment.
Interactions between Organisms and the Environment • Biogeography is the study of the past and present distribution of individual species. • The movement of individuals away from centers of high population density or from their area of origin, called dispersal, contributes to the global distributions of organisms. • Natural range expansions clearly show the influence of dispersal on distribution. • One direct way to determine if dispersal is a key factor in limiting distribution is to observe the results of intentional or accidental transplants of a species to areas where it was previously absent. • If a transplant is successful, then we can conclude that the potential range of the species is larger than its actual range.
Interactions Contd. • When individuals seem to avoid certain habitats, even when the habitats are suitable, their distribution may be limited by habitat selection behavior. • The inability to survive and reproduce may be due to negative interactions between other organisms in the form of predation, parasitism, disease, or competition. • The environment is characterized by both spatial heterogeneity and temporal heterogeneity. • Abiotic factors include temperature, water, sunlight, wind, and rocks and soil. • Climate is the prevailing weather conditions in a particular area and the components are temperature, water, sunlight, and wind. • Macroclimate is the patterns on the global, regional, and local level while microclimate is the very fine patterns.
Interactions Contd. • Ocean currents influence climate along the coasts of continents by heating or cooling overlying air masses, which may then pass across the land. • Mountains have a significant effect on the amount of sunlight reaching an area, as well as on local temperature and rainfall. • The changing angle of the sun over the course of the year affects local environments. • Turnover brings oxygenated water from a lake’s surface to the bottom and nutrient-rich water from the bottom and nutrient-rich water from the bottom to the surface in both spring and autumn. • Many features in the environment influence microclimates by casting shade, affecting evaporation from soil, and changing wind patterns.
Abiotic and Biotic Factors • Biomes are the major types of ecological associations that occupy broad geographic regions of land or water. • Aquatic biomes account for the largest part of the biosphere in terms of area, and all types are found around the globe. • Many aquatic biomes are physically and chemically stratified. • The upper photic zone has sufficient light for photosynthesis while little light penetrates the lower aphotic zone. • At the bottom of all aquatic biomes, the substrate is called the benthic zone which is made up of sand and organic and inorganic sediments. • The benthic zone is occupied by communities of organisms collectively called benthos.
Aquatic biomes contd. • A major source of food for the benthos is dead organic matter called detritus, which “rains” down from the productive surface waters of the photic zone. • In the ocean and in most lakes, a narrow stratum of rapid temperature change called a thermocline separates the more uniformly warm upper layer for a more uniformly cold deeper waters. • In both freshwater and marine environments, communities are distributed according to depth of the water, degree of light penetration, distance from shore, and open water versus bottom.
Climate • Because there are latitudinal patterns of climate over Earth’s surface, there are also latitudinal patterns of biome distribution. • We can see the great impact of climate on the distribution of organisms by constructing a climograph, a plot of temperature and precipitation in a particular region. • Annual means for temperature and rainfall are reasonably well correlated with the biomes that exist in different regions. • Often it is not only the mean or average climate that is important but also the pattern of climatic variation.
Climate contd. • Most terrestrial biomes are named for major physical or climatic features and for their predominant vegitation. • Veritcal stratification is an important feature of terrestrial biomes, and the shapes and sizes of plants largely defined the layering. • Terrestrial biomes usually grade into each other, without sharp boundaries. The area of intergradation, called an ecotone, maybe wide or narrow.
Climate contd. • Biomes are dynamic, and disturbance rather than stability tends to be the rule. • In many biomes, the dominant plants depend on periodic disturbance. • In many biomes today, extensive human activity has radically altered the natural patterns of periodic physical disturbance.