Frumkin, 2e Part 1: Methods and Paradigms. Chapter 1: ECOLOGY AND ENVIRONMENTAL HEALTH

Transcription

1 Frumkin, 2e Part 1: Methods and Paradigms Chapter 1: ECOLOGY AND ENVIRONMENTAL HEALTH

2 Ecology Ecology is the study of the interactions between organisms and their environments, including both the living (biotic) and nonliving (abiotic) components.

3 Ecology Ecology aims to understand how natural systems such as plant and animal communities are organized and function. This includes investigating the subsystems and other parts of natural systems, the relationships among them, and the processes at and above the level of the individual organism that allow biological systems to persist and evolve as dynamic entities. It evolved from natural history (described and catalogued plants and animals) and evolutionary biology (the study of natural selection and the adaptation and survival of species).

4 Ecology s Subsystems Ecosystem Ecology Community Ecology Population Ecology

5 Ecosystem Ecology Ecosystem ecology stresses energy flows and material cycles, including the ways in which energy and materials are modified by human activities. An ecosystem is formed by the interactions of living organisms with their physical environment.

6 Biosphere A biosphere is the largest known ecosystem, in which all other ecosystems are embedded; it consists of all the Earth s living organisms interacting with the physical environment. The biosphere provides us with a way of thinking about life, and an understanding of the processes that make it possible for life to have evolved and survive on Earth. This a systems view, with the Earth as a unit of interacting living and nonliving parts.

7 Community Ecology Focuses on the interactions of species, with an emphasis on species composition and diversity. Studies plants, animals, and microorganisms and their coexistence in a particular location.

8 Population Ecology Population ecology attempts to explain the dynamics of species populations and interactions among species as well as relationships between species and their physical environment.

9 Subdivisions of Ecology

10 Biomes The character of ecosystems is determined by critical features, including the amount of precipitation, the temperature, and the availability of soil nutrients. These features in turn predict the kind of vegetation that grows, defining the major ecological zones, or biomes. Biomes are the major geographic regions, including the tundra, boreal forest, temperate forest, tropical forest, scrubland, grassland and savannah, desert, and their relevant subtypes.

11 Ecosystem Processes and Functioning Naturally mediated and regulated ecological processes, such as the breakdown of organic waste and the recycling of chemical elements, are part of what is called ecosystem functioning. The hydrologic cycle and the biogeochemical cycles include the carbon cycle and nitrogen cycle. Ecosystems keep water clean, recycle wastes, regulate infectious disease, and control the climate.

12 Ecosystem Organization Ecosystems can be organized by trophic structure and nutrient cycles (the cyclical use and reuse of elements like Carbon, Nitrogen, Phosphorus, etc.).

13 Trophic Structure Trophic structure refers to the organization of ecosystems by feeding levels, often conveniently conceptualized as a pyramid. A trophic level is the position that an organism occupies on this pyramid (i.e. its place in the food chain). The first level is made up of autotrophs or primary producers, which convert sunlight into energy. Primary consumers feed upon primary producers, and are in turn fed upon by secondary consumers, or heterotrophs.

14 Humans and the Ecosystem The adaptive renewal cycle is repeated cycles of change that are exhibited by ecological systems when in interaction with humans. Ecological systems go through four distinct phases: exploitation, conservation, release, and reorganization. This system of cyclical monitoring and adjusting was named adaptive management. It is the central idea of ecosystem management and involves monitoring key indicators of the health of the ecosystem, such as measures of nutrient flow and animal stocks, and adjusting human actions accordingly.

15 Biodiversity Biodiversity refers both to organismic variety at the various levels of the organizational hierarchy and to genetic diversity among individual organisms. Ecosystems with greater numbers of species or with species populations harboring greater differences in their genetic makeup have greater biodiversity. Ecosystems that retain higher levels of biological diversity often retain superior air, water, and soil quality and regulate pathogens more effectively.

16 Communities The amount of space in a habitat plays a key role in determining the number of species present. As habitat area increases, so do the amount of resources and the variety of resources, termed habitat diversity. Greater extent and diversity of habitat translates into a larger number of species supported. This fact is known as the species-area relationship. The particular needs of a species and its role in its community are collectively known as its niche. The competitive exclusion principle states that no two species can occupy the same niche.

17 Communities in Equilibrium The equilibrium theory developed by Robert MacArthur and E. O. Wilson ( 1967 ), points out that the number of species in an isolated place can be described in terms of the rates of immigration and extinction An equilibrium number of species is maintained in a community only if the habitat remains intact and a pool of potential immigrants exists within dispersal distance. MacArthur and Wilson anticipated that neither of these conditions would exist for long.

18 Populations A population is a group of interbreeding individuals in a particular locality. The elemental factors affecting population size are births, deaths, immigration, and emigration.

19 Population In density-independent regulation of populations, factors such as temperature, humidity, and rainfall operate independently of population density and affect population size. In density-dependent regulation of populations, biotic factors such as competition, predation, and parasitism affect population size to a greater degree where there is greater population density. Populations are limited by the carrying capacity of habitats, that is the population size that can be supported in a given area within the limits of available food, habitat, water, and other needed resources.

20 Landscape The makeup of landscapes is an important concept in ecology. Heterogeneous landscapes tend to withstand disease and natural disasters better than homogenous landscapes.