Chapter 48 - Ecosystems and Human Interference

48.1 The Nature of Ecosystems

Biosphere - the part of the earth that can support life

Ecosystem - all the organisms in an environment (community) plus the nonliving factors (temperature, humidity..)

Autotrophs - producers, usually plants, that create organic nutrients using an outside energy source (photosynthesis)

Heterotrophs - consumers, gain their energy by feeding on other organisms

Carnivores - eat other animals
Omnivores - eat both plants and animals
Herbivores - eat plants
Detritivores - eat dead or decaying organisms

48.2 Energy Flow

- energy flows through an ecosystem starting from the sun, then to the producers and then to the consumers. At each level, some of the energy is lost as heat

Law of Thermodynamics

Energy exists in many forms, such as heat, light, chemical energy, and electrical energy. Energy is the ability to bring about change or to do work. Thermodynamics is the study of energy.

First Law of Thermodynamics: Energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe remains constant, merely changing from one form to another. Energy is always conserved, it cannot be created or destroyed. (This is often called the Law of Conservation of Energy)

Second Law of Thermodynamics: in all energy exchanges, if no energy enters or leaves the system, the potential energy of an end state will be less than its starting state. This is called ENTROPY. Living things must add energy to their systems to maintain order and life.

Food Webs and Food Chains

Food webs illustrate how energy is transferred in an ecosystem.

food web

Ecological Pyramids also illustrate relationships

ecological pyramid

Pyramids also illustrate the relative numbers of species.

In any system, there will be more individuals lower on a food chain. An ecosystem can only support a small number of top predators.

pyramid of numbers

46.3 Biogeochemical Cycles

Energy flows through an ecosystem, but most chemicals are recycled.

Carbon Cycle | Phosophorous Cycle | Water Cycle | Nitrogen Cycle


Environmental Issues

Habitat Destruction | Pollution | Biological Magnification | Climate Change