Ecology Basics

Environment and Ecosystem

• The environment consists of two parts: biotic and abiotic.
• The ultimate goal of Ecosystem Ecologists is to understand how ecosystems function.

Population, Species, Community, and Ecosystem

• A population is a group of organisms of the same species that live together in the same area at the same time.
• A species is a group of similar organisms whose members freely interbreed with one another in the wild to produce fertile offspring.
• A community is a natural association that consists of all the populations of different species that live and interact together within an area at the same time.
• An ecosystem includes all the biotic interactions of a community as well as the interactions between organisms and their abiotic environment.

Landscape and Ecosystems

• A landscape is a region that includes several interacting ecosystems.

Flow of Energy through Ecosystems

• Energy is the capacity or ability to do work.
• Energy exists as potential energy and kinetic energy.
• Thermodynamics is the study of energy and its transformations.
• The first law of thermodynamics states that energy cannot be created or destroyed, although it can change from one form to another.
• The second law of thermodynamics states that when energy is converted from one form to another, some of it is degraded into heat, a less usable form that disperses into the environment.
• Photosynthesis is a biological process that captures light energy and transforms it into the chemical energy of organic molecules.

Producers, Consumers, and Decomposers

• Producers are plants and other photosynthetic organisms that manufacture organic molecules from carbon dioxide and water.
• Consumers are organisms that consume other organisms as a source of food energy and bodybuilding materials.
• Primary consumers (herbivores) eat producers.
• Secondary consumers eat primary consumers.
• Tertiary consumers eat secondary consumers.
• Other consumers (omnivores) eat a variety of organisms.
• Detritus feeders consume detritus, organic matter that includes animal carcasses, leaf litter, and feces.
• Decomposers are organisms that break down dead organisms and waste products, such as bacteria and fungi.

Path of Energy Flow in Ecosystems

• Energy flow is the passage of energy in a one-way direction through an ecosystem.
• A food chain is a sequence of energy flow from one organism to the next.
• A food web is a complex of interconnected food chains in an ecosystem.
• The longer the food chain, the less energy is available for organisms at the higher trophic levels.
• Most of the energy going from one trophic level to the next in a food chain or food web dissipates into the environment.
• Ecological pyramids often graphically represent the relative energy values of each trophic level.