Notes: 1  When s is a string or Unicode string object the in and not in operations act like a substring test. In Python versions before 2.3, x had to be a string of length 1. 2  Values of n less than 0 are treated as 0 (which yields an empty sequence of the same type as s).
A food web describes the flow of energy and nutrients through an ecosystem, while a food chain is a linear path through a food web. Distinguish between food chains and food webs as models of energy flow in ecosystems. Organisms can be organized into trophic levels: primary producer, primary consumer, secondary consumer, and tertiary or higher-order consumer.
Radiant energy is a form of kinetic energy. Kinetic energy refers to the movement of the energy whether is is of atoms, molecules, waves, substances or objects. Other forms of kinetic energy include thermal energy, sound, motion energy and electrical energy. Without radiant energy, like that from the sun, life on Earth would not be possible. Radiant energy is the result of a change in configuration of electrons. It can travel through any substance including air, liquid, glass, and space. However, matter is not necessary for transmission of radiant energy. Even in a vacuum environment, radiant energy can move.